title: Considerations on ultra trace analysis of carbamates in water samples.
abstract: A new routine method for the ultra trace analysis of carbamates in water samples is presented, using solid-phase extraction followed by high-performance liquid chromatography coupled to atmospheric pressure electrospray ionisation mass spectrometry (SPE-LC-ESI-MS). Instrumental conditions of LC-ESI-MS in the selected ion monitoring (SIM) mode, showed excellent linear response for the six N-methyl carbamates studied (aldicarb, carbaryl, carbofuran, methomyl, oxamyl and pirimicarb) in the range from 1 to 50 microg/l and a precision having a relative standard deviation below 7.8% was achieved. Instrumental limits of detection of 0.10 microg/l were found for these carbamates, with the exception of methomyl for which 0.50 microg/l was measured. The SPE assays were shown to be easy, fast, very sensitive, requiring a low volume (50 ml) of water sample. For laboratory-spiked water samples having 0.03 and 0.30 microg/l of individual N-methyl carbamates, higher selectivities were achieved in cartridges having octadecylsilica, polystyrene-divinylbenzene and N-vinylpyrrolidane-divinylbenzene as solid phases, for which reasonable average recoveries were obtained. Ten replicates using octadecylsilica SPE cartridges, showed average recoveries between 73.7 and 92.6% with a relative standard deviation lower than 14.7%. The present methodology evidences good robustness, accuracy and precision for monitoring of N-methyl carbamates in water samples, and is shown to be a suitable alternative to replace the currently dedicated analytical systems. The limits of detection for the analysis of N-methyl carbamates in water samples reached in the present methodology (0.5 to 3 ng/l), clearly cover the maximum concentration admissible for pesticides, established by the European Union directive on water quality.
authors.affiliation: Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa and Centro de Ciências Moleculares a Materiais, Campo Grande Ed. C8-3o Piso, 1749-016 Lisbon, Portugal. nogueira@fc.ul.pt
authors.forename: J M F
authors.initials: JM
authors.lastname: Nogueira
authors.forename: Tom
authors.initials: T
authors.lastname: Sandra
authors.forename: Pat
authors.initials: P
authors.lastname: Sandra
mesh_terms: D000448:Aldicarb / Q000032:analysis; D002219:Carbamates / Q000032:analysis*; D012721:Carbaryl / Q000032:analysis; D002235:Carbofuran / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007202:Indicators and Reagents; D008724:Methomyl / Q000032:analysis; D008832:Microchemistry / Q000379:methods; D010573:Pesticide Residues / Q000032:analysis*; D011743:Pyrimidines; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014867:Water / Q000737:chemistry*; D014873:Water Pollutants / Q000032:analysis
chemical_list: D002219:Carbamates; D007202:Indicators and Reagents; D010573:Pesticide Residues; D011743:Pyrimidines; D014873:Water Pollutants; D014867:Water; C011994:pirimicarb; D008724:Methomyl; D000448:Aldicarb; D012721:Carbaryl; D002235:Carbofuran; C011960:oxamyl