Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan.
J Sep Sci. 2010 Mar;33(4-5):626-30. doi: 10.1002/jssc.200900662.
The technique of Hadamard transform was successfully coupled with GC/nonresonant multiphoton ionization/TOFMS, for the first time. 1,4-Dichlorobenzene and the fourth harmonic generation (266 nm) of a Nd:YAG laser were employed as a model sample and an ionization laser, respectively. A Hadamard-injector coupled with a capillary-based supersonic jet nozzle (capillary-injector) was also developed in this study. The Hadamard-injector was used to obtain the chromatogram, which was encoded by successive sample introduction based on Hadamard codes, and the capillary-injector was used for injection of GC-elutes into TOFMS. Compared with a conventional single injection method, the S/N ratios were substantially improved after inverse Hadamard transformation of the encoded chromatogram. Under optimized conditions, when Hadamard matrices of 103 and 255 were used, the S/N ratios of the signals for 1,4-dichlorobenzene (concentration level, 4 microg/1 mL ACN) were substantially improved to 4.1- and 6.6-fold, respectively, and those improvements are in good agreement with those obtained by theory (5.1- and 8.0-fold).
Hadamard 变换技术首次成功地与 GC/非共振多光子电离/TOFMS 相结合。1,4-二氯苯和 Nd:YAG 激光的四倍频（266nm）分别用作模型样品和电离激光。在这项研究中，还开发了一种带有毛细管喷射器的 Hadamard 注射器（毛细管注射器）。Hadamard 注射器用于获得色谱图，该色谱图通过基于 Hadamard 码的连续进样进行编码，而毛细管注射器则用于将 GC 洗脱物注入 TOFMS。与传统的单次进样方法相比，对编码色谱图进行逆 Hadamard 变换后，S/N 比得到了显著提高。在优化的条件下，当使用 103 和 255 个 Hadamard 矩阵时，1,4-二氯苯（浓度水平为 4μg/1mLACN）的信号的 S/N 比分别显著提高到 4.1 倍和 6.6 倍，并且这些改进与理论上的改进非常吻合（5.1 倍和 8.0 倍）。
