Simple and rapid assay for analyzing residues of carbamate insecticides in bovine milk: hot water extraction followed by liquid chromatography-mass spectrometry.

A simple, specific and rapid procedure for determining six largely used carbamate insecticides in bovine whole milk is here presented. This method is based on the matrix solid-phase dispersion technique with heated water as extractant followed by liquid chromatography (LC)-mass spectrometry (MS) equipped with a single quadrupole and an electrospray ion source. Target compounds were extracted from milk by water heated at 90 degrees C. After acidification and filtration, 0.2 mL of the aqueous extract was injected in the LC column. MS data acquisition was performed in the selected ion-monitoring mode, selecting three ions for each target compound. Heated water appeared to be an excellent extractant, since absolute recovery data ranged between 76 and 104% with R.S.D. not larger than 8%. Using butocarboxim (an obsolete carbamate insecticide) as surrogate internal standard, the accuracy of the analysis at three spike levels varied between 85 and 105% with R.S.D. not larger than 9%. On the basis of a signal-to-noise ratio of 10, limits of quantification were estimated to range between 3 ppb (propoxur) and 8 ppb (pirimicarb). The effects of temperature, volume and flow rate of the extractant on the analyte recovery were studied.