Signal enhancement in supercritical fluid chromatography‐diode‐array detection with multiple injection

Abstract

To circumvent the detrimental effects of large‐volume injection with fixed‐loop injector in modern supercritical fluid chromatography, the feasibility of performing multiple injection was investigated. By accumulating analytes from a certain number of continual small‐volume injections, compounds can be concentrated on the column head, and this leads to signal enhancement compared with a single injection. The signal to noise enhancement of different compounds appeared to be associated with their retention on different stationary phases and with type of sample diluent. The diethylamine column gave the best signal to noise enhancement when acetonitrile was used as sample diluent and the 2‐picolylamine column showed the best overall performance with water as the sample diluent. The advantage of multiple injection over one‐time large‐volume injection was proven with sulfanilamide, with both acetonitrile and water as sample diluents. The multiple injection approach exhibited comparable within‐ and between‐day precision of retention time and peak area with those of single injections. The potential of the multiple injection approach was demonstrated in the analysis of sulfanilamide‐spiked honey extract and diclofenac‐spiked ground water sample. The limitations of this approach were also discussed.

Advances in the limits of separation power in supercritical fluid chromatography

“…The importance of the injection solvent on the separation performance was studied in detail by Desfontaine et al [83] but still remains an important factor in the optimization of separations methods in SFC [84]. To circumvent the detrimental effect of large-volume injections, Sun et al investigated the feasibility of performing multiple subsequent small volume injections instead [85]. This method showed signal enhancement compared to a single large volume injection if the initial retention of the analytes was large enough to lead to concentration on the column head, which was achieved by starting their gradient in a 100% CO2 mobile phase.…”