Characteristics of an amperometric detector for capillary HPLC

The main characteristics of a dual-electrode amperometric detector with a cell of the “cylinder-in-flow” type with a working wire electrode have been investigated. The effective cell volume is 10–40 nl in a system with 0.2–0.4 mm i.d. packed fused-silica columns. Extra-column spreading at the optimum elution rate does not exceed 0.005 μl². The linear range is 10³ at a relative standard deviation of 0.009. The low noise level (2–3 pA) facilitates determination of electro-active substances. The detection limit for catecholamines is of the order of tenths of a femtomole.     

High-performance liquid chromatography of proteins on short capillary columns

A microchromatographic procedure for highly sensitive analysis of proteins has been developed by using short capillary columns with reverse-phase, ion-exchange, and hydrophobic interaction sorbents. The high analytical mass sensitivity on the level of several nanograms was attained by the miniaturization of the column and the optimization of gradient steepness.     

On the stability of micro-LC columns (packed fused silica capillary columns)

The life expectancy and resistance to flow, pressure shocks, solvent gradients, and bending of packed fused silica capillary columns (Micro-LC) are discussed.     

New method for the preparation of small diameter columns with polymeric stationary phases for open tubular liquid chromatography

The purpose of this report is to introduce a new method for use in coating polymeric stationary phase films on the inside wall of small bore diameter fused silica capillary tubing. This technique is being developed for use in fabricating capillary columns for open tubular liquid chromatography.     

Coupling miniaturized liquid chromatography to capillary gas chromatography (micro-LC-CGC): Possibilities of reversed phase LC

Retention gaps with different polarity treatments were evaluated for reversed phase solvents. Aminopropyl- and cyanopropyl-deactivated retention gaps showed the best results for methanol-water mixtures. A reversed phase packed fused silica capillary LC column is connected on-line with a capillary gas chromatography column. The combination was used for the analysis of diazepam in urine. Volume overloading on packed fused silica columns without loss of too much efficiency was demonstrated for propranolol.     

Liquid chromatography in packed fused silica capillaries or Micro-LC: A repeat of the capillary gas chromatography story?

Miniaturized and capillary techniques will gradually become more important in Liquid Chromatography (LC). Micro-LC, or the chromatography in fused silica packed capillary columns, has so many important advantages and characteristics that this is probably the form of miniaturized LC that has the greatest chance to make it. These advantages, as discussed in the present paper should lead to LC in less than 30 minutes with a plate number for the column of 20,000 to 50,000. Unlike Capillary GC which took about 25 years to assert itself Micro-IC will probably not take so long.     

Coupling micro-LC and capillary GC as a powerful tool for the analysis of complex mixtures

A multidimensional chromatography system with a packed fused silica Micro-LC column connected on-line with capillary gas chromatography is presented. The Micro-LC column is used for group separation. Whole peaks are injected into the capillary GC column via an on-column injector. The reproducibility of the proposed transfer system for polyaromatic hydrocarbons is 3% to 7% relative standard deviation. The potential of this on-line Micro-LC-GC system is demonstrated by the analyses of PAH's and of a complex light gasoline fraction.     

Direct measurement of mass fragmentograms for eluents from a micro-liquid chromatograph using an improved nebulizing interface

An improved vacuum nebulizing interface with a very short counter nozzle was developed for direct coupling of a micro-LC and a quadrupole MS with CI-chamber. With the LC-MS system using the nebulizing interface, it became possible to take mass fragmentograms for various less volatile compounds such as glutamic acid, steroids, aromatic amines and chlorine-containing insecticides.