Nebulized flame ionization detection in high performance liquid chromatography

A nebulized flame ionization detector interfaced with LC was examined and found to be more versatile in applications than common LC detectors, such as UV, RID, ELSD and CAD. The technique can be used for both volatile and non-volatile analytes. It is compatible with gradient elution and can be used for the analysis of non chromophore-possessing analytes. The calibration plots of non-volatile analytes were linear in contrast to other aerosol-based detectors, such as ELSD and CAD. The technique was examined in three consecutive stages; optimization of the FID, testing the response patterns of analytes (volatile and non-volatile) and applications to the analysis of compounds of diverse functional groups. The optimum conditions for the operation of the FID were: hydrogen, 157 ml/min; nitrogen, 250 ml/min; air, 654 ml/min; spray chamber internal diameter, 40 mm, collector internal diameter, 4mm and eluent (water), 1 ml/min. The calibration plots of all volatile analytes were linear while those of the non-volatile analytes were linear only when anions (in the form of sulfuric acid, nitric acid, hydrochloric acid, orthophosphoric acid, sodium sulphate and ammonium sulphate) were added to the eluent The separations of diverse analytes (alcohols, aldehydes, ketones, amines, amino acids, carboxylic acids and sugars) gave detection limits in the low μg range.