Colorimetric analysis, lead

Substituted ureas were determined, at the beginning, by colorimetric analysis. This determination is based on a basic or acidic hydrolysis leading to the corresponding aniline, followed by diazotation and coupling with /V-(l-naphthyl)-ethylendiamine (40,58,148-152), 1-naphthol (153), or /V-ethy I-1 -naphthylamine (154) to obtain an azo-dye. Nevertheless, this method is time consuming and does not differentiate between the pesticide and metabolites, unless they are previously separated (154). 

BIOLOGICAL PROPERTIES the biological half-life for lead in the bones of humans is 10 yrs can be detected in water by atomic adsorption or by colorimetric analysis or by inductively coupled plasma optical emission spectrometry, dissolved lead by 0.45 micron filtration prior to such analysis... 

N.Z. Aracama, A.N. Araujo, R. Perez-Olmos, Sequential injection analysis of lead using time-based colorimetric detection and preconcentration on an anionic-exchange resin, Anal. Sci. 20 (2004) 679. 

Fernandez and Kahn (F3) reported that the accuracy and precision of the Delves method are adequate for the determination of normal and excess lead levels in blood and that 30-50 samples could be analyzed in 1 hour. The correlation coefiicient between their results and those using a colorimetric dithizone procedure was 0.99. Heinemann (H4) was able to analyze a single heparinized blood sample in less than 5 minutes and 30-40 samples in 1 hour using the Delves procedure. He also analyzed untreated urine. Hicks et al. (H6) found a correlation coefficient of 0.96 between the Delves method and conventional macro atomic absorption measurements the coefficient of variation for the Delves method was 8% at 40 /tg of lead per 100 ml. In addition, the analysis of lead in capillary and intravenous blood samples correlated... 

If sodium is more abimdant, a mixed complex is formed with the composition K2Na[Co(N02)6]- The two complexes are alike in appearance. This reaction was used in the classical inorganic analysis to isolate potassium from the other alkali metals. The precipitate was isolated and washed and a determination was then performed colorimetrically on the cobalt ion. In many cases the silver, zinc, or lead salt of hexanitritocobaltate was used as a reagent. 

Determination of lead According to the AOAC (1965) method, after complete digestion, by the colorimetric dithizone determination procedure [Official Methods of Analysis of the AOAC, 1965, 24.053 (and 24.008, 24.009, 24.043j, 24.046, 24.047 and 24.048)]. Results are expressed as milligrams lead per kilogram. 

To enhance the applicability of UV spectrophotometry in pharmaceutical steroid analysis by increasing its selectivity and sensitivity, various methods have been developed based on chemical reactions leading to colored derivatives. Although their importance has decreased considerably, some of these methods are still in use in pharmacopoeias, mainly in the assay of formulations. For example, the A" -3-oxo and A " -3-oxo steroids can be determined as iso-nicotinoyl hydrazones (/Uax 380 and 410 nm 11500 and 17000, respectively). The dihydroxy-acetone side chain of corticosteroids at C17 reduces tetrazolium reagents to colored formazans (Amax 485 and 525 nm with triphenyl tetrazolium chloride and Tetrazolium Blue reagents, respectively e 16000 and 24000), thus creating the basis for a stability-indicating indirect colorimetric assay. Corticosteroids... 

OxyhydroPyrolysis Con girrafion—-Sample is injected at a constant rate into an air stream and introduced into a pyrolysis furnace. The sample flows through an inner tube within the furnace where it combusts with the oxygen in the air carrier. SO2 and SO3 are formed from the sulfur compounds in the sample. The sample then leaves the irmer tube within the pyrolyzer and is mix with hydrogen within the main reaction tube and is pyrolyzed at temperatures in the range of 1200°C to 1300 0 (see Fig. 1 ). The SO2 and SO3 formed within the inner tube are then reduced to H2S. Analysis is by rateometric detection of the colorimetric reaction of H2S with lead acetate. 

---