Validation of a multiclass multiresidue method and monitoring results for 210 pesticides in fruits and vegetables by gas chromatography-triple quadrupole mass spectrometry

A rapid, sensitive, accurate and reliable multiresidue method for the identification and quantification of 210 relevant pesticides in four representative fruit and vegetable commodities (tomato, potato, spring onion and orange) has been developed and validated by gas chromatography in tandem with triple quadrupole mass spectrometry. The method has been fully validated and applied to 292 samples from different countries. Prior to instrumental analysis, an extraction procedure based on a sample extraction of multiclass analytes, using the ethyl acetate method was employed. Mass spectrometric conditions were individually optimized for each compound in the selected reaction monitoring (SRM) mode to achieve maximum sensitivity. The pesticides were separated in less than 25 min. This was followed by an exhaustive control of the retention times. The Retention Time Locking Method was applied, working at a constant pressure throughout the analysis. System maintenance was reduced by using a purged capillary flow device that provided backflush capabilities by reversing column flow immediately after elution of the last compound of interest. Istotopically labelled internal standards were employed to improve the quality of the analytical results.     

Multiresidue analysis and evaluation of the matrix effect on 20 pesticides in Brazilian maize (Zea mays L.) flour

Abstract

Maize consists of a cereal widely used in the preparation of different food products. Brazil is one of the world's largest maize producers. Several types of pesticides have been applied in maize crop, which can lead to the contamination of the derived products. The present work aims at the validation of multiresidue method to analyze the matrix effect and level of pesticides in maize flour. Twenty residues were investigated in samples commercialized in the state of Ceará, Brazil. The method was satisfactorily validated, according to parameters recommended by European Union. About 55% of the pesticides had an intense negative matrix effect. Multiresidue analyzes showed the presence of traces of fenitrotion in 20% of maize flour samples. Detected levels were below maximum residue limits recommended for maize. The results indicate that maize products need continuous monitoring to ensure food security.     

Determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by liquid chromatography-tandem mass spectrometry

A sensitive method for determination of chloramphenicol, enrofloxacin and 29 pesticides residues in bovine milk by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. Residues of the targets were extracted from milk with acetonitrile, cleaned up by C₁₈-SPE cartridge, and then determined by HPLC-MS/MS. The MS detection was operated in positive or negative ionization mode, depending on the compounds. For confirmation of each target compound, two precursor ion > product ion transitions were selected by multi-reaction monitoring mode (MRM). The method showed good linearity for all the tested compounds over the studied concentration range with correlation coefficient higher than 0.9910. Recoveries for the studied compounds at three spiked levels (0.05, 0.10, 0.19 mg kg⁻¹) in bovine milk were in the range of 71-107% with RSDs not larger than 13.7%, except that recoveries of trifluralin ranged between 62% and 70% at the spiked levels. Limits of quantitation for the analytes were estimated to range between 0.03 × 10⁻³ and 14.5 × 10⁻³ mg kg⁻¹. The proposed method was applied for the determination of the analytes residues in real samples. The found levels of the analytes in milk samples were lower than maximum residues levels (MRL).     

Monitoring of pesticide residues in a cotton crop soil

Abstract

This paper reports on the residues of methyl parathion (O,O‐dimethyl O‐4‐nitrophenyl phosphorothioate), trifluralin (α, α, α‐trifluoro‐2, 6‐dinitro‐N, N‐dipropyl‐p‐toluidine), endosulfan [(1, 4, 5, 6, 7, 7‐hexachloro‐8, 9, 10‐trinorborn‐5‐en‐2, 3‐ylenebismethylene) sulfite] and dimethoate (O, O‐dimethyl S‐methylcarbamoylmethyl phosphorodithioate) in a cotton crop soil. Soil samples (0–15 cm) were collected at different periods from the cotton crop farm and subjected to Soxhlet extraction. The extracted material was analysed after clean‐up by a HP5890 II gas Chromatograph equipped with a ⁶³Ni electron‐capture detector (ECD‐⁶³Ni) and fitted with a 25m x 0,2mm i.d. fused silica capillary column [Ultra‐2 (5% phenylmethyl polysiloxane)]. The recoveries of the pesticide residues from the spiked control soil were determined after Soxhlet extraction and C₁₈ cartridges clean‐up by using radiotracer techniques with the corresponding ¹⁴C‐pesticides. The results show that in the cotton crop soil the pesticide residues under study were present in the range of 0.1 to 0.4 mg ? kg^‐1. Endosulfan was found to be rapidly degraded in the soil and formed a sulfate metabolite.     

20种农药在作物中多残留分析方法的研究

报道了20种有机氯、有机磷和拟除虫菊酯类农药在作物中多残留气相色谱分析方法。9种有机磷农药的最低检测浓度为0.34—22.30ppb,8种有机氯农药为0.13—9.76ppb,3种拟除虫菊酯为1.63—17.00ppb。20种农药在四种作物上的添加回收率大于80％,仅敌敌畏与速灭磷在低浓度(0.05ppm)时,回收率偏低。变异系数都小于10％。