Mass pesticides

There are many examples of this effect of pesticide use, which can seem unexpected at first glance. Epidemiologists achievements in using pesticides to suppress malaria-carrying mosquitoes are well known. Before pesticide use, 40 million people contracted malaria in India annually after mass pesticide treatments in the 1950s, this number decreased to 40,000 annually. However, 10-15 years later, the mosquitoes showed resistance to... 

Equation 1 describes the change of mass, pesticides, within the tank at any given time. The symbols used in this derivation are defined as follows ... 

Competitive format for small molecular mass (pesticide)... 

Pfleger, K., Maurer, H.H., and Weber, A., Mass Spectral and GC Data of Drugs, Poisons, Pesticides, Pollutants and Their Metabolites, VCH, Weinheim, Germany, 1992. 

Because many studies have shown a direct relationship between pesticide sorption and organic carbon content of sod, attempts have been made to develop a universal sorption coefficient based on sorption of the pesticide to sod organic carbon (44). Sorption based on sod organic carbon is expressed as C, where is pesticide sorbed per unit mass sod organic carbon, and C is pesticide solution concentration after equdibration. If. is the fraction of organic carbon, can be obtained from i in the equation. Assumptions in the use of this approach include... 

Figure 13.13 On-line trace eniicliment-RPLC-diode-aiTay detection (DAD) cliromatogram (at 230 nm) obtained from 200 ml of tap water spiked with various pesticides at levels of 1 p.g L. Reprinted from Chromatographia, 43, C. Aguilar et al., Deteimination of pesticides by on-line ti ace emicliment-reversed-phase liquid clrromatography-diode-aiTay detection and confirmation by paiticle-beam mass specti ometi y , pp. 592-598, 1996, with permission from Vieweg Publisliing.

Figure 13.19 Chromatograms obtained by on-line SPE-GC-MS(SIM) of (a) 10 ml of tap water spiked with pesticides at levels of 0.1 ng 1 (b) 10 ml of a sample of unspiked tap water. Peak identification foi (a) is as follows 1, molinate 2, a-HCH 3, dimethoate 4, simazine 5, ati azine 6, y-HCH 7, S-HCH 8, heptachloi 9, ametiyn 10, prometiyn 11, fen-itrothion 12, aldrin 13, malatliion 14, endo-heptachlor 15, a-endosulfan 16, teti achlor-vinphos 17, dieldrin. Reprinted from Journal of Chromatography, A 818, E. Pocumll et al., On-line coupling of solid-phase exti action to gas cliromatography with mass specti ometiic detection to determine pesticides in water , pp. 85-93, copyright 1998, with permission from Elsevier Science.

C. Aguilar, I. Feirer, R Bonnll, R. M. Marce and D. Barcelo, Monitoring of pesticides in river water based on samples previously stored in polymeric cartridges followed by on-line solid-phase extraction-liquid cliromatography-diode array detection and confirmation by atmospheric pressure chemical ionization mass spectrometry . Anal. Chim. Acta 386 237-248 (1999). 

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). 

C. Aguilar, R Bomtll and R. M. Marce, Determination of pesticides by on-line trace enrichment-reversed-phase liquid cliromatogr aphy-diode-array detection and confirmation by particle-beam mass spectrometry , Chromatographia 43 592-598 (1996). 

S. Lacorte and D. Barcelo, Determination of parts per trillion levels of organophospho-rus pesticides in groundwater by automated on-line liquid- solid extraction followed by liquid chr omatography/atmospheric pressure chemical ionization mass spectrometry using positive and negative ion modes of operation . Anal. Chem. 68 2464- 2470 (1996). 

I. Eeirer, M. C. Hennion and D. Barcelo, Immunosorbents coupled on-line with liquid chi omatography/atmospheric pressure chemical ionization/mass specti ometiy for the part per trillion level determination of pesticides in sediments and natural waters using low preconcenti ation volumes . Anal. Chem. 69 4508-4514 (1997). 

E. Pocurull, C. Aguilar, E. Borrull and R. M. Marce, On-line coupling of solid-phase extraction to gas cliromatography with mass spectrometric detection to determine pesticides in water , 7. Chromatogr. 818 85-93 (1998). 

Not all of these isomers are completely separated by the conditions given here, but all arc readily detected by plotting the masses of the molecular ions. Pesticides can interfere with polychlorinated biphenyl (PCB) analysis. 

If you frequently analyze pesticides, obtain the latest edition of Mass Spectrometry of Pesticides and Pollutants (Safe and Hutzinger. Boca Raton, FL, CRC Press). This book, combined with the list of most abundant ions (Table 25.1) and/or a computer library search, will be sufficient to identify most commercial pesticides. Also, see Chapters 17, 26, and 27. 

T. Cairns, E. G. Siegmund and R. A. Jacobson, Mass Spectral Data Compilation of Pesticides and Industrial Chemicals, Food and Drug Administration, Los Angeles, 1981. 

Figure 3.14 Background mass spectrum obtained from the LC-MS analysis of a pesticide mixture. From applications literature published by Micromass UK Ltd, Manchester, UK, and reproduced with permission.

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