Food and Pharmaceutical
A unique feature of SPE for application to analysis of food and drugs is its ability in some cases to extract substances from products without opening the package. For example, flavors present in wine can be checked before sale or purchase by introducing a fiber into the headspace of the wine through the cork of the bottle. Since only insignificant amount of flavor is extracted, the composition of the product does not change, and extracting solvent does not contaminate the product since the polymeric phase is not volatile. A similar process can be applied to on-line product monitoring of each individual item to ensure the best possible quality.
Food and pharmaceutical products are frequently contaminated by volatile organic solvents, which are used in manufacturing and processing of these goods. Considering the frequent complexity of their matrices, the analytical procedures can be quite involved. Static headspace is frequently used for this purpose, but SPE has been found to be good alternative for analysis of both contaminated pharmaceuticals and foods because of its superior sensitivity, especially for less volatile compounds. Samples can be analyzed by dissolving the product in water prior to determination or the analytes can be extracted directly from headspace above the product. Typically, standard addition is used for quantitation. The detection limit are similar to those obtained for environmental matrices.
Flavors are another very interesting topic of investigation. One strength of SPE is its small size, which enables it to extract compounds from small objects such as a single pill or small botanical. SPE has been used on wide range of food products, spices, oils, and beverages, and even black and white truffle aroma. Table 1, summarizes the detection limits of common flavor components obtained by PA fiber.
Figure 2 illustrates examples of chromatograms obtained for two fruit juices. Initial investigations indicate that to quantitation of volatile analytes in the matrix can be obtained after the solid components of the sample matrix are separated from aqueous phase by centrifuging.
Combining SPE extraction with GC separation, using the chiral stationary phase, provides information not only about composition of the product, but also their natural purity.
Figure 3 shows the separation of peppermint oil (a) and peppermint flavored candy (b) using b-cyclodextrin column.
Another interesting application of SPE to analysis of foods is to quantify caffeine in soft drinks. Figure 4 shows the result obtained for tea and cola. The most convenient quantization method for this determination is based on isotopically labeled standards which readily available. Figure 4 indicates that in addition to caffeine, flavor components are also detected in the same chromatographic run, suggesting that SPE could be very versatile quality control tool in the field of beverage production.