Signal Enhancement in HPLC/microcoil NMR using Automated Column Trapping

Department of Chemistry, Purdue University, ウェストラファイエット, Indiana, United States
Analytical Chemistry (Impact Factor: 5.64). 11/2006; 78(20):7154-60. DOI: 10.1021/ac0605748
Source: PubMed


A new HPLC NMR system is described that performs analytical separation, preconcentration, and NMR spectroscopy in rapid succession. The central component of our method is the online preconcentration sequence that improves the match between postcolumn analyte peak volume and microcoil NMR detection volume. Separated samples are collected on to a C18 guard column with a mobile phase composed of 90% D2O/10% acetonitrile-D3 and back-flushed to the NMR microcoil probe with 90% acetonitrile-D3/10% D2O. To assess the performance of our unit, we separated a standard mixture of 1 mM ibuprofen, naproxen, and phenylbutazone using a commercially available C18 analytical column. The S/N measurements from the NMR acquisitions indicated that we achieved signal enhancement factors up to 10.4 (+/-1.2)-fold. Furthermore, we observed that preconcentration factors increased as the injected amount of analyte decreased. The highest concentration enrichment of 14.7 (+/-2.2)-fold was attained injecting 100 microL of solution of 0.2 mM (approximately 4 microg) ibuprofen.

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    • "When samples are mass-limited, reducing the detection volume to match the sample size offers enhanced signal-to-noise ratio (SNR) performance, and significant efforts have been undertaken to perfect high-resolution spectroscopy in very small coils [1] [2] [3] [4] [5] [6] [7] [8] [9]. The integration of NMR with separation techniques such as liquid chromatography (e.g., [10]) or capillary electrophoresis [11] [12] proceeds more naturally when the NMR detection volume can be made compatible with the very small sample volumes and fluid handling tubing typical of the separation step. "
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    Full-text · Article · Oct 2007 · Journal of Magnetic Resonance
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    Full-text · Article · Mar 2008 · Proceedings of the National Academy of Sciences
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