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Short Communicationsother milk components. Proteins, triglycerides, and other high molecular weight compounds were not retained. We have determined the retention time of the 2,3,7,8-tetrachloro isomer, and the hexa-and heptachloro isomers of PCDD and PCDF, and the components of other commercial PCBs (e.9. Aroclor 1254); all have the same retention time as the OCDD.We have to report that these compounds penetrate through to the inner surfaces of the stationary phase and are therefore chromatographically retained. The fraction corresponding to the organochlorine compounds was collected and, after purification with alumina a s reported previously [2], analyzed by HRGC with ECD to confirm the nature of the compounds and the 100 % recovery of the added standard.The possibility of reducing the number of steps in the analysis of PCDD, PCDF, and PCB in human milk is very important. The first step, the isolation of the fat which contains the liposoluble compounds, must be exhaustive if the analysis is to be quantitative. It is usually performed by liquidliquid extraction with methanol, sodium oxalate, diethyl ether, and petroleum ether [3][4][5]. The second step, elimination of the fat, is normally performed either by digestion with sulfuric acid [6][7][8] or by gel permeation chromatography on Biobeds SX 3 [4, 51. As the use of the new Ultrabiosep stationary phase replaces these two steps (extraction and pre-clean-up) with only one, use of the ISRP reduces not only the analysis time but also the possibility of losses in the pre-clean-up steps. The final clean-up on alumina (usually the third step in this analysis) will usually be sufficient for HRGC-HRMS analysis.No changes in the performance and the pressure of the column were noticed during the experiments.The results obtained here represent the first attempts to evaluate the ISRP column for the determination of PCDDs, PCDFs, and PCBs human milk The method could be used without any modification for the levels of PCB isomers found in human milk (the ppb (ng/g) range) Levels of PCDD/F in human milk range from 3 to 300 ppt (pg/g) (from tetra to octa PCDDIF) relative to the amount of fat [3-81 As HRGC HRMS detection levels for tetra to octa PCDD/F isomers are in the range 0 1-1 pg per inlection into the system, it would be necessary to adapt the methodology for higher inlection volumes A 5 ml sample would contain enough PCDD/Fs to be detected bv HRGC-HRMS

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