High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part II: Comparative Study of Extraction Efficiencies of Three Sample Preparation Techniques

Abstract

This paper reports a study of the extraction efficiency for the multiresidue pesticides and chemical pollutants in tea with three methods over three stages. Method 1 adopts the Pang et al. approach: the targets were extracted with 1% acetic acid in acetonitrile and cleaned up with a Cleanert TPT SPE cartridge; Method 2 adopts the QuEChERS approach: the targets were cleaned up dispersively with graphitized carbon and primary-secondary amine (PSA) sorbent; Method 3 adopts the relatively commonly used approach of hydration for solid samples, with tea hydrated before being extracted through salting out with acetonitrile and the cleanup procedures identical to those of Method 1. The three stages comprised two phases of comparative tests on spike recoveries of 201 pesticides and chemical pollutants from different teas and a third phase on determination of the content of the 201 pesticides and chemical pollutants from aged tea samples. In stages I and II, test results of the spike recoveries of 201 pesticides and chemical pollutants demonstrated that 91.4% of the pesticide and chemical pollutant recoveries fell within the range of 70-110%, and 93.2% of the pesticides and chemical pollutants had RSD < 15%, with no marked difference obtained by Method 1 and Method 2 regardless of whether it was green tea or woolong tea, or GC/MS or GC/MS/MS was used for analysis. For pigment removal, Method 1 was superior to Method 2; in terms of easy operation, Method 2 outweighed Method 1. However, Method 3 obtained relatively low recoveries, with 94% of pesticide and chemical pollutant recoveries less than 70%, which proved that Method 3 was not applicable to the determination of multiresidue pesticides and chemical pollutants in tea. Stage III made a comparison of Method 1 and Method 2 for the extraction efficiency of pesticides and chemical pollutants in 165-day-aged samples of green and woolong tea. Test results showed that 94% of the pesticide and chemical pollutant content in the aged tea samples was recovered with Method 1, more than 10% higher than with Method 2 (30-50% higher on average). For green tea, 193 (GC/MS/MS) and 197 (GC/MS) pesticides and chemical pollutants accounted for 96.5% (GC/MS/MS) and 98.0% (GC/MS) with Method 1 higher than with Method 2. For woolong tea, 191 (GC/MS/MS) and 194 (GC/MS) pesticides and chemical pollutants accounted for 95% (GC/MS/MS) and 96% (GC/MS/MS) with Method 1, higher than with Method 2, respectively. In other words, there were definite differences in the test results for aged tea samples between Method 1 and Method 2, which suggests that Method 1 was capable of extracting more residual pesticides and chemical pollutants from the precipitated 165-day-aged tea samples. The reason can be traced to the possibility that Method 1 (high-speed homogenizing) has better extraction efficiency than Method 2 (vortex and oscillation). Therefore, Method 1 was chosen as the sample preparation technique for multiresidue pesticide and chemical pollutant analysis in tea.

Evolution and applications of the QuEChERS method

“…Some significant examples are shown in Table 5 {e.g., macrocyclic lactones [92], lipids [93], antioxidants and food additives [94], hormones [95], UV filters [95], endocrine disruptors [95][96][97], PCBs [32], flame retardants [32], PBDEs [32], perfluoroalkyl substances [98,99], phthalates [100], isoflavones [101] surfactants [102] and acrylamide [103,104]}. Such analytes have been determined in environmental matrices {including water [95], soils and sediments [95]}, foods {i.e., milk and its derivatives [92,94,98,105,106], fish and seafood [31,32,96,98], meat [98,105], honey and beehive products [97], and fruits, vegetables and derivatives [100,106,107]} and biological matrices {i.e., blood [108,109], urine [93,108], plasma [93], cerebrospinal fluid [108], stomach content [108] and human organs …”

“…Although QuEChERS provided better (or comparable) results in the majority of the manuscripts (in terms of not only efficiency and speed but also solvent and reagent consumption and economic cost), there are examples in which QuEChERS methods has been less efficient [97,107]. As an example, Domínguez-Álvarez et al [97] determined five endocrine disruptors in honey by CE-MS using QuEChERS (extraction with 10 mL of ACN, 6 g MgSO 4 and 1.5 g NaCl of 10 g of honey diluted with 5 g of water, and clean-up with 150 mg MgSO 4 and 50 mg PSA) and two different LLE methods (LLE 1: extraction with 9 mL of n-hexane of 25 g of honey diluted with 10 g of water, LLE 2: extraction similar to LLE 1, with a shaking step after centrifugation and then repetition of the centrifugation step).…”

A review of recent developments and trends in the QuEChERS sample preparation approach

“…The scope of pesticides covered by these methods is broad and huge variety of food products may be easily tested. Fan et al developed high-throughput analytical methodology for determination of residues of 653 multiclass pesticides and chemical pollutants in tea [51]. Other multiresidue QuEChERS or QuEChERSbased methods, which allow proper determination and quantification of pesticide contaminant in tobacco [52], fish [53], beeswax [54], coffee beans [55], high oil commodities [56], soybeans and pulses [57], nutraceutical products [58], different fruits and vegetables [59] and more are developed.…”

Determination of pesticide multi-residues in green tea using a modified QuEChERS extraction and liquid chromatography tandem mass spectrometry technique

“…Recently, QuEChERS method has been applied to extract pesticides from tea (STEINIGER et al, 2010;CHEN et al, 2011;LOZANO et al, 2012;GUAN et al, 2013;RAJSKI et al, 2013;SHOEIBI et al, 2013). To deal with the matrix effect problem, many techniques have been tried including a sample dilution, matrix calibration, various types and amounts of sorbent addition, or SPE cleanup (STAHNKE et al, 2012;FAN et al, 2013;GUAN et al, 2013;RAJSKI et al, 2013;WANG et al, 2013). However, the high amount of tannin in tea requires a method with a further clean-up step.…”

“…Pesticide multi-class, multi-residue determination relies on the QuEChERS extraction combined to LC-MS/MS and/or GC-MS(/MS) instrumentation could be used to identify a few hundreds of pesticides in one single test (LEHOTAY et al, 2005;NGUYEN et al, 2010;DAI et al, 2011). Its applications have also spread to other matrices like tea, herb, rice, and other grains (STEINIGER et al, 2010;CHEN et al, 2011;FAN et al 2013;GUAN et al, 2013;RAJSKI et al, 2013).…”