FOOD SAFETY TESTING

QuEChERS is the method of choice for multi-residue pesticide screening in produce, grains, meat, dairy, honey, juice, wine, and other food products. Regulatory agencies around the world rely on QuEChERS-based methods to monitor compliance with maximum residue limits (MRLs) for hundreds of pesticide compounds simultaneously. Explore UCT’s full range of QuEChERS extraction and cleanup products. 

DIVERSE MATRICES

Beyond traditional fruits and vegetables, the method has been successfully adapted for complex matrices including high-fat foods (avocado, nuts, olive oil), animal tissues (liver, kidney, muscle), cereals and grains, tobacco, cannabis, soil, and water. Each matrix type may require specific salt ratios or additional cleanup sorbents to manage interferences. 

ENHANCED PRODUCTIVITY

A single analyst can prepare large sample batches significantly faster using the QuEChERS approach. Compared to traditional liquid-liquid extraction methods that require large volumes of hazardous solvents and hours of processing time, QuEChERS dramatically reduces labor, solvent consumption, and waste generation. 

CONSISTENT RESULTS

When performed with pre-packaged, quality-controlled extraction salts and dSPE tubes, the QuEChERS method consistently delivers high recoveries with excellent reproducibility for a broad range of GC- and LC-amenable compounds — critical for meeting stringent regulatory quality assurance requirements. 

QuEChERS condenses sample preparation into an efficient, streamlined process that eliminates the complexity of traditional extraction techniques. While variations exist across the three official methods, the fundamental procedure follows the same core steps. 

Step 1: Sample Extraction

The process begins with a homogenized sample — typically 10 to 15 grams of food material that has been thoroughly blended to ensure uniform distribution of analytes. Acetonitrile is added as the extraction solvent because it provides excellent recovery for a broad range of pesticide polarities while producing minimal co-extraction of lipids compared to other solvents. The sample and solvent are vigorously shaken or vortexed to facilitate contact between the solvent and the matrix.

Next, a pre-measured combination of extraction salts is added. The specific salt mixture depends on the method being used: the Original method uses magnesium sulfate (MgSO₄) and sodium chloride (NaCl); AOAC 2007.01 uses MgSO₄ and sodium acetate (NaOAc) with 1% acetic acid in the acetonitrile; EN 15662 uses MgSO₄, NaCl, and a pair of citrate buffer salts. The salts serve two critical purposes — magnesium sulfate drives phase separation between the aqueous and organic layers (a process called “salting out”) and removes residual water, while the additional salts control pH and improve recovery of pH-sensitive analytes. After adding salts, the tube is shaken vigorously for one minute and then centrifuged, producing a clear organic supernatant layer containing the extracted analytes.

Step 2: Dispersive SPE Clean-Up

An aliquot of the organic supernatant is transferred into a second tube containing pre-weighed dSPE sorbents and additional MgSO₄. The sorbents selectively adsorb matrix interferences — co-extracted compounds like organic acids, sugars, lipids, pigments, and sterols that would otherwise interfere with chromatographic analysis and damage sensitive instrumentation.

Primary Secondary Amine (PSA) is the most commonly used dSPE sorbent and is effective at removing organic acids, certain sugars, and fatty acids. For samples with higher lipid content, C18 sorbent is added to target additional fats and nonpolar interferences. Samples rich in chlorophyll (such as leafy greens, herbs, and tea) require a pigment-removal sorbent — UCT’s proprietary ChloroFiltr® sorbent offers selective chlorophyll removal without the loss of planar analytes that traditional graphitized carbon black (GCB) can cause. The tube is shaken briefly, centrifuged again, and the resulting clean extract is ready for instrumental analysis.

Step 3: Instrumental Analysis

The purified extract is transferred to an autosampler vial and analyzed by gas chromatography coupled with mass spectrometry (GC-MS or GC-MS/MS) or liquid chromatography with mass spectrometry (LC-MS or LC-MS/MS). Because the extract is in acetonitrile, it is directly compatible with both LC and GC systems. Many laboratories run both GC and LC analyses on the same extract to maximize the number of detectable compounds, since some pesticides are more amenable to one technique than the other. The entire process — from raw sample to instrument-ready extract — takes approximately 15 to 30 minutes per sample, a fraction of the time required by legacy extraction methods.

Understanding each reagent’s function is essential for selecting the right QuEChERS products and troubleshooting extraction issues. QuEChERS salts play a critical role in extraction efficiency, phase separation, moisture removal, and analyte recovery. Each component in the QuEChERS workflow serves a specific analytical function. 

UCT offers QuEChERS products in multiple convenient formats to fit different laboratory workflows, throughput requirements, and automation configurations.

Common questions about the QuEChERS method and its applications.