P.Y. Communal and A. Royer, Girpa, Angers, France
C. Schauber and T. Faye, Varian, Inc., France
Phenoxy acids are used as herbicides in agricultural and domestic areas. These compounds have to be detected at trace level to ensure a safe drinking water and food supply and verify appropriate remediation of these pollutants from contaminated sites.
Among the analytical methods developed, LC/UV exhibits poor sensitivity and inadequate selectivity for complex vegetable matrices. Negative ion ESI LC/MS has exceptionally high sensitivity for these herbicides and, with the added selectivity of MS/MS, provides accurate analyses even for the most complex sample matrices.
A highly sensitive and fast method is described below for high throughput identification and quantitation four common herbicides in vegetable extracts (Figure 1).
Varian ProStar 410 AutoSampler
Varian ProStar 210 Solvent Delivery Modules
Varian 1200L LC/MS with ESI source
Materials and Reagents
Standard solutions: pesticides were provided by the GIRPA group, France. ASE 300 (Dionex)
Florisil (Carlo Erba)
Hydromatrix bulk material (Varian Part No. 198003)
All other chemicals are reagent grade or HPLC grade.
Sample Preparation and Extraction
Liquid/solid extraction is performed using the Varian Sample Preparation Products Hydromatrix (25g) and matrix (25g onion). Two grams of Florisil is added to the homogeneous mixture followed by Accelerated Solvent Extraction (ASE) with ethyl acetate (100 mL, 100 bar, 50 0C). After 100 μL of ndodecane is added to the extract, the solution is evaporated to dryness and the residue is dissolved wi