Agricultural chemicals typically analyzed by GC/MS can be identified and quantified more effectively and efficiently using LC/MS/MS. These agricultural compounds are extracted from plant materials, and thereby present matrix challenges.
Health and food safety organizations worldwide are placing great importance on the identification and quantitation of insecticides and herbicides in produce. Chlorinated pesticides have been largely replaced with organophosphorous and organonitrogen pesticides that degrade faster and are typically gentler to the environment.
Until very recently, these compounds had traditionally been analyzed by GC and GC/MS. Separation was often difficult due to the high polarity, low volatility and thermal lability of many pesticides. Difficult matrix effects were usually present since biocide compounds were often extracted from plant material.
Triple quadrupole performance in an economical benchtop format
Patented LINAC collision cell prevents crosstalk with shorter multiple reaction monitoring (MRM) dwell times and enhances quantitative accuracy
Curtain Gas interface protects the analyzer from contamination even with crude samples
API 2000 System is a compact, easy to use, triple quadrupole MS system ideal for routine quantitative analysis
The objective of this experiment was to design an LC/MS/MS method to identify and quantify eleven environmentally toxic compounds from two very different classes.
MRM was performed on the API 2000 LC/MS/MS System for enhancing the selectivity and specificity of these low molecular weight compounds.
Compounds of interest for this study include acephate, desethyl atrazine, cyanazine, dichlorvos, dicrotophos, dimethoate, hexazinone, mevinphos, omethoate, phosphamidon, and simazine. Past research experiments have proven acephate and omethoate to be difficult to separate.
Calibration curves were established over the entire analyte concentration range of 2 to 15 ng/mL (ppb). Reproducibility (%CV) was exceptionally good considering that results were acquired over an 18-hour period.
For these applications, triple quadrupole mass spectrometry offers advantages over single quadrupole operations since the API 2000 LC/MS/MS System can perform MRM scans which provide superior specificity for the identification of co-eluting chromatographic peaks. Additionally, the API 2000 LC/MS/MS System has the patented LINAC collision cell, which allows for shorter MRM dwell times and increased data confidence during quantitative analysis.
A rapid, sensitive, robust and specific method was developed using the API 2000 LC/MS/MS System. This method separated and quantitated organonitrogen and organophosphorous pesticides in a single chromatographic run and even identified cis- and trans-isomers of particular compounds. Signal-to-noise ratios greater than 5:1 were obtained for all compounds at 1 pg on column while delivering excellent reproducibility. The high sensitivity of this technique allows further dilution if necessary.