Helping Importers and Exporters Detect Contaminated Food

In recent years, consumers in the European Union (EU) have become very anxious about the safety of the food they eat. Their concern stems from the outbreak of "mad cow" disease or BSE (bovine spongiform encephalopathy) as well as incidents of bacterial, dioxin and pesticide contamination.

The list of synthetic substances that can trigger a food safety alert goes beyond toxic chemicals to include certain veterinary antibiotics. For years, these medicines have been used in food-animal production to prevent bacterial enteritis (from E. coli and Salmonella) in cattle, swine, fish and poultry. However, studies have shown that the nitrofuran family of antibiotics is potentially hazardous to humans.

Advances in analytical instrumentation have made it possible to measure trace amounts of nitrofuran in food-animal tissues, prompting agencies such as the European Food Safety Authority to tighten import controls and increase product testing. Even though these practices may seem restrictive to food exporters, one of the key goals is to restore consumers' confidence in the quality of the food they eat.

An unexpected discovery

In 1995, the EU banned the nitrofuran family of antibiotics from use in food-animal production (the U.S. followed suit in 2002). Four members of the nitrofuran family have been used as feed additives: furazolidone, furaltadone, nitrofurazone and nitrofurantoin. Even though these medicines are effective in preventing bacterial enteritis and promoting animal growth, research has shown that all four drugs may cause birth defects and cancer in humans.

In early 2002, EU inspectors found traces of nitrofuran in shipments of chicken and shrimp from Thailand. Food export is a multi-billion dollar industry for Thailand—it's the world's leading exporter of shrimp and rice—and the rejected shipments translated into an $84 million loss between March and August 2002. To help resolve this situation, the Thailand government needed to quickly identify and isolate nitrofuran in the food production chain. That's when Agilent stepped forward with equipment and expertise to help create a solution.

Overcoming the measurement challenge

Nitrofuran-family drugs are characterized by rapid metabolism, with in vivo half lives of less than a few hours. Although detection of the parent drugs is not practical, the metabolites of these drugs are formed in animal tissues and remain detectable for several weeks after administration.

Structure of a nitrofuran-family drug and its metabolite

Measurement is still a challenge, though, because the protein-bound metabolites are very small molecules that elute quickly out of a chromatography column and are not UV absorbing. To induce UV absorption in the molecule, and ensure reasonable retention on a column, they must be derivatized. For example, it's possible to release the metabolites from the proteins under moderately acidic conditions and then perform derivatization. The resulting derivatives can be analyzed with a combination of liquid chromatography, UV detection and mass spectrometry confirmation.

Shrinking the detection limit

The solution Agilent developed for the Thailand government is a routine and sensitive LC/MS method that simultaneously detects the four nitrofuran metabolite derivatives. This method is described in detail in the application note "Determination of the Metabolites of Nitrofuran Antibacterial Drugs in Chicken Tissue by LC-ESI-MS." As implemented with the Agilent 1100 series LC/MS system (and an electrospray ionization source), the detection limit of each analyte ranged from 0.05 to 0.2 ng/g in chicken muscle and liver tissues.

Agilent 1100 series LC/MS system

Of course, the story goes beyond the performance of the measurement system. Agilent staff conducted seminars on the system and technologies, and also provided ongoing support and education for impacted food export companies, the Thailand government and interested universities.

Testing can be performed on both sides of the export/import equation. Exporters can test food products all along the food chain to identify and isolate potential problems before anything is shipped overseas. Importers can analyze incoming shipments to ensure compliance with local regulations—and to give consumers greater peace of mind about the food they eat.

For more information

To learn more about Agilent's solutions, please see the LC and LC/MS Products section of our Web site. For additional information about these and other Agilent products and resources, please visit the Life Sciences/Chemical Analysis main page.