A previously developed method that uses a simplified sample preparation procedure and atomic absorption detection of liquid chromatographic eluates for the determination of methyl mercury in seafood has been collaboratively studied. The unique feature of the method involves the use of a specially designed interface for the generation of mercury vapor. Methyl mercury is isolated from the blended sample by chloroform elution from a diatomaceous earth-hydrochloric acid column. The organomercury compound is then extracted into a small volume of 0.01M sodium thiosulfate solution. An aliquot of this solution is injected onto a Zorbax ODS column and eluted with methanol-ammonium acetate solution (3 + 2), pH 5.7, containing 0.01% mercaptoethanol. Mercury is detected by flameless atomic absorption spectrophotometry using the interface. The samples analyzed in the study were unspiked swordfish, unspiked and spiked lobster, and unspiked and spiked tuna. The spiked samples contained methyl mercury both above and below the U.S. Food and Drug Administration guideline level of 1 microgram Hg/g. Reproducibility relative standard deviations ranged from 10.5% at 1 microgram Hg/g to 18.2% at about 0.1 microgram Hg/g. Accuracy, measured by comparison to reference values obtained by the Associate Referee, ranged from 94.4 to 99.6%. The method has been adopted official first action.

Animals↗

PubMedDate not supplied

Determination of sulfites in foods by simultaneous nitrogen purging and differential pulse polarography.

An improved technique has been developed for determination of sulfites in food by differential pulse polarography. A Teflon sleeve is fitted to the dropping mercury electrode capillary so that SO2 is purged from the sample and simultaneously detected at peak potential. Bound sulfite in the sample is released at room temperature by addition of base in the absence of oxygen. For some foods, the prepared sample was passed through a Sep-Pak C-18 cartridge to remove naturally occurring sulfur compounds so that only added sulfite is measured. The level of detection was approximately 1 microgram SO2/g. Results agreed with those obtained by the optimized Monier-Williams method for a variety of foods.

Food Analysis↗

PubMedDate not supplied

Improving and developing analytical methods ... a continuing challenge.

Explore the source record for details and available documents.

Iodine↗

PubMedDate not supplied

Interference by tin in AOAC dry-ash voltammetric method for determination of lead and cadmium in canned foods.

When lead and cadmium were determined in samples of canned food by the AOAC anodic stripping voltammetric method, an interference was observed which was believed to be tin(IV). This interference could cause false positive results for lead and cadmium. The electroactivity of tin(IV) was suppressed by increasing the concentration of tartaric acid in the supporting electrolyte from 0.005M to 0.1M after mixing with an equal volume of sample solution.

Cadmium↗

PubMedDate not supplied

Differential pulse polarographic determination of sulfites in foods: collaborative study.

A differential pulse polarographic (DPP) method for the determination of "free" and "total" sulfite in foods was collaboratively studied by 8 laboratories. The collaborators analyzed blind duplicate samples of shrimp, orange juice, peas, dried apricots, and dehydrated potatoes. Collaborators also analyzed the same samples spiked with sulfites at 2 levels, which ranged from 10 to 1100 micrograms added SO2/g. The variability of free SO2 results was excessive for quantitative analysis, but the method can be used for qualitative detection of free SO2. The method for total SO2 determination was suitable for as low as approximately 10 micrograms/g. Recoveries are comparable to those for the official Monier-Williams method at high levels and are superior at low levels. The method has been adopted official first action for determination of total SO2 in the foods studied.

Analysis of Variance↗

PubMedDate not supplied

Determination of methylmercury after supercritical fluid extraction.

A method, using supercritical fluid extraction, for determining methylmercury in seafood has been developed to eliminate use of toxic organic solvents. Seafood samples were treated with 1N NaOH and then acidified with HCl to release CH3HgCl. After mixing the sample with cellulose powder (40 mesh) containing stearic acid modifier at 5 mg/g, the extraction was performed with supercritical CO2 under the following conditions: pressure, 200 atm; temperature, 50 degrees C; time, 20 min; and trap, 0.01N Na2S2O3 in a conical tube immersed in a flask of warm water to prevent freezing. The extract was then analyzed by a suitable method, such as cold-vapor atomic absorption spectrophotometry. The accuracy of the procedure was verified by analyzing biological standard reference materials. Several commercial seafood samples and spikes have been analyzed.

Carbon Dioxide↗