COMPARISON OF PACKED AND CAPILLARY COLUMNS FOR QUANTITATIVE GAS-CHROMATOGRAPHY OF TRIGLYCERIDES IN MILK-FAT

Quantitative gas chromatography of triglycerides in conjunction with e stablished triglyceride formulae can be used to determine various milk fat parameters. Since the evaluation of, for example, iodine number o r content of non-milk fats (foreign fats) in milk fat requires only th e separation of triglycerides by carbon number and since repeatabiliti es, especially of the high-boiling triglycerides, have been less accep table with capillary columns in the past, packed columns have been use d exclusively. There is, however, an increasing demand for the use of capillary instead of packed columns and to that end the present invest igation has been carried out. To achieve a suitable resolution, with t his particularly exacting high-temperature application, a short 5 m ca pillary column of extreme temperature stability has been used. As well as modification of various analytical conditions different injection techniques have been investigated. On-column, PTV and split injection were compared with regard to repeatability. The cold-on-column injecti on technique was found to produce the best results, being comparable t o the excellent precision of a packed column. Thus, a method is now av ailable by means of which the determination of milk fat parameters by the triglyceride formulae, such as the amount of foreign fats in milk fat, can now be carried out with a standardized capillary column.