Trace-element determinations in biologicals using atomic-absorption spectrometry

Abstract

so far as possible, did not alter the chemical form of the element naturally present. The first point created problems, i.e., natural levels are close to the limits of reliable determination by atomic absorption spectrometry; dilution occurring on enzymolysis and separation of species produced nonmeasurable levels. One solution to this problem lies in the high sensitivity of ICP-MS [3] and the ability to use ICP-MS as a detector with LC columns.Particular attention has been paid to steric exclusion chromatography as one of the most gentle forms of separation achievable. It is also a relevant separation of soluble macro molecules (which are unlikely to be absorbed) from lower molecular weight species which are more likely candidates for absorption. Additionally, some work with reversed-phase HPLC linked to ICP-MS has also been carried out.With HPLC systems a guard column is used to protect the analytical column; post-column injections of standards are used for calibration checks. To minimize peak-broadening, aerosol transfer distance should be reduced by mounting the nebulizer system close to the torch. Flow rates above 0.5 to 0.7 mL/min can lead to signal instability unless precautions against condensation are taken. In an early piece of work, the cadmium content of crab meat with separation by HPLC and monitoring by UV and ICP-MS showed that the major protein peak has almost completely eluted before the cadmium peak corresponding to a somewhat lower molecular weight cadmium-containing protein.More recent studies of the HPLC separation of the proteins from pig kidney before and after cooking show that in the raw state there are three peaks-the higher molecular weight materials disappear during cooking, i.e., are rendered insoluble by heat denaturation, whereas the heat-resistant metallothionein remains intact.Another recent study concerns an organo-arsenical drug used in poultry production. In this, reversed-phase HPLC has been linked to the ICP-MS in much the same way for HPLC. This system allows good separation of "Roxarsone" from other low molecular weight substances and from interference from molecular ions formed from argon in the plasma in the presence of chloride ion.Arsenic in extracts from muscle of chickens fed on a base diet and one supplemented with "Roxarsone" have been compared. The "Roxarsone" peaks correspond to arsenic concentrations of 7 and 10 ng/g in the muscles from treated birds and demonstrates that in the untreated birds the concentration is less than 2 ng/g.The sensitivity foreseen with these systems is now a matter of reality rather than potential-and the ability to use it in speciation studies at tissue concentrations at the ng/g level is a matter of fact rather than of speculation. Lebensm. Unters Forsch. 180, 405 (1985). References[3] Dean, J. R., Ebdon, L., and Massey, R., J. Anal. Atomic Spectrose. 2, 369 (1987). The SIMAAC system consists of a 300 watt xenon arc lamp, an atomizer, an echelle polychromator modified for wavelength modulation, and a PDP 11/34 minicomputer responsible...

Atomic Absorption and Atomic Emission Spectrometry for the Determination of the Trace Element Content of Selected Fruits Consumed in the United States

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Nutritional Composition of Potato Foliage

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