Environmental Engineering Reference
In-Depth Information
TABLE 18.2 (Continued)
Maximum Residual Limits (Mrls) for Pesticide Residues in Milk and Milk Products
As per PFA,
d
India
(mg/kg)
Phorate 0.02 0.02 — 0.05
e
Phosalone 0.01 — — —
Propoxur 0.05 0.05 — —
Quintozene 0.01 0.01 — —
Simazine 0.05 — — —
Directives 86/363/EEC & 90/642/EEC. 1986. Maximum levels for Pesticide residues in and on
Food stuffs of animal origin.
Off. J. Eur
. L221: 43, 7 August 1986;
c
http//www.epa.gov/pesticides/
Commercial Law Publishers (India) Pvt. Ltd., Delhi (Edition 2011).
Weights on fat basis per
β-isomers.
As per FAO/
WHO,
a
(mg/kg)
As per EU,
b
(mg/kg)
As per USFDA,
c
(mg/kg)
Compound
18.7.1 Sample Preparation
This is the first step to provide a representative and composite sample from which sub-
samples can be taken for analysis. Milk is an emulsion of the oil-in-water type. Fat has a
tendency to come to the surface, so attention has to be paid to get homogenized and repre-
sentative samples. The sample should be handled carefully so that possible contamination
is prevented and the loss of volatile pesticides is avoided.
18.7.2 Extraction
Pesticides are extracted from the sample employing solvents such as acetonitrile, petro-
leum ether, hexane, dichloromethane, or acetone. The solvent is blended with the sample
and homogenized. In the case of milk, pesticides are either present in the fat phase in
free form or bound to the lipoprotein or protein. So, acetonitrile is used to deproteinize
the sample to release any pesticide bound to the protein and, at the same time, to precipi-
tate the fat and protein and bring pesticides to a dissolved form. Then, the pesticides are
partitioned to the petroleum ether phase. The extraction timing depends on the type of
pesticide, matrix, and physicochemical properties of the solvent. The most common prob-
lem faced is the incomplete recovery and formation of emulsion during the partitioning
process. This can be avoided by using a suitable solvent with sodium chloride added or by
one or more solvent combinations.
Different approaches and extraction methods may be used, such as solid-phase
extraction (SPE), solid-phase microextraction (SPME), accelerated solvent extraction
(ASE), matrix solid-phase dispersion (MSPD), and supercritical fluid extraction (SFE)
(Table 18.3).
18.7.3 Cleanup
Two types of preparative column chromatography are used for cleanup and purification:
adsorption and size exclusion. Materials used in adsorption chromatography are Florisil,
alumina, and silica gel.
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