Surface-modified electrochemical detector for liquid chromatography
Surface-modified electrochemical detector for liquid chromatography
复制标题
用于液相色谱的表面改性电化学检测器
DOI：
10.1021/ac00260a039
复制
发表时间：
1983
影响因子：
7.4
通讯作者：
G. S. Wilson
中科院分区：
文献类型：
--
作者：
G. Sittampalam;G. S. Wilson
主席先生：众所周知，固体电极很容易受到样品污染物和电化学反应产物的毒害(1，2)。这在含有多种蛋白质和其他成分的复杂生物基质(如血清、血浆、尿液)中尤其如此，这些蛋白质和其他成分强烈吸附在电极表面，从而削弱了产生观察到的信号的电极过程(3)。此外，样品中电活性干扰的存在可能导致不可接受的高背景信号。随着利用电化学检测(LCEC)的液相色谱和流动注射分析(LCEC)的出现，这些问题已经成为决定分析可靠性的关键。在大多数涉及生物基质的LCEC应用中，感兴趣的电活性物种在色谱分析之前被提取到合适的溶剂中。或者，一些样品，如尿液，可以被稀释(例如1：50稀释)，直接分析而不需要提取(4)。即使大量稀释，电极最终也会受到此类样品中污染物的影响，导致灵敏度下降。一种更合理的方法是在工作电极表面覆盖一层惰性膜，以防止蛋白质吸附，同时促进感兴趣的电活性物种向电极的选择性传输。这样的物理修饰将消除电活性干扰，同时保留电极的非均相电子转移特性。后者是在LCEC应用中与使用化学修饰电极相比的显著优势。我们以H202为电活性物种，研究了蛋白质对涂有醋酸纤维素(CA)膜的铂LCEC探测器响应的影响。与铂电极的结果对比表明，CA膜能有效地防止蛋白质吸附引起的电极中毒。此外，该膜选择性地消除了电极表面的一些电活性干扰，如抗坏血酸。因此，这种物理修饰电极的不同选择性似乎是可能的，这些预审结果如下。实验部分所有溶液都在KMn04蒸馏的去离子水中进行，并用0.45微米孔过滤器(密利孔公司，马萨诸塞州贝德福德)过滤，所有使用的试剂都是分析级的。过氧化氢(H202，30%)从新泽西州费尔劳恩的Fisher Science Co.购买，并通过用Ce4+溶液滴定来标准化，如在别处所述(5)。上述溶液经适当稀释后制成工作标准。单独的几组H202工作标准在相同的浓度下制成，但含有100 mg/dL葡萄糖、2.0 mg/dL
Sir: It is a well-known factthat solid electrodes are very susceptible to poisoning by sample contaminants as well as by the products of electrochemical reactions (1, 2). This is particularly true in complex biological matrices (such as serum, plasma, urine) containing a variety of proteins and other components which strongly adsorb on the electrode surface, thereby attenuating electrode processes that produce the observed signal (3). Further the presence of electroactive interferences in the sample can result in unacceptably high background signals. With theadvent ofliquid chromatography and flow injection analysis utilizing electrochemical detection (LCEC), these problems havebecome very critical in determining the reliability of the analysis. In most LCEC applications involving biological matrices the electroactive species of interest is extracted into a suitable solvent prior to chromatographic analysis. Alternatively, some samples such as urine can be diluted (1: 50 dilution, for ex-ample) and directly analyzed without extraction (4). Even with large dilutions the electrodes would eventually be affected by the contaminants in such samples, resulting in the loss of sensitivity. A more reasonable approach would be to coat the working electrode surface with an inert film that prevents protein adsorption and at the same time facilitates selective transport of the electroactive species of interest toward the electrode. Such physical modifications would eliminate the electroactive interferences while retaining the heterogeneous electron transfer properties of the electrode. Thelatter feature is a significant advantage over using chemically modified electrodes in the LCEC applications. We have examined the effects of proteins on the response of a platinum LCEC detector coated with a cellulose acetate (CA) film, using H202 as the electroactive species of interest. Comparison of these results with that of a bare platinum electrode clearly demonstrates that the CA film effectively prevents electrode poisoning arising from protein adsorption. In addition, the film selectively eliminates some electroactive interferences such as ascorbate from the electrode surface. Thus differential selectivity appears possible with such physically modified electrodes and the results of these pre-liminary findings are presented below.EXPERIMENTAL SECTION All solutions were made in deionizedwater distilled over KMn04 and filtered with 0.45 µ Millipore filter (Millipore Corp., Bedford, MA), and all reagents used were of analytical grade. Hydrogen peroxide (H202, 30%) was purchased from Fisher Scientific Co., Fair Lawn, NJ, and was standardized by titrating with Ce4+ solutions as described elsewhere (5). Working standards were made from the above solutions by appropriate dilution. The separate sets of H202 working standards were made at the same concentrations, but containing 100 mg/dL of glucose, 2.0 mg/dL