Interlaboratory studies of the determination of selected chlorobiphenyl congeners with capillary gas chromatography using splitless- and on-column injection techniques

The Community Bureau of Reference has organized a collaborative interlaboratory project to improve the analytical protocol for some specific chlorobiphenyls (CBs) within the European Community (EC). A series of test procedures were prescribed to optimize the gas chromatographic conditions for splitless and on-column injection, which substantially improved the quality of data. Important parameters included the initial column and injector temperatures and the choice of the polarity of the stationary phase. In a study with cleaned eel-fat extracts, coefficients of variation for reproducibility CV(R) ranging from 11 to 24% at the 0.04–0.3 mg/kg level per CB congener were obtained. No significant difference could be found between splitless- and on-column injection.     

The application of isotope dilution thermal ionization mass spectrometry to traceability of chemical measurement and interlaboratory comparisons

In this work, the method of isotope dilution thermal ionization mass spectrometry able to trace to SI was developed to accurately measure trace amount of Cd, Pb, Zn and Cu in sediment, rice, wine, and human serum samples for interlaboratory comparisons. The research focuses on how to apply the primary method correctly, uncertainty evaluation of measurement results, and how to achieve the meaning of traceability to SI by using ID-TIMS. As a result, the measurement results of Cu and Zn in the human serum 1 and 2 with 0.94, 0.83 and 0.49% combined uncertainty, respectively, were accepted by EC-JRC-IRMM as the certified values of the serum samples. The measurement results of Cd and Pb in CCQM-K13 and CCQM-K24 with 3.96, 1.62 and 1.03% combined uncertainty, respectively, are within the degrees of the equivalence. These comparisons at the highest level of measurement are proof that traceability of chemical measurement can be achieved as the traceability chain of ID-TIMS established in this work was used.     

有序处理连续比较的置信区间

为有序均值的连续比较提出了一个新的检验过程.他们的过程对满足简单序的均值有重要的应用价值,例如在研究增长剂量对药物效用的影响. 与其它检验过程相比(例:Hayter\ucite{4}中的检验), 其优点在于产生了更短的连续比较的置信限,从而能够提供更多机会发现在何药剂量处有不同的效用.但作为有序均值的齐性检验, 它的势表现远劣于其它检验.本文的目的是提出一检验过程在尽量保持Lee andSpurrier\ucite{8}检验的优点的同时大大地提高其势表现.     

The sixth meeting of CCQM, April 2000

A report is given of the sixth meeting of the Consultative Committee on Amount of Substance (CCQM). The CCQM has been active since 1993. It is the committee, established by the Comite International des Poids et Mesures, which is responsible for issues regarding metrology in chemistry. It has four established working groups in the fields of organic analysis, inorganic analysis, gas analysis and electrochemical analysis. A further twoad hoc working groups in the fields of surface analysis and metrology in biotechnology were established during the meeting. The working groups are involved in the identification, development and execution of a series of key comparisons, which will establish the technical basis for the mutual recognition of measurement capabilities among the National Measurement Institutes. 17 key comparisons are currently planned for the period 1999–2002, with 29 other international comparisons planned for the same period.     

Comparison of Integration Vs. Fixed-Time Methods For Kinetic Analyses

Abstract

Results for an integration method of enzymatic analysis are directly compared to concurrently-achieved fixed-time rate data. Two to fiftyfold enhancement of signal-to-noise ratios are obtained for the integration method vs. the fixed-time method for theoretically-calculated response vs. time data. the signal-to-noise ratio improves substantially as the number of increments increases for estimating the integral of changes in product concentration over time. Also, advantages of the integration method are enchanced as enzyme activities increase and as instrument noise decreases.     

Worldwide interlaboratory study on the determination of ochratoxin A in different wine type samples

Interlaboratory studies are decisive tools to help the validation of a specific analytical methodology or to assess the reproducibility of the use of different methods to analyze a given compound or compounds in certain sample matrices. In this work, homogeneous samples of two white wines (“White Wine” and “White Liqueur Wine”) and one red wine (“Red Fortified Wine”) from Portugal with different production techniques and characteristics, namely in alcohol strength (10.5%, 16.0% and 19.0% ethanolic content, respectively), were analyzed for their contents in ochratoxin A (OTA), a mycotoxin generated from fungal contamination. White Liqueur Wine was naturally contaminated, whereas the other two wine type were spiked with ethanolic OTA solutions. The participation of 24 laboratories from 17 countries of five continents was ensured for this study. Although with no restrictions in terms of analytical methodology to employ, 75% of the laboratories resorted to immunoaffinity columns clean-up followed by high performance liquid chromatography with fluorescence detection (HPLC-FD), most of them in accordance with the European Standard EN 14133. For White Wine samples, the general mean OTA concentration was 1.96 μg/l (two outliers) with interlaboratorial standard deviation (s_L) of 0.53 μg/l; for White Liqueur Wine, mean of 1.59 μg/l (one outlier), with s_L = 0.59 μg/l; and for Red Fortified Wine, mean of 2.73 μg/l (no outliers), with s_L = 0.96 μg/l. Outliers were determined by Cochran and Grubbs tests. The Horrat index, recommended by the Association of Official Analytical Chemists (AOAC) for the quality assurance of the collaborative study was, on average, 1.7. This study proved that OTA determination in wines is reproducible, regardless of the methodology employed.     

环境声质量分类评价体系的实验研究

本文针对我们已提出的环境声质量分类评价体系及与之相应的定量评价指标ESQ，进行了实验验证。研究结果表明：所提分类评价体系和ESQ是有效的，二者的评价结果是一致的。最后，针对整个实验研究过程进行了讨论，并指出有待进一步研究和改善的方面。     

Determination of hydrocarbons in water – interlaboratory method validation before routine monitoring

The clarification of hydrocarbon input into the Baltic sea via rivers is one of the priority issues of the 4th Pollution Load Compilation (PLC-4) within the framework of international Baltic Sea marine monitoring. An interlaboratory comparison was conducted to check the applicability of a new method for the determination of hydrocarbons by solvent extraction and gas chromatography. Surrogate oil solutions with known hydrocarbon content were distributed among the participants for preparation of water samples of different hydrocarbon concentration. In using these concentrations as assigned values and by setting target values for precision, the proficiency of participating laboratories could be tested as a qualifying step before involvement in PLC-4 routine monitoring. The results of the exercise indicate that hydrocarbons in water samples can be monitored as a mandatory test item within the framework of PLC-4. Received: 31 October 2000 Accepted: 3 January 2001     

Conjugate natural convection from an array of discrete heat sources: part 1 — two- and three-dimensional model validation

Two- and three-dimensional (2- and 3-D) numerical models have been developed for conjugate natural convection in a discretely heated cavity. Experimental results obtained for the same geometry, using water and FC-77 as the coolants, were in excellent agreement with the 3-D numerical predictions. In contrast, because of the inability to account for thermal spreading in the lateral direction, the 2-D model overpredicted measured average surface temperatures of the discrete heat sources. However, the 2-D model still predicted general trends and flow patterns that were experimentally obtained. The nature and extent of 3-D effects on the flow and heat transfer have been delineated.