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Precipitation Procedure (precipitation + procedure)
Selected AbstractsThe use of sodium formate for the recovery of precious metals from acidic base metal effluentsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2001Herman G Julsing Abstract Zinc was used for the reduction of the platinum group metals (PGMs) in acidic effluents. Due to the increasing cost of zinc, sodium formate was investigated as an alternative reductant. In a base metal-containing acidic effluent, called diethylenetriamine barren, sodium formate was used to precipitate the PGMs. This effluent was the filtrate obtained after a precipitation procedure had been used to remove rhodium and iridium. It was found that pH 1.5 was the optimum starting pH for sodium formate reduction. The pH increased to approximately 4.5 after the addition of sodium formate. The optimum concentration of sodium formate was found to be 30,g,dm,3 at a temperature of 100,°C where the process time was 6,h. Platinum and palladium were the most effectively reduced PGMs, both exhibiting an average precipitation efficiency of greater than 99%. Difficulty was experienced with the precipitation of iridium (average precipitation efficiency of 76%). The precipitated PGMs readily dissolved in hydrochloric acid (6,M) and sodium chlorate (2%). A reduction in costs resulted from the discontinuation of the use of zinc for reduction purposes. An additional advantage was that zinc was no longer introduced into the PGM refinery circuits. © 2001 Society of Chemical Industry [source] Determination of BAPTA-AM, the acetoxymethyl tetraester of BAPTA, in rat plasma by liquid chromatography tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2006Feng Zheng Abstract BAPTA-AM is the acetoxymethylester of the calcium chelator BAPTA and has demonstrated efficacy in several animal models of cerebral ischemia. This paper describes the development of a method for the determination of BAPTA-AM in rat plasma by liquid chromatography/tandem mass spectrometry. Owing to multiple ester groups in the structure of BAPTA-AM, [M + Na]+ was chosen as the analytical ion for quantification of BAPTA-AM. During the analytical method development, a high percentage of organic solvent and the addition of an amount of sodium acetate and formic acid in the mobile phase were found to favor the sensitivity and reproducibility of [M + Na]+. Poor fragmentation was usually observed in the MS/MS spectra of sodium adduct ions. However, abundant and reproducible fragment ions were observed for the BAPTA-AM sodium adduct ion, and therefore the traditional selective reaction-monitoring mode was used to further improve the sensitivity of MS detection. Because of the lability of the ester bond, a combination of fluoride and hydrochloric acid was applied to minimize the enzymatic hydrolysis, and acetonitrile was chosen to avoid the chemical hydrolysis or solvolysis during the sample collection and preparation procedure. On the basis of these studies, a rapid, sensitive and reproducible method for the determination of BAPTA-AM in rat plasma, using LC/ESI-MS/MS and a simple protein precipitation procedure, was developed and validated. Also, the present method was successfully applied to the determination of BAPTA-AM plasma concentrations for pharmacokinetic studies in rats. Copyright © 2006 John Wiley & Sons, Ltd. [source] Development of a low volume plasma sample precipitation procedure for liquid chromatography/tandem mass spectrometry assays used for drug discovery applicationsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2005Xiaoying Xu The demand for high sensitivity bioanalytical methods has dramatically increased in the drug discovery stage; in addition, there has been a growing trend of reducing the sample volume that is required for these assays. A sensitive high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) procedure has been developed and tested to meet these needs. The assay requires only a low plasma sample volume (10,µL) and employs a protein precipitation procedure using a 1:6 plasma/acetonitrile ratio. The supernatant is injected directly into the LC/MS/MS system using the selected reaction monitoring (SRM) procedure for detection. A generic HPLC gradient based on a methanol/water mobile phase with a flow rate set to 0.8,mL/min was used. The test method showed very good linearity between 0.1,1000,ng/mL (R2,=,0.9737), precision (%RSD,=,6,9), accuracy (%RE,=,,2) and reproducibility (%RSD,=,11). A drug discovery IV/PO study was assayed using both the new low volume method and our standard volume (50,µL) method. The correlation of the two sets of data from the two methods was excellent (R2,=,0.9287). This new assay procedure has been successfully used in our laboratory for over 100 different rat or mouse discovery PK studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Cassette-accelerated rapid rat screen: a systematic procedure for the dosing and liquid chromatography/atmospheric pressure ionization tandem mass spectrometric analysis of new chemical entities as part of new drug discoveryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2001Walter A. Korfmacher This report addresses the continuing need for increased throughput in the evaluation of new chemical entities (NCEs) in terms of their pharmacokinetic (PK) parameters by describing an alternative procedure for increasing the throughput of the in vivo screening of NCEs in the oral rat PK model. The new approach is called ,cassette-accelerated rapid rat screen' (CARRS). In this assay, NCEs are dosed individually (n,=,2 rats/compound) in batches of six compounds per set. The assay makes use of a semi-automated protein precipitation procedure for sample preparation in a 96-well plate format. The liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) assay is also streamlined by analyzing the samples as ,cassettes of six'. Using this new approach, a threefold increase in throughput was achieved over the previously reported ,rapid rat screen'. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||