A simple, accurate, and sensitive method for the spectrophotometric determination of captopril in bulk and dosage forms is reported. The method is based on the bromination of captopril with excess solution of n-bromosuccinimide (NBS) in HCl acid medium. The excess NBS is pursued by the assessment of the residual NBS based on its ability to bleach the rhodamine B dye and measuring the absorbance at 555 nm. The amount of NBS reacted coincides to the drug content. The different experimental parameters influencing the development and stability of the color are precisely studied and optimized. Beer’s law is valid within a concentration range of 0.3–1.0 μg/mL with a correlation coefficient R2 = 0.991. The limit of detection 0.169 μg/mL is attained and relative standard deviation values for five replicated measurements of 0.3, 0.7, and 1.0 μg/mL captopril were between 0.53% and 2.03%. No interference is detected from prevalent additives found in pharmaceutical preparations. The proposed method is profitably put on to the determination of captopril in the tablet formulations with mean recoveries 98.91–101.27% and the results were statistically confronted with those of a reference method by applying Student’s t-and F-test.

New reagent 2- hydroxybenzaldehydewas used in a coupling reaction for determination of paracetamol via spectrophotometric method. The proposition of simplicity, inexpensive, rapidity and sensitivity were conducted via spectrophotometric procedure. The method was based on diazotization of paracetamol and coupling with 2-hydroxybenzaldehyde in alkaline medium. Linear concentration range (0.50 - 12.00) µg/ml was comply Beer’s law at maximum wavelength 444 nm and detection limit (LOD) 0.05 µg/ml. The molar absorptivity and regression coefficient of (R2) were 1.2032×104 l/mol.cm, 0.9995, respectively. The suggested method was profitablyadapted for the determination of paracetamol in pharmaceutics. The results attained were in good agreement with thatone by standard method high performance liquid chromatography (HPLC).

A simple, rapid and sensitive batch and flow injection spectrophotometric methods have been developed for the determination of folic acid (FA) in pure form and in its pharmaceutical preparations. The proposed methods involve the addition of a measured excess of cerium (IV) ammonium sulphate (CAS) in acidic medium followed by determination of unreacted CAS by reacting with a fixed amount of methylene blue (MB) and measuring the absorbance at 665 nm. The optimum reaction conditions and other analytical parameters have been evaluated. Linearity was observed from 1-10 and 4.0-20.0 μg/ml folic acid by batch and flow injection procedures, respectively. Statistical analysis of the results and comparison with results by the British Pharmacopoeia method are also reported.