title: Electrospray liquid chromatography quadrupole ion trap mass spectrometry determination of phenyl urea herbicides in water.
abstract: Phenyl urea herbicides were determined in water by electrospray quadrupole ion trap liquid chromatography-mass spectrometry (ES-QIT-LC-MS). Over a wide concentration range [M - H](-) and MH(+) ions were prominent in ES spectra. At high concentrations dimer and trimer ions appeared, and sodium, potassium, and ammonium adducts also were observed. In the case of isopturon, source collision-induced dissociation (CID) fragmentation with low offset voltages increased the ion current associated with MH(+) and diminished dimer and trimer ion abundance. In the mass analyzer CID involved common pathways, for example, daughter ions of [M - H](-) resulted from loss of R(2)NH in N',N'-dialkyl ureas or loss of C(3)H(5)NO(2) (87 amu) in N'-methoxy ureas. A 2 mm (i.d.) x 15 cm C(18) reversed phase column was used for LC-MS with a linear methanol/water gradient and 0.5 mL/min flow rate. Between 1 and 100 pg/microg/L the response was highly linear with instrument detection limits ranging from <10 to 50 pg injected. Whereas the positive ES signal intensity was greater for each of the compounds except fluometuron, negative ion monitoring gave the highest signal-to-noise ratio. Analysis of spiked Colorado River water, a source high in total dissolved solids and total organic carbon, demonstrated that ES-QIT-LC-MS was routinely capable of quantitative analysis at low nanogram per liter concentrations in conjunction with a published C(18) SPE method. Under these conditions experimental method detection limits were between 8.0 and 36 ng/L, and accuracy for measurements in the 20-50 parts per trillion range was from 77 to 96%. Recoveries were slightly lower in surface water (e.g., 39-76%), possibly due to suppression of ionization.
authors: Sanitation and Radiation Laboratory Branch, California Department of Health Services, 2151 Berkeley Way, Berkeley, CA 94704, USA. Wdraper@dhs.ca.gov
authors: W M
authors: WM
authors: Draper
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006540:Herbicides / Q000032:analysis*; D010671:Phenylurea Compounds; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D006540:Herbicides; D010671:Phenylurea Compounds; D014867:Water