Chiang Mai Journal of Science

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The  capacity  factors  (k')  of  related  chlorinated  hydrocarbons,  ie.  1,2-dichlorobenzene (1,2-DCB),  1,3,5-trichlorobenzene  (1,3,5-TCB),  1,2,3,5-tetrachlorobenzene  (1,2,3,5- eCB), pentachlorobenzene (QCB), hexachlorobenzene (HCB), 2,2',6,6'-tetrachlorobiphenyl (2,2',6,6'-PCB) , 3,3',4,4'-tetrachlorobiphenyl (3,3',4,4'-PCB), 2,2',4, 6, 6'-pentachlorobiphenyl (2,2',4,6,6'-PCB)  ,  2,3,3',4,4'-pentachlorobiphenyl  (2,3,3',4,4'-PCB),  2,2',3,3',4,5',6,6'-octachlorobiphenyl (octa-PCB) and 2,2',3,3',4,4',5,6,6'-nonachlorobiphenyl (nona-PCB), in various HPLC systems were  related  to  the  organic  carbon  soil/water  partition  coefficient  (Koc  )  and  humic  acid/water partition coefficient (Khw) in order to mimic the behaviour of test compounds in polar and nonpolar regions in soil/water and humic acid/water systems. The capacity factors (k' w : the  capacity  factor  with  an  extrapolated  mobile  phase  of  100%  water)  of  chlorobenzenes, obtained from each of  the four stationary phases with different polarities, amino, C18, nitrile and silica, increase linearly with their log Koc and log Khw values . However, for chlorobenzenes and PCBs, the relationship between log k' of test compounds obtained from C18 stationary phase and their log Khw was nonlinear (log Khw = 0.2431 log k' + 2.8176, r2 = 0.57). This indicates some different characteristics between the C18 stationary phase and humic acid. The study was extended to the behaviours of test compounds on the combined stationary phases in HPLC systems, C18 connected with amino, C18 connected with nitrile, C18 connected with silica, in order to mimic the characteristics of soil/water and humic acid/water systems which contain polar and nonpolar portions. The study showed that the relationships between log Khw  and  log  k'  were  improved  especially  with  log  k'  obtained  from  combined  C18  and silica stationary phases (log Khw = 1.5119 log k' + 3.9835, r2 = 0.86). The improvement of the relationships by connecting relatively polar and nonpolar stationary phases indicated that the partitioning behaviour of hydrophobic compounds including superhydrophobic compounds (PCBs) on the combined stationary phases may mimic their behaviour in humic acid/water system since both systems contain of  similar polar and nonpolar portions.

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