CHROMATOGRAPHY
The analysis in Fig.1 was conducted on potato crisps
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 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. Tis 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
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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. Te 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. Te 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
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 Wiest is an LC Applications chemist at Restek.
www.restek.com
FIG. 2. The Allure Acrylamide column still meets EN 16618:2015 system suitability requirements even after 1,000 injections - over twice as many passing injections than a typical PGC column
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