We describe the performance of a colorimetric reagent kit (Diagnostic Systems Laboratories, Inc., Webster, TX 77598) for measuring calcium directly in urine, serum, and ultrafiltered serum, and compare the results with those obtained with atomic absorption spectrophotometry. The CV for within-run precision was 2.8 and 2.1% for urine and whole serum, respectively (n = 10 each). Between-run preci...

Conventional matrix characterization by visible spectrophotometry technique required sample destruction and limited to drug content assay. This study investigated the capacity of visible spectrophotometry technique to characterize both drug content and molecular characteristics of solid nifedipine-hydroxypropylmethylcellulose films stored at 25 and 50 % relative humidities in their intact form....

In this study, a new reaction system for quantitative determination of ascorbic acid was introduced. The developed method is based on inhibitory effect of ascorbic acid on the Orange G-bromate system. The change in absorbance was followed spectrophotometrically at 478 nm. The dependence of sensitivity on the reaction variables including reagents concentration, temperature and time was investiga...