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The design of an on‐line semi‐preparative LC–SPE–NMR system for trace analysis
Author(s) -
Xu Feng,
Alexander Anthony J.
Publication year - 2005
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1617
Subject(s) - chemistry , chromatography , analytical chemistry (journal) , elution , analyte , proton nmr , volumetric flow rate , nmr spectra database , nuclear magnetic resonance spectroscopy , mass spectrometry , spectral line , organic chemistry , physics , quantum mechanics , astronomy
This paper reports the design of an on‐line semi‐preparative LC–SPE–NMR system and its use in the structural analysis of mixture components at the 0.02–1% level. The combination provides at least a five fold mass sensitivity increase over that obtained from typical analytical LC–SPE systems and a >30‐fold total NMR sensitivity enhancement over analysis by LC–NMR. This is accomplished by using a novel on‐line device to store, dilute (1–100‐fold) and deliver (at an optimized flow‐rate) the isolated component of interest to an SPE trap unit. The SPE unit consists of two cartridges connected in parallel to increase the overall SPE capacity and also to decrease the flow‐rate through each trap for enhanced trapping efficiency. As the coupling of semi‐preparative LC with NMR (through SPE) is well matched in terms of optimal mass loading for both techniques, only one LC–SPE cycle is required to enrich a 50 µg ml −1 component (1% in a 5 mg ml −1 mixture) for the acquisition of heteronuclear 1 H– 13 C NMR data using a conventional NMR flow probe. Furthermore, analytes at the 0.02% level (∼1 µg ml −1 ) can be studied using 2D 1 H NMR techniques if peak cuts from replicate sample injections (≥3) are accumulated into the storage/dilution unit and the resulting solution processed by just one SPE trap and elute cycle. Copyright © 2005 John Wiley & Sons, Ltd.