Matrix Effects Affecting the Indirect Calibration of the Static Headspace-Gas Chromatographic Method Used for Dissolved Gas Analysis in Dielectric Liquids

To evaluate the effects of the density and polarity of the matrix on the dissolution of H2, O2, N2, CH4, CO, CO2, C2H2, C2H4, C2H6, C3H6, and C3H8 in various dielectric liquids, the gas−liquid partitioning coefficients (Ostwald coefficients) have been measured under the conditions of method C of ASTM D 3612-01 using a vapor−liquid-phase equilibrium technique. Altogether, 286 gas−liquid systems distributed throughout samples of mineral oils, vegetable oils, and synthetic oils were investigated with the aim of extending the scope of applicability of method C for dissolved gas analysis. The possibility of applying the method to a range of high-viscosity liquids (up to 120 cSt at 40 °C) was first demonstrated by measuring the equilibration of the species in the coexisting vapor phase of the samples. The effect of oil aging upon gas solubility was then addressed by assessing samples of a given mineral oil collected at different ages of in-service equipment. The oxidation of a weak polar dielectric was found to...