Microextraction in packed syringe (MEPS) for liquid and gas chromatographic applications. Part II--Determination of ropivacaine and its metabolites in human plasma samples using MEPS with liquid chromatography/tandem mass spectrometry

A new technique for sample preparation on-line with liquid chromatographic/tandem mass spectrometric (LC/MS/MS) assay was developed. Microextraction in a packed syringe (MEPS) is a new miniaturized, solid-phase extraction technique that can be connected on-line to gas or liquid chromatography without any modifications. In MEPS approximately 1 mg of the solid packing material is inserted into a syringe (100-250 microl) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising, very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. This paper presents the development and validation of a method for MEPS on-line with LC/MS/MS. Ropivacaine and its metabolites (PPX and 3-OH-ropivacaine) in human plasma samples were used as model substances. The method was validated and the calibration curves were evaluated by means of quadratic regression and weighted by the inverse of the concentration, 1/x, for the calibration range 2-2000 nM. The applied polymer could be used more than 100 times before the syringe was discarded. The extraction recovery was between 40 and 60%. The results showed high correlation coefficients (R(2) > 0.999) for all analytes in the calibration range studied. The accuracy, expressed as a percentage variation from the nominal concentration values, ranged from 0 to 6%. The precision, expressed as the relative standard deviation, at three different concentrations (quality control samples) was consistently about 2-10%. The limit of quantification was 2 nM.     

ZrC(111)弛豫表面电子结构及其吸附氢的理论研究

采用第一性原理的方法对ZrC（111）清洁和氢吸附表面的电子结构进行了研究 。构型优化结果表明，从表面深入到体相一定深度，层间距存在交替“收缩”和“ 扩张”的现象，其紧邻E_F以下的DOS峰对应于活性表面态，主要成分为表面Zr原子 4d_(xz)/d_(yz)轨道；与理想表面相比，表面弛豫对该表面态影响不大。对于氢吸 附表面，计算结果表明氢原子倾向于吸附在表面孔洞上方位置（正对着第三层Zr原 子），此时H的1s态从体相的电子态中分离出来。此外，本文中H/ZrC（111）和 H/NbC（111）体系的H 1s诱导态变化进行了解释，并对清洁的吸附表面的芯能级位 移以及功函的变化进行了探讨。     

加压溶剂萃取和在线检测可吸入固体颗粒物(PM10)中16种多环芳烃

建立了微池加压溶剂萃取（μ-PLE）-气相色谱在线联用测定可吸入固体颗粒物（PM10）中多环芳烃的方法和装置。研究了萃取压力在5～20MPa、萃取温度在50—200℃、萃取时间在2-15min对μ-PLE萃取效率的影响。实验结果表明：方法的回收率在24．3％-63％之间；对标准样品的检出限为2．2-9．5μg／L；对实际样品的检出限在0．01—2．03ng/m^3之间；相对标准偏差（RSD）为1．6％-26．4％。通过对萃取池小型化，利用毛细管气相色谱大体积柱内进样技术，实现了两者的在线联用。将萃取液全部转移到气相色谱中，样品利用率达到80％以上，检出灵敏度比现有样品预处理方法提高100倍以上，可以监测大气颗粒中短时间化学变化的有机成分。     

A hydride generation atomic fluorescence spectrometric procedure for selenium determination after flow injection on-line co-precipitate preconcentration

A flow injection (FI) on-line preconcentration procedure for ultra-trace inorganic selenium was developed with detection by atomic fluorescence spectrometry. Selenium (IV) is co-precipitated with lanthanum hydroxide and collected on a PTFE beads packed column, the precipitate is afterwards dissolved with hydrochloric acid followed by hydride generation with reduction by tetrahydroborate. A thorough scrutiny was made for chemical variables and FI parameters. With a sampling volume of 3.4 ml, quantitative retention of selenium (IV) was obtained, along with an enrichment factor of 11 and a sampling frequency of 38 h^− 1. The detection limit, defined as 3 times the blank standard deviation (3σ), was 5 ng l^− 1. The precision was characterized by a RSD value of 1.2% (at the 0.5 μg l^− 1 level, n = 11). The enrichment factor was further enhanced to 20 along with a detection limit of 3 ng l^− 1, with a sample loading volume of 6.8 ml. The procedure was validated with certified reference materials and biological samples. It was also applied to the speciation of inorganic selenium in surface waters.     

On-line coupling of ion chromatography and atomic spectrometry and use of direct graphite furnace atomic absorption spectrometry as new tools for ultra trace determinations in refractory metals

On-line coupling of inductively coupled plasma (ICP) techniques such as ICP-AES and ICP-MS with ion chromatography (IC) offers unique features for ultra-trace analysis. An on-line preconcentration procedure based on cation exchange enables sub-ng/g analysis in complex matrices like molybdenum and tungsten. The best dissolution reagent for these matrices is hydrogen peroxide, which can be cleaned to ultra high purity with the same metal free chromatography equipment used for the preconcentration. Preconcentration is possible for elements that show cationic reactions within acidic peroxide containing solutions. In this study 28 elements detrimental for microelectronics applications are observed. A comparison of the combinations IC-ICP-AES and IC-ICP-MS with glow discharge mass spectrometry (GDMS) for the analysis of today's purest tungsten samples shows the analytical power and accuracy of the coupled devices. Graphite furnace atomic absorption spectrometry (GFAAS) as an extremely sensitive analytical technique is applied with and without the same sample pretreatment as used for the on-line coupling. Direct GFAAS measurements of alkali metals are complementary to IC-ICP techniques. The data evaluated with these wet chemical techniques are compared to the usual manufacturers characterisation technique GDMS. With respect to the low concentrations present in these high purity materials (ng/g level in the solid) the discrepancies between all methods are acceptable. The sensitivity of IC-ICP-MS is in most cases far superior to IC-ICP-AES and for some elements also to GDMS. Furthermore the specific advantages of on-line coupling such as the elimination of isobaric interferences in ICP-MS or spectral interferences in ICP-AES are shown for ICP-AES and ICP-MS determinations.     

Blood lead and cadmium determination: Results of the Italian external quality assessment scheme

The procedures adopted in the Italian external quality assessment scheme (EQAS) for blood Pb (B-Pb) and Cd (B-Cd) determination, including the preparation of control materials, are described. Each scheme involves the use of internal quality control materials and the participation in periodical external quality assessment trials. All control materials are prepared at the Laboratory of Clinical Biochemistry, Italian National Institute of Health (Istituto Superiore di Sanità, ISS), as the reference centre. Computerized procedures have been adopted whenever possible, i.e. sample randomization, data transfer and treatment. The analytical performance of the participating laboratories, evaluated from the results obtained in ten years of activity, is reported. A total of eight phases has been carried out between 1983 and 1993. Over the course of these ten years, a positive trend was observed for B-Pb towards a smaller bias and a lower percentage of laboratories with poor performance. In the eighth phase, taking into account the results from all participants, the mean absolute inaccuracy for B-Pb was 32 g/l (mean Pb concentration in control samples, 165 g/l). The percentage of laboratories providing results within established acceptability limits for at least 80% of the examined samples (good performers) increased with time from 28% in the first phase to 48% in the last phase. The laboratories providing less than 50% of acceptable results (poor performers) decreased from 35% in the first phase to 22% in the last phase. As regards B-Cd, mean absolute inaccuracy decreased from 0.96 g/l to 0.55 g/l between the first phase and the sixth phase. The percentage of good performers increased from 45% to 62% and that of poor performers decreased from 31% to 5%. From the seventh phase a large group of new laboratories agreed to participate in the EQAS for B-Cd and the inaccuracy rose to 0.75 g/l (mean concentration: 2.7 g/l) and the percentage of poor performers rose to 24%, whereas the percentage of good performers remained almost unchanged.     

High‐efficiency,electrophosphorescent polymers with porphyrin–platinum complexes in the conjugated backbone: Synthesis and device performance

A series of soluble, conjugated, electrophosphorescent copolymers with (meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II) (PtTPP) complexes incorporated into the polymer main chain were synthesized through the copolymerization of narrow‐band‐gap monomeric porphyrin–platinum(II) complexes and wide‐band‐gap dialkyl‐substituted fluorene monomers by a modified Suzuki coupling reaction. The study of the photoluminescence decay indicated that poly[2,7‐(9,9‐dioctylfluorene)‐co‐2,12‐((meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II))] (PFO–PtTPP) was a triplet emitter. The electroluminescence emission from the fluorene segment was completely quenched for copolymers with PtTPP contents as low as 0.5 mol %. The PFO–PtTPP copolymers emitted deep red light. The device based on the porphyrin–platinum(II) copolymer PFO–5PtTPP (with 5 mol % PtTPP in the copolymer) showed the highest external quantum efficiency of 1.95% with an emission peak at 684 nm in an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polyvinylcarbazole (PVK)/70:30 (w/w) PFO–5PtTPP: 2‐(biphenyl‐4‐yl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole/Ba/Al device configuration. In comparison with the PFO–PtTPP copolymers synthesized via a postpolymerization metalation route, copolymerization from Pt metal complexes proved to be a more efficient synthetic route for high‐efficiency electrophosphorescent polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4174–4186, 2006     

局内状态下的进货管理问题及其竞争分析

局内进货管理问题是指在未来商品的需求不确定,对未来不作预测的情况下如何决策什么时候及购进多少货物的问题.如果我们用πOPTD表示局外问题的最优解,πAD表示局内算法A的最优解,那么竞争比可以表示为sup（πOPTD/πAD）,其中D表示任意的需求序列.决策者的目标是使得竞争比尽可能的最小.本文首先建立了一个简化的局内库存管理模型,在知道M和m（未来需求最大值和最小值）基础上设计了两种局内策略FNA和PDBA.讨论并证明了对于固定购买数量的竞争策略,我们给出的FNA策略具有最优的竞争比.而后分析了策略PDBA在需求满足各种不同情况下的竞争比.