The analysis of peppers for flavor profiles and food volatiles is not new. With a wide array of varieties, peppers find uses in not just food markets, but also pharmaceutical and cosmetic industries. Analyzing peppers isn't new. Finding ways to increase the sustainability and "green" qualities of those analyses, however, is an ongoing challenge, and one that Micaela Galletta, Mariosimone Zoccali, Donato Creti, Luigi Mondello, and Peter Q. Tranchida tackled in a recent study published in Green Analytical Chemistry.
Headspace solid-phase microextraction (HS-SPME) is a relatively solvent-less, non-destructive method of sample preparation that has been widely used since its introduction in 1990. However, with the complex matrices of peppers, HS-SPME results in challenging chromatograms to decode with simple 1D GC-MS. Galletta et al. decided to couple this HS-SPME preparation with GCxGC-MS to take advantage of the extra resolution a second column and therefore second dimension of separation can bring.
Comprehensive two-dimensional gas chromatography (GCxGC) works by using a modulator to capture the effluent from the first column and seamlessly inject it into the second column. Many modulators rely on liquid nitrogen to cryogenically focus the effluent, but a flow-based modulator like LECO's Flux™ flow modulator can perform the modulation without the use of added consumables. When combined with the use of hydrogen as a carrier gas, which can be generated with an in-lab generator, a Pegasus® BT 4D with Flux dramatically reduces the cost of food analyses while completely cutting the need for non-renewable helium gas.
By using HS-SPME to prepare the samples, solvent use is reduced to a nominal 10 μL per sample. The Flux flow modulator removes the need for liquid nitrogen or similar cryogenic fluid, while switching to a hydrogen carrier gas not only saved the cost of helium, but also cut the analysis time. By using an instrument configured for hydrogen instead of helium, Galletta et al. found their run times were approximately 25% shorter, with good comparability in MS fragmentation patterns and lower S/N values.
Greener, more sustainable methodology can only bring true value if it actually is equivalent to (or better than!) existing methods, and shorter runtimes alone weren't enough to satisfy this question. The study used ChromaTOF® Tile, an innovative software that used tile-based Fisher-ratios to compare the data sets without the need for chromatographic alignment. This software was able to differentiate between peppers of the same variety, quickly and effectively producing heat maps of statistically significant compounds of interest to allow for more targeted analysis.
The authors were very satisfied with the results of their study and encouraged the use of similar methodology for both pepper and other food analyses moving forward. To learn more about the details of their findings and methods, read the full study online at Green Analytical Chemistry. For more information on LECO's advances in sustainability and fast GC, fill out the form below.