Fractionating Polymer Microspheres as Highly Accurate Density Standards.
Fractionating Polymer Microspheres as Highly Accurate Density Standards.
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DOI：
10.1021/acs.analchem.5b01932
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发表时间：
2015-07
影响因子：
7.4
通讯作者：
William Bloxham;Jonathan W. Hennek;Ashok A. Kumar;G. Whitesides
中科院分区：
文献类型：
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作者：
William Bloxham;Jonathan W. Hennek;Ashok A. Kumar;G. Whitesides
本文描述了一种方法，分离小，高精度的密度标准珠和表征他们的密度使用准确和实验可追溯的技术。密度标准有各种各样的应用，包括密度梯度的表征，用于在各种领域中分离物体。玻璃密度标准珠可以非常精确（±0.0001克厘米（-3）），但对于许多应用来说太大（直径3-7毫米）。当需要更小的密度标准时，通常使用商用聚合物微球。这些微球的密度标准偏差范围为0.006至0.021克厘米（-3）；这些密度分布使得这些微球在密度要求小的应用中不切实际。在本文中，商业微球使用水相多相系统（AMPS）进行分馏，聚合物和盐的水相混合物自发分离成具有分子密度急剧变化的相，以分离出密度分布比原始微球窄得多的微球（标准偏差从0.0003到0.0008 g cm(-3)）。通过减少密度的不均匀性，该方法减少了任何特定珠的密度的不确定性，因此，在用于表征密度分布的校准标准的限制内提高了精度。
This paper describes a method of isolating small, highly accurate density-standard beads and characterizing their densities using accurate and experimentally traceable techniques. Density standards have a variety of applications, including the characterization of density gradients, which are used to separate objects in a variety of fields. Glass density-standard beads can be very accurate (±0.0001 g cm(-3)) but are too large (3-7 mm in diameter) for many applications. When smaller density standards are needed, commercial polymer microspheres are often used. These microspheres have standard deviations in density ranging from 0.006 to 0.021 g cm(-3); these distributions in density make these microspheres impractical for applications demanding small steps in density. In this paper, commercial microspheres are fractionated using aqueous multiphase systems (AMPS), aqueous mixture of polymers and salts that spontaneously separate into phases having molecularly sharp steps in density, to isolate microspheres having much narrower distributions in density (standard deviations from 0.0003 to 0.0008 g cm(-3)) than the original microspheres. By reducing the heterogeneity in densities, this method reduces the uncertainty in the density of any specific bead and, therefore, improves the accuracy within the limits of the calibration standards used to characterize the distributions in density.