Study of the Performance of Gas Chromatographic Columns Under Severe Injection Loading

A systematic study was conducted to observe the effect on column performance of a series of 600 consecutive injections of human adipose tissue extract, both cleaned and uncleaned. Ten different column packings were used and included single and mixed nonpolar and polar liquid phases. The column characteristics observed were peak height response, efficiency, on-column conversion of p,p’-DDT to p,p’- DDD, and peak configuration. Repetitive injections of uncleaned and high lipid content human adipose tissue extract resulted in decreased performance of most columns in response, efficiency, and compound conversion. However, all columns could be maintained and restored to full or nearly full performance capacity by daily changing of the glass injection port insert used for off-column injection and the glass wool plug at column inlet.

A New Flash Injector for Gas Chromatography of Organophosphorus Insecticides

A new "flash injector" is described which features the removal of solvent from organophosphorus insecticide solutions prior to gas chromatography, using the stacked flame ionization detector. A micro-thin film of sample is deposited on glass wool for instantaneous vaporization in the injection port by syringe-injecting an aliquot of sample into a Pyrex glass wool plug contained in a specially designed Pyrex glass tube that fits the injection port. After pre-vaporization of the solvent, flash injection is completed by inserting and sealing the tube in the injection port by a mechanical flash injector. The method prodvices good chromatographic peaks and resolution, eliminates solvent peaks and interferences, improves reproducibility, prolongs column life, eliminates the use of septums, and requires little or no cleanup of extracts. Errors due to blow-by in the syringe, caused by injection against high port pressures, are eliminated. Injections larger than 5 /il can be used to facilitate detection of organophosphorus residues in low concentrations without extinguishing the detector flames.