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.
Highlights
As a good complement to traditional reversed-phase liquid chromatography, SFC has drawn more and more attention in the past decade [1]
ACN was employed as sample diluent to evaluate the performance of the multiple injection technique
In modern analytical SFC with fixed-loop injection, the pursuit of higher detectability by increasing the injection volume is often associated with poor chromatographic performance. This issue can be partially circumvented by the use of a multiple injection technique as demonstrated in this work
Summary
As a good complement to traditional reversed-phase liquid chromatography, SFC has drawn more and more attention in the past decade [1]. Compared with reversed-phase liquid chromatography, SFC offers a wider range of stationary phase chemistry selectivities with a lower consumption of organic solvent [2]. Revolutionary development in modern SFC instrumentation has brought dramatic improvement in noise reduction, which opens up the possibility for trace analysis of environmental and biological samples [7,8,9,10]. For such analysis, SFC methods with enhanced analyte detectability are in most cases needed, enabling for lower detection limits. As the compounds can be temporarily trapped on the column head, analyte bands
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