Analysis of Phosphine in Dried Foodstuffs via Headspace-GC-MSD
Roland Perz, Anne Benkenstein, Ellen Scherbaum , Chemisches und Veterinäruntersuchungsamt (CVUA) Stuttgart
Phosphine is one of the most widely used, cost-effective and rapidly acting fumigants. In EU legislation , maximum residue limits for the sum of phosphine and phosphides in foodstuff are set to within a range of 0.01 and 0.1 mg kg-1, depending on the commodity. A highly sensitive headspace-GC-MSD method was developed achieving limits of quantitation as low as 0.1 µg kg-1; this enabled not only the monitoring of MRLs, but also the exposure of improper applications. In all, 115 samples of dried foodstuff from the local market such as cereals, nuts, and legumes were analyzed for phosphine residues. Of these, 35 samples contained phosphine in amounts exceeding 0.1 µg kg-1, while 14 samples (12 % of all) exceeded 1 µg kg-1. Interestingly, seven of these 14 samples were labeled as being from organic production, where phosphine application is not allowed. Monitoring activities will be continued.
Globalization has led to an increased trade of goods between countries from different continents. In 2011 maritime trade was estimated at 500 million containers, transporting goods from all parts of the world. However, stowaways such as pests are inevitably carried along with the goods as well. Fumigation of containers is common practice in the export and import of foods, both in order to preserve the foods during the long trip and to eliminate any pests that could be brought into a country with the food. Methyl bromide was previously among the most widely used fumigants but its production and use was restricted by the Montreal Protocol due to its role in ozone depletion. Nowadays phosphine (PH3) is one of the most widely used, cost-effective and rapidly acting fumigants not expected to leave higher residues on treated products. Cases of pests developing resistance to phosphine, however, have been reported from different parts of the world.