Evaluation of flame retardancy and flexural property on prepared plastic disks containing known concentrations of flame retardants through simulated weathering tests.

The standardized acrylonitrile-butadiene-styrene (ABS) or polycarbonate (PC) resin disk with added flame retardants (FRs) has a potential to be a suitable tool for predictions of both aging of the plastic materials and release rate of a flame retardants exposed under different outdoor and indoor conditions. The experiments examined the dynamics and kinetics of the release of dechlorane plus, tetrabromobisphenol A, triphenyl phosphate and antimony trioxide as FRs from a standardized plastic disk before and after exposure to artificial sunlight. Assessments were carried out independently to measure changes in the content of flame retardants and monitor the flame retardancy and flexural properties after exposure (60 W/m2) over a period of 200 h and 500 h, which are reasonable to predict a short-time tendency and to receive any advice for a safe re-use. The releases of three organic flame retardants and four elements (Cl, Br, P and Sb) from weathered ABS and PC disks were very limited, except for surface delamination and resin microparticles. Triphenyl phosphate was stable without hydrolysis, while the degradation of tetrabromobisphenol A was observed (approximately 20% decrease for ABS disk and approximately 50% decrease for PC disk). During the study, no significant differences in the flame retardancy and flexural properties of the disks could be detected. In practice, the results obtained from disks of acrylonitrile-butadiene-styrene or polycarbonate resin with selected flame retardants used in specific conditions may provide technical expertise regarding weathering processes.

Evaluation of supercritical fluid extraction for the determination of neonicotinoid pesticides in green onion.

A supercritical fluid extraction (SFE) method was presented for the determination of neonicotinoid pesticides in green onion. We optimized the SFE parameters, namely the pressure, temperature, type and concentration of the modifier solvent, and extraction time, by testing on the incurred green onion applied with four commercial neonicotinoid formulations at the harvesting stage. The analytical values of the four neonicotinoids, obtained by 5 min dynamic SFE with a 25% (v/v) methanol/supercritical carbon dioxide mixture at 80 °C and 25 MPa, were in good agreement with those obtained by solid-liquid extraction using a homogenizer. This latter homogenization method is employed as a Japanese official method for the analysis of pesticide residues in food. The SFE-to-homogenization analytical value ratios were in the range 98.8-100.0%. Spike-and-recovery testing with spiked green onion was also performed by optimized SFE. The ratios of the analytical-to-spiked concentrations for six neonicotinoids obtained by the SFE method were 96.1-102.1% for 0.4 mg/kg and 93.9-104.1% for 4.0 mg/kg spiking levels. These values satisfied the Japanese validation guidelines for the testing method of pesticides in food. These results indicate that SFE is applicable for the analysis of neonicotinoids in green onion and enables automatic extraction with a small amount of solvent.

Evaluation of pressurized liquid extraction for the determination of neonicotinoid pesticides in green onion.

A pressurized liquid extraction (PLE) method was presented for the determination of six neonicotinoid pesticides, acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam in green onion. The critical parameters of PLE, e.g. extraction solvent, temperature, pressure, number of cycles, and static extraction time, were optimized by test on the spiked green onion with six neonicotinoids and the incurred green onion applied with four commercial neonicotinoid insecticide formulations (acetamiprid, dinotefuran, imidacloprid, and thiamethoxam). As a result, the recoveries of six neonicotinoids obtained by one cycle PLE with acetonitrile at 140 °C and 50 bar for 10 min were 94.7-99.5%. These results were acceptable according to the validation guideline for testing method of agricultural chemicals in food by Ministry of Health, Labour, and Welfare in Japan. PLE was also validated by the test on the incurred green onion. The analytical values of four neonicotinoids obtained by PLE were good agreement with those obtained by solid-liquid extraction with homogenizer, which is employed for Japanese official method for the analysis of pesticide residues in food (the ratios of analytical values obtained by PLE to those obtained by solid-liquid extraction were 99.7-101.2%). These results indicate that PLE is applicable for the determination of neonicotinoids in green onion.

Evaluation of the impact of matrix effects in LC/MS measurement on the accurate quantification of neonicotinoid pesticides in food by isotope-dilution mass spectrometry.

The use of isotope-labeled internal standards is the most widely accepted approach to overcome the matrix effects on quantification of pesticides in food by LC/MS. We evaluated the impact of the matrix effects on quantification of six neonicotinoid pesticides, acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam, in food by using deuterated internal standards. The calibration curves for each pesticide were obtained by using matrix-free and matrix-matched calibration solutions with blank brown rice, carrot, and green onion extracts. For brown rice and carrot, the matrix effects were not observed. In contrast, the slopes of calibration curves for each pesticide were influenced by presence of green onion extracts in calibration solutions (variability of the slopes was 4-9%), because the ratios of peak area for native pesticide to those for internal standards were influenced by matrix. The spike-and-recovery test with green onion was also performed. The analytical values obtained by using matrix-free calibration solution were biased from the spiked concentration, whereas those obtained by using matrix-matched calibration solution were comparable to the spiked concentration. These results indicate that matrix-matched calibration solution should be used for accurate quantification of neonicotinoid pesticides in food by LC/MS using deuterated internal standards.

Development of plastic disks containing flame retardants for elucidating changes in their concentrations due to simulated weathering and the application of these disks to weathering tests.

Flame retardants (FRs) are useful because they can prevent combustion and delay the spread of fire after the ignition on commercial products containing plastics. However, such commercial products could be a primary source of environmental contamination with FRs. Plastic disks containing FRs were prepared to elucidate changes in the concentrations of the FRs after weathering tests. Acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) resin were separately kneaded with a combination of three organic FRs [Dechlorane plus (DP), tetrabromobisphenol A (TBBPA), and triphenyl phosphate (TPhP)] and one inorganic FR [antimony trioxide (Sb2O3)]. The concentrations of TBBPA/TPhP and DP/Sb2O3 in the final preparations were respectively 1000 and 500 mg/kg in compliance with the RoHS directive on organobromine FR. The concentrations of elements in the final preparations were 300 mg/kg for chlorine, 600 mg/kg for bromine, 100 mg/kg for phosphorus, and 400 mg/kg for antimony, respectively. The analytical concentrations (three FRs and four elements) were consistent with the expected concentrations (maximum difference -9.5% in the PC disks). The FRs and elements in the disks were sufficiently homogenous (maximum inhomogeneity 4.3% in the PC disks). The prepared disks were subjected to weathering tests; the concentrations of TBBPA in the disks decreased significantly (30 to 40%) whereas the concentrations of the elements did not change under the condition of this study. On the other hand, there were no drastic differences on relationships of FRs and elements such as DP/chlorine and TPhP/phosphorus.

Evaluation of the performance of 57 Japanese participating laboratories by two types of z-scores in proficiency test for the quantification of pesticide residues in brown rice.

A proficiency test for the analysis of pesticide residues in brown rice was carried out to support upgrading in analytical skills of participant laboratories. Brown rice containing three target pesticides (etofenprox, fenitrothion, and isoprothiolane) was used as the test samples. The test samples were distributed to the 57 participants and analyzed by appropriate analytical methods chosen by each participant. It was shown that there was no significant difference among the reported values obtained by different types of analytical method. The analytical results obtained by National Metrology Institute of Japan (NMIJ) were 3 % to 10 % greater than those obtained by participants. The results reported by the participant were evaluated by using two types of z-scores, that is, one was the score based on the consensus values calculated from the analytical results of participants, and the other one was the score based on the reference values obtained by NMIJ with high reliability. Acceptable z-scores based on the consensus values and NMIJ reference values were achieved by 87 % to 89 % and 79 % to 94 % of the participants, respectively.

Assessment of the long-term stability of pesticide residues under freezing conditions in brown rice and soybean certified reference materials.

The objective of this study was to assess the long-term stability of pesticide residues in brown rice and soybean. The long-term stability of pesticide residues in brown rice and soybean was assessed for 5415 days (over 14 years) and 1801 days (about 5 years), respectively. The samples-certified reference materials (CRMs) 7504-a (brown rice) and 7509-a (soybean) -were prepared by freeze-pulverization. Two target pesticides (etofenprox and fenitrothion) were selected for brown rice and four (chlorpyrifos, diazinon, fenitrothion, and permethrin) for soybean. Our analytical results for long-term stability based on highly reliable isotope dilution mass spectrometry were in the range of expanded uncertainty (k=2) for the certified values of each CRM. The concentration showed a decreasing trend in none of the target pesticides when the samples were stored at temperatures between -20 °C and -30 °C, which indicated that the target pesticides were stable for the tested long terms.

A simple reliable quantification of glyphosate in human urine using MonoSpin TiO extraction and isotope dilution mass spectrometry.

A method of quantifying glyphosate (Gly) in human urine by means of MonoSpin TiO extraction and 9-fluorenylmethoxycarbonyl chloride (FMOC-Cl) derivatization with isotope dilution mass spectrometry (IDMS) was investigated and optimized. The method's quantification limit under optimized conditions was 0.3 µg/kg for FMOC-Gly, which was comparable to or lower than those described in previous studies. When a spike test using human urine samples was carried out with optimized analytical conditions, the trueness for FMOC-Gly was as follows: 101.6-104.9% for a spike level of 0.5 µg/kg and 99.2-101.0% for a spike level of 30 µg/kg. The intra-day repeatability and inter-day reproducibility were <6.5%. The spike test results for validation between the "with" and "without" derivatization methods were comparable at 1 µg/kg. Our results indicate that using MonoSpin TiO extraction and FMOC-Cl derivatization with IDMS is an accurate method for analyzing Gly in human urine.

Quantitative Determination of Organophosphorus, Pyrethroid, and Dithiolane Pesticide Residues in Brown Rice Using Supercritical Fluid Extraction and Liquid Chromatography-Tandem Mass Spectrometry.

BACKGROUND: Supercritical fluid extraction (SFE) is a fast, versatile, and solvent-efficient automatic extraction method. Despite its advantages, the results of our proficiency tests imply that the applicability assessments of SFE for pesticide residues were insufficient. OBJECTIVE: In this study, as analytical method using SFE was optimized and validated by testing the incurred and fortified brown rice samples with organophosphorus (OP), pyrethroid (PYR), and dithiolane (DIT) pesticides. METHOD: A validation study using the incurred sample with etofenprox, fenitrothion, and isoprothiolane was performed by comparing the analytical results obtained using the SFE and solid-liquid extraction with homogenization (SLE), which is a well-validated official multi-residue extraction method. The tests on the fortified samples were also performed for seven pesticide residues, chlorpyrifos, diazinon, O-ethyl O-4-nitrophenyl phenylphosphonothioate (EPN), etofenprox, fenitrothion, isoxathion, and isoprothiolane, at three fortification levels, 0.001, 0.01, and 0.1 mg/kg. RESULTS: In the test on the incurred samples, optimized SFE-to-SLE analytical values (CSFE/CSLE) were 99.2-100.1%, with RSD lower than 3%. In contrast, the analytical-to-spiked concentrations in the tests on the fortified samples were 96.4-105.0%, with RSD lower than 8.8%. CONCLUSIONS: These results indicate that the proposed SFE method, which is well validated with the incurred brown rice sample, is useful for determining OP, PYR, and DIT pesticide residues in brown rice. HIGHLIGHTS: The proposed SFE method satisfies EU and Japanese maximum residue limits (MRLs). The consumption of solvent can be reduced to one-fourth of that of SLE using the proposed SFE method.

Evaluation of microwave-assisted extraction for the analysis of organophosphorus and pyrethroid pesticides in green onions.

The aim of this study was to evaluate the efficiency of microwave-assisted extraction (MAE) for the analysis of organophosphorus (OP) and pyrethroid (PYR) pesticides in green onions by GC/MS. We optimized MAE extraction solvent, temperature, and time by using a certified reference material. As a result, the concentrations of two OP and two PYR target pesticides obtained by MAE with acetonitrile at 110 degrees C for 10 min were in good agreement with certified concentrations and comparable to the results by homogenization used as reference extraction technique. When the recovery test, performed by spiking the target pesticides into blank samples (5.0 g), was carried out with our optimized MAE conditions, mean recoveries of 16 OP and 10 PYR pesticides were 72-108% for a 1.0 pg spiking level and 70-119% for a 0.2 microg level. These results were acceptable according to the validation guideline for testing method of agricultural chemicals in food by Ministry of Health, Labour, and Welfare in Japan. The results suggested that MAE can be used for the analysis of OP and PYR pesticides in green onions.

Evaluation of pressurized liquid extraction for determination of organophosphorus and pyrethroid pesticides in soybean.

The purpose of this study was to develop an analytical method for the determination of organophosphorus and pyrethroid pesticides in soybean by pressurized liquid extraction (PLE). Two organic solvents, acetone and acetonitrile, were evaluated as extraction solvents. In both cases, the amount of extract was enhanced with increasing extraction temperature. The extracts obtained using acetonitrile were measured by gas chromatography/mass spectrometry after a cleanup process based on the analytical method for the Japanese Positive List System for Agricultural Chemicals Remaining in Foods. The effect of extraction temperature (range: 40- 130°C) on extraction efficiency was evaluated by a recovery study using 21 organophosphorus pesticides and 10 pyrethroid pesticides as target analytes and acetonitrile as the solvent. The results indicated that at 130°C, some organophosphorus pesticides might be degraded, whereas extraction temperatures between 70°C and 100°C were optimal. Next, a prepared sample containing fenitrothion and permethrin was analyzed. Although the sample was not soaked in water prior to analysis, PLE provided analytical results comparable to those obtained by solvent extraction with homogenization. Therefore, PLE is considered a simple and alternative technique for the extraction of organophosphorus and pyrethroid pesticides in soybean.

Internationally harmonized certified reference materials and proficiency testings for pesticide residue analysis.

Matrix certified reference materials (CRMs) and proficiency testings (PTs) are effective for evaluation of the quality of analytical results. The National Metrology Institute of Japan has developed five kinds of CRMs and has provided eight PTs so far for the quantification of pesticide residues in foods. Target pesticides were sprayed on growing crops, and the harvests were used for the preparation of CRMs and PT samples. In most cases, multiple analytical methods based on isotope dilution mass spectrometry were used to ensure the reliability of certified values (for CRMs) and reference values (for PT samples). These activities were carried out with corresponding to the international standards such as ISO 17034 and ISO/IEC 17043. An overview of the development of CRMs and the implementation of PTs is described, with some examples.

Characterization of certified reference material for quantification of polychlorinated biphenyls and organochlorine pesticides in fish.

Fish certified reference material (CRM), NMIJ CRM 7404-a, for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) was developed by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Fish samples (Japanese seabass) used for the preparation of the CRM were collected from Tokyo Bay, and the edible part was freeze-dried, pulverized, sieved, homogenized, and sterilized by gamma-irradiation. This sample is in the form of a powder comprising approximately 10 g stored in a brown glass bottle. The certification was carried out using multiple analytical methods such as pressurized liquid extraction, Soxhlet extraction, saponification, and homogenization to ensure the reliability of analytical results; the certified values of target PCBs (PCB 28, PCB 70, PCB 105, PCB 153, and PCB 170) and OCPs (trans-nonachlor, dieldrin, p,p'-DDE, p,p'-DDT, and p,p'-DDD) were 1.05-14.0 microg kg(-1) and 1.57-18.0 microg kg(-1) for PCBs and OCPs, respectively. This is the first fish powder CRM in which PCBs and OCPs were determined by isotope dilution mass spectrometry.

Development of Artificial Urine Certified Reference Material for Quantification of Neonicotinoid Insecticides.

BACKGROUND: Neonicotinoid insecticides (neonicotinoids) are widely used, however, they can negatively affect human health. Thus, neonicotinoids and their metabolites in human urine are analyzed globally to assess exposure levels and health risks. To properly assess the exposure levels and health risks, accurate analytical results are a necessity. OBJECTIVE: This study aims to develop urine certified reference material (CRM), NMIJ CRM 7408-a, for the quantification of neonicotinoids. METHOD: To develop NMIJ CRM 7408-a, commercially available artificial urine was used as the raw material to which the target neonicotinoids were added. Analyses of neonicotinoids in NMIJ CRM 7408-a were carried out by isotope dilution mass spectrometry (IDMS). RESULTS: Sample homogeneity was assessed, with the results showing that acetamiprid, clothianidin, thiacloprid, and thiamethoxam exhibited sufficiently homogeneous distributions in the material. The relative uncertainties due to inhomogeneity were 1.2-7.0%. The results obtained from long-term stability assessment indicated that the target neonicotinoids were stable. The relative uncertainties due to instability were 9.4-17.2% (for an expiry date of 21 months). The characterization for providing concentration values was carried out using one (clothianidin and thiacloprid) or two (acetamiprid and thiamethoxam) analytical methods. The certified values of the target neonicotinoids (acetamiprid, clothianidin, thiacloprid, and thiamethoxam) were 0.19-1.38 µg/kg. CONCLUSIONS: This is the first frozen artificial urine CRM in which neonicotinoids were quantified by IDMS and will be useful for evaluating the accuracy of analysis and validation of analytical methods for the determination of neonicotinoids in urine. HIGHLIGHTS: NMIJ CRM 7408-a, which has been certified for four neonicotinoids, was developed by NMIJ.

Multiresidue analysis and monitoring of pesticides in rice by pressurized liquid extraction.

The aim of this study was to assess the performance of a method of analyzing pesticides in rice by using pressurized liquid extraction (PLE) and to perform a preliminary monitoring by using that method. The instrumental quantification limit, instrumental detection limit, method quantification limit, and method detection limit were determined. PLE temperature was also optimized for 6 target pesticides. Mean recoveries of spiked rice with target pesticides (4 ng/g and 40 ng/g) were 83%-109% with the repeatability of the analysis, represented as relative standard deviations, ranged from 1.3% to 11% (n = 5) for PLE at 130 degrees C. These results were satisfactory according to the method of positive list in Japan. In a preliminary analysis of 10 target pesticides in 54 commercial rice samples, ferimzone was detected in only one unpolished rice sample.

Proficiency testing by the National Metrology Institute of Japan for quantification of pesticide residues in grain samples from 2012 to 2018.

From 2012 to 2018, proficiency testings (PTs) were carried out to support the analytical skill development of participants. Grains were sprayed with various target pesticides and used as material samples for PTs. It was found that 27-56% and 10-43% of participants used the Japanese official multiresidue method and a solid-phase extraction technique with the Quick, Easy, Cheap, Effective, Rugged, and Safe (modified QuEChERS, known as "STQ" in Japan) method, respectively. Reported results were evaluated using two types of z-scores: one was based on consensus values calculated from the analytical results reported by the participants, and the other was based on values obtained by the National Metrology Institute of Japan (NMIJ). Acceptable z-scores based on the consensus values and NMIJ reference values were achieved by 78-95% and 67-94% of the participants, respectively. Many laboratories improved their z-scores by continuing participation in our PT.

Evaluation of microwave-assisted extraction for the analysis of polychlorinated biphenyls and organochlorine pesticides in fish.

The efficiency of microwave-assisted extraction (MAE) was evaluated for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish. An isotope dilution method was used for quantification via analysis of the samples by gas chromatography and mass spectrometry. MAE solvent, temperature, and time were optimized, and observed concentrations were compared. The MAE results were also compared to those of other extraction techniques (Soxhlet extraction, pressurized liquid extraction, saponification, and homogenization). Concentrations of PCBs and OCPs obtained by MAE at 120 degrees C for 10 min were comparable to those by the other techniques. The results suggest that MAE can be used for the analysis of PCBs and OCPs in fish.

Evaluation of pressurized liquid extraction for the analysis of four pesticides in unpolished rice.

The aim of to evaluate efficiency of this study was extraction pressurized liquid extraction (PLE) for the analysis of four pesticides, fthalide, etofenprox, fenitrothion, and isoprothiolane, in unpolished rice by comparing with homogenization as a reference technique. The concentrations of four selected pesticides obtained by PLE with acetonitrile at 130 degrees C for 10 min x 2 cycles were comparable to those by homogenization with water-soaking. The repeatability of the analysis, represented as relative standard deviations (RSDs), were 1.4-3.6% (n = 3) for PLE at 130 degrees C and 1.2-3.8% (n = 3) for homogenization with water-soaking. Recovery yields of surrogates were 75-88% and 87-109% for PLE at 130 degrees C and homogenization with water-soaking, respectively, and these were satisfactory according to the method of positive list. This study suggested that PLE can be applied for the analysis of selected four pesticides in unpolished rice as well as homogenization with water-soaking.

Effect of Long-time Heating for Elements from Flame Retardants in Acrylonitrile Butadiene Styrene and Polycarbonate Resin Disks.

The effect of long-time heating for elements from flame retardants (FRs) such as dechlorane plus (DP), tetrabromobisphenol A (TBBPA), triphenyl phosphate (TPhP) and antimony trioxide (Sb2O3) in both acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) resin disks was examined in the present study. The heating temperature by a drying oven was 80°C, which was expected to be a harder environment than that of usual dump site to discard electric and electronic equipment, and the long-time heating was carried out for up to 722 days. As a result, the increases for both ether (C-O-C) and ketone (C=O) groups and the decrease of C=C double bond as well as methylene group (=CH2) were found for an ABS resin disk by fourier transform infrared (FTIR) spectrometry, which was expected to result in an increase of mass of the disk up to ca. 4% due to oxidation during the long-time heating. The changes in concentrations for bromine (Br), chlorine (Cl), phosphorous (P) and Sb, which were originated elements from FRs contained, were also evaluated by energy dispersive X-ray fluorescence (ED-XRF) spectrometry and the decreases in concentrations of ca. 5% in ABS resin disk were observed which could be almost explained by increasing ca. 4% mass of the disk. On the contrary, the mass and chemical form of a PC resin disk as well as the concentrations of elements contained did not change during the long-time heating. From these results, it could be considered that most of the elements from DP, TBBPA, TPhP and Sb2O3 contained as FRs in the ABS and PC resin disks examined in the present study were not lost during the long-time heating, even though the color, shape, mass and chemical form of ABS resin disk were changed.

Comparison of Assigned Values from Participants' Results, Spiked Concentrations of Test Samples, and Isotope Dilution Mass Spectrometric Results in Proficiency Testing for Pesticide Residue Analysis.

The Hatano Research Institute (HRI) at the Food and Drug Safety Center has recently organized a series of proficiency-testing (PT) programs called the "External Quality Control for Food Hygiene" in order to evaluate the analytical capability of testing laboratories that inspect food samples in accordance with the Food Sanitation Act. In one of these programs, Pesticide I, consensus values calculated from the participants' analytical results were used as assigned values, and the spiked concentrations of the prepared test samples were used for evaluating variation among individual participants. In the present study, the values obtained in the 2013-2015 rounds have been assessed by comparing the analytical results of the target pesticides obtained by using two different isotope-dilution MS (IDMS) methods. These two IDMS methods are based on a combination of different pretreatment protocols and different GC separation columns. The weighted means of the observed analytical results were higher than the corresponding assigned values, but showed good agreement with the spiked concentrations. These results indicate that the spiking concentrations of the test sample from HRI are reliable, and therefore, these values can be used to evaluate the trueness of the participants' analytical method.