Maria Helena Wohlers Morelli Cardoso

Preparação de um material de referência certificado para controle de agrotóxicos em hortifrutigranjeiros: estudo da homogeneidade

This study reports on the efforts to ensure homogeneity of certified reference materials. Residues of four pesticides (γ-HCH, fenitrothion, chlorpyrifos, and procymidone) were added to tomato pulp in order to produce reference materials. The two most important properties of such materials are known to be homogeneity and stability. Before being shipped to other laboratories, reference materials must have their homogeneity certified. As part of a preliminary study, hundreds of samples were investigated in order to provide data on the most suitable treatments to minimize analytical variability and ensure the quality of samples intended for use as reference materials as well as to yield estimates of the uncertainty associated to the homogeneity data. In addition, the variance analysis provided accurate information on the bulk variability and the degree of non-homogeneity of contaminated samples. After preparation, the samples were exposed to 2 kGy of gamma radiation and submitted to an interlaboratory certification study. The certified concentrations of γ-HCH, fenithrotion, chlorpyrifos, and procymidone were 0.191 ± 0.047 mg.kg-1; 0.192 ± 0.068 mg.kg-1; 0.225 ± 0.076 mg.kg-1 , and 0.177 ± 0.051 mg.kg-1, respectively.

Monitoramento de resíduos de agrotóxicos da classe dos organofosforados por CG-DFC em amostras de leite fluído e em pó

Samples of whole fluid pasteurized, UHT and powdered milk were analyzed for the presence of organophosphorus pesticide residues (OPR) using the QuEChERS method with detection by GC-FPD and confirmation by UPLC-MS/MS. A total of 23% of fluid milk samples and 27% of powdered milk samples contained at least one organophosphorus residue. The OPR found in the samples showed these can reach the milk and remain even after pasteurization, sterilization and drying processes. Some domestic sanitary residues were also present in the powdered milk samples. These residues have no LMR in Brazilian food legislation and are therefore not taken into account in food intake evaluations. There was an unidentified chromatographic peak in 30% of all the liquid and powdered milk samples, indicating the presence of some other contaminant.

Implementação de método analítico para determinação de resíduos de organofosforados em leite por cromatografia a gás com detector fotométrico de chama

This paper regards the implementation of the QuEChERS method for the analysis by GC-FPD of 53 different pesticides from the organophosphate class, in whole UHT and pasteurized milk. Selectivity, linearity, repeatability, recovery and limits of detection and quantification were evaluated. Of all pesticide recoveries, 51 were considered satisfactory since the values ranged from 70 to 120% with RSD < 20%. The quantification limits ranged from 0.005 to 0.4 mg kg-1. The QuEChERS method was suitable for determination of 52 pesticides, presenting several advantages - quick, cheap, easy, effective, rugged and safe - with regard to other traditional methodologies.

Ensaio de proficiência para análise de ditiocarbamatos em polpa de banana

A proficiency assay of the determination of dithiocarbamate pesticide residues in banana was carried out. Fourteen laboratories participated in this study. Homogeneity and stability testing were performed by INCQS on the samples sent to the laboratories. Analytical results supplied by the pesticide residues laboratory of the VWA/KvW, Amsterdam, Holland, were used to define the designated value for the thiram concentration in the study samples. RESULTS: Fifty percent of the participating laboratories had satisfactory results. Efforts are needed to improve the precision of the analytical results and to decrease the number of false negative results observed.

Implementação da técnica de extração de dispersão da matriz em fase sólida ("MSPD") para determinação de resíduos de agrotóxicos em laranjas

A multiresidue method of extraction based on matrix solid-phase dispersion (MSPD) technique was optimized and validated for chromatographic analyses of twenty seven pesticides residues [hexachlorocyclohexane (HCH) isomers (α,β,γ,δ), dieldrin, endrin, heptachlor and its epoxide (HE),α and β-endosulfan, o,p’-DDD, p,p’-DDD, o,p’-DDE, p,p’-DDE, o,p’-DDT p,p’-DDT, dicofol, methoxychlor, mirex, hexachlorobenzene(HCB), chlorotalonil, parathion methyl, fenitrothion, malathion, folpet, diazinon, permethrin (cis and trans) in oranges. The sample was blended with C18and then the homogenized sample was introduced onto a glass column containing silica. Ten mL of ethylacetate was added to the column as elution solvent. The eluent was concentrated, diluted in isooctane and 1µL was injected intothe gas chromatograph. The analyses of pesticides were performed using a GC/ECD. Confirmation was done by mass spectrometry. The recovery ranged from 70 to 120% in the concentration range of 0.02 to 2.0mg/kg. The limits of quantification ranged from 0.01to 0.5mg/kg.