Exact‐mass library for pesticides using a molecular‐feature database

Abstract

An automated molecular-feature database (MFD) consisting of the exact monoisotopic mass of 100 compounds, at least one exact mass product ion for each compound, and chromatographic retention time were used to identify pesticides in food and water samples. The MFD software compiles a list of accurate mass ions, excludes noise, and compares them with the monoisotopic exact masses in the database. The screening criteria consisted of +/-5 ppm accurate mass window, +/-0.2 min retention time window, and a minimum 1000 counts (signal-to-noise (S/N) ratio of approximately 10:1). The limit of detection for 100 tested compounds varied from <0.01 mg/kg for 72% of the compounds to <0.1 mg/kg for 95% of the compounds. The MFD search was useful for rapid screening and identification of pesticides in food and water, as shown in actual samples. The combined use of accurate mass and chromatographic retention time eliminated false positives in the automated analysis. The major weakness of the MFD is matrix interferences and loss of mass accuracy. Strengths of the MFD include rapid screening of 100 compounds at sensitive levels compared with a manual approach and the ease of use of the library for any accurate mass spectrometer instrumentation capable of routine sub-5-ppm mass accuracy.

Fragmentation study of iridoid glycosides and phenylpropanoid glycosides in Radix Scrophulariae by rapid resolution liquid chromatography with diode‐array detection and electrospray ionization time‐of‐flight mass spectrometry

“…The accurate-mass capability of the TOF analyzer allows reliable confi rmation of the identity of the detected compounds in complex matrixes, normally with mass errors below 5 ppm in routine analysis (Ferrer et al, 2006), which is satisfi ed with the current analysis. With dynamic adjustment of the key role of the fragmentor voltage in TOF MS, the ESI-MS fragmentation behavior of IGs and PGs was investigated for the fi rst time and applied for the structural identifi cation of similar types of compounds in Radix Scrophulariae.…”

Construction of a simple evaluation system for the intestinal absorption of an orally administered medicine using <i>Bombyx mori</i> larvae

“…Pesticides with molecular weights of 50-450 have shown oral toxicity in insects (26); thus, compounds with molecular weights of ≤ 500 may be easily absorbed from the B. mori larval midgut. Using the isolated B. mori larval midgut, Hamamoto et al (12) reported that the relationship between the polarity and molecular weight of a compound determines their intestinal permeability.…”

Use of ultra‐high‐pressure liquid chromatography–quadrupole time‐of‐flight MS to discover the presence of pesticide metabolites in food samples

“…One publication related to food analysis [15] reports the identification of an imazalil degradation product (1-[2-(2,4-dichlorophenyl)-2-hydroxyethyl]-1H-imidazole) in apple and pear. However, the powerful deconvolution software required for detecting components in a sample along with vast mass spectral libraries may not be sufficient to discover a pesticide metabolite.…”