Page 27 - Volume 3, Issue 2, July 2010

1

Laboratory of Environmental Chemistry, Division III, De-

partment of Chemistry, University of Athens, Panepis-

timioupolis, GR-105 71 Athens, Greece

2

Laboratory of Pesticide Residues, Department of

Pesticides Control and Phytopharmacy, Benaki Phy-

topathological Institute, 8, St. Delta Str., GR-145 61 Ki-

fissia (Athens), Greece.

Corresponding author:

c.anagnostopoulos@bpi.gr

Hellenic Plant Protection Journal

3:

57-69, 2010

Validation of a multiresidue method for the determination of

multiclass pesticides by using representative analytes by gas

chromatography

N. Vlastaras

1

, E. Dasenakis

1

K.S. Liapis

2

, G.E. Miliadis

2

and C.J. Anagnostopoulos

2

Summary

The protection of crops against pests and diseases by various mostly synthetic pesticides

is a common approach in conventional farming. Even when pesticides are applied in accordance with

Good Agricultural Practices (GAP), they can leave residues on plants. Therefore, the need of finding de-

termination methods for pesticide residues with speed, facility and reliability is rendered imperative.

The estimation of reliability of a multiresidue method is achieved by the process of validation. Validat-

ing a multiresidue method is a time- and effort-consuming task, which usually requires 5-6 replicates

of recovery in at least two different levels for each compound and matrix combination of interest. In

this study, a different approach using a more effortless and fast method of validation is followed. A se-

lection of representative analytes was made; the number of the tested analytes was at least 20% of the

total number of each chemical pesticide class, covering selected physicochemical properties (polarity,

solubility in water, vapor pressure). In addition, the representative analytes included those for which

the worst performance was expected. Furthermore, validation in only one matrix per group commod-

ity is proposed. With the above process and by testing 44 representative analytes, the multiresidue

method by gas chromatography with electron capture (ECD) and nitrogen-phosphorous (NPD) detec-

tors used in this study for the determination of over 180 pesticides in crops, including organophos-

phorus, organochlorine, triazole, triazine, strobilurin, pyrethroid, dinitroaniline and nitrogen-contain-

ing pesticides, was validated. The matrixes were tomatoes and grapes, products of high consumption

in Greece.

Additional keywords:

analytes, GC-NPD, GC-ECD, multiresidue methods, representative, validation

Introduction

Monitoring of pesticides in food usually in-

volves the rapid, accurate and cost-effective

detection of a wide range of compounds

that belong to different chemical classes.

Thus, it is imperative to develop multires-

idue analytical methods in order to screen

the maximum possible number of com-

pounds. Laboratories perform method val-

idation to provide evidence that a method is

fit for the purpose for which it is to be used.

The method usually has to be fully validated

for all analytes included in the scope of the

method and probably for all matrixes. With

respect tomatrixes, representative onesmay

be used (4). Regarding analytes, we believe

that, by choosing representative ones from

each chemical class, multiclass multiresidue

methods with less time and effort, appro-

priate for laboratories performing pesticide

residue analysis and acceptable for accredi-

tation purposes can be validated.

In the present study, representative ana-

lytes for various chemical groups including

organophosphorus, organochlorine, triaz-

ole, triazine, strobilurin, pyrethroid, dinitroa-

niline and nitrogen-containing pesticides,

were selected according to their physico-

chemical properties. The physicochemical

properties used to select the representative

analytes were: