Chlortetracycline Bisulfate

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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(This monograph has been updated to the current USP style. No revisions or changes to tests have been made.) 

1 DEFINITION 

Chlortetracycline Bisulfate has a potency equivalent to NLT 760 µg/mg of chlortetracycline hydrochloride (C₂₂H₂₃ClN₂O₈.HCl), calculated on the dried and butyl alcohol-free basis. 

2 IDENTIFICATION 

A. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U 

Medium: 0.1 N hydrochloric acid 

Sample solution: 40 µg/mL 

Wavelength: 368 nm 

Acceptance criteria: Absorptivity, calculated on the dried and butyl alcohol-free basis, is NLT 83.0% and NMT 95.0% of that of USP Chlortetracycline Hydrochloride RS, the potency of the Reference Standard being taken into account. 

3 ASSAY

Procedure 

Standard: USP Chlortetracycline Hydrochloride RS 

Analysis: Proceed with Chlortetracycline Bisulfate as directed for chlortetracycline under Antibiotics–Microbial Assays 〈81〉. Acceptance criteria: NLT 760 µg/mg of chlortetracycline hydrochloride on the dried and butyl alcohol-free basis 

4 OTHER COMPONENTS 

Sulfate Content 

Sample: 1 g of Chlortetracycline Bisulfate 

Analysis: Transfer Sample to a 250-mL beaker, and dissolve in 100 mL of water. Neutralize the solution with 7.5 N ammonium hydroxide to litmus paper, and warm. Fifilter, and wash the filter with warm water. Neutralize the filtrate with 6 N hydrochloric acid to litmus, and add an additional 4 mL of 6 N hydrochloric acid. Heat the solution to boiling, and add, with constant stirring, sucient boiling barium chloride TS to precipitate all of the sulfate. Add an additional 2 mL of barium chloride TS, and digest on a steam bath for 1 h. Pass the mixture through ashless filter paper, transferring the residue quantitatively to the filter, and wash the residue with hot water until no precipitate is obtained when 1 mL of silver nitrate TS is added to 5 mL of washing. Transfer the paper containing the residue to a tared crucible. Char the paper, without burning, and ignite the crucible and its contents to constant weight. Perform a blank determination concurrently with the Sample determination, and subtract the weight of the residue from that of the Sample determination to obtain the weight of the residue attributable to the sulfate content of the Sample. 

Acceptance criteria: NLT 15.0%, calculated on the dried and butyl alcohol-free basis 

5 IMPURITIES 

Organic Impurities: Butyl Alcohol 

Solution A: 0.2 g/mL of ceric ammonium nitrate in 4 N nitric acid 

Standard solution 1: 3 mg/mL of butyl alcohol in water 

Standard solution 2: Transfer 10.0 mL of Standard solution 1 and 1 drop of dimethicone to a 50-mL distilling flask equipped with a condenser and an extension that reaches into a collecting tube maintained in an ice-water bath. Distill slowly, and collect about 8 mL of distillate. Warm the distillate to ambient temperature, and transfer with the aid of water to a 10-mL volumetric flask. Dilute with water to volume and mix. 

Sample solution: Transfer Chlortetracycline Bisulfate, equivalent to about 30 mg of butyl alcohol, to a 50-mL distilling flask equipped with a condenser and an extension that reaches into a collecting tube maintained in an ice bath. Add 25 mL of water and 1 drop of dimethicone to the distilling flask. Distill slowly, and collect about 8 mL of the distillate. Warm the distillate to ambient temperature, and transfer with the aid of water to a 10-mL volumetric flask. Dilute with water to volume and mix. 

Spectrometric conditions 

(See Ultraviolet-Visible Spectroscopy 〈857〉.) 

Mode: UV-Vis 

Analytical wavelength: Maximum absorbance, approximately 475 nm 

Blank: Water 

System suitability: 

Samples: Standard solution 1, Standard solution 2, and Blank 

To three separate test tubes add, respectively, 5.0 mL each of Standard solution 1, Standard solution 2, and Blank. To each add 2.0 mL of Solution A and mix. 

Suitability requirements: The absorbance of the solution from Standard solution 2 is NLT 98.0% of the absorbance of the solution from Standard solution 1. 

Analysis 

Samples: Standard solution 1, Standard solution 2, Sample solution, and Blank 

To four separate test tubes add, respectively, 5.0 mL each of Standard solution 1, Standard solution 2, Sample solution, and Blank. To each add 2.0 mL of Solution A and mix. 

Concomitantly determine the absorbances of the solutions from the Standard solutions and the Sample solution at the wavelength of maximum absorbance at about 475 nm, with a suitable spectrophotometer, using the Blank to set the instrument to zero. Calculate the percentage of butyl alcohol in the portion of Chlortetracycline Bisulfate taken: 

Result = (A_U/A_S) × (W_S/W_U) × 1000 

A_U = absorbance of the Sample solution 

A_S = absorbance of Standard solution 2 

W_S = weight of butyl alcohol taken to prepare Standard solution 1 (g) 

W_U = weight of Chlortetracycline Bisulfate taken to prepare Sample solution (mg) 

Acceptance criteria: NMT 15.0% 

6 SPECIFIC TESTS 

Crystallinity 〈695〉: Meets the requirements Loss on Drying 〈731〉 

Analysis: Dry sample in a vacuum at a pressure not exceeding 5 mm of mercury at 60° for 3 h. 

Acceptance criteria: NMT 2.0% 

7 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight, light-resistant containers. 

Labeling: Label it to indicate that it is intended for veterinary use only. 

USP Reference Standards 〈11〉 

USP Chlortetracycline Hydrochloride RS