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ty of Florida. With a ternary gradient on a C30 HPLC stationary phase, Lee was able to separate more than 25 saponified carotenoids within 40 min. With this method at hand, Lee could track the appearance and disappearance of the different compounds during fruit maturation.
... and those that are not so healthy For many, summer just wouldn’t be the same without the backyard barbecue. What outdoor cooks don’t realize is that too much charcoalgrilled meat can be harmful. That was the take-home message of more than one presentation at HPLC 2000. Mark Knize and co-workers at Lawrence Livermore National Laboratory have been investigating the role of dietary constituents in the development of human cancer. In particular, they’ve been investigating whether there are differences in the way individuals metabolize 2-amino1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), an aromatic amine that forms in meat during cooking. According to Knize, PhIP has been shown to be mutagenic in short-term tests and the cause of colon, breast, and prostate tumors in rats. Human urine samples were collected from individuals before and
Not to be outdone, Roger Trones and co-workers at G&T Septech, a Norwegian manufacturer specializing in micro-HPLC columns, along with Thomas Andersen and colleagues at the University of Oslo (Norway), showed that silica-based columns can be used with aqueous mobile phases above 90 °C, if boiling is suppressed through temperature programming and the column is exposed to high temperatures for only a short amount
after eating well-done chicken. Following consumption of the chicken, samples were collected every 6 h for a 24-h period. Each 5-mL sample was spiked with a deuterium-labeled metabolite, which served as the internal standard. Metabolites were removed from the sample using solidphase extraction, passed through an ion-exchange column, and concentrated on a C18 column. Using LC/MS/MS, the researchers detected four major PhIP metabolites in the urine samples. However, they were unable to detect the metabolites using only LC/MS. The amounts and times of metabolite excretion varied significantly among individuals, suggesting that metabolism may have an effect on whether an individual develops cancer or that other dietary constituents, such as fruits and vegetables, influence the absorption and types of metabolites produced from PhIP. Reseachers in Austria have also been investigating PhIP. Siegfried
of time. In nonaqueous mobile phases, the packing material was stable up to about 200 °C. The researchers attribute the ability of the columns to withstand high temperatures to very dense packing, which is achieved by using supercritical CO2 and sonication during the packing process. “We suspect that many liquid-packed columns are too loosely packed to retain their original structure when subjected to temperature ramping,” said Trones.
Zöchling and co-workers at Graz University of Technology studied the formation of PhIP during the cooking of meat and fish by varying the temperatures, heating times, and molar ratios of reactants. In addition, they tested various antioxidants for their ability to suppress the formation of PhIP. According to the researchers, the clean-up step is critical in the analysis of PhIP. They used liquid–liquid extraction but occasionally needed an additional blue cotton
COREL
capable of withstanding high temperatures. As Brian Jones of Selerity Technologies showed, going to high temperatures does not necessarily mean giving up on silica phases. He described the development of new phases that are bonded to a silica base. These ruggedized C8 and C18 phases have similar lifetimes under high-temperature conditions, as more traditional LC columns have at ambient temperature.
adsorption technique for further purification. Samples were then analyzed using HPLC with fluorescence detection. Results suggest that antioxidants, such as ascorbic acid, do indeed decrease the concentration of PhIP, whereas pro-oxidants, such as FeSO4, increase the formation of PhIP.
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