Image Credit:Shutterstock/Annette Shaff
The QuEChERS method has been shown to be a useful tool in pesticide analysis targeting a variety of sample types and complex matrices. Unfortunately, the process is a manual multi-step process and is therefore time-consuming. With the seemingly unending number of food matrices and pesticide residues to be analyzed, there is a need to create a faster and simplified extraction method. Furthermore, either by their nature or their economic value, some matrices may be difficult to analyze using only the QuEChERS method.
In this article, EDGE™ is proposed as an alternative to the QuEChERS method for the extraction of pesticides from food matrices including known difficult matrices. With its patent pending Q-Cup Technology™, the EDGE™ could extract a difficult food sample, including the dispersive solid phase cleanup, in less than five minutes in a single automated step.
Nowadays, consumers want to be informed about any chemical content of their food, including any presence of pesticides. While the list of available pesticides regulated throughout the world continues to increase, the need to analyze the chemical continues.
The QuEChERS method is a widely accepted method to extract pesticides from food matrices. Due to the large number of pesticides to monitor and their corresponding low method detection limits, pesticide analysis continues to be a challenge. What could aid in such challenges are faster and simpler alternative methods that provide improved recoveries for difficult matrices.
The manual multi-step process of the QuEChERS method requires multiple sample transfers. It also generates a lot of consumable waste. Using the EDGE, the sample and sorbents are kept together in one sample cell, enabling extraction and cleanup in just one step. In less than five minutes, the food sample is extracted using Q-Cup Technology, a mechanism that performs both sample extraction and cleanup.
The collected extract is filtered, cooled, and prepared for analysis. The run time includes the sample rinsing and system washing to avoid any carryover. EDGE offers the fastest pesticide extraction possible in one simple method.
The EDGE uses the Q-Cup Technology that combines pressurized fluid extraction and dispersive solid phase extraction in a single instrument that produces rapid and efficient extraction. The easy-to-assemble Q-Cup™ sample holder boasts of a unique open cell concept that creates a dispersive effect and facilitate rapid extraction and filtration. The result is fast, simple, and efficient extractions.
It is easy to setup a sample preparation using the EDGE. A Q-Disc™ must be placed in the Q-Cup base, and the two parts must be screwed together. A sorbent or drying agent may be added along with wet or dry food samples not exceeding five grams.
Figure 1. The EDGE Process
The EDGE will utilize only 40 mL of solvent per extraction, which includes solvent for diffusive extraction and sample rinse. During system cleaning, the device may use up to an additional 30 mL of solvent. The rapid heating of the extraction chamber combined with diffusive action enables a temperature of up to 180 °C to be achieved in less than two minutes.
Sample is Loaded
The Q-Cup is automatically loaded into the chamber by the auto sampler. The pressure cap then creates a pressurized seal on the top of the Q-Cup.
Solvent is Extracted
Solvent is first added through the bottom to fill the gap between the chamber and Q-Cup, aiding in heat transfer. The solvent is then added through the top of the Q-Cup to wet the sample.
As the chamber walls are heated, the pressure in the gap increases. This process overcomes the pressure inside the Q-Cup, forcing the solvent to disperse into the sample.
Extract is Collected
Once the sample reaches the target temperature, the solvent is dispensed through the Q-Disc, the cooling coil, and into a collection vial.
Procedure and Method
One gram of primary-secondary amine (PSA) was added to an assembled Q-Cup containing a Q-Disc. For strawberries, 5 grams of Na2SO4 was added to the Q-Cup prior to the PSA. Five grams of rice, strawberries, or avocado, spiked with 250 µl of a 500 ppm spiking solution, were then added to the Q-Cup.
The salt, sorbent, and sample were not mixed, and instead created layers. The Q-Cups were placed in the EDGE removable rack each with a collection vial. The rack was slid into place on the EDGE.
The One Touch Method™ for pesticide residues was utilized. The extracts were filtered through a 0.25 µm syringe and injected into a Waters Acquity UPLC with a Xevo TQD triple quad mass spectrometer for analysis. An Acquity UPLC BEH C18 1.7 µm 2.1 x 50 mm column with a flow of 0.45 mL per minute and a six minute ramp from 95% A (water with 10 mM ammonium acetate) and 5% B (methanol with 10 mM ammonium acetate) to 5% A and 95% B.
A 10 µL sample was injected into the UPLC. Two MSD transitions were used for quantification for each pesticide.
Strawberries, rice and avocado were obtained from a local grocery store and homogenized using a grinder. All samples were spiked with organophosphorus mix A from Sigma Aldrich. PSA and sodium sulfate were purchased from the same company. Meanwhile, spiked samples were extracted using the EDGE. Acetonitrile was used as the extraction and rinse solvent. The system was washed with water and acetonitrile.
Results and Discussion
The EDGE efficiently extracted the pesticides from rice, strawberries, and avocado in under five minutes, including sample cleanup, filtration, cooling and system washing. Table 1 presents the recovery data of multiple pesticides from rice, strawberries, and avocado. These food matrices show that EDGE is effective for both dry and wet samples.
In addition, avocado is a known difficult sample due to its high fat content, and the EDGE was able to yield an extract with sufficient cleanup in a single automated step that resulted in good recoveries. Despite the food sample, EDGE offers a fast and simple extraction method that includes the cleanup process. It is a good alternative to the QuEChERS method.
Table 1. % Recovery of Pesticides from Spiked Rice, Strawberry and Avocado
This information has been sourced, reviewed and adapted from materials provided by CEM Corporation - Analytical.
For more information on this source, please visit CEM Corporation - Analytical.