Non-Targeted Analysis

We analytical chemists are not renowned for having exciting lives. Traditionally, we’ve been a reactive rather than proactive breed. Tell us what the analyte is and we will design a method that can measure it to the nearest mg, μg, ng, or even pg. We can provide you with a method that is accurate, precise and robust. We can analyze hundreds of your samples and tell you if that analyte is there, and in what quantity. And when you have another set of analytes, we go through the process again and produce further accurate and precise methods to identify and measure them. 

Ask us what the problem is, or even if there is a problem, and we are less assured. The more forensic aspects may take us longer to solve; days, weeks, possibly months. One reason for this is that we haven’t had a great set of tools available for looking for unexpected analytes. We usually have to rely on a series of experiments to elucidate the analyte and diagnose the problem. 

A good example of where analytical chemists were found wanting was melamine contamination of baby food. Here, we didn’t know what the problem was – or even that there was a problem – until it was too late. Melamine, a molecule of high nitrogen content, was used by fraudsters to enhance the apparent protein content of foods. The incident highlighted two key problems with the methodology used. First, protein was being measured using an indirect method that analysed the nitrogen content of the food and converted it to apparent protein content through a nitrogen factor. Second, there were no systems in place for measuring unexpected analytes in the sample. Not only was the real protein overestimated, more importantly there was a failure to detect the melamine adulterant – with tragic results.  

Put simply, what analytical chemists really want are rapid methods and systems that can detect and identify analytes that shouldn’t be in the sample. But such information rich systems have not been available... until now.

It is an exciting time for analytical chemists and biochemists because of the step change in technology that is now available. The latest generation of mass spectrometers coupled with state of the art chemo-informatics provide some great tools for us to enhance our forensic capabilities. The next generation of high-resolution LC and GC mass spectrometers using “Time of Flight” technology provide excellent separating power and the ability to identify and quantify analytes in a non-targeted way. When combined with sophisticated chemometric outputs, these instruments have the potential to be used in a profiling mode, much like an infrared spectrometer. The difference being that the spectra are information rich, which allows for more rapid elucidation of the analyte.

At present, such technology is mainly confined to research institutes for discovery and characterisation work. The main stumbling block for greater uptake is the storage and interrogation of the huge data files generated. However, it is starting to be employed within food surveillance where, traditionally, considerable resources have been spent on ensuring that target analytes or multiple analytes are absent from samples. By measuring change in an intelligent way, we can quickly identify abnormal or contaminated samples and provide a much more efficient way of safeguarding and assuring the food supply. Whether undertaking large-scale food safety surveillance or assuring the quality of a globally produced food product, such systems allow us to be much more proactive. Instead of reacting to customer requests, we can now inform the customer of an issue before they are even aware it exists.

Please read the other articles in this series:
Foodomics
Regulating Food Allergens
Electronic Senses
Emerging Contaminants