Tailoring Noise Frequency Spectrum between Two Consecutive Second Derivative Filtering Procedures to Improve Liquid Chromatography-Mass Spectrometry Determinations

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• 作者：Shau-Chun Wang ; Chiao-Juan Lin ; Shu-Min Chiang ; Sung-Nien Yu
• 刊名：Analytical Chemistry
• 出版年：2008
• 出版时间：March 15, 2008
• 年：2008
• 卷：80
• 期：6
• 页码：2097 - 2104
• 全文大小：221K
• 年卷期：v.80,no.6(March 15, 2008)
• ISSN：1520-6882

文摘

This paper reports a simple chemometric technique toalter the noise spectrum of a liquid chromatography-mass spectrometry (LC-MS) chromatogram between twoconsecutive second-derivative filter procedures to improvethe peak signal-to-noise (S/N) ratio enhancement. Thistechnique is to multiply one second-derivative filteredLC-MS chromatogram with another artificial chromatogram added with thermal noises prior to the other second-derivative filter. Because the second-derivative filter cannot eliminate frequency components within its own filterbandwidth, more efficient peak S/N ratio improvementcannot be accomplished using consecutive second-derivative filter procedures to process LC-MS chromatograms.In contrast, when the second-derivative filtered LC-MSchromatogram is conditioned with the multiplicationalteration prior to the other second-derivative filter, muchbetter ratio improvement is achieved. The noise frequencyspectrum of the second-derivative filtered chromatogram,which originally contains frequency components withinthe filter bandwidth, is altered to span a broader rangewith multiplication operation. When the frequency rangeof this modified noise spectrum shifts toward the otherregimes, the other second-derivative filter, working as aband-pass filter, is able to provide better filtering efficiencyto obtain higher peak S/N ratios. Real LC-MS chromatograms, of which 5-fold peak S/N ratio improvementachieved with two consecutive second-derivative filtersremains the same S/N ratio improvement using a one-step second-derivative filter, are improved to accomplishmuch better ratio enhancement, approximately 25-fold orhigher when the noise frequency spectrum is modifiedbetween two matched filters. The linear standard curveusing the filtered LC-MS signals is validated. The filteredLC-MS signals are also more reproducible. The moreaccurate determinations of very low-concentration samples(S/N ratio about 5-7) are obtained via standard additionprocedures using the filtered signals rather than thedeterminations using the original signals.