Monensin, a common treatment to prevent coccidiosis.
within the European Union, yet [the drugs] are used globally," he says. He suggests that without stringent regulations and enforcement there is a very real possibility that residues might reach appreciable concentrations in produce. Legislation is expected to come into play later this year, which should help avoid this circumstance, but the lack of a fast and effective analysis could preclude effective implementation of the law. The protozoal infection coccidiosis is widespread in intensively farmed poultry and can cause bloody diarrhea, reduction in feed and water consumption, emaciation and loss of egg production and eventually death. The damage is often done before symptoms are spotted. So, a precautionary approach rather than a treatment is used, with farmers applying a blanket drug regime to their stock with various coccidiostatic preparations such as carboxylic acid ionophores like monensin and lasalocid. Rotation is used to minimize the risk of resistance. European Union and U.S. legislations strictly limit drug residues allowable in produce and, according to Elliott, for most compounds a two-tier screening and confirmatory testing system provides an efficient cost-effective approach. The European Union is soon to include ionophores in its guidelines, and, in anticipation, Elliott and his team set out to assess the available analytical procedures. The original methods for monensin are in vitro assays, which require lengthy incubation periods and so are not viable for lowcost routine analysis. Although currently used chromatographic techniques provide detection limits an order of magnitude lower than needed (at some 25 ug/kg), HPLC methods have deficiencies in detecting the numerous ionophores used in poultry farming.
Elliott's team also canvassed opinion from the regulatory laboratories involved in coccidiostats and found virtually unanimous agreement that the current analytical methods need improvement. There has been a recent move towards ELISA techniques for the initial screening, whereas LC/MS can be used in the confirmatory step of the two-tier testing; but there is, says Elliott, "a lack of fast and reliable multiresidue methods available." There is an urgent need to develop suitable tests. Currently it is very difficult to determine if ionophore residues detected in pig exactly the significance of such residues to the consumer. David Bradley
Laboratories that wish to participate in SETOC pay a fee of 1500 Dutch Guiiders (—730 USD) and select a code name. Every three months, participants receive four dried sediment samples, which they can analyze for the analytes of interest by any method they choose. The analytes evaluated so far have included polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, mineral oil, organic and inorganic carbon, and some heavy metals. Beginning this year, samples with detectable amounts of dioxins and furans will be included. The organizers at Wageningen calculate the median value and the median of the absolute deviation of the submitted analyses. Results are published every three months with codes to indicate the performInternational ing laboratory and the techniques used. round-robin for SETOC is only one of the programs run dioxins and furans by Wageningen. The three other international round-robins are the International Soil and plant analysis is a demanding task Plant Analytical Exchange Program (222 because of the heterogeneity of the materiparticipants), the International Soil Analytials, the large number of analytes of interest, and, in many cases, the low concentrattons. cal Exchange Program (300 participants), and the International Manure and Refuse Analytical results obtained by different laboratories may vary widely, and all labora- Exchange Program (54 participants). tories can benefit from some sort of outside Despite the participation of many facilievaluation. The need is even greater if diox- ties in SETOC, only approximately 1% oo the ins and furans must be analyzed reliably. participating laboratories are located in the United States. Programs run by the Council Currently, no international round-robin for these classes of compounds exists. How- of Soil and Plant Analysis and by AOAC Inever, that will change by autumn 1998 with a ternational may reduce participation by U.S. laboratories. Another problem is the existing program at the Agricultural University of Wageningen (The Netherlands), where one restrictions by the U.S. Customs on the imof the largest international programs of labo- port of plants and soils. ratory evaluation is located. The possibility Veronika R. Meyer of analyzing dioxins and furans is offered through the already existing international Sediment Exchange for Tests on Organic Contaminants (SETOC) program. The current push for a dioxin and furan round-robin was initiated by the Institute of Environmental Protection and Agriculture (Switzerland). The Swiss government requires that laboratories perform accurate analyses of these toxins; SETOC was chosen as the best platform to assess competence in dioxin and furan analysis. Victor Houba, the coordinator of SETOC and three other round-robins conducted at Wageningen, claims proudly: "We have accees to soil lamples with detectable amounts of these compounds!" The cost of the first or "reference" analyses of these soils will be paid by the Swiss government. Although 101 laboratories participate in SETOC Houba expects 15 laboratories from around the world to participate in the dioxin and furan round-robins. Making representative samples. Analytical Chemistry News & &eatures, August 1, 1998 5 0 7 A
