Evaluation of Hydromatrix and Magnesium Sulfate Drying Agents for Supercritical Fluid Extraction of Multiple Pesticides in Produce

Abstract

The simultaneous extraction of relatively polar and nonpolar pesticides has been problematic in multiresidue analysis using supercritical fluid extraction (SFE) with carbon dioxide. In fruit and vegetable samples, which typically contain 80-95% water, moisture acts to increase SFE recoveries of many polar pesticides, but a drying agent should be used to control water in SFE. Hydromatrix, a prevalent drying agent, has many desirable characteristics, but it reduces recovery of certain important pesticides, such as methamidophos, acephate, and omethoate. MgSO 4 has been shown previously to be applicable for the extraction of methamidophos and six other pesticides, but MgSO 4 has practical disadvantages in its use. In this study, properties and SFE results with the individual drying agents and their combination were evaluated. Simultaneous recoveries for polar and nonpolar pesticides were achieved for 71 pesticides fortified in apple using a mixture of 2 + 1 + 2 MgSO 4 •H 2 O-Hydromatrix-sample for extraction. The advantages of each drying agent were maintained by their combination. The analysis of real samples, however, showed that more study was needed to improve recoveries of nonpolar pesticides.

Evolution and applications of the QuEChERS method

“…Concerning the use of salts to induce phase separation, MgSO 4 , MgCl 2 , NaNO 3 , NaCl, Na 2 SO 4 , LiCl and fructose were tested {the use of drying salts (e.g., Na 2 SO 4 or MgSO 4 ) to improve recoveries of polar compounds had already been reported in a good number of occasions [10][11][12]}. Among the studied salts, MgSO 4 provided the most complete liquid-liquid phase separation and was better able to bind large amounts of water.…”

MSPD as sample preparation method for determination of selected pesticide residues in apples

“…SFE is used sporadically for the extraction of pesticide residues in laboratories due to the high instrumentation cost and the demand for optimisation of a high number of parameters for every matrix. The highest advantage of SFE in food analysis is the possibility of high extraction selectivity, the obtained extract is relatively pure and pre-concentrated (Eller, 1997).…”

Supercritical fluid extraction as a useful method for pesticides determination

“…In fa c t , H y d ro m at ri x appears as the best drying agent for SFE; it absorbs twice its mass in water, and enables extraction due to sample dispersion and reduced particle size. Alternatively, a combination of MgSO 4 and Hydro m at rix may be adva n t age o u s [28,29]. Nevertheless, drying agents must be used with great care as they may retain some pesticides.…”

“…Nevertheless, drying agents must be used with great care as they may retain some pesticides. For example celite, H y d ro m at rix and cellulose CF-1 we re shown to part i a l ly retain polar pesticides, s u ch as methamidophos, a c ep h at e and omethoate [18,27,28], while magnesium sulfate reduced the recoveries of non polar pesticides [28].…”