PubMed · 8900447
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1995-08-15. 1996 Lab Guide.. https://pubmed.ncbi.nlm.nih.gov/8900447/
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The applications of plasma chemistry to environmental problems and to green chemistry are emerging fields that offer unique opportunities for advancement. There has been substantial progress in the application of plasmas to analytical diagnostics and to waste reduction and waste management. This review discusses the chemistry and physics necessary to a basic understanding of plasmas, something that has been missing from recent technical reviews. The current status of plasmas in environmental chemistry is summarized and emerging areas of application for plasmas are delineated. Plasmas are defined and discussed in terms of their properties that make them useful for environmental chemistry. Information is drawn from diverse fields to illustrate the potential applications of plasmas in analysis, materials modifications and hazardous waste treatments.
Microwave-assisted extraction (MAE) is a process of using microwave energy to heat solvents in contact with a sample in order to partition analytes from the sample matrix into the solvent. The ability to rapidly heat the sample solvent mixture is inherent to MAE and the main advantage of this technique. By using closed vessels the extraction can be performed at elevated temperatures accelerating the mass transfer of target compounds from the sample matrix. A typical extraction procedure takes 15-30 min and uses small solvent volumes in the range of 10-30 ml. These volumes are about 10 times smaller than volumes used by conventional extraction techniques. In addition, sample throughput is increased as several samples can be extracted simultaneously. In most cases recoveries of analytes and reproducibility are improved compared to conventional techniques, as shown in several applications. This review gives a brief theoretical background of microwave heating and the basic principles of using microwave energy for extraction. It also attempts to summarize all studies performed on closed-vessel MAE until now. The influences of parameters such as solvent choice, solvent volume, temperature, time and matrix characteristics (including water content) are discussed.
A high-pressure liquid chromatography method has been developed for the analysis in urinary calculi of six purines: uric acid, 2, 8-dihydroxyadenine, xanthine, hypoxanthine, allopurinol, and oxypurinol. Separation was conducted isocratically on a reversed-phase column, using 50 mM phosphate buffer (pH 5.5) / methanol (97/3, v/v) as mobile phase. Limits of detection, depending on compound, ranged from 7 to 28 microg/g stone weight. Hitherto, no reports have appeared on other purines present with uric acid in stones, due to lack of a sensitive and specific analytical method. We have now found that all calculi with more than 4% uric acid also contained 1-methyluric and 7-methyluric acids and trace amounts of hypoxanthine, xanthine, and 2,8-dihydroxyadenine. Accurate identification and quantitation of purines in urinary calculi are important for the diagnosis of rare metabolic diseases leading to urolithiasis (xanthinuria, dihydroxyadeninuria), as well as for prevention of iatrogenic complications during treatment with allopurinol of uric acid urolithiasis. The method may be used for reference purposes in clinical laboratories and for research on the pathogenesis of urolithiasis in disorders of purine metabolism.