Organochlorine, Pyrethrin and Pyrethroid Insecticides: Single Class, Multiresidue Analysis of
Authors: Di Muccio Alfonso 
Published: September 2006

Organochlorine (OC) pesticides is a general term for a broad class of compounds including some well‐known compounds such as dichlorodiphenyltrichloroethane (DDT), lindane, dieldrin, endrin, heptachlor epoxide (HEPO), endosulfan, and chlordane. OC pesticides are the first class of compounds introduced in agricultural and civil uses to counteract noxious insects and insect‐borne diseases. In general they are lipophilic compounds with noticeable chemical and environmental stability. Although most OC pesticides have been progressively restricted and then banned in the 1970s in most industrialized countries, a widespread environmental pollution has resulted from their use in agriculture and civil uses.

Pyrethrins are natural insecticidal compounds found in the extract of pyrethrum flowers. Also, a number of pesticides have been synthesized that share the biologically relevant chemical moiety with the pyrethrins and are referred to as pyrethroids (PYR). These compounds possess equal or better biological activity and better chemical stability that allow their use in agriculture, husbandry, and civil applications. Both OC and PYR pesticides can occur in fruits and vegetables as well as in food of animal origin and environment. The levels can be different as a result of direct application or indirect contamination. Such different matrices and levels of contamination require different analytical approaches and resources.

A review is presented of the array of the analytical techniques most frequently applied for the extraction, cleanup and identification/determination. Extraction techniques include solvent extraction, supercritical fluid extraction (SFE), solid‐phase extraction (SPE), and solid‐phase microextraction (SPME). Solvent extraction is carried out in different ways depending on the type of matrix (fatty and nonfatty samples, soil, sediments, and water), such as Soxhlet, liquid–liquid extraction (LLE), pressurized liquid extraction (PLE), and matrix solid‐phase dispersion (MSPD).

Different cleanup techniques are presented that can be applied to fatty and nonfatty samples. They include liquid– liquid partitioning (LLP), size‐exclusion chromatography (SEC), sweep codistillation and assisted distillation, column adsorption chromatography, chromatography on SPE cartridges, high‐performance liquid chromatography (HPLC), thin‐layer chromatography (TLC) and degradative cleanup. The techniques are presented as modular steps that can be arranged in different ways to cope with cleanup requirements posed by different sample composition and different selectivity/sensitivity of the identification/determinative techniques. The performances of the cleanup steps are discussed in terms of matrix removal and amount of sample that can be handled. Also the possibilities of linking different steps and the chance for automation of the cleanup process are indicated. Some environmental pollutants, such as polychlorinated biphenyl (PCB), have similar analytical behavior to some OC pesticides and can occur in the same environmental matrices. Some cleanup steps useful for the group separation of PCB and OC pesticides are presented.

The techniques for identification and determination include gas chromatography (GC) with selective detectors, HPLC, and their combination with mass spectrometry (MS). The importance of the combination of responses from different analytical techniques to obtain reliable identification at trace levels is underlined.