College of Biological, Chemical Sciences and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing 314001, China.
Anal Bioanal Chem. 2012 Dec;404(10):3189-94. doi: 10.1007/s00216-012-6436-2. Epub 2012 Oct 3.
Near infrared spectroscopy (NIRS) has been proved to be a powerful analytical tool in different fields. However, because of the low sensitivity in near infrared region, it is a significant challenge to detect trace analytes with normal NIRS technique. A novel enrichment technique called fluidized bed enrichment has been developed recently to improve sensitivity of NIRS which allows a large volume solution to pass through within a short time. In this paper, fluidized bed enrichment method was applied in the determination of trace dimethyl fumarate in milk. Macroporous styrene resin HZ-816 was used as adsorbent material, and 1 L solution of dimethyl fumarate was run to pass through the material for concentration. The milk sample was pretreated to remove interference matters such as protein, fat, and then passed through the material for enrichment; after that, diffuse reflection NIR spectra were measured for the analyte concentrated on the material directly without any elution process. The enrichment and spectral measurement procedures were easy to operate. NIR spectra in 900-1,700 nm were collected for dimethyl fumarate solutions in the concentration range of 0.506-5.060 μg/mL and then used for multivariate calibration with partial least squares (PLS) regression. Spectral pretreatment methods such as multiplicative scatter correction, first derivative, second derivative, and their combinations were carried out to select the optimal PLS model. Root mean square error of cross-validation calculated by leave-one-out cross-validation is 0.430 μg/mL with ten PLS factors. Ten samples in an independent test set were predicted by the model with the mean relative error of 5.33%. From the results shown in this work, it can be concluded that the NIR technique coupled with on-line enrichment method can be expanded for the determination of trace analytes, and its applications in real liquid samples like milk and juice may also be feasible.
近红外光谱（NIRS）已被证明是不同领域中一种强大的分析工具。然而，由于近红外区域的灵敏度较低，因此使用常规 NIRS 技术检测痕量分析物是一个重大挑战。最近开发了一种新型的富集技术，称为流化床富集，以提高 NIRS 的灵敏度，从而允许大量溶液在短时间内通过。本文将流化床富集方法应用于牛奶中痕量富马酸二甲酯的测定。大孔苯乙烯树脂 HZ-816 用作吸附材料，将 1 L 富马酸二甲酯溶液流过材料进行浓缩。牛奶样品经过预处理以去除蛋白质、脂肪等干扰物质，然后通过材料进行富集；之后，直接对富集在材料上的分析物进行漫反射近红外光谱测量，无需任何洗脱过程。富集和光谱测量过程易于操作。在 900-1700nm 范围内收集浓度范围为 0.506-5.060μg/mL 的富马酸二甲酯溶液的近红外光谱，并使用偏最小二乘法（PLS）回归进行多元校正。进行了乘法散射校正、一阶导数、二阶导数及其组合等光谱预处理方法，以选择最佳的 PLS 模型。通过留一交叉验证计算的交叉验证均方根误差为 0.430μg/mL，具有十个 PLS 因子。通过模型对十个独立测试集中的样品进行预测，平均相对误差为 5.33%。从本工作的结果可以得出结论，近红外技术与在线富集方法相结合可以扩展到痕量分析物的测定，并且其在牛奶和果汁等实际液体样品中的应用也是可行的。
