Agricultural chemicals are used to increase crop yields, control weeds and pests, and to prevent diseases to crops and livestock. These chemicals include pesticides, herbicides, plant growth regulators, growth hormones, and veterinary drugs/antibiotics. Food producers must test plants and animals for residues from these chemicals to prevent health hazards to consumers. Dionex applications, listed under the tabs above, facilitate determination of numerous agricultural chemicals.

Some pesticides that pose severe health or environmental risks have been banned in many countries around the world, but are still used in others. Build up of legal pesticides in foods can also pose a health risk to humans and animals, with the severity depending on the type of pesticide and the length of exposure. Agricultural chemical residues can be found in fruits, vegetables, grains, and spices, and may also be absorbed by fish and livestock.

N-methylcarbamates and N-methylcarbamoyloximes are among the most widely used pesticides in the world. Gas chromatographic analysis has proven unsuccessful due to degradation of the analyte compounds during vaporization. Post-column derivatization with fluorescence detection after a reversed-phase HPLC separation delivers highly sensitive determinations of carbamate compounds. When even more sensitivity is required, HPLC with positive mode electrospray ionization mass spectrometry is a powerful alternative.

Chromatogram of a standard mixture of 10 carbamates (2.5 µg/mL) plus two reference compounds (peaks 10 and 12) separated using an UltiMate^® 3000 system and Acclaim^® 120 C18 column.

Most organochloride pesticides have been removed from the market due to health and environmental concerns, but are still used in some countries. They are persistent in the environment, and can accumulate in soil and plants. When ingested in animal feed, these pesticides tend to accumulate in certain animal products, especially those rich in fat, such as meat, milk, and butter. Exposure to organochlorides can cause both acute and chronic health effects, including cancer, neurological damage, and birth defects. Many organochlorines are also suspected endocrine disruptors.

Although not persistent in the environment, organophosphate pesticides (OPPs) are acutely toxic, and can affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Some OPPs cause developmental or reproductive harm, some are carcinogenic, and some are known or suspected endocrine disruptors.

Dionex ASE systems can be used for the extraction of pesticides, such as organophosphates, organochlorides, and carbamates, from solid and semisolid food samples rapidly, and with far less solvent than Soxhlet or sonication.

Veterinary drugs and antibiotics are used in the animal breeding industry to treat, prevent, and control diseases caused by viruses, bacteria, protozoa, and fungi. Unfortunately, some of these drugs are also added to animal feed to stimulate growth and produce leaner meat. The Union of Concerned Scientists estimates that 70% of all U.S. antibiotics are fed to healthy cows, pigs, and chickens as part of routine industrial meat/dairy production practices. They also state that ~25 million pounds/year of antibiotics are used on farms in animal feed. In humans, these drugs can cause allergic reactions, bacterial resistance to antibiotics, and even cancer. Regulatory agencies have established maximum contamination levels for a variety of antibiotics, and some have been banned for use in livestock or feed.

Extraction and Determination of Sulfonamides

Sulfonamides are used as veterinary antibiotics, both to combat infection and to promote growth. Some livestock companies have abused these drugs to increase growth and profits. Approximately 3% of the human population is allergic to sulfonamides. High levels of these antibiotics may create drug-resistant pathogens, and can cause acute or chronic health problems. American and European regulatory agencies have established maximum residue levels (MRLs) for veterinary antibiotics in meat and milk products. ASE^® Accelerated Solvent Extraction systems are ideal for extraction of sulfonamides from meats, with high recoveries.

Samples like milk can be notoriously difficult to analyze, due to the complexity of the matrix. Standard separation procedures require two injections with different mobile phases to resolve all eight compounds commonly found in milk. With a Dionex HPLC system, Acclaim 120 C18 column, gradient separation, and UV-Vis detection, sulfonamide antibiotic residues in milk can be determined easily in one injection.

Determination of eight sulfonamide residues in milk: The gradient program separates the compounds in one injection, and UV detection allows determination of the sulfonamides without interference from the milk matrix.

Determination of Tetracyclines

Tetracyclines are wide-spectrum antibiotics commonly used for infections in humans and livestock. Animal studies show that tetracycline can cross the placental barrier, and can have toxic effects on developing fetuses. Long term exposure in humans may also lead to the development of antibiotic-resistant strains of bacteria. Tetracycline contaminants in a pork sample are rapidly and easily quantified using a Dionex HPLC system and UV detection.

Determination of tetracycline in pork: The gradient program separates four tetracyclines in less than 5 minutes.

Determination of Nitrofurans

Nitrofuran antibiotics were widely used for treatment of infection in cattle, pigs, and poultry, but have been banned because of their genotoxic and mutagenic properties. These antibiotics enter the food chain not only from use in livestock, but also from contaminated feed. Nitrofurans in animal feed can be separated quickly and easily using an Acclaim 120 C18 column.

Determination of nitrofurans in animal feed. Four nitrofurans are well resolved even at low concentrations.