3.2.P.5Quality Control of Preparations

Quality Standards

Gadopentetate Dimeglumine Injection

This product is a sterile aqueous solution of gadopentetate dimeglumine. It contains gadopentetate dimeglumine (C₁₄H₂₀GdN₃O₁₀•2C₇H₁₇NO₅)

Should be 95.0% to 105.0% of the labeled amount.

【Description】 The product is a clear, colorless to pale yellow or pale yellowish-green liquid.

【Identification】 (1) Carry out the test as described in the Thin-layer Chromatography method (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 0502).

Test solution Take an appropriate amount of the product, dilute with water to prepare a solution containing approximately 35mg of gadopentetate dimeglumine per 1ml (equivalent to meglumine14.6mg).

Reference Solution Dissolve an appropriate amount of gadopentetate dimeglumine reference standard in water and dilute to prepare a solution containing approximately 56mg per 1ml (equivalent to 14.6mg of dimeglumine).

Chromatographic Conditions Use a silica gel GF₂₅₄ thin-layer plate, with a developing solvent system of n-butanol-glacial acetic acid-water (4︰1︰2).

Assay Spot 2μl each of the test solution and the reference solution on the same thin-layer plate, develop, dry, spray with ninhydrin-cadmium acetate solution (prepared by dissolving 0.1g of ninhydrin and 0.25g of cadmium acetate in 1ml of glacial acetic acid, diluting with ethanol to 50ml, and mixing well), and heat at 120°C for 10 minutes to develop the color.

Result Interpretation The position and color of the principal spot in the test solution should be identical to those of the principal spot in the reference solution.

(2) Carry out the test as described in Thin-layer Chromatography (Chinese Pharmacopoeia 2020 Edition, General Rule 0502).

Test solution Dilute an appropriate amount of the product with water to prepare a solution containing about 35mg of gadopentetate dimeglumine per 1ml (equivalent to 20.4mg of gadopentetic acid).

Reference solution Dilute the reference solution from Identification (1) with water to prepare a solution containing about 28mg per 1ml (equivalent to 20.4mg of gadopentetic acid).

Chromatographic conditions Use silica gel GF₂₅₄ thin-layer plates, with a mobile phase of methanol-acetonitrile-water-glacial acetic acid (5︰2︰2 ︰0.2).Assay Method Draw 2μl each of the test solution and the reference solution, spot them on the same thin-layer plate, develop, and air-dry. Spray with a cerium sulfate-arsenite solution (take 5g of cerium sulfate, place it in a 100ml volumetric flask, set it in an ice bath, add 50ml of 0.5mol/L sulfuric acid solution cooled to 0°C, shake to dissolve, filter, and refrigerate as solution A; separately, take 2.5g of sodium arsenite, dissolve it in 15ml of 1mol/L sodium hydroxide solution, refrigerate at 0°C, carefully add it to 32.5ml of 1mol/L sulfuric acid solution cooled to 0°C, dilute with water to 50ml as solution B; mix equal volumes of solution A and solution B immediately before use, and use within 5 minutes), then spray with a 1% o-phenylenediamine acetone solution.

Result Interpretation The position and color of the principal spot in the test solution should be identical to those of the principal spot in the reference solution.

(3) In the chromatograms obtained in the assay, the retention time of the principal peak in the test solution should correspond to that of the principal peak in the reference

solution.

(4) Take 5 ml of the product, place it in a 25 ml volumetric flask, dilute with water to the mark, mix well, and measure according to the ultraviolet-visible spectrophotometry

(Chinese Pharmacopoeia2020 Edition, Part IV, General Rule0401). The maximum absorption is observed at a wavelength of275 nm.

For the above items (2) and (3), either one may be selected for testing.

[Inspection] pH value: Take the product and inspect it according to the method (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 0631 pH Value Determination Method). The pH value should be

7.0 to 7.9.

Color Take the sample and examine it according to the method (General Rule 0901, Method I of Part IV, Chinese Pharmacopoeia 2020 Edition), comparing it with yellow No. 4 or yellow-green

No. 4 standard color solution, and it should not be darker.

Meglumine Take the sample and measure the optical rotation at 25°C according to the method (General Rule 0621 of Part IV, Chinese Pharmacopoeia 2020 Edition), calculate using the following formula

The calculated meglumine content should be 39.6%~43.9% of the labeled amount of gadopentetate dimeglumine.

Meglumine content (%)=measured optical rotation*1000

24.9*469 × 100%

Pentetic acid Accurately measure 2ml of the sample, place it in a 100ml conical flask, add 20ml of water, and 10ml of dilute xylenol orange solution.

Shake well, adjust the pH to 5.0 with 0.1mol/L sodium hydroxide solution or glacial acetic acid, and titrate with gadolinium sulfate solution (0.001mol/L).

Titrate until the solution changes from yellow to reddish-purple. Each 1ml of gadolinium sulfate solution (0.001mol/L) is equivalent to 0.7867mg of

pentetic acid (C₁₄H₂₃N₃O₁₀). Each 1ml of the preparation should contain 230–450μg of pentetic acid.

Gadolinium Determine by atomic absorption spectrophotometry (Chinese Pharmacopoeia 2020 Edition, General Rule 0406 , Method I).

Cesium Chloride Solution Take an appropriate amount of cesium chloride, dissolve it in water, and dilute to the mark to prepare a solution containing100mg per1ml.

Blank Solution Mix cesium chloride solution, hydrochloric acid (spectral pure), and water in a ratio of20:10:70 (V/V/V) to obtain.

Test Solution Precisely measure5ml of the sample (equivalent to gadopentetate dimeglumine 2.3g), place in a porcelain crucible, add nitric acid

1.0ml, mix well, place on an electric stove, and slowly char until completely carbonized. Incinerate at about800°C until completely ashed (approximately 1 hour),

After cooling, transfer to a desiccator, allow to cool to room temperature, then take out, add 5ml of water and (spectral purity) hydrochloric acid10ml, heat to dissolve

, transfer to a100ml volumetric flask, add 20ml of cesium chloride solution, dilute with water to the mark, and use as the test solution.

Standard stock solution Accurately weigh 5.75g of gadolinium oxide, place in a 100ml volumetric flask, add (spectral purity) hydrochloric acid10ml

and an appropriate amount of water, heat to dissolve, cool to room temperature, then dilute with water to the mark to obtain.

Reference solution Accurately transfer 1ml, 2ml, 3ml, 4ml, and 5ml of the standard stock solution1ml, 2ml, 3ml, 4ml, 5ml, respectively, into separate 50ml

volumetric flasks, add 10ml of cesium chloride solution10ml and 10ml of hydrochloric acid (spectral purity)10ml, dilute with water to the mark, and prepare solutions containing

1ml of gadolinium element1000μg, 2000μg, 3000μg, 4000μg and 5000μg, respectively.

Spectral line search 3000μg/mL reference solution.

AssaySubtract the background with blank solution, accurately measure the reference solution and test solution at368.4nmwavelength

Measure the absorbance and calculate using the standard curve method. (This method is a flame continuous emission spectrometry, requiring the use of a high-temperature burner and

Nitrous oxide-acetylene gas (no gadolinium hollow cathode lamp required)

Limit The gadolinium content of this product is15.9%-17.5% of the labeled amount of gadopentetate dimeglumine.

Related substancesDetermined by high-performance liquid chromatography (Chinese Pharmacopoeia2020 Edition, Part IV General Rule0512).

Copper nitrate solution Take 12.88g of copper nitrate trihydrate, dissolve in water and dilute to1000ml.

Copper nitrate sodium citrate solution Take 12.88g of copper nitrate trihydrate, 38.0g of sodium citrate dihydrate, dissolve in water and dilute

to1000ml.

Test solution Accurately measure1ml of the sample (approximately equivalent to gadopentetate dimeglumine469mg), transfer to a20ml volumetric flask,

Dilute to the mark with copper nitrate sodium citrate solution, and mix well.

Reference solution (1) Take an appropriate amount of nitrilotriacetic acid reference substance and ethylenediaminetetraacetic acid reference substance, accurately weigh, dissolve in copper

nitrate solution and quantitatively dilute to prepare a solution containing approximately0.02mg of nitrilotriacetic acid and0.4mg of ethylenediaminetetraacetic acid per1ml.

Mixed solution.

Reference solution (2) Accurately measure 1 ml of reference solution (1)1ml, transfer to a 20ml volumetric flask, and dilute with copper nitrate solution to

the mark, and mix well.

Mixed solution of reference solution (1) and test solution Accurately measure 1 ml of reference solution (1)1ml, transfer to a 20ml volumetric

Into the flask, dilute to the mark with the test solution, and mix well.

Chromatographic conditions Use octylsilane-bonded silica gel as the filler (MOS-1Hypersil, 125mm×4.6mm, 5μm,

ora chromatographic column with equivalent performance); using10%(W/V) aqueous solution of tetrabutylammonium hydroxide10ml, methanol10ml,

water 170ml, mix well, adjust the pH to 7.5±0.1 with phosphoric acid, then add methanol 90ml, and dilute with water to a final volume of

1000ml as mobile phaseA,using10%(W/V) aqueous solution of tetrabutylammonium hydroxide10ml, methanol 10ml,

water 170ml, mix well and adjustpHto7.5±0.1withphosphoric acid, add methanol450ml, and dilute with water to

1000ml as mobile phase B; perform gradient elution according to the table below at a flow rate of 2ml per minute; the detection wavelength is

254nm; injectionvolume20μl; after injection, elute with mobile phaseAandrecord the chromatogram until20min;

After the recording is completed, elute theB column with mobile phase for 20min, then equilibrate the column with mobile phaseA.

System Suitability RequirementsIn the mixed solution of reference standard solution (1), the nitrilotriacetic acid peak and copper nitrate

The resolution between the peaks of copper nitrate and EDTA should meetthe requirements (for nitrilotriacetic acid and ethylenediaminetetraacetic acid

In thetest solution and reference solution (2), the retention times may vary slightly).

Assay Accurately measure copper nitrate solution, reference solution (2), copper nitrate sodium citrate solution, and test solution,

Reference solution (1) and test solution mixture20μl, inject into the chromatograph separately, and record the chromatograms.

Limit In the chromatogram of the test solution, if any impurity peaks appear between the start (excluding the solvent peak) and the copper nitrate peak,

Calculate by the external standard method using the peak area of nitrilotriacetic acid in the reference solution (2), record from the copper nitrate peak to the end of the chromatogram,

If any impurity peaks appear, calculate by the external standard method using the peak area of ethylenediaminetetraacetic acid in the reference solution (2), related substances

The total amount shall not exceed 0.3% of the labeled amount of pentetic acid (each 1ml of this product contains a total of 197mg of pentetic acid).

Heavy metals Take an appropriate amount of the product(equivalent to gadopentetic acid dimeglumine1.0g), add 20ml of water and sodium hydroxide test solution

5ml, shake well, and examine as directed (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 0821 , Method III). The heavy metal content shall not

exceed 20 parts per million.

Bacterial Endotoxins Take the product and test according to the method (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 1143 Method 1),

The amount of endotoxin in each 1ml should be less than 0.5EU.

Sterility Take the product, process it by membrane filtration, and test according to the method (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 1101),

It should comply with the requirements.

Others should comply with the relevant requirements for injections (Chinese Pharmacopoeia2020 Edition, Part IV, General Chapter0102).

【Assay】 Determine by high-performance liquid chromatography (Chinese Pharmacopoeia2020 Edition, Part IV, General Chapter0512).

Test solution Pipette accurately2ml of the product, transfer to a200ml volumetric flask, dilute with water to volume, and mix well,

Pipette accurately15ml, transfer to a100ml volumetric flask, add10ml of acetonitrile, dilute with water to volume, and mix well.

Reference Solution Accurately weigh an appropriate amount of gadopentetate meglumine reference standard, dissolve in10%acetonitrile solution, and quantitatively

diluteto prepare a solution containing approximately0.6mgper1ml.

Chromatographic Conditions Use octadecylsilane-bonded silica gel as the stationary phase; the mobile phase is tetrabutylammonium perchlorate solution (dissolve

1.7gof tetrabutylammonium perchlorate in100mlof acetonitrile, dilute with water to1000ml); the detectionwavelength is

195nm; injection volume20μl.

System suitability requirements The number of theoretical plates, calculated based on the gadopentetate dimeglumine peak, should not be less than3000.

Assay Accurately measure the test solution and reference solution, inject them separately into the liquid chromatograph, and record the chromatograms.

Calculate using the external standard method based on peak area, multiply the obtained result by1.263.

【Category】 Diagnostic agent.

【Specification】Calculated asC₁₄H₂₀GdN₃O₁₀•2C₇H₁₇NO₅ (1)10ml:4.69g (2)12ml:5.63g(3)15ml:7.04g(4)20ml:9.38g

【Storage】 Protect from light, store tightly closed at a temperature not exceeding30°C.

【Shelf life】36 months

【Reviewing authority】Guangdong Institute for Drug Control

【Marketing Authorization Holder】 Guangzhou Kangchen Pharmaceutical Co., Ltd.

Analytical Methods

Analytical Methods

Appearance

Inspection method: Visual inspection.

Method: Take the product and observe visually.

Acceptance criteria: Should be a clear, colorless to pale yellow or pale yellowish-green liquid.

Identification 1

Test method: Thin-layer chromatography.

Test conditions: Silica gel GF₂₅₄ thin-layer plate was used, with n-butanol-glacial acetic acid-water (4:1:2) as the developing solvent.

Procedure:

Test solution: Take an appropriate amount of the sample, dilute with water to prepare a solution containing approximately 35mg of gadopentetate dimeglumine per 1ml

(equivalent to 14.6mg of meglumine).

Reference solution Dissolve an appropriate amount of gadopentetate dimeglumine reference standard in water and dilute to prepare a solution containing approximately 56mg per 1ml (equivalent to 14.6mg of dimeglumine).

Assay method Pipette 2μl each of the test solution and reference solution, spot them on the same thin-layer plate, develop, dry, and spray with ninhydrin-cadmium acetate solution (dissolve 0.1g of ninhydrin, 0.25g of cadmium acetate, and 1ml of glacial acetic acid in ethanol, dilute to 50ml, and mix well). Heat at 120°C for 10 minutes to develop the color.

Standard limit: The position and color of the principal spot in the test solution should be the same as that of the principal spot in the reference solution.

Identification 2

Test method: Thin-layer chromatography.

Test conditions: Silica gel GF254 thin-layer plate was used, with a mobile phase of methanol-acetonitrile-water-glacial acetic acid (5:2:2:

0.2) as the developing solvent.

Operation method:

Test solution Take an appropriate amount of the product, dilute with water to prepare a solution containing approximately 35mg of gadopentetate dimeglumine per 1ml

(equivalent to 20.4mg of gadopentetic acid).

Reference solution Take the reference solution from the identification(1), dilute with water to prepare a solution containing approximately 28mg per

1ml (equivalent to 20.4mg of gadopentetic acid).

Assay Method Draw 2μl each of the test solution and the reference solution, spot them on the same thin-layer plate, develop, dry, spray with cerium sulfate-arsenious acid solution (take 5g of cerium sulfate, place it in a 100ml volumetric flask, place in an ice bath, add cooled to 0°C 0.5mol/L sulfuric acid solution 50ml, shake to dissolve, filter, refrigerate, as solution A; take 2.5g of sodium arsenite, add 1mol/L sodium hydroxide solution 15ml to dissolve, refrigerate at 0°C, carefully add to cooled 0°C 1mol/L sulfuric acid solution 32.5ml , dilute with water to 50ml, as solution B; immediately before use, mix equal volumes of solution A and solution B, use within 5 minutes), then spray with 1%o-phenylenediamine acetone solution.

Standard limit: The position and color of the principal spot in the test solution should be identical to that of the principal spot in the reference solution.

Identification 3

Test method: HPLC (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 0512).

Test conditions: See the Assay section.

Procedure: See the Assay section.

Standard limit: The retention time of the main peak in the test solution should match that of the main peak in the reference solution.

Identification 4

Test method: Ultraviolet-visible spectrophotometry (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 0401).

Test conditions: Sample solution, water, ultraviolet-visible spectrophotometer.

Operating procedure:

Transfer 5ml of the sample to a 25ml volumetric flask, dilute to volume with water, mix well, and determine by ultraviolet-visible spectrophotometry (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 0401).

Standard limit: Maximum absorption at 275 nm wavelength.

pH value

Test method: pH determination (Chinese Pharmacopoeia 2020 Edition, Part IV General Chapter 0631).

Test conditions: pH meter, freshly boiled and cooled distilled water, potassium hydrogen phthalate buffer solution (pH 4.00), mixed phosphate buffer (pH 6.86), and sodium tetraborate standard buffer solution (pH 9.18).

Procedure: Take 1 vial of the product, immerse the electrode into the test solution, gently shake to equilibrate and stabilize, then take the reading.

Acceptance criteria: pH value should be 7.0~7.9.

Color

Test method: Solution color test method, Chinese Pharmacopoeia 2020 Edition, Part IV General Principles 0901 Method 1.

Test conditions: Standard colorimetric solution.

Procedure: Take 1 vial of the product, observe visually, and compare with yellow 4 or yellow-green 4 standard colorimetric solution.

Acceptance criteria: No deeper color allowed.

Meglumine

Test method: Optical rotation determination (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 0621).

Test conditions: Polarimeter.

Procedure: Take the sample and measure the optical rotation at 25°C according to the method, then calculate the meglumine content using the following formula

Meglumine content (%)=^{Measured optical rotation×1000} × 100%

24.9×469

Standard limit: Should be 39.6%~43.9% of the labeled amount of gadopentetate dimeglumine.

Pentetic Acid

Test method: Titration.

Test conditions: Dilute xylenol orange solution, 0.1mol/L sodium hydroxide solution, glacial acetic acid, gadolinium sulfate titrant (0.001mol/L).

Procedure: Accurately measure 2ml of the sample, transfer to a 100ml conical flask, add 20ml of water and 10ml of dilute xylenol orange solution, mix well. Adjust the pH to 5.0 using 0.1mol/L sodium hydroxide solution or glacial acetic acid. Titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple. Each 1ml of gadolinium sulfate titrant (0.001mol/L) is equivalent to 0.7867mg of pentetic acid (C14H23N3O10).

Standard limit: Each 1ml of the product should contain 230~450μg of pentetic acid.

Elemental impurities (not included in quality standard method)

Test Method: Inductively Coupled Plasma Mass Spectrometry (Chinese Pharmacopoeia 2020 Edition General Chapter 0412).

Test Conditions: ICP-MS.

Operating Procedure:

Test Solution: Accurately measure 215μl of Gadopentetate Dimeglumine Injection into a 100ml volumetric flask, using diluent

(Measure 10ml of hydrochloric acid and 200μl of Au standard solution (1mg/ml), dilute with water to 1000ml, and mix well.) Dissolve and dilute to the mark, mix well to obtain the solution.

Accurately measure each element standard solution and dilute with diluent according to the table below to prepare standard curve solutions:

Internal standard solution: Prepare by diluting Ge, In, Re, Bi standard solutions with water to obtain a mixed solution containing 20ng/ml of each.

Standard limits:

钆

Perform according to the Atomic Absorption Spectrophotometry method (General Rule 0406, First Method, Chinese Pharmacopoeia 2020 Edition).

Cesium Chloride Solution Take an appropriate amount of cesium chloride, dissolve it in water, and dilute to the mark to prepare a solution containing 100mg per 1ml.

Blank Solution Mix cesium chloride solution, hydrochloric acid (spectral grade), and water in a ratio of 20:10:70 (V/V/V) to obtain the blank solution.

Test Solution Accurately measure 5ml of the sample (equivalent to 2.3g of gadopentetate dimeglumine), place it in a porcelain crucible, add 1.0ml of nitric acid, shake well, and heat gently on an electric stove until completely charred. Ignite at approximately 800°C until completely ashed (about 1 hour). After cooling, transfer to a desiccator, cool to room temperature, then remove, add 5ml of water and 10ml of hydrochloric acid (spectral grade), heat to dissolve, transfer to a 100ml volumetric flask, add 20ml of cesium chloride solution, and dilute with water to the mark to prepare the test solution.

Standard Stock Solution Accurately weigh 5.75g of gadolinium oxide, place it in a 100ml volumetric flask, add 10ml of hydrochloric acid (spectral grade) and an appropriate amount of water, heat to dissolve, cool to room temperature, and dilute with water to the mark to obtain the standard stock solution.

Reference Solution Precisely transfer 1ml, 2ml, 3ml, 4ml, and 5ml of the standard stock solution into separate 50ml volumetric flasks. Add 10ml of cesium chloride solution and 10ml of hydrochloric acid (spectral purity), then dilute with water to the mark to prepare solutions containing 1000μg, 2000μg, 3000μg, 4000μg, and 5000μg of gadolinium per 1ml, respectively.

Spectral Line Search 3000μg/mL reference solution.

Assay Subtract the background with a blank solution. Precisely measure the reference solution and the test solution, and determine the absorbance at a wavelength of 368.4nm. Calculate using the standard curve method. (This method employs flame continuous emission spectrometry, requiring a high-temperature burner and nitrous oxide-acetylene gas, without the need for a gadolinium hollow cathode lamp.)

Limit The gadolinium content in this product is 15.9%-17.5% of the labeled amount of gadopentetate dimeglumine.

Related substances

Test method: High-performance liquid chromatography (Chinese Pharmacopoeia2020 Edition, Part IV, General Chapter 0512).

Test conditions: High-performance liquid chromatograph equipped with an ultraviolet detector or diode array detector, detection wavelength at 254nm; column packed with octylsilane-bonded silica gel (MOS-1 Hypersil, 125mm

×4.6mm, 5μm, or equivalent performance column); flow rate at 2.0ml/min; column temperature at 25°C; injection volume of 20μl, mobile phase 1: take 10% (W/V) tetrabutylammonium hydroxide aqueous solution 10ml, 10ml meth

Alcohol and water 170ml are mixed, adjust the pH to 7.5±0.1 with phosphoric acid, add methanol 90ml, and dilute with water to 1000ml. Mobile phase 2: Take 10%(W/V) tetrabutylammonium hydroxide aqueous solution 10ml, methanol 10ml, and water 170ml, mix, adjust the pH to 7.5±0.1 with phosphoric acid, add methanol 450ml, and dilute with water to 1000ml. Perform gradient elution according to the table below. After injection, elute with mobile phase 1 and record the chromatogram until 20min; after recording is complete, elute the column with mobile phase 2 for 20min , then equilibrate the column with mobile phase 1.

The injection sequence is: copper nitrate solution, reference solution (2), copper nitrate sodium citrate solution, test solution, mixed solution of reference solution (1) and test solution (1:20), and reference solution (1). The resolution between the nitrilotriacetic acid (NTA) peak and the copper nitrate peak, and between the copper nitrate peak and the EDTA peak, should meet the requirements. The retention times of NTA and EDTA in the test solution and reference solution (2) may slightly differ.

Operation method:

Solvent Copper nitrate solution (take 12.88g of copper nitrate trihydrate 12.88g, dissolve in water and dilute to 1000ml). Copper nitrate sodium citrate solution (take 12.88g of copper nitrate trihydrate 12.88g, 38.0g of sodium citrate dihydrate 38.0g, dissolve in

water and dilute to 1000ml).

Test solution Accurately measure 1ml of the sample (1ml(approximately equivalent to 469mg of gadopentetate dimeglumine 469mg), transfer to a 20ml

volumetric flask, dilute to the mark with copper nitrate sodium citrate solution, and mix well.

Reference Solution (1) Accurately weigh an appropriate amount of nitrilotriacetic acid reference standard and ethylenediaminetetraacetic acid reference standard, dissolve in copper nitrate solution, and quantitatively dilute to prepare a solution containing approximately 0.02mg of nitrilotriacetic acid and 0.4mg of ethylenediaminetetraacetic acid per 1ml.

Reference Solution (2) Accurately measure 1ml of Reference Solution (1), transfer to a 20ml volumetric flask, dilute with copper nitrate solution to the mark, and mix well.

Mixed Solution of Reference Solution (1) and Test SolutionAccurately measure 1ml of Reference Solution (1), transfer to a 20ml volumetric flask, dilute with the test solution to the mark, and mix well.

Assay Accurately measure 20μL each of Reference Solution (2), test solution, and dilution solvent, inject into the liquid chromatograph in the sequence specified in the system suitability test. When calculating the test solution, the corresponding peak of copper nitrate sodium citrate solution should be deducted.

Standard limits:

In the chromatogram of the test solution, if any impurity peaks appear between the start (excluding the solvent peak) and the copper nitrate peak, calculate them using the external standard method based on the peak area of nitrilotriacetic acid in reference solution (2). From the copper nitrate peak to the end of the chromatogram, if any impurity peaks appear, calculate them using the external standard method based on the peak area of ethylenediaminetetraacetic acid in reference solution (2). The total amount of related substances must not exceed 0.3% of the labeled amount of pentetic acid (each 1 mL of this product contains a total of 197 mg of pentetic acid).

Insoluble particles

Test method: Light obscuration method (Chinese Pharmacopoeia 2020 Edition, Part IV, General Chapter 0903).

Test conditions: Clean bench, insoluble particle analyzer.

Procedure: Take 4 vials of the test sample, carefully open the containers, add water for testing or a suitable solvent,combine and dissolve to 50ml, place in a sampling cup, and let stand for 2 minutes or an appropriate time to remove bubbles, then place on the sampler. Turn on stirring to mix the solution (avoiding bubble formation),and perform the measurement 4times, sampling 5mleach time.Discard the first measurement data and take the average of the subsequent 3measurements as the result. Based on the sampling volumeand dilution volume, calculate the number of particles per container.

Standard limit: Each test container must contain no more than 10µm and 10µm or larger particles exceeding 6000

particles, and no more than 25µm and 25µm or larger particles exceeding 600 particles.

Visible particles

Inspection method: Visual inspection method, 2020 edition of the Chinese Pharmacopoeia, General Rule 0904.

Test conditions: Clarity inspection apparatus.

Procedure: Take 20 vials of the product, place the test solution just outside the edge of the light shield. During inspection, the illumination at the location of the test sample should be 1000–1500 lx. Hold the container by the neck, gently rotate and invert it to suspend any potential visible particles in the solution. Visually inspect against both black and white backgrounds, repeating the observation.

4)Standard limits: The test sample must not contain metal shavings, glass fragments, fibers longer than 2 mm, particles larger than 2 mm in diameter, or visible smoke-like particulate deposits that appear after standing for a certain period and gentle rotation, uncountable particle clusters or insoluble precipitates, or clearly visible protein flocculates that are difficult to count within the specified time. If fine visible particles such as dots, short fibers less than 2 mm, or small particles are detected in the test sample: if 2 or more vials are found with such particles, the product does not meet the specification. If 1 vial is found, an additional 20 vials should be tested. The total of initial and retest samples is 40 vials. If more than 1 vial is found with particles, the product does not meet the specification, meaning none of the 20 retest vials should show such particles.

Fill volume

Test method: Filling volume according to Chinese Pharmacopoeia 2020 edition, General Chapter 0102

Test conditions: Graduated cylinder.

Procedure: Take 3 vials of the product, open them carefully to avoid loss, and withdraw the contents completely using a dry syringe with an appropriate needle size. Then slowly and continuously inject the contents into a calibrated measuring cylinder (the cylinder size should be such that the volume to be measured occupies at least 40% of its nominal capacity, without emptying the liquid remaining in the needle). Examine at room temperature.

The cylinder size should ensure that the volume to be measured occupies at least 40% of its nominal capacity, without emptying the liquid remaining in the needle. Examine at room temperature.

Standard limit: Each vial (bottle) must contain no less than the labeled amount.

Bacterial endotoxins

Test method: Gel method (Chinese Pharmacopoeia 2020 Edition IV General Chapter 1143)

Experimental conditions: Constant-temperature tube apparatus, vortex mixer, clean bench, pipette, pyrogen-free pipette tips, pyrogen-free tubes, bacterial endotoxin test water, limulus amebocyte lysate (lyophilized product, specification 0.1ml/vial, sensitivity of 0.06EU/ml), bacterial endotoxin working standard, etc.

Operation Method:

First calculate the MVD, dilute the product with bacterial endotoxin test water, the dilution factor must not exceed MVD, and use it as the test solution; dilute the bacterial endotoxin standard with bacterial endotoxin test water to prepare a 2λ concentration of endotoxin standard solution as the positive control solution; prepare the bacterial endotoxin standard with the test solution to make a 2λ concentration of endotoxin solution as the test positive control solution, and use bacterial endotoxin test water as the negative control solution. Take 8 tubes of reconstituted limulus amebocyte lysate (LAL), of which 2 tubes are added with 0.1ml of test solution as the test tubes, 2 tubes are added with 0.1ml of positive control solution as the positive control tubes (PC), 2 tubes are added with 0.1ml of test water as the negative control (NC), 2 tubes are added with 0.1ml of test positive control solution as the test positive control tubes (PPC).Gently mix the solution in the test tube, then seal the tube opening with sealing film and place it vertically in a suitable constant temperature incubator at 37°C ± 1°C, maintaining the temperature for (60 ± 2) min.

Result judgment: (1) The experiment is considered valid only when all positive controls are positive, all test sample positive controls are positive, and all negative controls are negative.

If both tubes of the test sample are negative, the sample is considered compliant; if both tubes of the test sample are positive, it is considered non-compliant; if one of the two tubes is positive and the other is negative, follow the above method to take an additional

4 test sample tubes for retesting. If 1 out of the 4 tubes is positive, it is considered non-compliant.

If during the first test, the dilution factor of the test sample is less than MVD and the results show 2 tubes as positive or 2 tubes with 1 tube positive, a retest shall be conducted using the same method, requiring dilution to MVD during the retest.

Standard limit: The amount of endotoxin in each 1ml of gadopentetate dimeglumine injection should be less than 0.5EU.

Sterility

Test method: Membrane filtration method (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 1101).

Experimental conditions: Clean bench, biochemical incubator, alcohol lamp, tweezers, etc.

Test drugs and disinfectants:75% ethanol, 0.1% benzalkonium bromide solution. Control strain: Staphylococcus aureus.

Culture media: Thioglycollate fluid medium, Tryptic Soy Broth.

Operating procedure:

Operating procedure: Take 30 samples of this product, and perform the test according to the membrane filtration method specified in (Chinese Pharmacopoeia 2020 Edition, Part IV 1101 Sterility Test).

Take 30 units of the product, and use the membrane filtration method with 10 units per filter. Rinse with pH7.0 sterilesodium chloride-peptonebuffer solution, 100ml each time, for a total of 3 rinses. Add tryptic soy agar medium to one filter and incubate at 20~25°C for 14 days. To the other filter, add 100ml of thioglycollate fluid medium. For the positive control, add less than 100cfu of Staphylococcus aureus suspension to the final rinse solution, filter, add 100ml of thioglycollate fluid medium, and incubate at 30~35°C for 14 days.

Result judgment: If all test tubes are clear, or if turbidity is observed but confirmed to be sterile, the product can be deemedqualified. If any test tube shows turbidity and microbial growth is confirmed, the product is deemed unqualified unlessit can be sufficiently demonstrated that the test results are invalid, i.e., the growth is not attributable to the product.

Assay

Test method: High-performance liquid chromatography (2020 edition of the Chinese Pharmacopoeia, Part IV, General Chapter 0512).

Test Conditions: Use octylsilane-bonded silica gel as the stationary phase (Symmetry C8, 4.6mm × 150mm, 5μm); tetrabutylammonium perchlorate solution as the mobile phase, with a flow rate of 1.0 ml per minute; injection volume of 20μl; column temperature of 25°C; detection wavelength of 195 nm.

Operating Procedure

Test Solution Accurately measure 2ml of the sample, transfer to a 200ml volumetric flask, dilute with water to the mark, and mix well. Accurately transfer 15ml to a 100ml volumetric flask, add 10ml of acetonitrile, dilute with water to the mark, and mix well.

Reference Solution Accurately weigh gadopentetate dimeglumine reference standard, dissolve in 10% acetonitrile, and quantitatively dilute to prepare a solution containing approximately 0.6mg per 1ml.

System Suitability Requirements The number of theoretical plates, calculated based on the gadopentetate dimeglumine peak, should not be less than 3000.

Assay Method Accurately measure the test solution and reference solution, inject them separately into the liquid chromatograph, and record the chromatograms. Calculate the results using the external standard method based on peak area, then multiply the obtained results by 1.263.

Standard Limit: The content of gadopentetate dimeglumine (C₁₄H₂₀GdN₃O₁₀•2C₇H₁₇NO₅) should be 95.0%~105.0% of the labeled amount.

Method Screening and Optimization

Description, Identification (1), Identification (2), Identification (3), Identification (4), and the following items under Tests: pH, color, sterility, insoluble particles, visible foreign matter, fill volume, and assay method remain unchanged from the current official standard (Chinese Pharmacopoeia 2020 Edition, Part II).

In response to changes during the study and potential degradation products, the quality standard for Gadopentetate Dimeglumine Injection was screened and optimized based on pharmacopoeial standards from various countries and the product's quality profile. The screening and optimization process for related substances, pentetic acid, elemental impurities, and other test items in the standard are described in detail.

The pentetic acid method was compared between the Chinese Pharmacopoeia 2020 Edition Part II and the import registration standard (consistent with USP43 standards). The import registration standard includes this pentetic acid test method, where in a pH5 buffer solution, dilute xylenol orange is used as an indicator. When titrated with 0.001mol/L gadolinium sulfate titrant, the endpoint changes from yellow to reddish-purple, with a clear and easily discernible transition, demonstrating good accuracy and reliability. The pentetic acid method in the Chinese Pharmacopoeia 2020 Edition Part II uses xylenol orange indicator at a concentration more than 10 times higher than the dilute xylenol orange solution in the import registration standard. The endpoint color change ranges from yellow to orange, which is less distinct compared to the import registration standard method.

Neither the Chinese Pharmacopoeia 2020 Edition nor the USP43 standard includes a method for related substances. Our company referenced the import registration standard to draft and establish the related substances test, without revising the method or limits.

The assay methods in the Chinese Pharmacopoeia 2020 Edition, USP43 standard, and import registration standard are largely consistent in terms of the mobile phase system and chromatographic conditions, with only minor differences in sample preparation and mobile phase ratios. Our company referenced the current assay method for gadopentetate dimeglumine injection in the Chinese Pharmacopoeia 2020 Edition Part II for drafting, without revisions. 3.2.P.5.2.2.1 Related Substances

Method Source

Refer to the test method for "Related Substances" under the quality standard of Gadopentetate Dimeglumine Injection in the imported registration standard (JX20020190).

Related Substances Determine by high-performance liquid chromatography (Chinese Pharmacopoeia 2020 Edition, Part IV, General Chapter 0512). Solvent Copper nitrate solution (dissolve 12.88g of copper nitrate trihydrate in water and dilute to 1000ml). Copper nitrate sodium citrate solution (dissolve 12.88g of copper nitrate trihydrate and 38.0g of sodium citrate dihydrate in water and dilute to

1000ml).

Test solution Accurately measure 1ml of the sample (equivalent to approximately 469mg of gadopentetate dimeglumine) and transfer to a 20ml

Into a volumetric flask, dilute to the mark with copper nitrate sodium citrate solution, and mix well.

Reference Solution (1) Accurately weigh an appropriate amount of nitrilotriacetic acid reference standard and ethylenediaminetetraacetic acid reference standard, dissolve in copper nitrate solution, and quantitatively dilute to prepare a solution containing approximately 0.02mg of nitrilotriacetic acid and 0.4mg of ethylenediaminetetraacetic acid per 1ml.

Reference Solution (2) Accurately measure 1ml of Reference Solution (1), transfer to a 20ml volumetric flask, dilute to the mark with copper nitrate solution, and mix well.

Chromatographic Conditions and System Suitability Use octylsilane-bonded silica gel as the filler (MOS-1Hypersil, 125mm×4.6mm,5μm, or a column with equivalent performance), Mobile Phase 1: Take 10% (W/V) aqueous tetrabutylammonium hydroxide solution 10ml, 10ml methanol and water 170ml, mix, adjust the pH to 7.5±0.1 with phosphoric acid, add 90ml methanol, and dilute with water to 1000ml.Mobile phase 2: Take 10% (W/V) tetrabutylammonium hydroxide aqueous solution 10ml, methanol 10ml, and water 170ml, mix, adjust the pH to 7.5±0.1 with phosphoric acid, add methanol 450ml, and dilute with water to 1000ml. Perform gradient elution according to the table below. After injection, elute with mobile phase 1 and record the chromatogram until 20min; after recording, elute the column with mobile phase 2 for 20min , then equilibrate the column with mobile phase 1.

The flow rate was 2ml per minute, and the detection wavelength was 254nm. The injection sequence was: copper nitrate solution, reference solution (2), copper nitrate sodium citrate solution, test solution, reference solution (1), and a mixed solution of test solution and reference solution (1:20), followed by reference solution (1). The separation between nitrilotriacetic acid (NTA) peak and copper nitrate peak, as well as between copper nitrate peak and EDTA peak, should meet the requirements. The retention times of NTA and EDTA in the test solution and reference solution (2) may slightly differ.

Assay Accurately inject 20μL each of reference solution (2), test solution, and dilution solvent into the liquid chromatograph following the system suitability test injection sequence. For the test solution calculation, the corresponding peak of copper nitrate sodium citrate solution should be deducted. If any impurity peaks appear between the injection and the copper nitrate peak, calculate them using the external standard method based on the NTA reference peak area. From the copper nitrate peak to the end of the chromatogram, if any impurity peaks appear, calculate them using the external standard method based on the EDTA

Calculated based on the reference standard peak area, the total related substances shall not exceed 0.3% of the labeled amount of pentetic acid (each 1ml of this product contains a total of 197mg of pentetic acid).

Method screening conclusion

Copper nitrate solution and copper citrate nitrate solution do not interfere with the detection of related substances in this product, nitrilotriacetic acid

(NTA) peak and copper nitrate peak, copper nitrate peak and edetate peak meet the resolution requirements. This method can be used for the control of related substances in this product.

Pentetic Acid

Method source

Chinese Pharmacopoeia 2020Edition Part II, Import Registration Standard JX20020190, and USP43 standards all include the pentetic acid test method. Method comparison is shown in Table 3.2.P.5-3

Method screening conclusion

Table3.2.P.5-3Pentetic Acid Test Method Screening

Content

Method source

Table3.2.P.5-4Content test method comparison table

The content determination method in the Chinese Pharmacopoeia 2020 edition and USP43 standard, as well as the imported registration standard mobile phase system and chromatographic conditions, are basically consistent. Only the sample preparation method and mobile phase ratio differ slightly. Our company referenced the content determination method for gadopentetate dimeglumine injection in Part II of the current Chinese Pharmacopoeia 2020 edition for drafting, with no revisions made.

Refer to the "Content" determination method under the quality standard for gadopentetate dimeglumine injection in Part II of the Chinese Pharmacopoeia 2020 edition. The determination is performed according to the high-performance liquid chromatography method (Chinese Pharmacopoeia 2020 edition, General Chapter 0512).

[Assay] Perform the test as described under High Performance Liquid Chromatography (Chinese Pharmacopoeia 2020 Edition, Part IV, General Rule 0512).

Test solution Accurately measure 2ml of the sample, transfer to a 200ml volumetric flask, dilute with water to volume, and mix well. Accurately transfer 15ml to a 100ml volumetric flask, add 10ml of acetonitrile, dilute with water to volume, and mix well.

Reference solution Take gadopentetate dimeglumine reference substance, accurately weigh, dissolve in 10% acetonitrile, and dilute quantitatively to prepare a solution containing approximately 0.6mg per 1ml.

Chromatographic conditions Use octyl-bonded silica gel as the stationary phase; use tetrabutylammonium perchlorate solution (dissolve 1.7g of tetrabutylammonium perchlorate in 100ml of acetonitrile, dilute with water to 1000ml) as the mobile phase; detection wavelength is 195nm; injection volume is 20μl.

System Suitability Requirements The number of theoretical plates, calculated based on the gadopentetate dimeglumine peak, should not be less than 3000.

Assay Procedure Accurately measure the test solution and reference solution, inject them separately into the liquid chromatograph, and record the chromatograms. Calculate the results using the external standard method based on peak area, then multiply the obtained results by 1.263.

Figure 3.2.P.5-2 Overlay Chromatograms of Blank Solvent, Reference Solution, and Test Solution for Content Determination

Method Screening Conclusion

The blank solvent does not interfere with the detection of gadopentetate dimeglumine, and this method is proposed to be adopted as the content determination method.

Validation of Analytical Methods

In accordance with the "Technical Guidelines for Validation of Analytical Methods for Quality Control of Chemical Drugs," "Technical Guidelines for the Standardization Process of Establishing Quality Standards for Chemical Drugs," "Technical Guidelines for the Study of Impurities in Chemical Drugs," and the "Chinese Pharmacopoeia" 2020 Edition, General Chapter 9101 "Guidelines for Validation of Analytical Methods for Drug Quality Standards," the methodology for related substances, elemental impurities, meglumine, pentetic acid, content, bacterial endotoxins, and sterility in the quality standards of gadopentetate dimeglumine injection was validated. Since the methods for meglumine and elemental impurities, as well as their limits, are identical to those for the gadopentetate dimeglumine raw material, the validation content refers to the raw material, and no further validation is conducted for gadopentetate dimeglumine injection. The specific details are as follows:

Pentetic Acid

Test drugs, reagents, and instruments

Table3.2.P.5-5Test Reagent Information Sheet

Table3.2.P.5-6Test Reagent Information Sheet

Table3.2.P.5-7Test Equipment Information List

Determination Method for Pentetic Acid Content

Pentetic Acid Accurately measure 2ml of the sample, place it in a 100ml conical flask, add 20ml of water, and 10ml of dilute xylenol orange solution. Shake well, adjust the pH to 5.0 using 0.1mol/L sodium hydroxide solution or glacial acetic acid, and titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple. Each 1ml of gadolinium sulfate titrant

(0.001mol/L) is equivalent to 0.7867mg of pentetic acid (C14H23N3O10). Each 1ml of the sample should contain 200~450μg of pentetic acid.

Amount of pentetic acid=^{(V–V0)×T×F} × 1000

2

V:Volume of titrant consumed,ml

V0:Volume of titrant consumed in blank test,ml

TTiter:0.7867 corresponds to 1ml of gadolinium sulfate standard titrant[=0.001000mol/L], expressed in mg units

FTitrant correction factor 2: Volume of solution transferred,ml

Validation Results Table

The specific validation summary is shown in Table 3.2.P.5-8 below:

Table 3.2.P.5-8 Summary of Pentetic Acid Methodology Validation Results

Specificity

Experimental Design and Requirements

Prepare a blank solution, and the volume of titrant consumed by the color change of the blank solution should not exceed 0.1ml. 3.2.P.5.3.1.4.2 Experimental Procedure

Solution Preparation

Blank solution: Take 20ml of water, place it in a 100ml conical flask, add 10ml of dilute xylenol orange solution, and mix well.Sodium acetate buffer solution: Take approximately 50g of sodium acetate and place it in a 1000ml volumetric flask, add about 10ml of glacial acetic acid, and add water

to the mark, mix well, and adjust the 0.1mol/L sodium hydroxide solution or glacial acetic acid to pH 5.0.

Xylenol orange solution: Take 50.8mg of xylenol orange, place it in a 100ml volumetric flask, dissolve in water, and dilute to themark, then mix well.

Dilute xylenol orange solution: Take 30ml of sodium acetate buffer solution and 3ml of xylenol orange solution, place them in the same 200ml

Transfer to a volumetric flask, add water to the mark, and mix well.

Gadolinium sulfate titrant (0.001mol/L): Take 0.7468g of gadolinium sulfate octahydrate, place it in a 1000ml volumetric flask, dissolve in water, and dilute to the mark.

Determination

Using a blank solution as reference, titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple, and record the volume of titrant consumed.

Experimental Results

Table3.2.P.5-9Specificity Test Results

Result analysis

Two blank solutions were measured, with titrant consumption volumes of 0.01ml and 0.01ml, both less than 0.10ml, meeting the specificity requirement.

Solution Stability

Experimental Design and Requirements

Sample solutions were prepared and measured at 0h, 2h, 4h, and 6h. The requirement is that the ratio of the tiaprofenic acid content at each time point compared to 0h should be within 95.0%-105.0%.

Test Procedure

Sample Solution

Blank Solution: Take 20ml of water, place it in a 100ml conical flask, add 10ml of dilute xylenol orange solution, and mix well. Sample Solution: Accurately measure 2ml of the sample, place it in a 100ml conical flask, add 20ml of water, and add dilute xylenol

orange solution 10ml, mix well, adjust the pH to 5.0 using 0.1mol/L sodium hydroxide solution or glacial acetic acid, and titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple.

Sample Determination

Prepare sample solutions and perform measurements at 0h, 2h, 4h, 6h respectively, recording the volume of titrant consumed.

Experimental Results

Table 3.2.P.5-10 Stability Test Results of Pentetic Acid Solution

Result Analysis

6h The ratio of pentetic acid measured at 0h compared to 95.0%~105.0%, indicating the solution is stable within 6h .

Linearity and Range

Experimental Design and Requirements

The linearity range is set at 50%-150%. Acceptance criterion: the correlation coefficient R of the regression line must not be less than

0.990,Y-axis intercept and the ratio between the 100% theoretical concentration should be ≤25.0%.

Experimental procedure

Solution Preparation

Blank solution: Take 20ml of water, place it in a 100ml conical flask, add 10ml of dilute xylenol orange solution, and mix well. Pentetic acid solution (400μg/ml): Take 40mg of pentetic acid, weigh accurately, and place in a 100ml volumetric flask, add

water to dissolve and dilute to the mark. (LSS)

Linear Solution Preparation

Use a pipette to transfer the following solutions

Table3.2.P.5-11Linear Solution Preparation Table

Prepare linear solutions according to Table 3.2.P.5-11, perform titration as per the proposed method, and record the volume of titrant consumed.

Experimental results

Table 3.2.P.5-12Results of linear solutions

The linear equation is y=792.2086x+14.0943, with a correlation coefficient of 0.9995 , which is greater than 0.990;the y-axis intercept ratio to the 100% concentration is 1.8%, less than 25%, indicating good linearity of the solution.

Accuracy

Experimental Design and Requirements

Prepare spiked solutions of pentetic acid at concentrations of 50%, 100%, and 150%. The recovery rate of pentetic acid at each concentration should be within 90.0%-110.0%, and the relative standard deviation (RSD) of the recovery data should be ≤10.0%.

Experimental Procedure

Solution Preparation

Pentetic Acid Solution (400μg/ml):Weigh accurately 40mg of pentetic acid, transfer it to a 100ml volumetric flask, and dissolve and dilute to volume with water.

Accuracy Solution

The preparation and transfer volumes of pentetic acid solutions at various concentrations are shown in Table 3.2.P.5-13

Table3.2.P.5-13Preparation of Accuracy Test Solutions

Prepare sample solution and spiked solution, determine using the proposed method, and record the volume of titrant consumed.

Experimental results

Table3.2.P.5-14Accuracy Results

Result Analysis

50%, 100%, 150% spike recovery rates were 98.0%, 97.1%, 97.8%, respectively, within the range of 90.0%~110.0%

; RSD values were 1.2%, 0.6%, 0.0%, all below 10.0%, meeting the accuracy requirements.

Precision

Experimental Design and Requirements

Repeatability: Prepare 6 sample solutions, analyze using the proposed method, calculate the 6 sample RSD values, with the requirement RSD not exceeding 5.0%;

Intermediate precision: Another analyst prepares 6 sample solutions, analyzes using the proposed method, calculates 12

sample RSD values, with the requirement not exceeding 5.0%.

Experimental procedure

Solution Preparation:

Blank solution: Take 20ml of water, place it in a 100ml conical flask, add 10ml of dilute xylenol orange solution, and mix well. Sample solution: Precisely measure 2ml of the sample, place it in a 100ml conical flask, add 20ml of water, and add dilute xylenol

orange solution 10ml, mix well, adjust the pH to 5.0 using 0.1mol/L sodium hydroxide solution or glacial acetic acid, and titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple.

The sample solution was prepared and measured using the proposed method, and the volume of titrant consumed was recorded.

Experimental Results

Table3.2.P.5-15Precision Measurement Results

Result Analysis

6The RSD of pentetic acid content measured in 6 test sample solutions was 0.5%; another analyst measured the 6 test sample solutions with an RSD of pentetic acid content of 0.4%, and the RSD of pentetic acid content in 12 test sample solutions was 0.5%, meeting the precision requirements.

Robustness

Experimental Design and Requirements

Prepare sample solutions and place them at 20°C, 25°C, and 30°C respectively. The measured content at each temperature point should have a ratio of 25°C within the range of 90.0%-110.0%.

Experimental Procedure

Solution Preparation:

Blank solution: Take 20ml of water, place it in a 100ml conical flask, add 10ml of dilute xylenol orange solution, and mix well. Sample solution: Precisely measure 2ml of the product, place it in a 100ml conical flask, add 20ml of water, and add dilute xylenol

orange solution 10ml, mix well, adjust the pH to 5.0 using 0.1mol/L sodium hydroxide solution or glacial acetic acid, and titrate with gadolinium sulfate titrant (0.001mol/L) until the solution changes from yellow to reddish-purple.

Prepare the sample solution, place it at 20°C, 25°C, and 30°C, respectively, and measure according to the proposed method, recording the volume of titrant consumed.

Experimental results

Table3.2.P.5-16Robustness Verification Results