阿達瑪轉換法在液相層析/拉曼光譜法之應用

Abstract

本研究首次將阿達碼轉換（Hadamard transform）技術應用在液相層析/拉曼光譜法（liquid chromatography/Raman spectrometry, LC/RS）上。分析物溶液置於精密注射針內，配合注射泵（syringe pump）推擠進樣，在三向連接頭（Tee connector）中，與來自液相層析泵的流析溶劑匯流以後，共同經過層析分離管柱。經分離之分析物的拉曼訊號則由市售拉曼光譜儀（Renishaw Invia Raman spectroscope）收集。配合阿達瑪序碼（Hadamard code）的使用，由電腦可以控制注射泵的進樣順序，因此可以得到阿達碼-層析圖碼。此編碼之層析圖經過阿達碼轉換以後，可還原得到解碼之液相層析/拉曼光譜圖。實驗結果發現，此方法非常有助於提高雜訊比值，亦有助於提高偵測靈敏度。當以結晶紫（crystal violet, CV）作為測試樣品，編碼後的層析圖譜經由阿達瑪轉換後，訊號/雜訊比提高了7.29倍。這數值與理論值8.02 相當接近。再者，本研究同時發現，經過層析分離管柱後的分析物若能與奈米銀溶液再次匯流混合的話，藉由表面增強拉曼光現象，可提升拉曼散射光的強度，使分析物的的偵測極限下降。即使分析物的濃度為 500 ppb，依舊可觀察到清楚的拉曼光譜圖。The technique of Hadamard transform (HT) was successfully coupled with liquid chromatography/Raman spectrometry (LC/RS), for the first time. Crystal violet (CV) and a commercial Raman system (Renishaw Invia Raman Spectroscope) were employed as a model sample and detection instrument, respectively. Sample injection device was aslo developed to achieve multiple sample injections for the use of Hadamard transformation. The sample solution was placed in a reservoir and was pushed out by a commercial syringe pump, which was controlled by a personal computer. Compared with a conventional single injection method in LC, the S/N ratios were substantially improved after inverse Hadamard transformation of the encoded chromatogram. Under optimized conditions, when Hadamard matrix of 255 was used, the S/N ratio of the signals for crystal violet (concentration level, 0.5 ppm) was substantially improved to 7.29-fold, and the improvements are in good agreement with those obtained by theory (8.0-fold). The limit of detect was further improved when the method of surface enhanced Raman scattering (SERS) was applied.