The concentrations of mercury in forty, commercially available dietary supplements, were determined using a new, inexpensive analysis technique. The method involves thermal decomposition, amalgamation, and detection of mercury by atomic absorption spectrometry with an analysis time of approximately six minutes per sample. The primary cost savings from this approach is that labor-intensive sample digestion is not required prior to analysis, further automating the analytical procedure. As a result, manufacturers and regulatory agencies concerned with monitoring lot-to-lot product quality may find this approach an attractive alternative to the more classical acid-decomposition, cold vapor atomic absorption methodology. Dietary supplement samples analyzed included astragalus, calcium, chromium picolinate, echinacea, ephedra, fish oil, ginger, ginkgo biloba, ginseng, goldenseal, guggul, senna, St John's wort, and yohimbe products. Quality control samples analyzed with the dietary supplements indicated a high level of method accuracy and precision. Ten replicate preparations of a standard reference material (NIST 1573a, tomato leaves) were analyzed, and the average mercury recovery was 109% (2.0% RSD). The method quantitation limit was 0.3 ng, which corresponded to 1.5 ng/g sample. The highest found mercury concentration (123 ng/g) was measured in a concentrated salmon oil sample. When taken as directed by an adult, this product would result in an approximate mercury ingestion of 7 µg per week.

A method has been developed to permit the simultaneous sampling of S02 and N02 from ambient air. Sulfur dioxide and N02 are collected on triethanolamine-impregnated glass fiber filters. After sampling, the filters are extracted, and the extract Is analyzed for sulfate, nitrite, and nitrate using Ion chromatography. Ambient concentrations are computed from the recovered nitrogen and sulfur and the sampled air volume. Laboratory tests were conducted to evaluate the performance of the method under various species concentrations and loadings, sampling rates, humidities, temperatures, flushing conditions, and Interferences. Results of these tests are described. Field measurements using the developed method compared favorably with other established methods. On the basis of the precision of field blanks, S02 and N02 detection limits of 0.3 and 0.2 ppb for 24-h samples and 0.04 and 0.03 ppb for 7-day samples were estimated. Precision estimates of better than ±15% were found, and accuracy within ±10% was observed.

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A microwave-assisted method for preparing samples for determination of elements In solid waste has been developed (draft EPA Method 3051). Validation of the sample preparation method was performed through a collaborative study to determine its precision and accuracy. Fifteen independent laboratories digested 4 National Institute of Standards and Technology (NIST) standard reference materials (SRMs) and 1 solvent recovery waste in duplicate. Digestates were analyzed for 19 elements using inductively coupled plasma (ICP) emission spectroscopy. The precision and bias of the method were evaluated. When compared with an open vessel hot-plate digestion method (SW-846 Method 3050), the microwave method produced similar analytical results with better overall precision. Bias for the 1 sample that allowed this determination was found to be excellent.

Bioanalytical methods are used to quantitatively determine the concentration of drugs, biotransformation products or other specified substances in biological matrices and are often used to provide critical data to pharmacokinetic or bioequivalence studies in support of regulatory submissions. In order to ensure that bioanalytical methods are capable of generating reliable, reproducible data that meet or exceed current regulatory guidance, they are subjected to a rigorous method validation process. At present, regulatory guidance does not necessarily account for nuances specific to trace element determinations. This paper is intended to provide the reader with guidance related to trace element bioanalytical method validation from the authors' perspective for two prevalent and powerful instrumental techniques: inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-MS.

The techniques which are typically used to prepare RCRA wastes for analysis for metals and other elements are generally relatively time consuming, requiring several hours to several days to complete. They also often involve the use of acid digestions and thermal decomposition steps which may result in analyte losses, incomplete recoveries, or sample contamination. These limitations are well known to the analytical community and to the end users of these data in EPA, States, and industry. The resulting inefficiency of these techniques reduces laboratory sample throughput, drives up the cost of analytical testing, and impedes decision making. Given these concerns, the OSW Methods Section is interested in developing cost effective sample preparation techniques for metals and other elements in environmental and process waste samples. Once developed, these techniques can then be written as methods for inclusion in Test Methods for Evaluation of Solid Waste SW-846 and made available to the user community. This paper reports on the evaluation of a microwave assisted sample preparation method for determining elements in solid waste. The Method was evaluated for microwave digestion of sediments, sludges, soils, and oils.

The validation of a method for the determination of total chromium in Fischer-344 rat feces by inductively coupled plasma optical emission spectrometry following a rapid, atmospheric-pressure microwave digestion is described. The performance of the method was evaluated over the concentration range of 5.00 to 200 μg Cr/g feces. Data for method linearity, accuracy, precision, digest stability, and storage stability are presented along with limit of detection and limit of quantitation data. Data from a cross-validation method for B6C3F1 mouse feces are also presented. Following validation, the method was applied to analyze samples collected in support of two chronic toxicological investigations.

The validation of a method for the determination of chromium (Cr) in F-344/N rat tissues by inductively coupled plasma-mass spectrometry is described. Samples were analyzed after a rapid, open-vessel microwave digestion procedure. Performance of the method was evaluated using kidney tissue across a concentration range of 0.50-5.00 microg Cr/g tissue. Data for method linearity, accuracy, precision, digest stability, and storage stability are presented along with limits of detection and quantitation data. Data from a method cross-validation for B6C3F1 mouse kidney tissue are also presented. After validation, the method was applied to analyze samples collected in support of two chronic toxicity and carcinogenesis studies conducted by the National Toxicology Program.