Lead Acetate Analysis

An adverse effect of lead on pregnancy rate has been noted in some animal studies (Kennedy et al. 1975). Acute-duration gavage administration of 390 mg lead/kg/day as lead acetate to rats resulted in a sharp decrease in pregnancy rates. This effect was not noted at 39 mg lead/kg/day. The study limitations include a lack of measurement of blood lead levels and lack of statistical analysis of pregnancy incidence. A decrease in the number of implantations was noted in untreated female mice that were mated to males that had been treated with 141 mg/kg/day lead chloride in the drinking water for 3 months... 

Melroy and co-workers88 recently reported on the EXAFS spectrum of Pb underpotentially deposited on silver (111). In this case, no Pb/Ag scattering was observed and this was ascribed to the large Debye-Waller factor for the lead as well as to the presence of an incommensurate layer. However, data analysis as well as comparison of the edge region of spectra for the underpotentially deposited lead, lead foil, lead acetate, and lead oxide indicated the presence of oxygen from either water or acetate (from electrolyte) as a backscatterer. 

Elemental composition H 5.92%, S 94.08. Hydrogen sulfide may be distinguished by its characteristic odor. The gas turns a paper soaked in lead acetate solution black. Many infrared sensors are commercially available for in-situ measurements of H2S. It may be monitored semiquantitatively by Draeger tubes. It also may be analyzed by GC following trapping over molecular sieves and thermal desorption. Either a flame photometric detector or a sulfur chemiluminescence detector may be used for GC analysis. It may be separated on a capillary column such as Carboxen 1006 PLOT or SPB-1 SULFUR (Supelco Catalog 1999 Supelco Inc., BeUefonte, PA). 

For analysis by titration with Fehling s solution, the sample is treated with lead acetate to precipitate protein and fat, filtered, and the filtrate titrated with alkaline CuS04, while heating. The reactions involved are summarized in Figure 2.37. 

ANALYZER (Reagent-Tape). The key to chemical analysis by this method is a tape (paper or fabric) that has been impregnated with a chemical substance that reacts with the unknown to form a reaction product on the tape which lias some special characteristic, e.g., color, increased or decreased opacity, change in electrical conductance, or increased or lessened fluorescence. Small pieces of paper treated with lead acetate, for example, have, been used manually by chemists for many years to determine the presence of hydrogen sulfide in a solution or in the atmosphere. This basic concept forms the foundation for a number of sophisticated instruments that may pietreat a sample gas, pass it over a cyclically advanced tape, and, for example, photo-metrically sense the color of the exposed tape, to establish a relationship between color and gas concentration. Depending upon tile type uf reactiun involved, the tape may he wet or dry and it may be advanced continuously or periodically. Obviously, there are many possible variations within the framework of this general concept. 

In 1940, Murakami published a study21 of the constitution of verbascose. To prepare this sugar, Murakami extracted the finely ground roots with 95% alcohol, clarified the extract with lead acetate, and precipitated the verbascose with barium hydroxide and alcohol. After processing the barium complex in the usual way, and precipitating the saccharide several times from an aqueous solution by alcohol, Murakami obtained verbascose in 0.5-mm. spherocrystals composed of fine needles these had m.p. 253°, [a]20D + 170.2° (in water). The elementary analysis and the cryoscopic molecular-weight values were appropriate for a pentasaccharide. 

Chukhlantsev and Tomashevsky [57CHU/TOM] prepared lead selenite by mixing an acidified 0.2 M solution of lead acetate and a 0.1 M sodium selenite solution in stoichiometric amounts. The precipitate was crystalline. Chemical analysis confirmed the 1 1 ratio between Pb(Il) and Se(IV). No X-ray diffraction measurements were performed. The solubility of the specimen in dilute solution of nitric or hydrochloric acid was measured at 293 K. The experiments were performed and the data recalculated as described in Appendix A, [56CHU]. The result for ... 

Analysis of figure 8.60 allowed us to observe stacking of molecules of ai-acid glycoprotein. In fact, dilTcrenl types of constraints, that correspond to objects of diflcrcnt nature (protein matrix, carbohydrate residues and lead acetate), arc observed (not shown)... 

Erythrocyte suspensions (20 % hematocrit) of 3 types were prepared with 2mM of ZnS04 with 10 pM of lead acetate, and the blank sample. The suspensions were fixed by two-perent solution of glutaraldehyde and were used for preparation of samples to AFM analysis. 

In this work, two methods for the determination of caffeine in energy drinks by derivative spectrophotometry and by partial least-squares multivariate spectropho-tometric calibration (PLS-1) are described. Proposed methods involve background correction methods that interferences from vitamins, taurin and food colours were minimized by treating the sample with basic lead acetate and NaHCOj for the analysis of caffeine in energy drinks. 

Fears, T.R., R.M. Elashoff, and M.A. Schneiderman. 1989. The statistical analysis of carcinogen mixture experiment. 111. Carcinogens with different target systems, aflatoxin Bl, N-butyl-N-(4-hydroxybutyl) nitrosamine, lead acetate, and thiourcil. Toxicol. Ind. Health 5(1) 1-23. 

Cleanup procedures vary considerably depending on both the mycotoxin(s) and the commodity to be analyzed. For many commodities slurries of freshly precipitated iron(III) hydroxide and copper(II) carbonate have proved effective in removing co-extractives. Flocculation of impurities with aqueous lead acetate or zinc acetate has also been used. Some mycotoxins can be adsorbed onto silica gel and/or florosil and subsequently eluted. Indeed, a range of commercially available prepared columns, such as Sep-Pak, have proved very convenient as a cleanup stage for crude extracts of mycotoxins before subsequent analysis. 

PRECIPITATION AND COMPLEX FORMATION The interfering substance can be sometimes removed by precipitation. Thus, for example, the interfering wave of formaldehyde can be eliminated by dimedone.< > Lead acetate is sometimes suitable for the separation of interfering substances in the analysis... 

For analysis of sugars from biological sources and from en rme reactions it is usual to remove proteinaceous material by the Sevag technique, basic lead acetate treatment (90,164), barium hydroxide and cadmium sulfate method (164), or heat or alcohol treatment (140). 

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. 

Crucibles fitted with permanent porous plates are cleaned by shaking out as much of the solid as possible, and then dissolving out the remainder of the solid with a suitable solvent. A hot 0.1 M solution of the tetrasodium salt of the ethylenediaminetetra-acetic acid is an excellent solvent for many of the precipitates [except metallic sulphides and hexacyanoferrates(III)] encountered in analysis. These include barium sulphate, calcium oxalate, calcium phosphate, calcium oxide, lead carbonate, lead iodate, lead oxalate, and ammonium magnesium phosphate. The crucible may either be completely immersed in the hot reagent or the latter may be drawn by suction through the crucible. 

Solvolyses of these cyclic vinyl triflates at 100 in 50% aqueous ethanol, buffered with triethylamine, lead exclusively to the corresponding cyclo-alkanones. Treatment of 176 with buffered CH3COOD gave a mixture of cyclohexanone (85%) and 1-cyclohexenyl acetate (15%). Mass spectral analysis of this cyclohexanone product showed that the amount of deuterium incorporation was identical to that amount observed when cyclohexanone was treated with CH3COOD under the same conditions. This result rules out an addition-elimination mechanism, at least in the case of 174, and since concerted elimination is highly unlikely in small ring systems, it suggests a unimolecular ionization and formation of a vinyl cation intermediate in the solvolysis of cyclic triflates (170). The observed solvent m values, 174 m =. 64 175 m =. 66 and 16 m =. 16, are in accord with a unimolecular solvolysis. 

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