Saccharin

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₇H₅NO₃S 183.18 

1,2-Benzisothiazol-3(2H)-one, 1,1-dioxide; 

1,2-Benzisothiazolin-3-one 1,1-dioxide CAS RN®: 81-07-2. 

1 DEFINITION 

Saccharin contains NLT 98.0% and NMT 102.0% of saccharin (C₇H₅NO₃S), calculated on the dried basis. 

2 IDENTIFICATION 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K 

3 ASSAY 

Procedure 

Solution A: 50 mM dibasic potassium phosphate (K2HPO4) buffer in 0.1% (v/v) phosphoric acid solution 

Solution B: Methanol 

Mobile phase: See Table 1. 

Table 1 

Diluent: Methanol and water (50:50 v/v) 

System suitability solution: 0.1 mg/mL of phthalic anhydride and 0.1 mg/mL of USP Saccharin RS in Diluent 

Standard solution: 0.1 mg/mL of USP Saccharin RS in Diluent 

Sample solution: 0.1 mg/mL of Saccharin in Diluent 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 230 nm 

Column: 4.6-mm × 15-cm; 3.5-µm packing L1 

Column temperature: 20 ± 5° 

Flow rate: 1.0 mL/min 

Injection volume: 10 µL 

Run time: 15 min 

System suitability 

Samples: System suitability solution and Standard solution 

[Note—The retention times for phthalic anhydride and saccharin are about 6.3 and 7.3 min, respectively. Phthalic anhydride is a potential impurity.] 

Suitability requirements 

Resolution: NLT 1.5 between the phthalic anhydride and saccharin peaks, System suitability solution 

Tailing factor: NMT 1.5, Standard solution 

Relative standard deviation: NMT 0.73% for ve replicate injections, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of saccharin in the portion of Saccharin taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100  

r_U = peak area of saccharin from the Sample solution 

r_S = peak area of saccharin from the Standard solution

C_S = concentration of USP Saccharin RS in the Standard solution (mg/mL) 

C_U = concentration of Saccharin in the Sample solution (mg/mL) 

Acceptance criteria: 98.0%–102.0% on the dried basis 

4 IMPURITIES 

Residue on Ignition 〈281〉: NMT 0.2%, using an ignition temperature of 600 ± 50° 

Limit of Toluenesulfonamides 

Internal standard solution: 0.25 mg/mL of caffeine in methylene chloride 

Standard stock solution: 20.0 µg/mL of USP o-Toluenesulfonamide RS and 20.0 µg/mL of USP p-Toluenesulfonamide RS in methylene chloride 

Standard solution: Evaporate 5.0 mL of the Standard stock solution to dryness in a stream of nitrogen. Dissolve the residue in 1 mL of the Internal standard solution. 

Sample solution: Suspend 10 g of Saccharin in 20 mL of water, and dissolve using 5–6 mL of 10 N sodium hydroxide. If necessary, adjust the solution with 1 N sodium hydroxide or 1 N hydrochloric acid to a pH of 7–8, and dilute with water to 50 mL. Shake the solution with four quantities each of 50 mL of methylene chloride. Combine the lower layers, dry over anhydrous sodium sulfate, and filter. Wash the filter and the sodium sulfate with 10 mL of methylene chloride. Combine the solution and the washings, and evaporate almost to dryness in a water bath at a temperature not exceeding 40°. Using a small quantity of methylene chloride, quantitatively transfer the residue into a suitable 10- mL tube, evaporate to dryness in a stream of nitrogen, and dissolve the residue in 1.0 mL of the Internal standard solution. 

Blank solution: Evaporate 200 mL of methylene chloride to dryness in a water bath at a temperature not exceeding 40°. Dissolve the residue in 1 mL of methylene chloride. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: GC 

Detector: Flame ionization 

Column: 0.53-mm × 10-m fused silica; coated with a 2-µm lm of phase G3 

Temperatures 

Injector: 250° 

Column: 180° 

Detector: 250° 

Carrier gas: Nitrogen 

Flow rate: 10 mL/min 

Injection volume: 1 µL 

Injection type: Split ratio, 2:1 

System suitability 

Samples: Standard solution and Blank solution 

[Note—The substances are eluted in the following order: o-toluenesulfonamide, p-toluenesulfonamide, and caffeine.] Suitability requirements: No peaks at the retention times for the internal standard, o-toluenesulfonamide, or p-toluenesulfonamide; Blank solution 

Resolution: NLT 1.5 between o-toluenesulfonamide and p-toluenesulfonamide, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Acceptance criteria: See Table 2. If any peaks due to o-toluenesulfonamide and p-toluenesulfonamide appear in the chromatogram of the Sample solution, the ratio of their areas to that of the Internal standard solution is NMT the corresponding ratio in the chromatogram of the Standard solution. 

Table 2 

Limit of Benzoate and Salicylate 

Sample solution: 10 mL of a hot, saturated solution of saccharin 

Analysis: Add ferric chloride TS dropwise to the Sample solution. 

Acceptance criteria: No precipitate or violet color appears in the liquid. 

5 SPECIFIC TESTS 

Melting Range or Temperature 〈741〉: 226°–230° 

Loss on Drying 〈731〉 

Analysis: Dry at 105° for 2 h. 

Acceptance criteria: NMT 1.0% 

Change to read: 

Readily Carbonizable Substances Test 〈271〉 

Matching uid A: Cobaltous chloride CS, ferric chloride CS, cupric sulfate CS, and water (0.1:0.4:0.1:4.4) Sample solution: 40 mg/mL in sulfuric acid maintained at 48°–50° for 10 min 

Acceptance criteria: The Sample solution has no more color than Matching uid A, when viewed against a white background. 

Clarity of Solution 

[Note—The Sample solution is to be compared to Reference suspension A in diffused daylight 5 min after preparation of Reference suspension A.] 

Diluent: 200-g/L solution of sodium acetate 

Hydrazine solution: 10.0 mg/mL of hydrazine sulfate. [Note—Allow to stand for 4–6 h.] 

Methenamine solution: Transfer 2.5 g of methenamine to a 100-mL glass-stoppered flask, add 25.0 mL of water, insert the glass stopper, and mix to dissolve. 

Primary opalescent suspension: Transfer 25.0 mL of Hydrazine solution to the Methenamine solution in the 100-mL glass-stoppered flask. Mix, and allow to stand for 24 h. [Note—This suspension is stable for 2 months, provided it is stored in a glass container free from surface defects. The suspension must not adhere to the glass and must be well mixed before use.] 

Opalescence standard: Dilute 15.0 mL of the Primary opalescent suspension with water to 1000 mL. [Note—This suspension should not be used beyond 24 h after preparation.] 

Reference suspension A: Opalescence standard and water (1 in 20) 

Reference suspension B: Opalescence standard and water (1 in 10) 

Sample solution: 200 mg/mL in Diluent 

Analysis 

Samples: Diluent, Reference suspension A, Reference suspension B, Sample solution, and water 

Transfer a sufficient portion of the Sample solution to a test tube of colorless, transparent, neutral glass with a at base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of Reference suspension A, Reference suspension B, water, and Diluent to separate matching test tubes. Compare the solutions in diffused daylight, viewing vertically against a black background (see Visual Comparison 〈630〉). [Note—The diffusion of light must be such that Reference suspension A can readily be distinguished from water, and that Reference suspension B can readily be distinguished from Reference suspension A.] 

Acceptance criteria: The Sample solution shows the same clarity as that of water or Diluent, or its opalescence is NMT that of Reference suspension A. 

Color of Solution 

Diluent A: 200-g/L solution of sodium acetate 

Diluent B: 10-g/L solution of hydrochloric acid 

Standard stock solution: Ferric chloride CS, cobaltous chloride CS, cupric sulfate CS, and Diluent B (3.0:3.0:2.4:1.6) Standard solution: Standard stock solution and Diluent B (1 in 100). [Note—Prepare the Standard stock solution and Standard solution immediately before use.] 

Sample solution: Use the Sample solution from the test for Clarity of Solution. 

Analysis 

Samples: Diluent A, Standard solution, Sample solution, and water 

Transfer a sufficient portion of the Sample solution to a test tube of colorless, transparent, neutral glass with a flat base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of the Standard solution, Diluent A, and water to separate, matching test tubes. Compare the solutions in diffused daylight, viewing vertically against a white background (see Visual Comparison 〈630〉). 

Acceptance criteria: The Sample solution has the appearance of water or Diluent A, or is not more intensely colored than the Standard solution. 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in well-closed containers. Store at room temperature. 

USP Reference Standards 〈11〉 

USP Saccharin RS 

USP o-Toluenesulfonamide RS 

USP p-Toluenesulfonamide RS