Landon Wiest introduces a new approach for analysing acrylamide in food
Acrylamide is a hazardous chemical that forms in food when sugars and the amino acid asparagine react during high-heat cooking processes such as frying, roasting, grilling or baking. The detection of acrylamide in food was first reported in 2002 by the Swedish National Food Administration, and, since then, global efforts have been growing to better understand its origin in food and feed, the magnitude of contamination in various foodstuffs, and the potential health effects related to dietary exposure. To safeguard public health, more efficient methods for analysing acrylamide in foods and beverages are needed. Here, we compare typical approaches to an improved process that yields faster analysis times and longer periods of sample throughput without system suitability failures.
The current approach to acrylamide analysis
Europe has formalised a method for acrylamide analysis in food – EN 16618:2015 – and it calls for the use of LC guard and analytical columns that contain porous graphitised carbon (PGC), in part because of the difficulty of analysing acrylamide using more traditional reversed-phase (RP) retention mechanisms. PGC columns are now commonly used because they can retain acrylamide sufficiently to separate it from coextracted matrix components. The PGC column is also able to operate in 100% aqueous mobile phase, a condition under which many RP columns would undergo a phenomenon known as “dewetting,” which results in retention time loss and requires that the column be regenerated by a time-consuming flush with 100% organic mobile phase.
Following method EN 16618:2015, eight minutes are required to analyse acrylamide in food. To meet system suitability requirements, acrylamide must elute no earlier than 1.7 minutes, but the additional time spent after acrylamide elution is necessary to flush the column of matrix components that remained in the sample extract even after the two-step SPE sample preparation process outlined in the EN method. Matrix components are strongly retained on PGC columns, and if not sufficiently purged between analyses, can degrade performance to the point of failure to meet the 1.7 minute retention time system suitability requirement.
Reversed-phase retention can increase acrylamide sample throughput
As labs approach the system suitability threshold when using PGC columns, they must either conduct the lengthy column regeneration procedure or replace the current guard, and possibly the analytical column. Both are time-consuming and costly propositions that halt sample throughput. A new approach using an Allure Acrylamide column is a better alternative: the reversed-phase chemistry incorporates a novel polar ligand that retains acrylamide, is compatible with 100% aqueous conditions, and offers faster run times and longer column lifetimes than PGC columns. This guard and analytical column combination retains acrylamide long enough to meet the EN system suitability requirement while also not retaining coextracted matrix compounds so strongly that they cannot be flushed from the column quickly between analyses. As a result, labs can analyse more samples using fewer columns.
Because matrix compounds elute quickly from the Allure Acrylamide column, it is able to equilibrate and be ready for the next injection faster than even a PGC column run under optimised conditions. Fig. 1 shows an example of two different methods for acrylamide analysis in potato crisps, one with an Allure Acrylamide column and one with a representative PGC column. The PGC column method was further optimised from the EN method, shortening the analysis time from 8 to 7 minutes, while still providing the optimal column flushing and equilibration time. Any further flushing provided no significant benefit to column lifetime. The acrylamide analysis on the Allure Acrylamide column met the method requirement of 1.7 minute retention with good separation from matrix components, but with much shorter equilibration times. A per analysis savings of 2.5 minutes compared to EN 16618:2015 and 1.5 minutes compared to the optimised PGC column method, allows more samples to be analysed per shift, increasing lab output.
Fig. 2 illustrates the extreme stability of acrylamide retention time achieved with the Allure Acrylamide column compared to a representative PGC column, which showed loss of retention almost immediately and ultimately failed the 1.7 minute retention time requirement after 475 injections of a coffee sample, extracted and cleaned up per EN 16618:2015. In contrast, even after 1000 injections, the Allure Acrylamide performance remains steady and ready for the next injection. Its ability to elute coextracted matrix compounds rather than strongly retain them is the key to its extremely stable performance over hundreds of repeat matrix injections with little to no column maintenance.
A better solution to acrylamide analysis
Although the PGC columns used in EN 16618:2015 do sufficiently retain acrylamide, their strong retention of coextracted matrix components requires long equilibration times and shortens column lifetime. Faster overall acrylamide analysis can be achieved using reversed-phase Allure Acrylamide columns because they ensure sufficient retention of acrylamide while allowing matrix compounds to be flushed out more efficiently and effectively. As a result, method system suitability requirements can be maintained over more injections, allowing more samples to be analysed before maintenance is needed.
Landon West is an LC Applications chemist at Restek