Pesticides reference materials

The pesticides spiking solution for RM15 was prepared using pesticides reference materials (Pestanal ) from Riedel de Haen in form of neat crystals (apart from chlor-fenvinphos which is liquid). Stock solutions were properly diluted with acetonitrile to the final concentrations. The stock solution for simazine was prepared in methanol. 

Office of Standard Reference Materials, National Bureau of Standards, Gaithersburg, MD 20899. "Nitrated PAH s do not fluoresce but can be made to fluoresce by passing through a Zn or Pt column to reduce nitro groups to amino groups. Information values for other organics in certificate. Certified values for pesticides and PCB s. 

Schantz MM, Koster BJ, Oakley LM, Schiller SB, and Wise SA (1995b) Certification of polychlorinated biphenyl congeners and chlorinated pesticides in a whale blubber standard reference material. Anal Chem 67 901-910. 

DE Boer J (1997) The preparation of biological reference materials for use in interlaboratory studies on the analysis of chlorobiphenyls, organochlorine pesticides and trace metals. Mar Poll Bull 35 84-92. 

Many pesticides are neurotoxicants poisoning the nervous system. A number of pesticides are acetyl cholinesterase inhibitors (Serat and Mengle 1973). Generally, pesticides determination has been performed by GC since the 1960 s (Morrison and Durham 1971 Fournier et al. 1978). There are no reference materials for pesticides in urine or serum, although as with PAHs there are a number biological matrices certified for the content of various pesticides available for environmental food and agriculture analysis and which may have some application in clinical chemistry. 

This validation typically requires samples with radiolabeled analytes. However, alternative approaches are proposed which involve (i) comparison with extraction of samples using a procedure which has been previously validated rigorously, (ii) comparison with extraction of samples by a very different technique or (iii) analysis of a certified reference material. Generally, this validation should be performed with samples containing analyte incurred by the route by which residues would normally be expected to arise. The simplest option (i) requires fully validated and documented enforcement methods provided by the manufacturer of a pesticide. 

In contrast to many other validation protocols, the description of the NMKL validation process starts with the protocol of planned validation. This protocol should include, e.g., the needs of the client, available equipment, the chemical form in which the analyte occurs (i.e., in pesticide analysis the residue definition), matrix types, the availability of reference materials and the working range. Consequently, an extra paragraph is dedicated to the requirements for the documentation of validation results, which refers to the rules in Section 5.4.4 of EN 45001 (amended by ISO 17025). 

Quantification is usually achieved by a standard addition method, use of labeled internal standards, and/or external calibration curves. In order to allow for matrix interferences the most reliable method for a correct quantitation of the analytes is the isotope dilution method, which takes into account intrinsic matrix responses, using a deuterated internal standard or carbon-13-labeled internal standard with the same chemistry as the pesticide being analyzed (i.e., d-5 atrazine for atrazine analysis). Quality analytical parameters are usually achieved by participation in interlaboratory exercises and/or the analysis of certified reference materials [21]. 

In this paper, the supercritical fluid extraction (SFE) of organic compounds from sand spiked with 36 nitroaromatic compounds, 19 haloethers, and 42 organochlorine pesticides, and from a standard reference material certified for 13 polynuclear aromatic hydrocarbons (PAH), dibenzofuran, and pentachlorophenol was examined using a two- and a four-vessel extractor. Although the results achieved by SFE for the sand and the standard reference soil samples were very encouraging, previous data obtained in our laboratory on the standard reference soil and a few other standard reference marine sediments were less favorable. It was therefore decided that an investigation of seven variables for their influence on the analyte recoveries from the standard soil sample would be useful. Two tests were conducted in which these variables were investigated. In Test 1, the seven variables selected were pressure, temperature, moisture content, cell volume, sample size, extraction time, and modifier volume. In Test 2, the seven variables were pressure, temperature, volume of toluene added to the matrix, volume of solvent in the collection vessel,... 

Lopez-Avila et al. [8] published a study in 1993 that evaluated the Soxtec extraction of 29 target compounds (seven nitroaromatic compounds, three haloethers, seven chlorinated hydrocarbons, and 12 organochlorine pesticides) from spiked sandy clay loam and clay loam. Among the five factors investigated (matrix type, spike level, anhydrous sodium sulfate addition, total extraction time, and immersion/extraction time ratio), matrix type, spike level, and total extraction time had the most pronounced effects on method performance at the 5% significance level for 16 of the 29 target compounds. The two solvent mixtures, hexane-acetone (1 1) and methylene chloride-acetone (1 1), performed equally well. Four compounds were not recovered at all, and apparently were lost from the spike matrix. Limited experimental work was performed with 64 base-neutral-acidic compounds spiked onto clay loam, and with three standard reference materials certified... 

Wong, C.S. Hoekstra, P.E Karlsson, H. Backus, S.M. Mabury, S.A. Muir, D.C.G., Enantiomer fractions of chiral organochlorine pesticides and polychlorinated biphenyls in Standard and Certified Reference Materials Chemosphere 2002, 49, 1339-1347. 

Along with the matrix RMs, a series of other quality control tools such as calibrants and standard solutions was also produced. On the occasion of the first set of reference materials, calibrants for trace elements and major components were also prepared and sent to the laboratories in order to minimize the differences in results produced by the use of different calibrants. For the other two sets of materials, multi component standard solutions for PAHs and pesticides were prepared and distributed in order to check the analytical performance of the chromatographic methods used. 

The results obtained within the SWIFT-WFD project, dealing with the preparation of water reference materials, will contribute to the future developments of such materials, especially for the analysis of pesticides and PAHs at low concentration levels. The two different strategies employed, direct fortification in the laboratory by using spiking solutions following detailed protocols, and fortification of the material before dispatch, led to homogeneous and satisfactory stable reference materials for quality control purposes. 

Schantz MM, Parris RM, Kurz J, et al. 1993a. Comparison of methods for the gas-chromatographic determination of PCB congeners and chlorinated pesticides in marine reference materials. Eresenius J Anal Chem 346(6-9) 766-778. 

Martm-Esteban, A., Fernandez, P., Camara, C., Kramer, G. N., and Maier, E. A., The preparation of a Certified Reference Material of polar pesticides in freeze-dried water (CRM-606), Fresenius J. Anal. Chem., 363, 632-640, 1999. 

Method performance in air analysis involves terms such as accuracy, storage stability, capacity, sampling rate, recovery, and sensitivity. To evaluate the performance of a developed method, certified reference materials for particulate matter, such as urban dust SRM 1649a particulate matter from NIST (Gaithersburg, MD, USA) can be purchased. In addition, a standard reference material has been recently developed for the determination of organic compounds in house dust the SRM 2585 is intended for using in method validation for the analysis of PAHs, PCBs, chlorinated pesticides, and PBDEs (Poster et al. 2007). 

Surrogate recovery standards are added to each sample at the extraction step to monitor the performance of the extraction and cleannp steps. PCBs 30 and 204 are often used because they are not present in commercial PCB mixtnres. For samples to be analysed by mass spectrometry, these surrogates are usually deuterated (PAHs) or C labelled (most OC pesticides. PCDD/Fs and PCB congeners). Sample batches (6-12 samples) should include a blank (aU reagents except sediment) and a certified reference material. Soxhlet extraction times vary widely but relatively long contact times i.e., >6 hrs are generally used. For OC pesticides and PCBs, most laboratories use dichloromethane or acetone hexane. For PCDD/Fs, which are sparingly soluble in DCM, toluene is recommended as the extraction solvent for sediment either by itself or as a second extraction (Oehme et al., 1993). 

See also-. Extraction Solvent Extraction Principles. Pesticides. Quaiity Assurance Quality Control Reference Materials. Sampling Theory. Water Analysis Overview. 

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