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排序方式: 共有218条查询结果,搜索用时 312 毫秒
1.
The evaluation of a badge-type diffusive sampler for measuring formaldehyde using 3-methyl-2-benzothiazolinone hydrazone (MBTH) was investigated. On average, the formaldehyde concentration in blanks was reduced by approximately 31% by cleaning procedures. The cleaning techniques did not significantly differ in effectiveness. The maximum sampling rate was 22.4 +/- 3.5 mL min(-1) at MBTH concentrations of 0.05%. The formaldehyde concentration in blanks did not appreciably increase over a period of about 1 month at room temperature, and was 0.36 +/- 0.03 microg, with a relative standard deviation of 8%. The diffusive sampler had good precision and accuracy for measuring formaldehyde in indoor environments. For a 24-h exposure time, the limits of detection and quantification calculated with the field blanks were 9.7 and 13.8 ppb, respectively. The minimum exposure times were calculated based on the measured and calculated limits of quantification, the sampling rate, and the atmospheric formaldehyde concentration. The capacity of the diffusive sampler with 0.5% MBTH was 3 ppm h(-1), approximately 1.5-times the capacity when the MBTH concentrations were 0.05%. 相似文献
2.
Pal R Yang M Lin R Johnson BN Srivastava N Razzacki SZ Chomistek KJ Heldsinger DC Haque RM Ugaz VM Thwar PK Chen Z Alfano K Yim MB Krishnan M Fuller AO Larson RG Burke DT Burns MA 《Lab on a chip》2005,5(10):1024-1032
An integrated microfluidic device capable of performing a variety of genetic assays has been developed as a step towards building systems for widespread dissemination. The device integrates fluidic and thermal components such as heaters, temperature sensors, and addressable valves to control two nanoliter reactors in series followed by an electrophoretic separation. This combination of components is suitable for a variety of genetic analyses. As an example, we have successfully identified sequence-specific hemagglutinin A subtype for the A/LA/1/87 strain of influenza virus. The device uses a compact design and mass production technologies, making it an attractive platform for a variety of widely disseminated applications. 相似文献
3.
Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry 总被引:1,自引:0,他引:1
Myung SW Chang YJ Min HK Kim DH Kim M Kang TK Yoo EA Sohn YT Yim YH 《Rapid communications in mass spectrometry : RCM》2000,14(21):2046-2054
Using the high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) technique, together with established trends from the literature, the structures of metabolites and impurities of amiodarone, an anti-arrhythmic drug, have been assigned. By comparing analyses of products of incubation with rat liver microsomes with controls in which glucose 6-phosphate dehydrogenase was omitted, metabolites could be distinguished from impurities. Structures for the two proposed metabolites and four impurities are proposed. 相似文献
4.
E R Werner G Werner-Felmayer D Fuchs A Hausen G Reibnegger G Wels J J Yim W Pfleiderer H Wachter 《Journal of chromatography. A》1991,570(1):43-50
An assay for 6-pyruvoyl tetrahydropterin synthase, the second enzyme in the conversion of guanosine triphosphate into tetrahydrobiopterin, has been developed. Cell extracts were incubated with enzymatically prepared dihydroneopterin triphosphate (80 microM) in the presence of Mg2+ (12 mM), excess sepiapterin reductase (EC 1.1.1.153) (2 nmol/min) and NADPH (2 mM). 6-Pyruvoyl tetrahydropterin, the product of the reaction, was thus converted into tetrahydrobiopterin. After oxidation of the reduced biopterin derivatives in acidic iodine solution, biopterin was enriched and separated from the abundant neopterin phosphates by solid-phase extraction on a strong cation exchanger. Biopterin was then directly eluted on a reversed-phase liquid chromatographic column and detected fluorimetrically using excitation at 353 nm and emission at 438 nm. The biopterin concentrations formed by the coupled enzyme reaction increased linearly with incubation times up to 90 min. The assay allows the quantification of 6-pyruvoyl tetrahydropterin synthase in cultured human cells. 相似文献
5.
A sequential injection analysis (SIA) system was developed to monitor the concentration of l-cysteine in biological processes on-line. It is based on the redox reaction of l-cysteine with iron(III) in the presence of 1,10-phenanthroline (phen) and the detection of the red-iron(II)-phen complex with a spectrophotometry. The system was fully automated using software written in the LabVIEW™ development environment. A number of system variables such as the flow rate of the carrier buffer solution, the volume ratio of the sample to the reagents, and the reaction coil length, etc., were evaluated to increase the sensitivity and performance of the SIA system. Under partially optimized operating conditions the performance of the SIA system was linear up to a concentration of l-cysteine of 1 mM (R2 = 0.998) with a detection limit of 0.005 mM and a sample frequency of 15 hr−1. The SIA system was employed to monitor the concentration of l-cysteine on-line in a continuously stirred reactor and a fermentation process of Saccharomyces cerevisiae. The on-line monitored data were in good agreement with the off-line data measured by a HPLC with a fluorescence detector (n = 15, R2 = 09899). 相似文献
6.
K W Yim 《Journal of chromatography. A》1991,559(1-2):401-410
This paper reports the fractionation of recombinant human tissue plasminogen activator (rtPA) glycoforms, a complex mixture to demonstrate the high resolving power of capillary zone electrophoresis (CZE) and capillary isoelectric focusing (cIEF). rtPA is a glycoprotein with a complex carbohydrate structure. The electropherograms and IEF patterns have been discussed in light of the known carbohydrate structures of rtPA. rtPA was treated with neuraminidase which removes the sialic acids from the carbohydrate chains. The desialylated rtPA was analyzed by both CZE and IEF and the results were compared to those of untreated rtPA. The usefulness of CZE and cIEF in the characterization of glycoproteins proteins is also discussed. 相似文献
7.
Suzuki-Miyaura coupling was achieved on a variety of aryl chlorides by using di(2,6-dimethylmorpholino)phenylphosphine (L1) as a bulky electron-rich monoaryl phosphine ligand. We report the couplings of various chlorobenzenes and heteroaryl chlorides. 相似文献
8.
Seung Wha Jo Ji-Hyun An Dong-Shin Kim Eun Jung Yim Hyeon-Jin Kang Hyun-Jin Kim 《Molecules (Basel, Switzerland)》2022,27(19)
Aspergillus oryzae (A. oryzae) is an important starter in the fermentation of koji and moromi. However, the effect of different A. oryzae strains on the quality of moromi has rarely been studied. For this reason, this study analyzed the physicochemical properties, enzyme activity, sensory quality, and metabolite profiles of moromi samples fermented using two strains (A. oryzae KCCM12012P (moromi-1) and KCCM12804P (moromi-2)), which were newly isolated from fermented soy foods, and compared them to those of a commercialized A. oryzae strain (control). Amino-type nitrogen contents of moromi-1 and moromi-2 samples were higher than that of control moromi, and their amylase and protease activities were also higher. Moreover, metabolite profiles of moromi were significantly altered according to strains. In particular, the levels of many amino acids, peptides, nucleotides, and acidic compounds were altered, which resulted in changes in the sensory quality of moromi. Although volatile compounds were not investigated, the results suggested that the quality of moromi was significantly different for newly isolated strains, especially A. oryzae KCCM12804P, and they were superior to the commercial strain in terms of taste-related substances. Therefore, these strains could be used as good starters to produce moromi and soy sauce with good sensory quality. 相似文献
9.
10.