Analysis Pesticides, Carbamate

Although an excellent detector for PAEis, the fluorometer is not widely used in environmental analysis, as the number of environmental pollutants with fluorescent spectra is limited. The sensitivity and selectivity of the fluorometer are also used in the A-methyl carbamate pesticide analysis (EPA Method 8318). These compounds do not have the capacity to fluoresce however, when appropriately derivatized (chemically altered), they can be detected fluorome-trically. The process of derivatization takes place after analytes have been separated in the column and before they enter the detector. This technique, called post column derivatization, expands the range of applications for the otherwise limited use of the fluorometer. 

A Note on Post-Column Reaction Techniques A post-column reaction unit is an online derivatization system that supplies reagents to the column eluent into a heated chamber to convert the analytes into more chromophoric forms for higher sensitivity detection. Some common applications of post-column reaction systems are amino acid analysis using ninhydrin (with visible detection), and carbamate pesticide analysis using o-phthaldehyde (with fluorescence detection).]... 

Typical examples of enzymes involved in food applications are cholinesterase for organophosphorous and carbamate pesticide analysis tyrosinase or laccase for analysis of phenols, quinones, and related compounds glucose oxidase for sugar content analysis, carboxyl esterase, alcohol oxidase, carboxypeptidase, L-aspartase, peptidase, aspartate... 

Belisle AA, Swineford DM. 1988. Simple, specific analysis of organophosphoms and carbamate pesticides in sediments using column extraction and gas chromatography. Environ Toxicol Chem 7 749-752. 

Lord and Pawliszyn" developed a related technique called in-tube SPME in which analytes partition into a polymer coated on the inside of a fused-silica capillary. In automated SPME/HPLC the sample is injected directly into the SPME tube and the analyte is selectively eluted with either the mobile phase or a desorption solution of choice. A mixture of six phenylurea pesticides and eight carbamate pesticides was analyzed using this technique. Lee etal. utilized a novel technique of diazomethane gas-phase methylation post-SPE for the determination of acidic herbicides in water, and Nilsson et al. used SPME post-derivatization to extract benzyl ester herbicides. The successful analysis of volatile analytes indicates a potential for the analysis of fumigant pesticides such as formaldehyde, methyl bromide and phosphine. 

E.B. Tribaldo, Residue analysis of carbamate pesticides in water, in Food Science Technology, Marcel Dekker, New York, pp. 537-570 (2000). 

A Cis disk has been used to remove chlorotriazine, atrazine, metabolites, organophosphorus compounds, phenylurea, and carbamate pesticides from seawater prior to analysis by HPLC [392],... 

Chromatographic Conditions for Analysis of Carbamate Pesticides Extracted from Solution... 

High-performance LC is the favored technique for the determination of carbamates, since many of them lack the thermal stability necessary for gas chromatographic analysis. Most HPLC methods for methyl and phenyl carbamate pesticides have employed reversed-phase chromatography with C18 or C8 columns and aqueous mobile phases (47,50,105,106). Two different solvent sys-... 

Carbamate pesticides can be determined using different detectors in GC or HPLC analysis. A characteristic feature of a carbamate molecule is the nitrogen atom, which can form the bases for quantitation and some carbamates also contain chlorine, sulfur, or other heteroatoms in the molecule. This allows the use of various detection techniques for their determination (139,140), such as electrical conductivity (165), alkali flame (141) photometry, and mass spectrometry (44,166). 

BGL Schlagbauer, AWJ Schlagbauer. The metabolism of carbamate pesticides—a literature analysis. Residue Reviews 42 1-90, 1972. 

RT Krause. Multiresidue methods for carbamate pesticides. Emerging Strategies for Pesticide Analysis 5 99-123, 1992. 

G Blaicher, W Pfannhauser, H Woidich. Problems encountered with the routine applcation of HPLC to the analysis of carbamate pesticides. Chromatographia 13 438-446, 1980. 

The use of NBD-Cl for the fluorescence analysis of alkylamine-generating pesticides has been investigated [173]. A two-phase reaction system is employed for the hydrolysis and labeling of N-methyl- and N,N-dimethyl-carbamate pesticides. The residue is hydrolyzed in 0.1 M sodium carbonate and the liberated amine is treated with NBD-Cl in an organic phase (IBMK, isobutyl methyl ketone) above the aqueous layer. An aliquot portion of the organic layer is used for chromatography. The reactions involved are shown in Fig. 4.65. 

Thiocholine was studied first as a standard thiol compound because of its importance in environmental analysis. Determination of thiocholine is in fact usually carried out to evaluate the degree of inhibition of acetylcholinesterase, a target enzyme of pesticides, as a means for indirect measurements of organophosphorous and carbamate pesticides. 

OP compounds and carbamate are widely used as insecticides, pesticides, and warfare agents [20,21], Detection of pesticides is usually carried out by multiresidue methods (MRMs) of analysis, which are able to detect simultaneously more than one residue and have been developed mainly based on chromatographic techniques. Two groups of MRMs are used (i) multiclass MRMs that involve coverage of residues of various classes of pesticides, and (ii) selective MRMs, which concern multiple residues of chemically related pesticides (e.g., IV-methyl carbamate pesticides (NMCs), carboxylic acids, phenols, etc.). As foods are usually complex matrices all of the pre-analytical steps (matrix modification, extraction, and clean-up) are often necessary. 

Air analysis for carbamate pesticides may be performed by sampling air over 1 pm PTFE membrane. The analytes collected over the membrane are extracted with methylene chloride, exchanged into methanol, and analyzed by HPLC using postcolumn derivatization technique as described above. Certain pesticides may be analyzed too by the colorimetric method (see Part 3 under individual compounds). 

Yang, G. and S. Kang. 2008. SPR-based antibody-antigen interaction for real time analysis of carbamate pesticide residues. Food Sci. Biotechnol. 17 15-19. 

The increased use of derivatisation reactions is evident from the gradual increase in the number of publications dealing with the subject. Figure 1 shows the yearly variation in numbers of publications dealing with derivatisation in pesticide analysis over the period 1963 to 1978. While the interest in derivatisation techniques in organophosphorus insecticide analysis has remained fairly constant and a low level of activity, the OC insecticides underwent an increased period of attention from 1968-1972 which has stablized over the last few years. It is in the insecticidal carbamate and herbicide areas that an overall steady increase in the use of derivatisation reactions for quantitative and con-... 

The electrolytic conductivity detector for gas chromatography was developed by Coulson (15, 16, 17), who described modes of operation for the detection of chlorine, sulfur, or nitrogen, but did not establish the reliability of the detector for pesticide residue analysis or the minimum detectability for each molecular species. Cassil et al. (11) described the use of the detector for determining residues of carbamate pesticides and compared its response with that of the microcoulometric detector, as mentioned earlier, finding them equal in response and selectivity and usable over a range of 3 to 200 ng of nitrogen. An improved pyrolysis tube was described, and nickel wire or turnings was used as the catalyst... 

K.S. Chiu, A. Van Langenhove, C. Tanaka, LC-MS-MS analysis of carbamate pesticides, Biomed. Environ. Mass Spectrom., 18 (1989) 200. 

In case of the qualitative test applied for the qualitative analysis of organophosphate and/or carbamate pesticides, the inhibition of the biosensor was observed both in RM08 and RM10, thus detected the presence of the organophosphate and/or carbamate pesticides. The applied test is simple, easy-to-use and rapid, thus suitable for field measurement. However, provides information only about the presence of the representatives of the organophosphate and carbamate groups and does not allow the identification of the compounds that are present. 

While most HPLCs are general-purpose instruments, many are dedicated analysis systems packaged with specific columns and reagents. They often come with guaranteed performance from the vendor. Examples are systems for the analysis of amino acids (Figure 4.15c), carbamate pesticides, or sugars (see Chapter 7). 

Sanchez-Brunete, C., Rodriguez, A., and Tadeo, J. L., Multiresidue analysis of carbamate pesticides in soil by sonication assisted extraction in small columns and liquid chromatography, J. Chromatogr. A, 1007, 85-91, 2003. 

---