Electrospray Liquid Chromatography Quadrupole Ion Trap Mass Spectrometry Determination of Phenyl Urea Herbicides in Water

• Published in: Journal of agricultural and food chemistry Vol. 49; no. 6; pp. 2746 - 2755
• Main Author: Draper, William M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-06-2001
• Subjects: Analysis methods; Applied sciences; Chromatography, High Pressure Liquid - methods; Exact sciences and technology; Freshwater; Herbicides - analysis; Natural water pollution; Phenylurea Compounds; Pollution; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Mass, Electrospray Ionization - methods; Water - chemistry; Water treatment and pollution; USA, Colorado R; Pesticides; Liquid chromatography; Electrospray; Herbicide; Chemical pollution; Pollutant; Ion trap; Analysis method; Surface water; Water quality; Ureas; Water pollution; River water; Mass spectrometry; Quantitative analysis
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0011539

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 R2NH in N‘,N‘-dialkyl ureas or loss of C3H5NO2 (87 amu) in N‘-methoxy ureas. A 2 mm (i.d.) × 15 cm C18 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/μL 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 C18 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. Keywords: Electrospray; phenyl urea; herbicides; water