QuEChERS-超高效液相色谱-串联质谱法快速测定3种叶菜中矮壮素和丙环唑残留

建立了菜心、芥蓝和小白菜中矮壮素和丙环唑残留的分析方法.以QuEChERS法进行样品前处理,采用含1％ HAc的乙腈溶液提取,无水MgSO4、C18及PSA吸附剂净化,超高效液相色谱-串联质谱(UPLC-MS/MS)法测定.对提取溶剂、吸附剂和色谱柱的选择进行了研究探讨.结果表明矮壮素在1～1 000 μg/L、丙环唑在1～500 μg/L浓度范围内均有良好的线性关系.矮壮素和丙环唑的检出限分别为0.1 μg/kg和0.01 μg/kg;在0.010、0.10和0.50 mg/kg 3个添加浓度水平下,菜心、芥蓝和小白菜中矮壮素和丙环唑回收率为75.0％～96.2％;相对标准偏差为0.9％～8.3％;方法定量限为最低添加浓度0.010 mg/kg.该方法快速、简便、准确,满足叶菜中矮壮素和丙环唑残留分析的要求.     

液相色谱串联质谱法测定蔬菜中四聚乙醛残留量

建立了测定蔬菜中四聚乙醛残留量的液相色谱串联质谱方法.蔬菜样品经乙腈提取,盐析后吹干乙腈提取液,再用氟罗里硅土固相萃取小柱净化,用正已烷/丙酮(80:20,V/V)混合溶剂洗脱,氮吹后用乙腈-20mmol/L,乙酸铵溶液(70:30,V/V)溶解后进行仪器分析.分析采用XBridgeTM C18色谱柱分离,乙腈-20m...     

Quantitative trace analysis of eight chloramphenicol isomers in urine by chiral liquid chromatography coupled to tandem mass spectrometry

Chloramphenicol is a broad-spectrum antibiotic with, apart from its human medicinal use, veterinary abuse in all major food-producing animals. Chloramphenicol occurs in four stereoisomers (all para-nitro substituted) and furthermore four meta-nitro analogs of chloramphenicol exist. In this paper these are referred to as eight chloramphenicol isomers. According to EU regulations an analytical method should be able to discriminate the analyte from interfering substances that might be present in the sample, including isomers. For the first time a quantitative method for the analysis of trace levels of eight chloramphenicol isomers in urine by chiral liquid chromatography in combination with tandem mass spectrometric detection is reported. The separation of the isomers on the analytical column, the clean-up of urine and the selectivity of the monitored product ions turned out to be critical parameters. To obtain reproducible retention isocratic elution on a chiral AGP column was applied. For urine samples matrix compounds present in the final extract caused decreased retention of the isomers on the chiral stationary phase and a lack of chromatographic resolution. Therefore an extended clean-up procedure that combines solid phase extraction and liquid-liquid extraction had to be developed. The final method was fully validated and showed satisfactory performance for all isomers with decision limits (CCα) ranging from 0.005 to 0.03 μg L(-1) and within-laboratory reproducibility of all isomers below 20% at the minimum required performance limit level of 0.3 μg L(-1).     

A ruled residue theorem for function fields of conics

The ruled residue theorem characterises residue field extensions for valuations on a rational function field. Under the assumption that the characteristic of the residue field is different from 2 this theorem is extended here to function fields of conics. The main result is that there is at most one extension of a valuation on the base field to the function field of a conic for which the residue field extension is transcendental but not ruled. Furthermore the situation when this valuation is present is characterised.     

关于模n的剩余类环■_n的注记

本文从模n的剩余类环n中一类特殊元素———幂等元出发,充分运用同余关系的运算,阐明幂等元的存在与其确定方法,并由给定整数构造以该整数为幂等元的环中的乘法群,揭示了n及其乘法群之间的一个内在联系.     

The Residue Determinant

ABSTRACT

The purpose of this paper is to present the construction of a canonical determinant functional on elliptic pseudodifferential operators (ψdos) associated to the Guillemin–Wodzicki residue trace.

The resulting residue determinant functional is multiplicative, a local invariant, and not defined by a regularization procedure. The residue determinant is consequently a quite different object from the zeta function determinant, which is nonlocal and nonmultiplicative. Indeed, the residue determinant does not arise as the derivative of a trace on the complex power operators and does not depend on a choice of spectral cut. The identification of a certain residue determinant with the index of an elliptic ψdo shows the residue determinant to be topologically significant.     

Determination of nitrofuran and chloramphenicol residues by high resolution mass spectrometry versus tandem quadrupole mass spectrometry

An ultra-high performance liquid chromatography based method, coupled to high resolution mass spectrometry (UHPLC–HRMS), was developed to permit the detection and quantification of various nitrofuran and chloramphenicol residues in a number of animal based food products. This method is based on the hydrolysis of covalently bound metabolites and derivatization with 2-nitrobenzaldehyde. Clean-up is achieved by a liquid/liquid and a reversed phase/solid phase extraction. Not only are the four conventional nitrofurans (nitrofurantoin, furazolidone, nitrofurazone and furaltadone) detected, but also nifursol, nitrovin and nifuroxazide. Furthermore, an underivatizable nitrofuran (nifurpirinol) and another banned drug (chloramphenicol) can be quantified as well. The compounds are detected in the form of their precursor ions, [M + H]⁺ and [M − H]⁻, respectively. The mass resolving power of 70,000 FWHM, and the applied mass window ensure sufficient selectivity and sensitivity. Confirmation is obtained by monitoring the HRMS resolved product ions which were derived from the unit-mass resolved precursor ions. The multiplexing capability of the utilized Orbitrap instrument provides not only highly selective, but also sensitive confirmatory signals. This method has been validated according to the CD 2002/657/EC for the following matrices: muscle, liver, kidney, fish, honey, eggs and milk.     

Multivariate optimization and comparison between conventional extraction (CE) and ultrasonic-assisted extraction (UAE) of carotenoid extraction from cashew apple

Carotenoids are an essential component of cashew and can be used in pharmaceuticals, cosmetics, natural pigment, food additives, among other applications. The present work focuses on optimizing and comparing conventional and ultrasound-assisted extraction methods. Every optimization step took place with a 1:1 (w:w) mixture of yellow and red cashew apples lyophilized and ground in a cryogenic mill. A Simplex-centroid design was applied for both methods, and the solvents acetone, methanol, ethanol, and petroleum ether were evaluated. After choosing the extractor solvent, a central composite design was applied to optimize the sample mass (59–201 mg) and extraction time (6–34 min). The optimum conditions for the extractor solvent were 38% acetone, 30% ethanol, and 32% petroleum ether for CE and a mixture of 44% acetone and 56% methanol for UAE. The best experimental conditions for UAE were a sonication time of 19 min and a sample mass of 153 mg, while the CE was 23 min and 136 mg. Comparing red and yellow cashews, red cashews showed a higher carotenoid content in both methodologies. The UAE methodology was ca. 21% faster, presented a more straightforward composition of extracting solution, showed an average yield of superior carotenoid content in all samples compared to CE. Therefore, UAE has demonstrated a simple, efficient, fast, low-cost adjustment methodology and a reliable alternative for other applications involving these bioactive compounds in the studied or similar matrix.     

结合工程实例论工业废渣在道路建设中的应用

本文论述了粉煤灰及煤矸石用于道路铺筑不仅能改进道路的路用性能,并能减少环境污染,变废为宝,并结合咸阳地区工程实例来分析工业废渣应用于道路铺筑的有效性。     

Development and in-house validation of an LC-MS/MS method for the determination of stilbenes and resorcylic acid lactones in bovine urine

Stilbenes and zeranol are nonsteroidal estrogenic growth promoters which are banned in the European Union (EU) for use in food-producing animals by Council Directive 96/22/EC. A liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed for the screening and confirmation of stilbenes (diethylstilbestrol, dienestrol, hexestrol) and resorcylic acid lactones (zeranol and its metabolites taleranol and zearalanone as well as the mycotoxins α-zearalenol, β-zearalenol and zearalenone) in bovine urine. The method permits the confirmation and quantification of stilbenes and resorcylic acid lactones at levels below 1 μg L⁻¹ and 1.5 μg L⁻¹, respectively. The validation was carried out according to Commission Decision 2002/657/EC, Chap. 3.1.3 “alternative validation” by a matrix-comprehensive in-house validation concept. Decision limit CCα, detection capability CCβ, recovery, repeatabiliy, within-laboratory reproducibility and the uncertainty of measurement were calculated. Furthermore, a factorial effect analysis was carried out to identify factors that have a significant influence on the method. Factors considered to be relevant for the method in routine analysis (e.g. operator, matrix condition, storage duration of the extracts before measurement, different cartridge lots, hydrolysis conditions) were systematically varied on two levels. The factorial analysis showed that different cartridge lots, storage durations and matrix conditions can exert a relevant influence on the method.