04.02.2014

Phosphonic acid and fosetyl – analysis at ifp

The analysis and evaluation of residual phosphonic acid has caused uncertainty within the organic food industry. ifp Institut für Produktqualität offers the analysis of residual fosetyl and phosphonic acid in foods using HPLC-MS/MS.

Unspecific residues of the substance may derive from phosphorous fertilizer (which is permitted in organic crop growing), but also from three different agents used in pesticides: fosetyl-aluminium, disodium phosphonate and potassium phosphonate. Fosetyl-Al, which is widely used as a fungicide, is tolerated in conventional crop growing, yet not in organic cultivation.

Disodium phosphonate and sodium phosphonate, which are no hazard to health, were used up until 2013 as plant health improvers in organic crops, but have now been classified as pesticides. It is therefore no longer permitted to use them in organic crop growing. However, the German Ministry of Food, Agriculture and Consumer Protection (BMEL) has submitted an application for approval of sodium phosphonate to the EU. This could significantly reduce the use of ecologically critical yet currently alternativeless copper products in organic wine growing. So far the relevant legislation has not changed, however.

The Association of Organic Processors, Wholesalers and Retailers (Bundesverband Naturkost Naturwaren (BNN) e.V.) has relaxed its demand for strict implementation of the BNN guide value of 0.01 mg/kg because of the difficulty to identify the origin of phosphonic acid, and now recommends identifying the origin if the levels detected are 0.1 mg/kg or more.

Even in conventional crop growing, the legal situation is not at all clear: with regard to fosetyl-Al (residue definition: sum of fosetyl and phosphonic acid and their salts, expressed as fosetyl), the annexes of (EC) Regulation No. 396/2005 list maximum residue levels for various foods. When it comes to disodium phosphonate (residue definition: phosphonic acid and its salts, expressed as phosphonic acid), however, the general maximum level of 0.01 mg/kg as per Art. 18 (1)(b) is applied to all foods, while the EU database entry for sodium phosphonates (residue definition: phosphonic acid and its salts, expressed as phosphonic acid) in turn refers to the maximum levels of fosetyl-Al. Yet these are calculated differently (“expressed as fosetyl“). So once phosphonic acid with an unidentified route of entry has been detected, it is unclear on which legal basis this should be assessed.

Incidentally, the maximum residue levels for fosetyl-Al were verified by the EU member states in 2012. In this context, proposals to change the residue definition of fosetyl-Al to “Phosphonic acid and its salts, expressed as phosphonic acid” were made, along with proposals to change various maximum levels. If these proposals are enacted, there will be three pesticide agents that lead to identical residues. So it remains to be hoped that the maximum residue levels for the three substances will be harmonized.