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OPCW Proficiency Test: a practical approach also for interlaboratory test on detection and identification of pesticides in environmental matrices.

ABSTRACT: An overview of general strategy, standard procedures, and critical points, which may be found during carrying out an OPCW Proficiency Test concerning detection and identification of scheduled compounds relevant to Chemical Weapon Convention, has been presented. The observations have been illustrated following the case of the Eight OPCW Designated Laboratories Proficiency Test, which was performed in the OPCW Laboratory in Rijswijk in November and December 2000. Various useful hints, comments, and practical observations concerning the case study have been included as well. The same methodology and procedures may be also applied for detection, identification, and environmental analyses of pesticides and biocides, especially organophosphorus compounds.

SUBMITTER: Konopski L

PROVIDER: S-EPMC3919092 | biostudies-other | 2014

REPOSITORIES: biostudies-other

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Project description:Carbon nanotube (CNT) production is rapidly growing, and there is a need for robust analytical methods to quantify CNTs at environmentally relevant concentrations in complex organic matrices. Because physical and thermal properties vary among different types of CNTs, we studied 14 single-walled (SWCNTs) and multiwalled CNTs (MWCNTs). Our aim was to apply a classic analytical air pollution method for separating organic (OC) and elemental carbon (EC) (thermal optical transmittance/reflectance, TOT/R) to environmental and biological matrices and CNTs. The TOT/R method required significant modification for this analysis, which required a better understanding of the thermal properties of CNTs. An evaluation of the thermal properties of CNTs revealed two classes that could be differentiated using Raman spectroscopy: thermally "weak" and "strong." Using the programmed thermal analysis (PTA) method, we optimized temperature programs and instituted a set of rules for defining the separation of OC and EC to quantify a broad range of CNTs. The combined Raman/PTA method was demonstrated using two environmentally relevant matrices (cyanobacteria (CB) and urban air). Thermal evaluation of CB revealed it to be a complex matrix with interference occurring for both weak and strong CNTs, and thus a pretreatment method was necessary. Strong CNT masses of 0.51, 2.7, and 11 ?g, corresponding to concentrations of 10, 54, and 220 ?g CNT/g CB, yielded recoveries of 160 ± 29%, 99 ± 1.9%, and 96 ± 3.0%, respectively. Urban air was also a complex matrix and contained a significant amount (12%) of background EC that interfered greatly with weak CNTs and minimally with strong CNTs. The current detection limit at 99% confidence for urban air samples and strong CNTs is 55 ng/m(3) (0.33 ?g). Overall, the PTA method presented here provides an initial approach for quantifying a wide range of CNTs, and we identify specific future research needs to eliminate potential interferences and lower detection limits.

Project description:BackgroundProficiency testing (PT) is a tool for ensuring the validity of results of testing laboratories and is essential when laboratories are working with assays authorised for emergency use or implementing novel techniques for detecting emerging pathogens.MethodsIn collaboration with the National Health Institute of Colombia and with international support, we developed a qualitative PT for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by reverse transcription polymerase chain reaction (RT-PCR). A proficiency test item (PTI) based on reference material (research grade) produced by the National Institute of Standards and Technologies (NIST) was prepared and characterised using three positive samples with varying concentrations of SARS-CoV-2 ribonucleic acid (RNA) and two negative (control) samples. Tests were distributed to 121 laboratories across the national network of public health laboratories in Colombia.ResultsPositive samples had varying concentrations of SARS-CoV-2 RNA and were quantified by digital PCR (RT-ddPCR) assays for the E gene of SARS-CoV-2. We tested the ability of laboratories to detect low and high levels of viral RNA using samples with SARS-CoV-2 RNA concentrations of 1417 ± 216, 146 ± 28, and 14 ± 10 copies /uL (expanded uncertainty, k = 2, 95% confidence level) We also performed a semiquantitative analysis of instrumental responses (Ct values) reported by participating laboratories and homogeneity, stability, and characterisation studies of the produced materials to determine the adequacy of these materials and methods for use in the qualitative PT scheme. The PT evaluated reports for individual target genes from each laboratory; 98.3% of laboratories had satisfactory performance and the remaining 1.7% of laboratories had unsatisfactory performance for the detection of at least one of the reported genes.ConclusionsThis PT scheme identified the potential metrological weaknesses of laboratories in the detection of SARS-CoV-2 by RT-PCR and may facilitate improvements in the quality of measurements from the perspective of public health surveillance.

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OPCW Proficiency Test: a practical approach also for interlaboratory test on detection and identification of pesticides in environmental matrices.

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