Chromatographic Measurement of the Relative Variance of Capillary Diameters in Multichannel Tubes

Abstract

A device for measuring the dispersion of capillary diameters in multichannel tubes (MCT) used as a source of raw material in production of multicapillary columns is described. Principle of operation consists in correlation between the capillary diameter and time of non-sorbing compound passage through the capillary, i.e., using the parameters of a chromatographic peak of non-sorbing compound run through the MCT (methane). With equal capillary length and pressure difference across the capillaries, the flow rate of a carrier-gas and, hence, of methane sample definitely correlates with the capillary diameter, thus providing determination of the dispersion of the capillary diameters of the MCT from the variance of time of the methane passage through the capillaries. The device is a chromatograph operating at room temperature provided with a system of quick gaseous sample injection, flame-ionization detector, gas unit and recorder. A distinguishing feature of the device design is a possibility of attaching MCT of different length (50 - 1200 mm) and diameter to the sample injector (SI) and detector, due to mobility of SI and quick-detachable fittings of various standard sizes. The characteristics of the device: the accuracy of measurements is about 3%, correction for contribution of the methane peak of exrtacolumn broadening σ² ec = (7.21 ± 0.24) x 10⁴ sec². Examples of measurements performed for different batches of multichannel tubes are presented.