Ian Wark Research Institute, University of South Australia, Adelaide, SA, Australia.
Anal Chem. 2015 May 5;87(9):4757-64. doi: 10.1021/acs.analchem.5b00860. Epub 2015 Apr 20.
The goal of most analytical techniques is to reduce the lower limit of detection; however, it is sometimes necessary to do the opposite. High sample concentrations or samples with high molar absorptivity (e.g., dyes and metal complexes) often require multiple dilution steps or laborious sample preparation prior to spectroscopic analysis. Here, we demonstrate dilution-free, one-step UV-vis spectroscopic analysis of high concentrations of platinum(IV) hexachloride in a micropillar array, that is, "pillar cuvette". The cuvette is spontaneously filled by wicking of the liquid sample into the micropillar array. The pillar height (thus, the film thickness) defines the optical path length, which was reduced to between 10 and 20 μm in this study (3 orders of magnitude smaller than in a typical cuvette). Only one small droplet (∼2 μL) of sample is required, and the dispensed volume need not be precise or even known to the analyst for accurate spectroscopy measurements. For opaque pillars, we show that absorbance is linearly related to platinum concentration (the Beer-Lambert Law). For fully transparent or semitransparent pillars, the measured absorbance was successfully corrected for the fractional surface coverage of the pillars and the transmittance of the pillars and reference. Thus, both opaque and transparent pillars can be applied to absorbance spectroscopy of high absorptivity, microliter samples. It is also shown here that the pillar array has a useful secondary function as an integrated (in-cuvette) filter for particulates. For pillar cuvette measurements of platinum solutions spiked with 6 μm diameter polystyrene spheres, filtered and unfiltered samples gave identical spectra.
大多数分析技术的目标是降低检测下限；然而，有时需要做相反的事情。高浓度的样品或具有高摩尔吸光率的样品（例如染料和金属配合物）通常需要在光谱分析之前进行多次稀释步骤或繁琐的样品制备。在这里，我们展示了在微柱阵列中（即“柱池”）无需稀释即可一步进行高浓度六氯合铂（IV）的紫外可见光谱分析。通过液体样品吸入微柱阵列，池会自动填充。柱高（因此，膜厚）定义了光程长度，在本研究中，光程长度缩短至 10 至 20 μm（比典型池小 3 个数量级）。仅需要一个小液滴（约 2 μL）的样品，并且对于准确的光谱测量，分配的体积不需要精确甚至不需要分析员知道。对于不透明的柱子，我们表明吸光度与铂浓度呈线性关系（比尔-朗伯定律）。对于完全透明或半透明的柱子，成功地对柱子的分数表面覆盖率和柱子和参考的透光率进行了校正，从而对吸光度进行了校正。因此，不透明和透明的柱子都可以用于高吸光度的微升样品的吸收光谱测量。这里还表明，该柱阵列具有作为微粒的集成（池内）过滤器的有用的次要功能。对于用 6 μm 直径聚苯乙烯球加标铂溶液的柱池测量，过滤和未过滤的样品给出了相同的光谱。
