Henry's law constants of carbonyl-pentafluorobenzyl hydroxylamine (PFBHA) derivatives in aqueous solution

In situ derivatization of airborne carbonyls can increase the efficiency of sampling methods aimed at the quantification of these trace components in urban and rural atmospheres. The design of efficient samplers based on aqueous solutions of the derivatization reagent O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBRA) requires knowledge of how the carbonyl-PFBHA derivatives partition between water and air. We have determined the Henry's law constant at 25 degreesC for 16 PFBHA derivatives of carbonyls that represent typical analytes present in the ambient environment. The inert gas stripping method was employed, followed by measurement of the aqueous concentration of the derivatives by GC-ion trap mass spectrometry (GC/ITMS). The values of the Henry's law constants ranged from (37 to 268) Pa(.)m(3).mol(-1). We evaluated several molecular descriptors to investigate quantitative structure-property relationships (QSPRs) for the partition behavior of these compounds. The molecular volume, the molecular surface area, and the polarizability correlate better with k(H), while the dipole moment proved to be an extremely insensitive descriptor. The temperature dependence of kH in the range (5 to 25) degreesC was evaluated. These data led to the estimation of DeltaAH(infinity) and DeltaS(infinity), which ranged from DeltaH(infinity) = (17 to 60) kJ(.)mol(-1) and DeltaS(infinity) = (36 to 170) J(.)K(-1.)mol(-1).