A kinetic spectrophotometric method based on the initial rate measurement has been developed for the determination of N-acetyl L-cysteine. The developed method is based on the oxidation of N-acetyl L-cysteine with iodate. The reaction product was studied and characterized using the mass spectrometry and the structure of the product was proposed. From the mass spectrometric studies it was concluded that the oxidation of the drug resulted in the formation of a disulfide. The developed method was validated as per the guidelines of international conference on harmonization. The developed initial rate method was found to be linear in the concentration range of 1.25 - 30 µg ml-1. The detection and quantitation limits were found to be 0.018 and 0.056 µg ml-1. In the current study, the degradation product of N-acetyl L cysteine was also prepared and identified using mass spectrometry.

A spectrophotometric method based on the formation of ion-pair complex between haloperidol and eriochrome black T (EBT) at pH 1.85 has been described. The formed complex was extracted quantitatively into chloroform and measured at 510 nm. Infra red (IR) studies were performed to confirm the formation of ion-pair complex. Beer's law was obeyed in the concentration range of 2.0-9.0 µg mL-1 with molar absorptivity of 2.67 × 10(4) L mol-1 cm-1. The detection limit was found to be 0.18 µg mL-1. Statistical comparison of the results of the proposed method with those of the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.

A simple and sensitive kinetic spectrophotometric method was developed for the determination of labetalol (LBT) hydrochloride. The method was based on the kinetic investigation of the oxidation of the drug with alkaline potassium permanganate at room temperature (25 ± 1°C). The increase in absorbance of coloured manganate ions was measured at 605 nm. All experimental variables affecting the development of the colour were investigated and optimized. The initial rate and fixed time (at 6 minute) methods were adopted for determining the drug concentration. The calibration graphs were linear in the concentration ranges of 2-14 μg mL-1 and 1-10 μg mL-1, using the initial rate and fixed time methods, respectively. The method was successfully applied to the determination of labetalol in laboratory made tablets and commercial tablets. The results were validated statistically and through recovery studies.

Un método simple y sensible de espectrofotometría cinética se desarrolló para la determinación del clorhidrato de labetalol (LBT). El método se basó en la investigación de la cinética de oxidación de la droga con permanganato de potasio alcalino a temperatura ambiente (25 ± 1°C). El aumento de la absorción de iones de manganato coloridos se midió a 605 nm. Se investigaron y optimizaron todas las variables experimentales que afectan al desarrollo del color. Asimismo, se adoptaron la velocidad inicial y el tiempo fijado (a los 6 minutos) de los métodos para la determinación de la concentración del fármaco. Las curvas de calibración fueron lineales en los intervalos de concentración de 2-14 μg mL-1 y 1-10 μg mL-1, haciendo uso de la velocidad inicial y de los tiempos fijados de los métodos, respectivamente. El método se aplicó con éxito a la determinación en el laboratorio de labetalol realizados en tabletas y tabletas comerciales. Los resultados se validaron estadísticamente y mediante estudios de recuperación.