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A simple, rapid, reverse phase liquid Chromatographic method for the determination of phenolphthalein in commercial formulations has been developed. The method also separates tetramisole. Three mobile phases are suggested, out of which the mobile phase consisting of only methanol has been found to be most satisfactory. The method is linear over the concentration range of 0–70 μg/ml. A mean recovery of 99.8% was obtained. The proposed high-performance liquid Chromatographic method was verified for linearity, precision, accuracy, reproducibility, and applicability.

A spectrophotometric method for the determination of rutin has been developed. The method is based on the oxidative coupling of rutin with 3-methylbenzthiazolinone-2-hydrazone using acidic ceric ammonium sulfate as the oxidizing agent. The solution is made alkaline with a buffer and the absorbance measured at 430 nm against a reagent blank. The method is precise and accurate. The applicability of the method was tested by analyzing the pure drug and commercial formulations of rutin.

A simple method for the estimation of Δ 9 -tetrahydrocannabinol (Δ 9 -THC) in cannabis is reported. The method involves the oxidative coupling of cannabinoids in cannabis with 3-methyl benzthiazolinone-2-hydrazone. The derivatized products are separated by thinlayer chromatography and one of the isomeric derivatives of Δ 9 -THC is utilized for spectrophotometric estimation of Δ 9 -THC. The nature of the derivative is studied using both infrared and mass spectrometry and the reaction mechanism is proposed. The method is precise and accurate and compares favorably with the established high-performance liquid Chromatographic method. Substances like mace, henna, and nutmeg do not interfere with the method.

A sensitive Spectrophotometric method for the determination of phenolphthalein using 3-methylbenzthiazolinone-2-hydrazone in the presence of eeric ammonium sulfate as an oxidizing agent is presented. Beer's law is obeyed in the concentration range of 0–8 μg ml−1. The method is accurately reproducible and can be applied in the analysis of phenolphthalein and its formulations. The thin layer Chromatographic and infrared studies of the colored coupling products were also performed.

A study on the spectrophotometric determination of pentazocine by its oxidative coupling with 3-methyl benzthiazolinone-2-hydrazone is reported. The method is simple, rapid, and sensitive. Precision, reproducibility, and recovery studies are presented along with the applicability of the method to the analysis of pharmaceutical and forensic samples.

A simple, sensitive, and rapid spectrophotometric method for the determination of aspirin by oxidative coupling of salicylic acid, the hydrolysis product of aspirin, with 3-methyl benzthiazolinone-2-hydrazone is described. Precision, reproducibility, and recovery studies are presented along with the applicability of the method to the assay of aspirin in formulations. Several drugs do not interfere in the proposed method.

An improved extractive spectrophotometric method for the determination of salbutamol sulfate based on its oxidative coupling with 3-methylbenzthiazolinone-2-hydrazone in the presence of ceric ammonium sulfate as an oxidizing agent is presented. The chloroform-extracted color which obeys Beer's law in the concentration range 0–15 μg ml −1 is measured at 530 nm to get the concentration of the drug. The method is accurate, reproducible, and applicable to the analysis of salbutamol sulfate and its formulation. The infrared and mass spectral studies on the coupling product are also presented.

A simple sensitive visible spectrophotometric method, an alternative to the existing UV spectrophotometric method of the U.S. Pharmacopoeia, for the determination of microgram quantities of free salicylic acid in aspirin and its formulations based on the formation of a color by oxidative coupling of 3-methylbenzthiazolinone-2-hydrazone with salicylic acid is presented. Nonphenolic compounds and common excipients present in the formulations do not interfere with the proposed method. The proposed method gives reproducible and accurate results comparable with the established pharmacopoeial method.