Polar pesticides

Barcelo, D. Hennion, M. C. Sampling of Polar Pesticides from Water Matrices, Anal. Chim. Acta 1997, 338, 3-18. 

E. A. Hogendoom, U. A. Th Brinkman and P. van Zoonen, Coupled-column reversed-phase liquid cliromatography-UV analyser for the determination of polar pesticides in water , 7. Chromatogr. 644 307-314 (1993). 

Another example is the determination of bentazone in aqueous samples. Bentazone is a common medium-polar pesticide, and is an acidic compound which co-elutes with humic and/or fulvic acids. In this application, two additional boundary conditions are important. Eirst, the pH of the M-1 mobile phase should be as low as possible for processing large sample volumes, with a pH of 2.3 being about the best that one can achieve when working with alkyl-modified silicas. Secondly, modifier gradients should be avoided in order to prevent interferences caused by the continuous release of humic and/or fulvic acids from the column during the gradient (46). 

This method can also be used to analyse soil samples. For instance, fenpropi-morph, which is a non-polar pesticide with good UV sensitivity but poor selectivity, has, after treatment, been determined in soil samples (31). In this example, an amount of soil was extracted overnight with acetonitrile this was then poured into a Buchner filter and rinsed with the same solvent. The acetonitrile solution was concentrated and, prior to LC analysis, the extract was diluted with water and 100 p.1 were then injected into the LC system. 

Figure 13.7 Selectivity effected by employing different step gradients in the coupled-column RPLC analysis of a surface water containing 0.40 p-g 1 bentazone, by using direct sample injection (2.00 ml). Clean-up volumes, (a), (c) and (d) 4.65 ml of M-1, and (b) 3.75 ml of M-1 transfer volumes, (a), (c) and (d), 0.50 ml of M-1, and (b), 0.40 ml of M-1. The displayed cliromatograms start after clean-up on the first column. Reprinted from Journal of Chromatography, A 644, E. A. Hogendoom et al, Coupled-column reversed-phase liquid chromatography-UV analyser for the determination of polar pesticides in water , pp. 307-314, copyright 1993, with permission from Elsevier Science.

Chlorophenoxy acids are relatively polar pesticides which are usually determined by LC because volatile derivatives have to be prepared for GC analysis. This group of herbicides can be detected by multiresidue methods combined with automated procedures for sample clean-up, although selectivity and sensitivity can be enhanced by coupled-column chromatographic techniques (52). The experimental conditions for Such analyses are shown in Table 13.1. 

J. Slobodnik, O. Ostezkizan, H. Lingeman and U. A. Th Brinkman, Solid-phase extraction of polar pesticides from environmental water samples on grapliitised carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns , J. Chromatogr. 750 227-238 (1996). 

R. M. Marce, H. Prosen, C. Crespo, M. Calull, R Boirull and U. A. Th Brinkman, Online ti ace enrichment of polar pesticides in environmental waters by reversed-phase liquid cliromatography-diode array detection-particle beam mass spectrometry , J. Chromatogr. 696 63-74 (1995). 

H. Bagheri, E. R. Brouwer, R. T. Ghijsen and U. A. Th Brinkman, Low-level multiresidue determination of polar pesticides in aqueous samples by column liquid chr O-matography-thermospray mass specrtometry , J. Chromatogr. 657 121-129 (1993). 

T. H. M. Noij, M. E. Margo and M. E. van der Kooi, Automated analysis of polar pesticides in water by on-line solid phase extr action and gas cliromatography using the cosolvent effect , 7. High Resolut. Chromatogr. 18 535-539 (1995). 

Organophosphate flame retardants and plasticisers Perfluorinated compounds Pharmaceuticals and personal care products Polar pesticides and their degradation/transformation products Surfactants and their metabolites... 

Note A range of pesticides can be detected on cellulose layers using 3-hydroxyflavones without prior bromination. Thus, the natural fluorescence of robinetin or fisetin, which is weak in a non-polar environment, is significantly enhanced by the presence of polar pesticides [2, 5, 7, 8],... 

Martin-Esteban a, Fernandez P, Camara C, Kramer GN, Maier EA 1997) Preparation, homogeneity and stability of polar pesticides in freeze-dried water interlaboratory exercise. Int. J Environ Anal Chem 67 125-141. 

This ring test had been conducted with specially selected polar pesticides, and therefore the results are not representative of all pesticides. However, irrespective of this, the study clearly showed that validation smdies must be conducted with standards in a matrix. In recovery determinations, conducted with standards in a solvent, the analyst cannot be sure that a bad recovery is not masked by matrix effects. 

Prior to the development of modern SPE formats, liquid-solid partitioning with charcoal, silica, Florisil, and/or alumina was common to aid in the removal of lipids in the determination of nonpolar pesticides, but these sorbents are less useful in the cleanup of semi-polar and polar pesticides owing to the large elution volumes needed. Applications of modern SPE are discussed in Section 3.2. 

Activated carbon disks have also been used for the extraction of polar pesticides from environmental water samples. Slobodnik et alP used an Empore activated carbon disk (EACD) and Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water. 

Alba et al. used ethyl acetate to extract imidacloprid residues from fruits and vegetables. A 15-g sample of vegetable or fruit is weighed into a blender tube and 60 mL of ethyl acetate and 15g of sodium sulfate are added. The mixture is homogenized for 30 s, using a Polytron, and filtered. The filtrate is evaporated and the residue obtained is dissolved in acetonitrile-water (1 1, v/v). Alba etal. considered the low recoveries of these polar pesticides as the major disadvantage of the acetone extraction method. In their previous work they evaluated the efficacy of ethyl acetate for the extraction of pesticide residues. 

SPE has been applied to phthalate esters (plasticisers in PVC), polar pesticides (agricultural usage) and for other continuous pollution monitoring problems and environmental analyses [272]. For these applications SPE has largely displaced LLE as the preferred technique for the preparation of liquid samples, e.g. EPA method 506 is concerned with the determination of phthalates and adipate esters in drinking water. 

Kock-Schulmeyer M, Ginebreda A, Gonzalez S, Cortina JL, de Alda ML, Barcelo D (2012) Analysis of the occurrence and risk assessment of polar pesticides in the Llobregat River Basin (NE Spain). Chemosphere 86(1) 8-16... 

Fig. 3 Scientific studies in water. Ph pharmaceuticals Ft phthalates Fu fungicides HA acidic herbicides HCB hexachlorobenzene PCBs polychlorinated biphenyls OCs organochlorine pesticides PPs polar pesticides...

A part from the general monitoring studies, other studies have been performed focusing the hotspots areas of the Ebro river basin, mainly the Ebro delta [30, 31] and the Vero-Cinca tributaries [98-100], and specific groups of compounds like semi-polar pesticides, DDTs and dioxin-like compounds. 

Kuster M, de Alda MJL, Barata C, Raldua D, Barcelo D (2008) Analysis of 17 polar to semi-polar pesticides in the Ebro river delta during the main growing season of rice by automated on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry. Talanta 75(2) 390-401... 

Lopez de Alda M, Koch M, Martinez E, la Farre M, Navarro A, Ginebreda A, Barcelo D (2010) Polar pesticides at the Ebro River delta Occurrence and toxicity in water and biota. Hdb Env Chem (in this volume)... 

Because of their particular physico-chemical properties, every compound was not detected in all compartments. Thus, polar pesticides were usually detected in... 

Occurrence and distribution of a wide range of priority and emerging contaminants (pharmaceuticals, drugs of abuse, polar pesticides, etc.)... 

One of the known disadvantages of the use of GC is the need for previous derivatization of some of the most polar pesticides before analysis can be carried out [40]. These derivatization steps might produce low-efficiency results in complex wastewater matrices, which make the analysis rather difficult and cumbersome. However, the reproducibility in retention times when using GC techniques is so precise, that specific identifications of pesticides can be made even in complex environmental samples. 

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