Zinc determination

Finished zinc and zinc aHoys are usuaHy analyzed for metals other than zinc by emission spectroscopy and the zinc determined by difference. ASTM method E 27 describes a technique using a dissolved sample and photographic detection. The internal standard is the zinc line at 267.0 nm. However, procedures using soHd samples are generaHy preferred and photoelectric detection often replaces optical detection. Samples are cast and machined on the surface where the arc is stmck. Up to 15 elements can be determined in a few minutes by modem automatic spectrometers. ASTM gives wet chemical methods for metals other than zinc (79). 

High tendency of ZnfSCN) ion to extraction into organic phase is widely used for zinc determination by extraction photometry method. Recently it was shown that when single-chai ged anions ai e exchanged for double-chai ged ones, the selectivity of this process depends on the number of methyl substitutients in quaternary ammonium salt (QAS) cation. 

Chool, M. K., Todd, J. K., and Boyd, N. D. "Effect of Carbon Cup Aging on Plasma Zinc Determination by Flameless Atomic Absorption Spectrometry". Clin. Chem. (1975), 21, 632-634. 

Quevauviller Ph, Kramer KJM, Vinhas T (1996) Certified reference material for the quality control of cadmium, copper, nickel and zinc determination in estuarine water (CRM 505). Fresenius J Anal Chem 354 397-404. 

Fig. 6.12. Three-dimensional calibration plot for the zinc determination using a plain model for the relationship peak height vs zinc content and sample weight... 

Because of differing sensitivities and the natural levels of free metal or the anodic scanning voltammetric labile metal, cadmium, and copper in seawater are analysed using a 10 minute plating time, a -1.0V plating potential, and scanning in 6.67 mV/s increments. Zinc determinations can be made on a fresh aliquot of sample to eliminate any possible effects due to Cu-Zn inter-... 

Methodology of Zinc Determinations and the Role of Zinc in Biochemical Processes... 

Dumkiewicz et al. [462, 463] have investigated the ion-selective electrode with a chelating pseudo-liquid membrane for zinc determination. 

Voltammetric/Amperometric Sensors Thick-film carbon-containing screen-printed electrodes modified with formazan [473] were used for zinc determination. 

Determining the Equivalent of Zinc. (Determine the equivalent of zinc as in the preceding experiment.) Weigh about 1.3 g of granulated zinc on an analytical balance with an accuracy up to 0.01 g. Calculate the amount (by volume) of a 20% sulphuric acid solution that is needed for dissolving the zinc. Measure the calculated amount of acid with a measuring glass and add an excess of 100%. To acce-... 

Calculate the equivalent of zinc. Determine the magnitude of the error in computing it in per cent. Enter the results of your calculations and observations into your laboratory notebook as in the preceding experiment, using Form 5. Proceeding from the known valence of magnesium and zinc and your results, calculate the atomic masses of these elements. Compare the values obtained with tabulated data. 

M. C. Yebra-Biurrun, A. Moreno-Cid and S. Cancela-Perez, Fast on-line ultrasound-assisted extraction coupled to a flow injection-atomic absorption spectrometric system for zinc determination in meat samples, Talanta, 66(3), 2005, 691-695. 

Alcohol dehydrogenase is also obtained from yeast. Yeast alcohol dehydrogenase (YADH) was the first pyridine nucleotide-dependent dehydrogenase to be crystallized by Negelein and Wulff in 1937.1342 YADH is a tetramer of molecular weight 140000-150000. The amount of zinc determined varies,1343 but there are strong indications that the subunits of YADH and LADH have similar structures, including the presence of two zinc atoms. 

In addition to the classical symptoms of zinc deficiency mentioned above, the following unusual conditions have been reported liver and spleen enlargement, abnormal dark adaptation and abnormalities of taste. Several laboratory procedures for diagnosing zinc deficiency are available. Measurement of zinc levels in plasma is useful in certain cases. Levels of zinc in the red cells and hair may be used for assessment of body zinc status. More accurate and useful parameters are neutrophil zinc determination and quantitative assay of alkaline phosphatase activity in neutrophils. Determination of zinc in 24 h urine may help diagnose deficiency if sickle cell disease, chronic renal disease and liver cirrhosis are ruled out. A metabolic balance study may clearly distinguish zinc-deficient subjects. 

Figure 20.3 shows that increased amounts of both aluminum and zinc lower the Ms temperatures of copper-zinc-aluminum alloys. For both aluminum and zinc, determine ATI Ac where T is the Ms temperature and c is the atomic % solute. Note that the compositions in Figure 20.3 are in wt. %. 

M. D. Silvestre, M. J. Lagarda, R. Farre, C. Martinez-Costa, J. Brines, Copper, iron and zinc determinations in human milk using FAAS with microwave digestion, Food Chem., 68 (1999), 95-99. 

Samples must be free of traces of organic compounds and of other Ions which Interfere with analysis. The oxides and fluorides of Ca, Cr, Fe, Nl, Ge, Sc, T1 and V, Interfere with zinc determinations ( ). Since naturally occurring zinc contains only 0.62% Zn, 1 mg of natural zinc contains 6 Hg of Zn. Even 1 yg of an Interfering element In the sample, 1/1000 of the total zinc, equal 15% of the Zn and adversely affects Zn analysis. Signal Intensity from zinc Is low compared to other Interfering minerals like calcium. As a result calcium In amounts much less than 1 yg could Interfere with zinc analysis. 

Although the benzene-insoluble residue at 200° C contained 1.41% zinc (determined by atomic absorption), no correlation between the zinc content in various reaction products and the solubility in benzene was observed. Moreover, severe and prolonged treatment with IN HCl would certainly decompose the complex and restore the solubility, but this was not observed. 

M4. Margerum, D. W., and Santacana, F., Evaluation of methods for trace zinc determination. Anal. Chem. 32, 1157-1161 (1960). 

Our data indicate that during the zinc-deficient state the subjects were in a more positive balance for zinc. This would suggest that perhaps a test based on oral challenge of zinc and subsequent plasma zinc determination may be able to distinguish between zinc-deficient and zinc suflBcient-states in human subjects. 

Analyses for "copper, cadmium, and lead were carried out continually by DPASV. Zinc determinations were excluded to permit use of a lower electrolysis potential. The samples were analyzed at pH 4.9 by sparging with carbon dioxide. An 8-min. electrolysis at —1.0 V vs. silver/ silver chloride and a 25-mV pulse were used during the Seattle-Saanich portion of the trip (Leg 1) while a 10-min. electrolysis and a 50-mV pulse were used from Saanich to Seattle (Leg 2). Application of the DPASV technique resulted in greater sensitivity and thus shorter plating times for the low levels encountered. It also afforded better resolution for "copper than linear-sweep ASV. It should be pointed out, however, that DPASV does not result in shorter analyses times because the stripping portion of the analysis is very slow. Nevertheless, it is worthwhile to limit the time of electrolysis because this also reduces the concentrations of interfering metals accumulated in the mercury fllm. Under the... 

Zinc phosphate is used as a dental cement. A 50.00-mg sample is broken down into its constituent elements and gives 16.58 mg oxygen, 8.02 mg phosphorus, and 25.40 mg zinc. Determine the empirical formula of zinc phosphate. 

Some wet chemical sample preparation such as pH or oxidation state adjustment is normally required for most metal ion determinations. Then complexometric titration using EDTA, as already mentioned, or diphenylthio-carbazone ( dithazone Eq. 4.27) may be used for cadmium, copper, lead, mercury, or zinc determinations. 

Unless otherwise indicated, metal content is given in micrograms per gram of protein. All zinc determinations by the dithizone method in duplicate, and in quadruplicate for the crystalline enzyme preparations. Copper determined by the sodium dithiocarbamate method. Spectrographic analyses were done in duplicate, and separately on two different instruments. 

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