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排序方式: 共有140条查询结果,搜索用时 15 毫秒
1.
ICP-AES法测定富锗酵母中微量元素 总被引:2,自引:0,他引:2
本文采用美国LeemanLabs公司中阶梯光栅光谱仪测定了人工培养的富锗酵母中高含量锗及镁、铜、锌、铁、钾、钠等微量元素,研究了富锗样品的前处理方法,样品加标回收率在90%-103%之间,测量相对标准偏差:锗10%,镁、铜、锌、铁、钾、钠等元素小于7%。 相似文献
2.
The application of the recently introduced ethylchloroformate derivatization method for the separation and determination of selenomethionine and selenocystein in selenium-enriched yeast and yeast-free tablets by means of a gas chromatography-mass spectrometry (GC-MS) system has been studied. The efficiency of three methods for the extraction of selenomethionine from the tablets were compared. Total selenium content of the same tablets were measured using inductively coupled plasma (ICP)-MS and it was found that in the selenized yeast tablets about 80% of the total selenium is present as selenomethionine. The results were in agreement with the values in the labels and with the literature. The accuracy of the total selenium analysis was controlled by the analysis of a reference material. 相似文献
3.
Ion mobility spectrometry (IMS) measurement combined with unsupervised neurocomputing is considered as a new potential method for on-line monitoring of fermentation and other processes producing volatile compounds that involve micro-organisms. This was demonstrated in a model system in which a strain of brewer’s yeast (Saccharomyces cerevisiae) was cultivated in a bench-top fermenter. Five phases of yeast growth could be detected from measurements of the exhaust gases from the fermenter, as indicated by the changes in ion mobility spectra analysed by computational methods.The data were first processed using the Self-Organizing Map (SOM) algorithm, the results showing that the phases of fermentation can be detected and identified. The cultivations were also shown by Sammon’s mapping to be comparable to a certain level of accuracy. Contaminated cultivation could be detected by its distinctive ion mobility spectrometry profile. 相似文献
4.
Inorganic arsenic was separated using the yeast-immobilized column. Saccharomyces cerevisiae was covalently bonded unto the controlled pore glass, which showed selective preconcentration of As5+ over As3+. The effluent was directly connected to hydride generation (HG) to increase sensitivity. The optimum pH condition for the retainment of arsenic at the column was 7. As5+ and As3+ were completely separated in a few minutes with the flow rate of 1.5 ml min−1. Three molars of nitric acid was adequate both for the elution of As5+ and hydride generation. The accuracy of the technique was tested with NIST SRMs. Quantitative analysis of arsenic species for herbicide, pesticide, and cigarette were performed, and the results showed good agreements with the suggested values. Yeast-immobilized column-HG-ICP showed a promising future for the arsenic speciation study. 相似文献
5.
6.
Ke Wang Zuyi Li Chengye Yuan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1797-1800
Bioreduction of 2-oxo-3-halo (or azido) alkanephosphonates and 4-ethoxy-4,2-dioxobutanephosphonates by baker's yeast afforded 3-substituted 2-hydroxyalkanephosphonates in moderate to good yields and ee value. Moreover, a regio- and stereoselective bioreduction of 2,3-dioxoalkanephosphonates and 2,4-dioxoalkanephosphonates by baker's yeast was studied also. The resulting chiral hydroxy compounds can be used as chirons for the stereoselective synthesis of biologically active molecules. 相似文献
7.
Cheng-ye Yuan Ke Wang Jinfeng Li Zu-yi Li 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2391-2397
Bioreduction of 3-substituted-2-oxoalkanephosphonates by baker's yeast afforded corresponding 2-hydroxy-alkanephosphonates in good yields and ee value. These compounds ( 2a,b ) could serve as useful chirons for the stereoselective synthesis of phosphorus analogs of (R)-Carnitine and (R)-GABOB. 相似文献
8.
This paper presents size exclusion chromatography data with on-line coupling to UV and inductively coupled plasma mass spectrometry (ICP-MS) of water soluble metal-binding compounds present in zinc, copper, chromium and iodine enriched yeast nutritional supplements. Molecular weight estimates of the extracted metal-containing compounds are given and are shown to vary substantially from 1.2 kDa to larger than 668 kDa. Seven proteins suspected of containing chromium were identified from one of the chromium-containing fractions. Four of these identified proteins are known to form complexes with other metal ions. The metal chromatographic profiles of zinc, copper and chromium-enriched yeasts were compared to their respective native metal profiles in non-enriched yeast samples. The chromium profiles are shown to be markedly different while those of zinc and copper are qualitatively similar. Only iodide ions or weakly bound, non-aromatic, low molecular weight ( 1.2 kDa) iodine species were observed in the iodine-enriched yeast samples. 相似文献
9.
A method is presented for the simultaneous determination of Cr(III) and Cr(VI) in yeast using species-specific double-spike
isotope dilution (SSDSID) with anion-exchange liquid chromatography (LC) separation and sector field inductively coupled plasma
mass spectrometric (SF-ICP-MS) detection. Total Cr is quantitated using ID SF-ICP-MS. Samples were digested on a hot plate
at 95±2 °C for 6 h in an alkaline solution of 0.5 M NaOH and 0.28 M Na2CO3 for the determination of Cr(III) and Cr(VI), whereas microwave-assisted decomposition with HNO3 and H2O2 was used for the determination of total Cr. Concentrations of 2,014±16, 1,952±103 and 76±48 mg kg−1 (one standard deviation, n=4, 3, 3), respectively were obtained for total Cr, Cr(III) and Cr(VI) in the yeast sample. Significant oxidation of Cr(III)
to Cr(VI) (24.2±7.6% Cr(III) oxidized, n=3) and reduction of Cr(VI) to Cr(III) (37.6±6.5% Cr(VI) reduced, n=3 ) occurred during alkaline extraction and subsequent chromatographic separation at pH 7. Despite this significant bidirectional
redox transformation, quantitative recoveries for both Cr(III) and Cr(VI) were achieved using the SSDSID method. In addition,
mass balance between total Cr and the sum of Cr(III) and Cr(VI) concentrations was achieved. Method detection limits of 0.3,
2 and 30 mg kg−1 were obtained for total Cr, Cr(VI) and Cr(III), respectively, based on a 0.2-g sub-sample. 相似文献
10.
G.Ch. Lainioti J. Kapolos A. Koliadima G. Karaiskakis 《Journal of chromatography. A》2010,1217(11):1813-1820
In the present work two separation techniques, namely the gravitational field-flow fractionation (GrFFF) and the reversed-flow gas chromatography (RFGC), are proposed for the distinction of the growth phases of Saccharomyces cerevisiae (AXAZ-1) yeast cycle at different temperatures (30 °C, 25 °C, 20 °C, and 15 °C) and pH (2.0, 3.0, 4.0 and 5.0) values. During the fermentation processes, differences observed in the peak profiles, obtained by GrFFF, can be related with the unlike cell growth. The distinction of the phases of AXAZ-1 cell cycle with the GrFFF, was also confirmed with the RFGC technique, which presented similar fermentation time periods for the alcoholic fermentation phases. Simultaneously, the reaction rate constant for each phase of the fermentation process and the activation energies were determined with the aid of the RFGC technique. Finally, the application of both the GrFFF and the RFGC techniques, in combination with high-performance liquid chromatography, allowed us to find the ideal experimental conditions (temperature and pH) for the alcoholic fermentation by AXAZ-1. The results indicate that S. cerevisiae cells performed better at 30 °C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. Moreover, the pH of the medium (pH 5.0) resulted in higher fermentation rates and ethanol productivities. 相似文献