About the Method

Learn more about the QuPPe Method in the following chapters.

Method

The QuPPe method is a quick and easy procedure for the analysis of highly polar pesticides and their metabolites in food. The procedure entails a simple one-step/single-phase extraction with a methanol/water mixture. For some complex commodities, major matrix components, such as lipids and proteins are separated via simple precipitation or via dSPE. Depending on the matrix, water is added for the adjustment of the total extract volume. Measurement sensitivity allowing, a dilution of the final extract prior or during injection is recommended, as an optional step, to reduce matrix load.

QuPPe thus allows the analysis of multiple highly polar pesticides in food within a short time and using one single extraction step. This obviates the need for cumbersome derivatization procedures for individual analytes.
QuPPe has been successfully validated for more than 50 highly polar pesticides and their metabolites in various matrices. A large number of Matrix/Compound combinations were validated within interlaboratory trials. To correct for volume variations and matrix effects and to assist identification, isotopically labelled internal standards (IL-ISs) are used. As a result, method bias is typically very low.

The final aqueous extract is suitable for liquid or ion chromatography with tandem mass spectrometry (LC- or IC-MS/MS) using various types of HILIC, graphitized carbon or ion chromatography columns.

In brief, the standard procedure entails the following steps:

  • Weighing of 10 g of sample
  • Addition of water to adjust total extract volume (in many cases optional)
  • Addition of 10 mL acidified methanol (containing 1 % formic acid)
  • Shaking
  • Freezing-out of vessels containing sample material and raw extract
  • Centrifuging (while still cold)
  • Filtering of extract into an autosampler vial
  • Determinative analyzed by LC- or IC-techniques

The detailed procedures are described in CEN/TC275.

Scope

Commodities

  • Commodities with high water content (≥ 80 %)
  • Commodities with intermediate water content (> 40 % to < 80 %)
  • Commodities with low water content (15 % to 40 %)
  • Honey
  • Commodities with very low water content (< 15 %)
  • Commodities of animal origin (water content > 30 %)
  • Fat and Lipids

Modifications depending on the matrix composition

  • Water addition to adjust total extract volume
  • Freeze-out for the precipitation of poorly soluble co-extractives
  • Addition of EDTA solution for the complexation of metal cations especially when analysing glyphosate
  • dSPE with C18-sorbent for the removal of fat and lipids (for high fat and low protein matrices)
  • Precipitation with acetonitrile for the removal of proteins (for high protein matrices)
  • Precipitation with acetonitrile combined with dSPE using C18 sorbent for the removal of proteins and fat (for high fat and high protein matrices)
  • Ultrafiltration using cut-off filters of 5 or 10 kDa (optional)
  • Dilution to reduce matrix load

Analytes

  • Highly polar molecules (typically with log Kow values <  -1) and molecules with permanent or pH dependent ionic character.
  • Examples ESI pos:
    Chlormequat, Nicotine, Matrine, Propamocarb, Melamine, …
  • Examples ESI neg:
    Glyphosate, Glufosinate, Fosetyl, Chlorate, Perchlorate, Trifluoroacetic acid, …

Chromatography

Measurement and instrumental analysis of the QuPPe extract can be conducted by LC-MS/MS and IC-MS/MS. Chromatography is performed on columns based on graphitized porous carbon (GPC) material, hydrophilic interaction liquid chromatography (HILIC) or ion exchange chromatography (IC).

Examples for possible analytical columns are listed in CEN/TC275 and in the QuPPe document.

History

Since the 1990's, the number of pesticides with highly polar character has risen. Due to their chemical properties, they are not amenable to the widely used QuEChERS method and another approach was necessary.

The QuPPe method was developed by the EURL-SRM, hostet at the CVUA Stuttgart, between 2006 and 2008 and has been in routine use at the pesticide residue laboratory of the CVUA Stuttgart since 2007.

The method was first presented at the EPRW in June 2008 in Berlin, followed by the first "QuPPe-PO Document" placed online in January 2009. At that early stage, the method entailed two instrumental LC-MS/MS methods, one operating in the ESI-neg. and one in the ESI-pos. mode and covering only five analytes. The method has been gradualy expanding since then. In 2012, V7 was published entailing seven chromatographic methods including a method involving separation on a column using carbon material. Since version V12 and July 2022, the QuPPe-PO Document additionally entails an ion chromatographic (IC) method and contains 21 chromatographic methods covering about 55 analytes in total.

With each version the scope of the method was enlarged, the text revised and improved and modifications added, such as the use of EDTA solution for the analysis of glyphosate in commodities that contain large amounts of metal ions in Version V10.1 in 2019.

Besides describing the extraction procedure, chromatographic conditions and validation data, the document entails a collection of hints for the successful application of this method.

For commodities of animal origin, a separate document was introduced ("QuPPe-AO") in March 2013.

Interlaboratory validation studies were organised by the EURL-SRM with laboratories from various countries participating. The first one in 2014 covered nine analytes amenable to LC-MS/MS in the ESI positive mode. The second one focused on inorganic anions (chlorate, perchlorate, phosphonate, bromide) and the third one in 2019/2020, covered eleven pesticides and metabolites amenable to the ESI-neg. mode, such as glyphosate.