Spectrophotometric Indirect Determination of Captopril through Redox Reaction with n-bromosuccinimide and RB dye in Pharmaceutical Products

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.

L-Tryptophan as Fluorescent Probe for Determination of Folic Acid in Pharmaceutical Products

A new fluorescent probe L-Tryptophan was reported for the determination of folic acid (FA), based on its quenching effect of the fluorescence intensity of L-Tryptophan. The concentration of folic acid was proportional to the quenched fluorescence intensity of L-Tryptophan at an emission wavelength of 365 nm in Britton– Robinson (BR) buffer solution of pH 7. Optimized conditions of pH, time, order of addition of the reagent, potential interferences, concentrations of L-Tryptophan and buffer were investigated. Folic acid was determined in a linear range of 2.0 to 16.0 μg ml-1 with a correlation coefficient R2 0.9974. The limits of detection LOD and quantification LOQ values were 0.09 μg ml-1 and 0.27 μg ml-1, respectively. The standard deviation (RSD) values for five replicated measurements of 2, 8, 16 μg ml-1 folic acid were between 0.23 % and 1.07%. This method is efficient for routine analysis and quality control assay as it is relatively interferences free.

Evaluation of Filter Media Options for High Volume PM2.5 Sampling

Polytetrafluoroethylene (PTFE), glass fiber, and cellulose fiber filter media were evaluated under controlled conditions to determine their suitability for high volume PM2.5 sampling. Repeated mounting and unmounting events of new filters not exposed to ambient particulate matter were conducted in a laboratory environment and differences in the filter weight recorded. After the initial mounting and unmounting event, the filters exhibited weight changes of -2.24 mg, -0.61 mg, and 0.18 mg for cellulose, PTFE, and glass fiber filters, respectively. The standard deviation of replicated measurements after the first event was 1.76 (n = 9), 0.50 (n = 10), and 0.31 (n = 10) for cellulose, PTFE, and glass fiber filters, respectively. The combination of weight loss and standard deviation made the cellulose filter unsuitable for use in high volume PM2.5 samplers. However, improved performance over PTFE filters, suggests that glass fiber filters similar in specification to PTFE filters should be considered as acceptable substitutes in high volume PM2.5 sampling. Keywords: Air quality, Error, Filters, Measurement, Particles, Sampling technique.

A Multiepoch Regression Model used in Geodesy

An investigation of the deformations of large buildings (bridges, dams, etc.) needs replicated measurements in special types of geodetical networks. They are characterized by two groups of points creating the network; one group is formed by points with stable positions and the other one is formed by points located on the building and characterizing its deformations. A statistical analysis of measurement results is done after each epoch ofmeasurement and also after several epochs. It is of a practical importance to develop an algorithm of estimation which enables us to use the partial results obtained after each epoch for results after several epochs.