Measurement uncertainty is a non-negative parameter that characterizes the dispersion of the quantity values attributed to a measurand, based on the information used. This work outlines top-down ...evaluations of the measurement uncertainty in the analysis of pesticide residues by using precision and bias data. Since 2009, a European Standard for vegetable products has been issued which describes a multi-method for the analysis of pesticide residues in foods of plant origin such as fruits, vegetables and cereals. This method makes testing for hundreds of compounds quick and easy in a single extraction, but technical difficulties nevertheless have arisen in the highly polar pesticides in these specific cases; methods suitable for single pesticide residues are used. Consequently, we defined a workflow to estimate measurement uncertainty depending on method type selection. The calculation of individual Measurement Uncertainty (MU) may not always be possible for multi-residue method; then, an alternative approach was applied to estimate a generic MU using data from different proficiency tests selected for the three main product groups (fruit, vegetable and cereal) in combination with intra-laboratory precision. This approach shows a limitation due to the minimum number of proficiency test results that prevents their effective implementation in single residue methods. Therefore, a specific approach based on internal laboratory quality control for individual pesticides in a specific family group of products on real samples was applied to estimate the Measurement Uncertainty. The Flonicamid residue in vegetable products was the selected case study for the Single Residue Method.
The objective of this study consists of being able to develop a precise, reliable, easy, cheap and quick method to identify and quantify the presence of pesticide metabolites and their parents in ...human urine. In order to reach our purpose we selected the pesticides and their metabolites with intended uses on permanent crops such as orchards and vineyard. The activity planning started with the identification of the target list carried out by UHPLC-MS/MS and GC-MS/MS, succeeded by several tests oriented to determine the best sample treatment having recourse to instrumental analysis in the range 5-100 ng/mL. Several purifications were also investigated combining different adsorbents (PSA, EMR-lipid and final polish pouch). The use of formic acid during the extraction step has no impact on the recoveries, whereas the PSA adsorbent in the cleanup step negatively affects the results for all investigated metabolites. Any substantial differences were not observed in urine matrix for parent compounds achieving recoveries higher than 80% and RSD less than 20%. The final polish in combination or not with Enhanced Matrix Removal EMR-lipid did not show statistically significant difference in term of trueness and precision for both metabolites and parents, as evaluated by one-way ANOVA. The 3-OH THPI was the most critical compound with not acceptable results for linearity, trueness and precision.
The present paper describes a case of shoe contact dermatitis from DMF identified by the Poison Control Centre of Milan (PCCM), Italy, in 2009. A 35 year old woman was affected by irritant reactions ...while wearing shoes contaminated with DMF. Exposure to these shoes was limited to a 8 hour period and was not repeated. In the following days the patient suffered feet blistering and swelling limited to the area in contact with shoe vamp. Topical application of cortisone did not prevent development of bullous eczema. After 20 days from exposure, the lesions were healed but the skin remained red, dry and very sensitive. Chemical analyses of shoes quantified an average concentration of DMF of 383 mg/kg. The patient refused to be patch tested. The observation here reported confirm that DMF should be considered a possible causal agent in shoe contact dermatitis. Documentation of cases exposed to this chemical provide a relevant support to characterize clinical manifestations and to identifying contaminated articles.
The data reported in the frame of proficiency testing (PT) exercises organized from 2007 to 2016 have been statistically re-evaluated using Algorithm A of the ISO 13528:2015, and the relative ...standard deviation for reproducibility of multi-residue methods for the determination of pesticides in olive oil was evaluated. Usually, the assigned between-laboratories variability in PTs on pesticide residues is fixed/set to 25 %. This value was compared to the calculated robust relative standard deviation (RRSD). A total of 1527 analytical results were collected in the ten PTs for the determination of pesticides in olive oil. An RRSD of 21 % was obtained, below the maximum value of 25 %. If all participants use the same analytical approach (e.g., multi-residue method and same instrumental technique), a lower value of the reproducibility standard deviation should be expecting. The QuEChERS method, coupled with LC–MS/MS and GC–MS/MS, has become an important methodology for the analysis of pesticide residues. This is due to its simplicity, the use of low quantities of acetonitrile, the possibility to analyze a large number of pesticides with fewer steps and high efficiency. This method may harmonize the future of pesticide residue analyses. Recently, it was successfully applied to the analysis of olive oil by 70 % of the laboratories participating to our last PT exercise. An expanded uncertainty of 50 % was systematically applied in Europe since 2006 for the analyses of pesticides; the use of the QuEChERS methodology may reduce to 40 %. This work could contribute to promote the comparability of measurements of pesticide residues in foodstuffs.
The Italian National Reference Laboratory (NRL) for pesticide residues yearly organizes proficiency tests (PTs) on olive oil in cooperation with the International Olive Council, addressed to European ...laboratories (NRLs, official control laboratories, and private laboratories), involved in the National and European monitoring programs. The main aim of these PTs is to compare the performances of the laboratories in Mediterranean and European countries and to promote mutual acceptance of pesticide residue data regarding the analytical controls of olive oil. In this paper, a description of the last PT named COIPT-16 is presented. The test material consisted of a commercial olive oil spiked with six different pesticides. The assigned value of each analyte was determined as a consensus value based on the results of the participants calculated using Algorithm A of the ISO 13528:2015. As relative target standard deviation in the
z
score formula, the 25 % of the robust mean value was considered. The global performance of each participating laboratory was assessed by calculating the average of the squared
z
scores only for laboratories that have detected at least 80 % of the analytes present in sample achieving the sufficient scope as indicated in the initial protocol. Two compounds, alpha-endosulfan and beta-endosulfan have been analyzed again in this PTas in the previous PT to compare the performances of the laboratories whose supplied results both PTs. The quick, easy, cheap, effective, rugged, and safe methodology was used by the majority of laboratories corresponding to 64 % of participants.
A multiresidue method was developed and optimized for the identification/quantification of organochlorine pesticides (OCPs) and pyrethroids (PYRs) in beef meat samples. Samples extraction was ...performed by an automated solvent extractor and the extracts were cleaned-up by a tandem-cartridge system consisting of an Extrelut NT3 combined with a Sep-Pack C18 cartridge and a florisil minicartridge. Analysis was finally carried out by gas chromatography coupled with quadrupole mass spectrometry (GC/MS). The performance of the method was investigated in terms of linearity, accuracy, precision, detection limit (LOD) and quantification limit (LOQ). Good linearity was obtained, with correlation coefficients (r
2
) higher than 0.98. Mean recoveries were found in the ranges 70-110 % and 84-99 % for the investigated OCPs and PYRs, respectively, with the exception of extremely volatile hexachlorobenzene (HCB). RSD% turned out to range from 2 to 15 %. LOQ values were in the range 0.005-0.1 mg/kg for either class of compounds. The method developed was successfully tested on 50 commercial beef meat samples from the market area of Rome (Italy), proving to be a useful tool in routine multiresidue analysis of OCPs and PYRs for monitoring purposes. None of the compounds of interest were observed above their respective LOQ.
The Italian National Reference Laboratory (NRL) for pesticides in Food of Animal Origin and Commodities with High Fat Content yearly organizes proficiency tests (PTs) on olive oil, addressed to: ...Mediterranean laboratories of International Olive Council, European laboratories (NRLs, official control laboratories and private laboratories), involved in the national and European monitoring programs. The main aim of these PTs was to compare the performances of the laboratories in Mediterranean and European countries in order to promote mutual acceptance of pesticide residue data regarding the analytical controls of olive oil. Since 2011, the protocol of the last three PTs has not been changed and also the list of participants has been steady, in the range of 40–44 laboratories. The test material consisted of commercial olive oil spiked with six different pesticides chosen in each exercise from a possible list of 25–26 compounds. In particular, the pesticide residues selected in our PTs are mainly those considered in the official control plans, with spiked mass fraction levels around their reference values set in the European Regulations. Pertinent and detailed information regarding multi-residue methods has been demanded to all participants, and an overall evaluation by means of a combined index of performance, such as the sum of the weighted
z
-scores,
SWZ
, and the sum of squared
z
-scores,
SZ
2
, has been performed. This type of exercise provides the possibility for the laboratories to control and improve the performance of their analytical methods employed during the official control on more parameters over the years. In this paper, a comparison of the overall performance of the laboratories was shown by using the
SWZ
or
SZ
2
indexes, giving significance to the Italian participants as required by the NRL aim. During the three investigated COIPTs, 91 % of the laboratories obtained satisfactory results with
SWZ
or
SZ
2
not exceeding 3. Focusing on the results of Italian laboratories, the performance improved during the selected PTs, respectively, from 70 % to 100 %. Moreover, the effect of the analytical methods on the dispersion of the results was evaluated in order to review the long-term performance of the participants.
A simple and rapid method has been studied for the determination of acidic herbicides (2,4-D, Dichlorprop, Dichlorprop-p, Fluazifop, Fluroxypyr, MCPA, Mecoprop and Mecoprop-p) on cereals (rye). The ...method involves an alkaline hydrolysis with sodium hydroxide in order to release covalently bound compounds, prior to QuEChERS extraction, followed by neutralization and analysis via liquid chromatography-double mass spectrometry LC/MS/MS. The performance of the method either with or without alkaline hydrolysis was studied in terms of recovery rates and limit of quantification (LOQ). In either case, recoveries were determined at four spiking levels (0.02 mg/kg, 0.05 mg/kg, 0.1 mg/kg and 0.5 mg/kg) with 5 replicates for each level. Mean recoveries ranged from 90 to 120 %, whereas relative standard deviations (RSD %) proved to be less than 20 %. Quantitative analysis was carried out by the internal standard (Nicarbazin) and the LC/MS/MS analysis was performed in electrospray ionisation (ESI) negative mode using a Zorbax XCB Eclipse column. The developed method was applied to the analysis of several cereals commercially available like as rye flour, oat meal, oat flakes and dehusked oat. Residue levels were found below the limit of quantification (LOQ) of the method. The method has been tested in EU Proficiency Tests for cereals with good results.
The implementation of the internal quality assurance program allows for demonstration of the performance characteristics of a method, as well as the avoidance of erroneous results. There is ...increasing concern in testing laboratories to ensure that the analytical process remains stable, giving reliable results under statistical control. Robustness is tested by introducing variations in experimental conditions and examining the effects on the results. The European document SANCO/12495/2011, “Method validation and quality control procedures for pesticide residue analysis in food and feed”, defines robustness as a parameter that can be derived from ongoing method verification. Internal quality control tools, such as the recovery control chart, were employed in this study to enhance the stability of the recovery rates and to investigate the experimental conditions that have a major influence on the quantification of recovery rates. The method investigated in this study permitted us to investigate eighteen pesticides in olive oil by using a gas chromatography–mass spectrometry technique. This method has been accredited to ISO/IEC 17025:2005 standards and was applied for 1 year in routine conditions for pesticide residues at the Italian National Reference Laboratory. The recovery control chart has showed that all recovery rates for 1 year were close to the maximum limit (120 %) of recovery performance criteria. Consequently, a “positive” bias has affected all data over longer periods of time. A robustness test was planned in order to investigate the grounds that most influenced the variability of the results. The robustness test involved the following three parameters: solvent used to dissolve the final extract, internal standards, and type of olive oil.
The aim of this study was to highlight the need to extend the lifetime of stock standard solutions employed for the analysis of pesticide residues with respect to the quality control standards in ...use. The importance of this survey concerns the possibility to extend the solution lifetime up to year when the standard solutions are stored in refrigerator at 4 °C. In order to allocate a solution lifetime up to year, the guideline document SANCO/12571/2013 was followed. During the time 2010–2013, the stability data were collected for 82 different active substances from the Italian National Reference Laboratory (NRL) for pesticide residues, accredited to the ISO/IEC 17025. A statistical analysis was performed on the overall data. Some aspects have been monitored such as the solvent and detection method used, the relative standard deviations (RSDs) of the mean responses of the old and fresh stock solutions investigated, the percentage difference of the mean responses of the old and fresh stock solutions, and finally the uncertainty measurement of the standard preparation.
