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111.
112.
高效液相色谱-串联质谱法同时测定表层水体中5类40种抗生素 总被引:1,自引:0,他引:1
建立了固相萃取-高效液相色谱-串联质谱(SPE-HPLC-MS/MS)同时检测表层水中5类40种抗生素的分析方法。水样经过滤、固相萃取柱富集净化后,以乙腈-0.2%(v/v)甲酸水溶液为流动相进行梯度洗脱,采用电喷雾电离源,在多反应监测、正离子模式进行定性定量分析。结果显示,40种抗生素在1~200 μg/L水平下线性关系良好,平均加标回收率为41.3%~112.6%。采用该方法对长江南京段表层水体进行检测,共检出13种抗生素,含量为13.4~780.5 ng/L,其中喹诺酮类抗生素恩诺沙星检出率达100%,大环内酯类抗生素克林霉素最高检出水平达739.4 ng/L。该法高效、灵敏、可靠,可用于实际水样中多种抗生素的分析。 相似文献
113.
Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC. 相似文献
114.
ZNF191 (243-368), a new human zinc finger protein, probably relates to some hereditary diseases and cancers, To obtain adequate amount of ZNF191(243-368) for the study of its property, structure and function, three different expression systems of inclusion-body, glutathione S-transferase (GST), and hexahistidine (6 × His) were used and compared. Among these systems, the expression level of ZNFI91(243-368) was increased in inclusion body system under a higher isopropylthio-β-D-galactoside (IPTG) concentration, but the non-target proteins were also increased more, which made its purification more difficult and the yield lower. The expression of His-tag fusion protein was almost not affected by IPTG concentration, temperature and inducing time. At a high IPTG concentration the highest expression yield for GST fusion protein was obtained. And the fusion proteins can be partially purified by a single affinity chromatography step. The fusion protein systems show advantages for expression of these proteins. 相似文献
115.
Summary Due to the carcinogenity and ubiquity of polycyclic aromatic hydrocarbons in the environment they are of ongoing interest
to analytical chemistry. In this study, a comparison of the classic Soxhlet extraction and, fluidized-bed extraction, has
been conducted. The extraction of polycyclic aromatic hydrocarbons by this technique has been optimized considering as experimental
variables the variation of the number of extraction cycles and the holding time after reaching the heating temperature by
means of a surface response design. The significance of the operational parameters of the fluidized-bed extraction on the
performance characteristics has been investigated. For the determination of the analytes a selective clean-up of the extracts
followed by a fast gas chromatography method with mass spectrometric detection was used, resulting in low limits of detection
(0.2 pg μL−1). The accuracy of the complete analytical method was established by extraction and analysis of reference materials. 相似文献
116.
117.
Pucci V Bugamelli F Mandrioli R Ferranti A Kenndler E Raggi MA 《Biomedical chromatography : BMC》2004,18(1):37-44
An accurate and precise high-performance liquid chromatographic method using diode array detection for the determination of the novel antiepileptic, Levetiracetam, has been developed. Three clean-up procedures for the analysis of Levetiracetam in human plasma were implemented and evaluated, namely solid-phase extraction, deproteinization by addition of organic solvents and formation of insoluble salts. Adenosine was used as the internal standard for all three sample pretreatment procedures. Among the several cartridges used for solid-phase extraction, the hydrophilic-lypophilic balance (Oasis) HLB) phase provides the best extraction yield of Levetiracetam, together with high precision. With the two other clean-up procedures involving plasma deproteinization by addition of methanol or zinc sulphate, lower sensitivity and precision of the assays were obtained. However, they are cheaper and faster when compared with the solid-phase extraction procedure. 相似文献
118.
Binal N. Shah 《Thermochimica Acta》2006,443(1):78-86
Protein crystals are usually grown in multi-component aqueous solutions containing salts, buffers and other additives. To measure the X-ray diffraction data of the crystal, crystals are rapidly lowered to cryogenic temperatures. On flash cooling, ice frequently forms affecting the integrity of the sample. In order to eliminate this effect, substances called cryoprotectants are added to produce a glassy (vitrified) state rather than ice. Heretofore, the quantity of cryoprotectant needed to vitrify the sample has largely been established by trial and error. In this study, differential scanning calorimetry (DSC) was used to measure the melting (Tm), devitrification (Td) and glass transition (Tg) temperatures of solutions with a range of compositions typical of those used for growing protein crystals, with the addition of glycerol as cryoprotectant. The addition of cryoprotectant raises the Tg and lowers the Tm of bulk solution thereby decreasing the cooling rates required for vitrification of protein crystals. The theoretical Tg value was calculated using the apparent volume fraction using the Miller/Fox equation extended for multi-component systems. The experimental values of Tg were within approximately ±4% of that predicted by the model. Thus, the use of the model holds the promise of a rational method for the theoretical determination of the composition of cryoprotectant requirement of protein crystallization solutions. 相似文献
119.
High-level expression of soluble human β-defensin-2 fused with green fluorescent protein in Escherichia coli cell-free system 总被引:2,自引:0,他引:2
Human β-defensin-2 (hBD2), a small cationic peptide, exhibits a broad range of antimicrobial activity and does not acquire
any microbial resistance. To produce this uneasily detectable, degradable, and toxic polypeptide efficiently, an alternative
approach based on the Escherichia coli cell-free biosynthesis system was proposed. The approach implies that a polypeptide of interest is synthesized as a fusion
protein linked to a green fluorescent protein (GFP) through a cleavable spacer. With batch-mode operation, a significant amount
of hBD2 fused with GFP (0.25 mg/mL) can be expressed in this cell-free system. The productivity of the fusion protein can
be improved up to 1.2 mg/mL by employing a continuous-exchange cell-free system. Furthermore, the GFP moiety provides directly
visible and quantitative monitoring of the polypeptide synthesis, and the product is soluble and stable. This work will be
helpful in allowing the rapid and visible expression of other similar defensins using an in vitro cell-free system. 相似文献
120.
Young-ah WooChang-hee Cho Hyo-jin Kim Jong-soo YangKi-yong Seong 《Microchemical Journal》2002,73(3):299-306
A rapid and nondestructive near infrared (NIR) method using soft independent modeling of class analogy (SIMCA) for the classification of cultivation area (Korea and China) was evaluated and confirmed. Raw, first, and second derivative NIR spectra were compared to develop a robust classification rule. The chemical properties of ginseng samples were also investigated to find out the differences between Korean samples and Chinese samples. These differences make NIR spectroscopic method viable. The average value of each Korean and Chinese ginseng sample for crude fiber, crude protein, starch, and 10 inorganic constituents were measured and compared with F-test and t-test. The inorganic constituents were also measured by induced coupled plasma-atomic emission spectroscopy (ICP-AES). It could be found that the amount of starch and ten inorganic elements for example Na, Mg, P, K, Ca, Mn, Fe, Ni, Cu and Zn in ginseng samples are considerably different based on cultivation area. SIMCA has been applied to the inorganic data to investigate the possibility of ICP-AES as classification tool. However, it was observed that the result was not equal to than NIR spectra data. The overall results showed the availability of NIR method using SIMCA would be adequate for classification of cultivation of ginseng, since NIR spectra includes useful and various information on chemical properties in spite of broad and overlapped bands. 相似文献