VALIDATION OF A GLC METHOD TO DETERMINE GAS-LIQUID PARTITION COEFFICIENTS USING CAPILLARY COLUMNS

Richárd Kresz, András Dallos

Department of Physical Chemistry, University of Veszprém, H-8201 Veszprém, Hungary

The partition gas chromatography is a useful and rapid method to determine gas-liquid partition coefficients of solutes at infinite dilution. The measurements need usually a gas chromatograph fitted with precision equipment and highly loaded packed columns with long retention times. In order to avoid making this long, costly and complicated measurements for all of the solutes, the authors’ laboratory developed and validated a capillary GLC method that used the retention index system to determine gas-liquid equilibrium parameters (specific net retention volumes, Henry coefficients and limiting activity coefficients).

This work deals with the investigation of method validation data elements on the sets of relative retention data (Kováts’s retention indices) measured for different classes of solutes by gas chromatography at temperatures from 373 K to 453 K using fused silica capillary columns coated by 19,24-dioctadecyldotetracontane (C78, C₇₈H₁₅₈) as stationary phase.

The structure of C78 on C78 from packed and capillary columns

Comparison of specific retention volumes

The experimental data obtained were tested by the key method performance factors (accuracy, bias, repeatibility or long-term precision, robustness, matrix suitability, laboratory reproducibility for multiple operators) and the applicability of the method is demonstrated.

It is shown that if absolute retention data of n-alkanes on a given stationary phase are known, the retention index of a substance permits calculation of the gas-liquid partition coefficient of a substances. Gas-liquid partition coefficients of a series of molecular probes of varying polarity obtained on WCOT capillary columns coated with C78 solvent film agreed well with those measured on packed column.

With the financial support of Hungarian Scientific Research Foundation (OTKA), grant No. T35220.