sodium-dodecyl-sulfate and sulfuric-acid

A simple flow injection colorimetric procedure for determining lead was established. It is based on the reaction of lead in sulfuric acid with 1,5-diphenylthiocarbazone and sodium dodecyl sulfate, resulting in an intense red-blue complex with a suitable absorption at 500 nm. A standard or sample solution was injected into the sulfuric acid stream (flow rate of 2.0 ml min(-1)), which was then merged with sodium dodecyl sulfate stream (flow rate of 2.0 ml min(-1)) and 1,5-diphenylthiocarbazone stream (flow rate of 1.5 ml min(-1)). Optimum conditions for determining lead were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 1.0-12.0 microg ml(-1) and the detection limit was 0.027 microg ml(-1) (s/n=3). The relative standard deviation of the proposed method calculated from 12 replicate injections of 4.0 and 8.0 microg ml(-1) of lead was 0.42% and 0.38%, respectively. The sample throughput was 80 h(-1). The proposed method has been satisfactorily applied to the determination of lead in water samples.

Topics: Absorption; Color; Dithizone; Flow Injection Analysis; Lead; Micelles; Reproducibility of Results; Sodium Dodecyl Sulfate; Spectrophotometry; Sulfuric Acids; Time Factors; Water

A new resonance light scattering (RLS) probe for determining proteins is presented. The weak RLS of pyronine Y-SDS can be enhanced substantially by adding proteins in the presence of H2SO4, resulting in a strong and wide RLS band in the region 310-425 nm. The interaction of pyronine Y-SDS with proteins was studied on the basis of this behavior and a new quantitative method was developed for determining proteins. The enhanced RLS intensity is proportional to the concentration of proteins in the range 0.15-3.6 microg mL(-1) for bovine serum albumin (BSA) and 0.06-4.8 microg mL(-1) for human serum albumin (HSA), with detection limits of 21.0 and 12.0 ng mL(-1), respectively. This method is characterized by high sensitivity, rapidity of reaction, and simplicity. Four synthetic samples were determined satisfactorily and recovery was 99.5-101.5%. Results for human serum and urine samples were in agreement with those obtained by the Bradford method, with relative standard deviations (RSD) of 1.5-3.1%.

Topics: Animals; Cattle; Humans; Proteins; Pyronine; Reproducibility of Results; Scattering, Radiation; Sensitivity and Specificity; Serum Albumin; Serum Albumin, Bovine; Sodium Dodecyl Sulfate; Sulfuric Acids; Surface-Active Agents

Tests of HPLC columns with restricted access, polymer covered alumina, polymer, and different ODS phases showed that base-acid compatible ODS columns gave the best peak shapes of cortisol, internal standard, as well as of plasma/serum (P/S) matrix components. Further trials with cortisol in P/S showed that three separation steps were essential in order to obtain chromatographic data which were superior to immunoassay data. Also, sufficient confidence in results required determination of each sample with two newly developed separation methods: (a) pre-separation with a restricted access column, concentration of the desired cut with a 20 mm base-acid compatible ODS column, and analysis with a 250 mm column filled with the same ODS; (b) pre-separation with an ultrafilter followed by the last two steps in (a). For detection UV was preferred over fluorescence. This twin multistep chromatography showed that immunoassays were very treacherous in that they produced a spectrum of results ranging from good to untenable without any warning whatever about functionality. The measurement of official controls, with reference values derived via gas chromatography-isotope dilution mass spectrometry, also demonstrated the superiority of the double HPLC method.

Topics: Chromatography, High Pressure Liquid; Enzyme-Linked Immunosorbent Assay; Humans; Hydrocortisone; Immunoassay; Indicators and Reagents; Polyethylene Glycols; Quality Control; Sodium Dodecyl Sulfate; Sulfuric Acids; Ultrafiltration

A simple and sensitive colorimetric assay for protein phosphatase activity based on the determination of released Pi by an improved malachite green procedure (A. A. Baykov, O. A. Evtushenko, and S.M. Avaeva, 1988, Anal. Biochem. 171, 266-270) is described. Proteins must be removed or stabilized prior to Pi determination with 0.25 N sulfuric acid or 3% (w/w) perchloric acid. Alternatively, to avoid possible acid hydrolysis of phosphate groups from organic compounds during deproteinization, the protein present in the phosphatase assay mixture can be stabilized with sodium dodecyl sulfate. In this case, the excess detergent is subsequently removed by precipitation with KCl because it colors with the malachite green reagent. The above procedure was applied to the determination of phosphorylase phosphatase activity in bovine brain extracts and the results are comparable to those obtained with the radioisotopic phosphatase assay.

Topics: Animals; Chemical Precipitation; Colorimetry; Kinetics; Muscles; Perchlorates; Phosphates; Phosphorylase a; Phosphorylase b; Rabbits; Rosaniline Dyes; Sodium Dodecyl Sulfate; Solutions; Sulfuric Acids