By September 17, 2020

Agricultural and food products are extensively tested in the laboratory to ensure they meet compositional requirements, that they are authentic, free of adulteration, and comply with regulatory limits for residues and contaminants. Additionally, processed foods need to be analyzed so they can be labeled for nutritional purposes, checked for levels of food additives, and finally any packaging system used to provide protection during transport and storage must be checked so that it does not lead to trace levels of contamination. Sophisticated techniques have been developed to facilitate this food testing ranging from field-tests used for rapid screening to complex multitarget instrumental analysis to be used in the analytical food laboratories.

Analytical chemistry has made tremendous advances over the last 10–15 years with dramatic improvements in methods of analysis exemplified by significantly higher sensitivity and vastly improved specificity of detection. The improved sensitivity has meant that detection of residues and contaminants in foods at parts per billion (ppb) levels (ng g–1) is now carried out routinely. Improved specificity means that complex food matrices can be analyzed, with a high degree of confidence in the correct identification and accurate quantification of the targeted residue or contaminant. With increased specificity, the time spent on sample extraction and cleanup has been reduced and many multimethods have been developed enabling screening for a large number of analytes in a single analytical run.

Despite these significant developments in trace analysis, one should not underestimate the degree of difficulty in testing foods for residues and contaminants. First, foods are complex and diverse in composition making it difficult to develop a single method to cover all food types. Second, the limits for permitted levels of residues and contaminants in foods that are required by regulations in some instances are exceedingly low. This means that high concentration factors are required and sample preparation of necessity means removing as much of the background co-extractives from food as possible, before instrumental analysis.

A trend that has been apparent in recent years has been an increased emphasis on ensuring the quality of analytical data. It is now generally accepted that to demonstrate reliability of data, food laboratories should be accredited to the International Organization for Standardization’s (ISO) Standard 17025, should only use validated methods of analysis, and should prove analytical competence through participation in proficiency testing.