Measurement of octanol–air partition coefficients using solid-phase microextraction (SPME)—application to hydroxy alkyl nitrates

Multifunctional organic compounds are thought to constitute a major component of the organic matter found in atmospheric particles. Their partitioning into the organic matter depends on their structure, their chemical properties and the properties of the absorbing matrix. It was recently shown that octanol is a suitable surrogate for organic particles and the octanol–air partition coefficient (KOA) was suggested as a useful tool for estimating the partitioning of organic compounds into atmospheric particles that contain high organic mass fractions. In this paper, we present a new and simple technique for the determination of KOA using solid phase microextraction (SPME) relative to a known Henry's law constant. We apply the technique for the determination of KOA of β-, γ- and δ-C3–C5 hydroxy alkyl nitrates. The temperature dependence of KOA for some of the compounds is also measured. It is shown that the solubility constants of these compounds are higher in octanol than in water and that the solubility in octanol increases with the length of the hydrophobic chain and with increasing distance between the hydroxy and the nitrooxy groups. Partition coefficients between the gas and particulate phase (Kp) are calculated using the determined KOA values and their atmospheric implications are discussed.