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J. Agric. Food Chem. 2003, 51, 4468−4471
Organophosphorus Pesticide Residues in Mexican Commercial Pasteurized Milk JOSEÄ HUMBERTO SALAS,† MARIÄA MAGDALENA GONZAÄ LEZ,† MARIO NOA,‡ NORMA ALICIA PEÄ REZ,*,† GILBERTO DIÄAZ,§ REY GUTIEÄ RREZ,† HEÄ CTOR ZAZUETA,§ AND ISIDRO OSUNA§ Departamento de Produccio´n Agrı´cola y Animal, Universidad Auto´noma Metropolitana-X. Calz. Del Hueso 1100. Col. Villa Quietud, C.P. 04960, Me´xico, D.F., Mexico; Departamento de Prevencio´n, Facultad de Medicina Veterinaria, Universidad Agraria de la Habana, Km 23 y Carretera Tapaste, C.P. 32700, San Jose´ de las Lajas, Habana, Cuba; and Laboratorio de Estudios Ambientales, Facultad de Ciencias del Mar, Universidad Auto´noma de Sinaloa, Paseo Klaussen s/n, Mazatla´n, Sinaloa, Mexico
A study was conducted to measure residues of 13 organophosphorus (OP) pesticides, widely used as dairy cattle ectoparasiticides or in crops used for animal feed, in homogenized and pasteurized Mexican milk samples. Four different milk brands with high distribution were collected biweekly during a 12 month period (n ) 96) in supermarkets. OP pesticide residues were measured by gas chromatography with a flame photometric detector. Approximately 39.6% of the samples contained detectable levels of OP pesticide residues. Eight samples contained residues exceeding established maximum residue limits (MRL), and the OP pesticides present in these samples were dichlorvos (five samples), phorate, chlorpyrifos, and chlorfenvinphos (one sample, respectively). Average residues of 13 OP pesticides measured were below established MRLs ranging between 0.0051 and 0.0203 ppm. KEYWORDS: Organophosphorus pesticides; residues; pasteurized milk
INTRODUCTION
MATERIALS AND METHODS
Organophosphorus (OP) pesticides can appear in milk due to several possible causes: (a) use of insecticides directly on dairy cattle for ectoparasite control; (b) pasture, forages, or animal feed manufactured from plant material that has been treated with insecticides; and (c) use of insecticides in stables or diary factories. It is well-known that OP pesticides are less stable and persistent than organochlorine pesticides; however, there are several reports of their presence in cow’s milk (1-7). Residues of diazinon, chlorpyrifos, and malathion in levels of 0.0050.586 ppm (8-10), 0.059 ppm (5), and 0.110 ppm (5), respectively, have been reported in milk. OP pesticides are widely used in Mexico in animal husbandry and in pasture, alfalfa, and crops for animal feed production. No reports were found in the literature about OP pesticide residue levels in milk produce in our country. Because monitoring studies to detect pesticide residue levels in milk are very important to determine dietary exposure, the aim of this work was to study the possible presence in milk of the most commonly used OP pesticides implicated in milk production in our country.
Sampling. Three commercial brands (A-C), with wide national distribution, and one brand (D) produced and distributed by the government for people of low resources were selected. Sampling was done every 2 weeks over the course of a year, in supermarkets (brands A-C) and in government stores (brand D). Analytical Method. The Ministry of Welfare, Health and Cultural Affairs, Leidschendam, The Netherlands, multiresidue method 5 (submethod 3) for the analysis of organophosphorus compounds in milk (11) was used. Milk (50 mL) was blended with ethyl acetate (100 mL). Sodium sulfate (50 g) was added, and the mixture was shaken and then allowed to stand for 2-3 min. The upper layer was decanted, and a 50 mL aliquot was evaporated to dryness in a rotating film evaporator (35 °C). The residue was dissolved in hexane (10 mL) and then extracted with 2 × 25 mL of acetonitrile, saturated with hexane. Combined acetonitrile phases were evaporated to dryness, as described above. The residue was dissolved in 2 mL of ethyl acetate. Chromatographic Analysis. The OP pesticides analyzed were chlorfenvinphos, chlorpyrifos, coumaphos, diazinon, dichlorvos, dimethoate disulfoton, ethion, fenthion, malathion, mevinphos, parathion-methyl, and phorate. A Hewlett-Packard model 5890 GC system equipped with a flame photometric detector and a phosphorus filter (526 nm) was used. The capillary column was a 25 m, 0.2 mm i.d., 0.25 µm, HP-1 (100% methyl silicone). The GC conditions were as follows: helium carrier gas flow, 1 mL/min; temperature program, from 40 °C (2 min) to 170 °C (30 °C/min) and finally to 280 °C (3 °C/min). A three-point external standard calibration using the standard mixture at 1, 5, and 10 µg/mL
* Corresponding author (e-mail
[email protected]). † Universidad Auto ´ noma Metropolitana-X. ‡ Universidad Agraria de la Habana. § Universidad Auto ´ noma de Sinaloa.
10.1021/jf020942i CCC: $25.00 © 2003 American Chemical Society Published on Web 06/18/2003
Pesticide Residues in Pasteurized Milk
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Table 1. Summary of Analytical Results
e
pesticide
% recovery (CV)a
MDLb (ppm)
no. of samples > MDL
residue level range (ppm)
residue meanc (ppm)
95th percentiled (ppm)
MRLe (ppm)
dichlorvos mevinphos phorate dimethoate diazinon disulfoton parathion-methyl malathion fenthion chlorpyrifos chlorfenvinphos ethion
63.0 (15.4) 60.2 (16.7) 75.1 (12.8) 81.1 (9.1) 83.6 (9.8) 33.0 (10.6) 60.0 (5.0) 47.2 (22.1) 75.5 (11.9) 94.4 (6.6) 98.9 (5.0) 43.3 (13.8)
0.014 0.016 0.014 0.012 0.013 0.0050 0.0050 0.019 0.013 0.0090 0.0080 0.0090
6 1 2 1 0 1 4 1 0 1 3 0
0.0146−0.2994 0.0160−0.0354 0.0481−0.1728 0.0120−0.0161
