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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.12, #7)
Development of a validated method for the simultaneous determination of amphetamine, methamphetamine and methylenedioxyamphetamines (MDA, MDMA, MDEA) in serum by GC-MS after derivatisation with perfluorooctanoyl chloride by Folker Westphal; Cornelia Franzelius; Jon Schäfer; Hans Werner Schütz; Gertrud Rochholz (pp. 335-342).
A rapid and simple method for the simultaneous detection and quantitation of amphetamine, methamphetamine, methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA) and methylenedioxyethylamphetamine (MDEA) in human serum was developed and fully validated. Serum samples were extracted with cyclohexane, derivatised with perfluorooctanoyl chloride without prior evaporation of the solvent and analysed with gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode (SIM). For quantitation, deuterated analogues were used as the internal standards. The limit of detection (LOD) and lower limit of quantitation (LLOQ), bias and within-day and between-day precision were determined. LODs calculated as the average of the six calibration curves were below 5 ng/mL for all of the measured compounds; LLOQs obtained in the same manner were below 20 ng/mL, with the exception of MDA (24.1 ng/mL). The coefficients of variation were below 7% within series, 10% or less between series and the bias was below 8% for all compounds. The calibration curves were linear between the lower limits of quantitation and 800 ng/mL.
Keywords: Amphetamines; Methylenedioxyamphetamines; GC-MS; Quantitation; PFOC-derivatisation after LLE
Preparation and characterization of a proficiency test material “Polish mushrooms” supported by the International Atomic Energy Agency (IAEA), Vienna by Halina Polkowska-Motrenko; Matthias Rossbach (pp. 343-350).
Mushroom reference material has been prepared and characterized for use in proficiency test exercises within the frame of an IAEA Interregional Technical Cooperation Project. Laboratories from 14 countries provided results for homogeneity testing and the assignment of property values. The contents of 11 elements have been assigned. The material was used for conducting a proficiency test in Poland and the results obtained by Polish laboratories are presented and discussed.
Keywords: Mushroom reference materials; Proficiency testing; Test material preparation; Homogeneity; Assignment of property values
Novel method for bulk resistance evaluation in conductivity measurement for high-purity water by Song Xiaoping; Petra Spitzer; Uwe Sudmeier (pp. 351-355).
A major issue with the electrolytic conductivity measurement for pure water is the lack of standard or reference methods. A primary method traceable to SI and suitable for pure-water conductivity measurement was developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, as the base for the calibration method for the conductivity measuring devices at the low conductivity level. This paper provides a novel method to calculate the bulk resistance of pure water using impedance measured at a single frequency, which is one of the key procedures for the primary methods.
Keywords: Electrolytic conductivity; Pure water; Bulk resistance; Equivalent circuit
Uncertainty of the result of TOC determination in water samples by Brigita Tepuš; Marjana Simonič (pp. 357-364).
It is becoming increasingly important to have a reliable and rapid technique for determining total organic carbon (TOC) in wastewater as procedures for wastewater purification could be better applied by knowing the amount of TOC in the wastewater. We describe here an evaluation of the uncertainties associated with TOC determinations in wastewater. TOC was determined by combustion and an infrared (IR) detection method, as described in the standard procedures of the International Organization for Standardization (1999; no. 8245). The major sources of uncertainty in the measurements were identified as being contributions from the linear least square calibration, repeatability, recovery and stability of the sample (storage conditions). A 10% relative expanded uncertainty of TOC measurement in the range of 0.2 to 500 mg L−1 TOC was calculated, which also includes the uncertainty due to sampling.
Keywords: Measurement uncertainty; Sampling; TOC
A new approach in assessing microbiological results in water analysis proficiency testing by H. R. Veenendaal; P. M. van Berkel; G. de Jong; P. K. Baggelaar (pp. 365-368).
Due to the relatively large spread in the results of microbiological proficiency tests, the z-scores are often not able to detect zero or low results as being ‘bad’ results. This paper describes an adapted z-score based on the average or the standard deviation of the 50% ‘highest’ results. The combination of the adapted z-scores of four samples enables a better judgement of the performance of each laboratory.
Keywords: Proficiency testing; Microbiology; z-scores
Internal quality control and ISO 15189
by Xavier Fuentes-Arderiu; Joan Batista-Castellví; Francesca Canalias; Dolors Dot-Bach; Mariano Martínez-Casademont; Jaume Miró-Balagué (pp. 369-375).
Uncertainty from sampling: workshop to launch a Nordtest handbook on sampling uncertainty estimation and control by Jette Bjerre Hansen; Christian Grøn; Ulla Lund; Bertil Magnusson; Astrid Nordbotten; Anke Oberender; Michael H. Ramsey (pp. 377-381).
A workshop on uncertainty in sampling was held in Hillerød, Denmark, on 12–13 April 2007 to launch a new handbook on sampling quality assurance and uncertainty estimation. The participants of the workshop were approximately 60 delegates from 15 European countries, representing institutions performing sampling, users of the data, research institutions, as well as accreditation bodies. Materials from the workshop, including examples, tools, and calculation aids for the work can be found at http://www.samplersguide.com . The Nordtest handbook Uncertainty from sampling will be made available on the Nordtest web site at http://www.nordicinnovation.net/nordtest.cfm under NT technical reports, report number NT tec 604. Until the final report is available on the Nordtest web site, an advance draft of the Nordtest handbook is available from http://www.samplersguide.com .
Keywords: Uncertainty; Quality assurance; Sampling; Nordtest
International Laboratory Accreditation Cooperation (ILAC) Update
by Alan Squirrel; Annette Dever (pp. 383-385).