Dynamic pressure gradient modulation (DPGM) is investigated for comprehensive two-dimensional gas chromatography (GC × GC) with time-of-flight mass spectrometry (TOFMS) detection. With DPGM, a commercial pneumatic "pulse" valve is opened to introduce a suitably high auxiliary gas pressure at a T-junction connecting the first dimension (1D) and second dimension (2D) columns during the modulation period (PM), temporarily stopping the 1D flow. The valve is then closed for the duration of a pulse width (pw) to "re-inject" temporally focused 1D eluate onto the 2D column for separation. This flow modulation technique is observed to be compatible with TOFMS detection using a 2D flow rate of 4 ml/min for the separation of a 90-component test mixture. A 25 min separation window using a PM = 1 s and pw = 200 ms for full modulation (and 100% duty cycle) provided an average 1Wb = 4.5 s and 2Wb = 130 ms for a 2D peak capacity of nc,2D = 2700 (100 peaks per min). The detector response enhancement factor (DREF) serves as a metric for the enhanced sensitivity of the modulated relative to the unmodulated 1D peaks, with DREFs ranging between 10 and 20 and about a 5-fold improvement in signal-to-noise ratio (S/N). The bilinear "quality" of the GC × GC data is studied using the chemometric method parallel factor analysis (PARAFAC). Since PARAFAC requires sufficiently trilinear data, the reproducibility of the 2D peak shape for a given analyte is confirmed using lack-of-fit (LOF) and percent variation (R2) metrics. The limit-of-detection (LOD) for the representative analyte hexadecane is determined using PARAFAC, providing an LOD of 0.7 ppb (±0.03 ppb) for three replicates. Seven heavily overlapped analytes are also fully resolved by PARAFAC down to the part-per-million (ppm) concentration level, producing reproducible spectra with a majority of spectral match values (MV) over 800 (RSD ≤ 7.1%). This study provides promising results for DPGM as a flow modulation technique compatible with GC × GC-TOFMS, providing high sensitivity data suitable for chemometric analysis.

中文翻译：

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动态压力梯度调制，用于具有飞行时间质谱检测的全面二维气相色谱。

研究了动态压力梯度调制（DPGM）用于具有飞行时间质谱（TOFMS）检测的综合二维气相色谱（GC×GC）。使用DPGM，可打开商用气动“脉冲”阀，以在调制周期（PM）期间在连接第一维（1D）和第二维（2D）柱的T型接头处引入适当高的辅助气体压力，从而暂时停止一维流 然后将阀关闭一段脉冲宽度（pw），以将暂时聚焦的1D洗脱液“重新注入”到2D色谱柱上进行分离。观察到该流动调节技术与使用4 ml / min的2D流速进行TOFMS检测兼容，可分离90组分的测试混合物。对于全调制（和100％占空比），使用PM = 1 s和pw = 200 ms进行25分钟的分离窗口可提供2W峰值容量nc，2D = 2700的平均1Wb = 4.5 s和2Wb = 130 ms（每分钟100个峰值）。检测器响应增强因子（DREF）用作衡量调制相对于未调制1D峰值的灵敏度的度量标准，DREF介于10到20之间，信噪比（S / N）。使用化学计量学方法并行因子分析（PARAFAC）研究了GC×GC数据的双线性“质量”。由于PARAFAC需要足够的三线性数据，因此使用失配（LOF）和百分比变化（R2）度量标准可以确认给定分析物的2D峰形的重现性。使用PARAFAC确定代表性分析物十六烷的检测限（LOD），重复三次可提供0.7 ppb（±0.03 ppb）的LOD。PARAFAC还可以完全分离出七种高度重叠的分析物，降低至百万分之一（ppm）的浓度水平，从而产生可重现的光谱，其中大部分光谱匹配值（MV）超过800（RSD≤7.1％）。这项研究为DPGM作为与GC×GC-TOFMS兼容的流量调节技术提供了可喜的结果，提供了适合化学计量分析的高灵敏度数据。产生具有800以上（RSD≤7.1％）的大多数光谱匹配值（MV）的可重现光谱。这项研究为DPGM作为与GC×GC-TOFMS兼容的流量调节技术提供了令人鼓舞的结果，提供了适合化学计量分析的高灵敏度数据。产生具有800以上（RSD≤7.1％）的大多数光谱匹配值（MV）的可重现光谱。这项研究为DPGM作为与GC×GC-TOFMS兼容的流量调节技术提供了令人鼓舞的结果，提供了适合化学计量分析的高灵敏度数据。