Efficiency of methods for Karl Fischer determination of water in oils based on oven evaporation and azeotropic distillation.

The efficiency of azeotropic distillation and oven evaporation techniques for trace determination of water in oils has recently been questioned by the National Institute of Standards and Technology (NIST), on the basis of measurements of the residual water found after the extraction step. The results were obtained by volumetric Karl Fischer (KF) titration in a medium containing a large excess of chloroform (> or = 65%), a proposed prerequisite to ensure complete release of water from the oil matrix. In this work, the extent of this residual water was studied by means of a direct zero-current potentiometric technique using a KF medium containing more than 80% chloroform, which is well above the concentration recommended by NIST. A procedure is described that makes it possible to correct the results for dilution errors as well as for chemical interference effects caused by the oil matrix. The corrected values were found to be in the range of 0.6-1.5 ppm, which should be compared with the 12-34 ppm (uncorrected values) reported by NIST for the same oils. From this, it is concluded that the volumetric KF method used by NIST gives results that are much too high.

Investigation of the volatile organic substances that cause the characteristic odor of pentachlorophenol treated wood utility poles.

The nature of the volatile organic compounds that could be at the origin of the characteristic odor of treated wood utility poles was investigated by the study of compositional changes in the chromatographic profiles of fresh-pentachlorophenol (PCP) solvent samples and weathered samples collected from an in-service red pine pole. Over 99 peaks were identified in the chromatogram of the fresh solvent from which a large portion of the C3-, C4-, C5-, C6-alkylbenzene isomers and early eluting n-alkanes was missing from the analysis of weathered samples. Three domains in the chromatographic profile (volatile, semivolatile, and nonvolatile components) were confirmed by assessing the headspace of fresh-PCP solvent samples using direct syringe sampling and solid-phase microextraction. A first level of field validation was achieved using an emission cell for measuring substances emanating from sapwood specimens at different temperatures. The average latent heat of vaporization (deltaHvap) of the PCP-solvent components was estimated at 99.9 kJ/mol from these results. Finally, the analysis of airborne substances at a treating plant and a utility pole storage site confirmed that the C4-, C5-, and C6-alkylbenzene isomers could contribute to the characteristic odor perceived by humans.