Equivalence of packed and capillary GC columns for detection of foreign fat in butter by use of the triglyceride formula method

In conjunction with triglyceride formulae the analysis of triglycerides (TG ) by low-resolution gas chromatography can be used for the detection of for eign fat in butterfat. The equivalence of a 5-m capillary column (HT-SimDis t) and the commonly used packed column (OV-1) was checked by testing the pu rity of 50 widely varying samples of milk fat in accordance with regulation 2771/99 of the European Community (EC). As well as the resolution the anal ysed TG contents and the relative standard deviations were virtually equiva lent for both types of column, and were in accordance with the EC regulatio n. For instance, the mean absolute differences between the TG C-54 content of 50 samples (+/- standard deviation) determined by use of the capillary c olumn and two different packed columns were only 0.05 (+/-0.04) and 0.11 (/-0.07)%, respectively; the correlation coefficients were r = 0.9996 and 0. 9993, respectively. The same applied to the repeatability of S values, calc ulated from TG formulae for qualitative and quantitative detection of forei gn fat. Irrespective of the column used, none of the samples exceeded stipu lated limits for S values of pure milk fats. For all the samples the differ ences between S values obtained from packed and capillary column data did n ot exceed the reproducibility limits stipulated by EC regulation 2771/99. T his resulted in a correlation coefficient of r = 0.94 for S values (n = 50) calculated by use of the total TG formula. The corresponding correlation c oefficient between results obtained with the two packed columns was r = 0.9 5. Although these results establish the equivalence of packed and capillary columns for low-resolution TG analysis, this equivalence should not be tak en for granted but, because of occasional difficulties, be re-checked by ea ch laboratory wishing to use a capillary rather than packed column to monit or the purity of milk fat.