Explore this issueJune/July 2013
As the tools of analytical measurement continue to get more sensitive, more specific, and faster, the industries using these tools must keep up with the changes. New methods of testing for food quality continue to be developed alongside improving traditional methods of analysis. All of these advancements set new standards and protocols on how the quality of foods and of their ingredients is defined and monitored. Understanding some of the general trends is needed to plan for what lies ahead.
Use of liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) has grown rapidly in the field of food testing. LC-MS/MS is being utilized more in food company quality and R&D divisions as a flexible alternative to traditional methods due to its high sensitivity and faster throughput.
An excellent overview on the use of LC-MS/MS to monitor for food contamination was published in the February/March 2011 issue of Food Quality1 where Andre Schreiber and Art Sims highlighted the advantages of LC-MS/MS technology. Since that publication, those advantages have been further leveraged for the analysis of food nutrients.
Analytical methods which use LC-MS/MS are being rapidly developed due to the technique’s high sensitivity, selectivity, accuracy, and increased availability of isotopic standards. An additional advantage is the reduced amount of clean-up required because of the mass spectrometer’s high specificity. As the resolution of and software for MS detectors increase and improve, the ability of the MS detector to “filter out” potential interferences is taken advantage of by the new methods.
AOAC International has recently adopted LC-MS/MS methods for the analysis of vitamin D (AOAC 2011.11, 2011.12, 2011.13, 2012.11). Each of these methods takes advantage of the points highlighted above alongside the additional advantage of LC-MS/MS simultaneously using MS/MS to confirm the identity of the vitamins being tested. After a vitamin’s parent ion is identified, two daughter ions are created by fragmenting the parent ion, and these daughters are used to confirm the identity of the vitamin. The daughter ion levels are also used to quantify both vitamin D2 and vitamin D3.
LC-MS/MS analysis of certain vitamins is complicated for vitamins which are bioactive in several forms, with some of those forms typically in low concentrations. The recently adopted method, AOAC 2011.062 for the measurement of total folates (vitamin B9) does quantify six forms of vitamin B9 including the common fortifying form of folic acid3. Research is underway to measure other vitamins present is various bioactive forms. The common approaches include converting the different forms into one form (i.e., saponification converting the multiple forms of vitamin A into the retinol form, and conversion of multiple forms of vitamin B12 into cyanocobalamin).
UPLC and UHPLC Technology
Ultra Performance Liquid Chromatography (UPLC) and its equivalent Ultra High Performance Chromatography (UHPLC) are recently developed companions to traditional high performance liquid chromatography (HPLC). UPLC and UHPLC can separate compounds in less time than HPLC while using less solvent. This is due to the development of columns containing uniform, smaller particle sizes (in the 1.7 µm scale) which increase the column’s theoretical plates, thus improving peak separation efficiency (better peak resolution). The time needed for peak separation is therefore decreased. To use these columns, higher pressures are needed to push mobile phase through the bed of smaller particle-sized stationary phase.
When this technology first appeared, a somewhat limited number of columns were available. As the efficiency and reliability of this technology was recognized, the number of columns has increased dramatically. Use of this technology is becoming more common.
Advances in Methods
In the world of pesticides testing, the QuEChERS extraction is becoming more prevalent. The acronym of Quick Easy Cheap Effective Rugged Safe highlights desired method attributes by the laboratory, by the customers, and by management who sets financial budgets.