Using Chromatography to Detect Chemical Contamination

This is probably best illustrated by the unfortunate incident of 2007-2008 where ingredients used in the manufacture of pet food and infant formula were intentionally contaminated (i.e., adulterated) with melamine to fraudulently increase the measured protein content. The scheme initially succeeded because the prescribed test used to measure the protein content (the 100+ year-old Kjeldahl test for total organic nitrogen) can’t distinguish between the nitrogen content of protein and melamine. The Kjeldahl test lacks the ability to speciate specific organic nitrogen compounds and is not fit for the purpose of measuring the protein content of food, at least in the face of a chemical contamination threat from melamine. A sophisticated high performance liquid chromatography (HPLC) test for melamine was subsequently developed, which put an end to that particular contamination threat.

The melamine tragedy brought rapid realization of the vulnerability of many older food testing methods for preventing chemical contamination, whether accidental or intentional. This vulnerability arises from an inherent lack of specificity of older food testing methods—the inability to accurately speciate individual toxic chemical species in a complex food matrix. This inability is particularly stark when one compares the technology underlying the older methods to the much greater capabilities of modern analytical technology. This has led to a broad-based, method modernization effort on the part of government agencies (FDA, NIOSH, EFSA, etc.) and standard setting institutions (AOAC, USP, etc.) to enable the ability to measure, and therefore prevent, the chemical contamination of food. Modern chromatography has played a major role in this food method modernization movement and the ability to prevent food contamination.

Impact of Modern Chromatography

In the introduction to this article, I stated that the term “chromatography” probably isn’t the first thing that comes to mind when considering the subject of food contamination. But, perhaps it should be; at least in the case of chemical contamination. Modern chromatography has an unsurpassed ability to isolate, differentiate, and identify diverse potential contaminants in food. There are many diverse opportunities for food to become chemically contaminated. One needs only to consider the great number of toxic compounds in commerce and the many potential exposure routes from farm to table. The potential for contamination is so diverse, it is impossible to generalize the power of chromatography to prevent food contamination. Instead, I will present a series of thumbnail sketches that illustrate the breadth and depth of recent chromatographic method developments.

The following images are all examples taken from the recently published Phenomenex Food Testing Applications Guide that contains over 150 liquid chromatography (LC), gas chromatography (GC) and solid phase extraction (SPE) applications.

Diversity of Potential Chemical Contamination Scenarios

(click to enlarge)

Mycotoxins: Mycotoxins from cereal based goods by SPE and LC/MS/MS. Produced by certain molds that can grow on grains, mycotoxins are a class of compounds that are highly toxic and carcinogenic.

PAHs: Polycyclic aromatic hydrocarbons (PAHs) in water by GC/MS. PAHs are a class of carcinogenic compounds that arise from the inefficient combustion of petroleum-based products and can contaminate the environment and foods.

PFASs: 23 per-polyfluoronated alkyl substances (PFAS) by UHPLC/MS/MS. PFAS compounds have been widely used in food packaging; they are able to leach into food at trace levels, and since they are extremely bioaccumulative, they can build up in the fat tissue of the consumer.

Melamine: Melamine and cyanuric acid in milk and baby formula products by SPE, LC/MS, and GC/MS. This relates directly to the melamine contamination/adulteration crisis of 2007-8.

Acrylamide: Acrylamide from coffee by SLE and LC/MS/MS. Acrylamide can be found in certain starch-containing foods that have been exposed to heat. Acrylamide is classified as a carcinogen so its presence in food, even at low concentrations, is a concern.