Introduction to QuEChERS

Pradeep Kumar. G.T

QuEChERS (“catchers”)Quick

Easy

Cheap

Effective

Rugged

Safe

The QuEChERS-method was

developed by Michelangelo in the

year 2001 for the analysis of

veterinary drugs in animal tissues.

After realizing its great potential in the extraction of

polar and particularly basic compounds it was also

tested on pesticide residue analysis in plant material

with great success.

Now QuEChERS is known as amulticlass, multiresidue method (MRM)for analysis of pesticides from highwater content (80-95%) matrices.

The QuEChERS method now publishedas AOAC method 2007.01“Determination of Pesticide Residues inFoods by Acetonitrile Extraction andPartitioning with Magnesium Sulfate”.

The preferred solvent isacetonitrile because it has beenshown to provide extraction ofthe broadest range of organiccompounds without co-extractionof large amounts of lipophilicmaterial.

This method is validated for theanalysis pesticide residue in dryproducts like cereals, dried fruits,tea and fatty foods like fish, meat.

Step 1: Sample preparation and extraction

Commodities are uniformly ground

Extract using required quantity of acetonitrile

Centrifuge the extract

Cleaned up using DSPE.

Bulk drying salts and DSPE sorbent

packings.Remove excess water and unwanted

contaminants.

Agitation and centrifugation

Vortex mixing for 30sec and

centrifuge at 3000 rpm for 5min

Freezing out The acetonitrile phase is

transferred into a centrifuge tube and stored in a freezer (min 2hrs) removal of lipids, waxes, sugars, and other matrix co-extractives with low solubility in acetonitrile.follow DSPE.

D-SPE with a PSA/MgSO4-mixture (for most samples)

The acetonitrile phase is transferred into a PP-centrifugation tube already containing PSA and magnesium sulfate and agitate.

SPE(Solid Phase Extraction)

DSPE(Dispersive Solid Phase Extraction)

Required 30 minutes to 1hr to complete

Few minutes

This type of cleanup is recommended for extracts of test samples containing more than 50 mg of lipids.

removal of chlorophyll and carotenoids .

Samples like red sweet pepper, spinach and vine leaves.

Concentration of the extract in Turbovap evaporator (2 to 5 mL)

made up to volume with suitable solvent.

For GC n-Hexane is used and for LC methanol.

Analysis was done either by GC/MS or LC/MS

AdvantageConventional method QuEChERS

Time-Consuming, Complicated

or Error-prone Steps

Simplified Alternatives

Sample

Processing/Homogenization

No Way Around this

Blending/shaking for long time Homogenisation for 30 Sec

Filtration Centrifugation

Multiple Partitioning Steps Single Partitioning (“On-line”-

Approach)

Separation/Transfers of Entire

Extract

Take Aliquots

Use of a Lot of Glassware A few glassware

Evaporation/Reconstitution of

large volume

Evaporation/Reconstitution of

small volume

Classical Steps/Classical SPE with

Columns & Manifold

Dispersive SPE

Procedure schematically

(for 25 g sample)

Weigh 25 g sample into a 250 ml centrifuge

bottle (with screw cap)

Add 50 ml acetonitrile and shake well

Add 10 g NaCl, shake each tube to dissolve salt.

Homogenise for 30 Sec (1st . extraction step)

5g Na2SO4 added to an aliquot

From above step an aliquot is transferred to mixture of 0.2g PSA and 0.75g MgSO4

Aliquot is concentrated and reconstituted.

Centrifuge for 5 min at 3000 U/min

Mix well in vortex (2nd extraction with phase separation)

References

www.quechers.com

http://www.eurl-pesticides-datapool.eu/

GCB-Graphitised Carbon Black