Simple Colorimetric Method for Quantification of Surface Carboxy Groups on Polymer Particles

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• 作者：Andreas Hennig ; Angelika Hoffmann ; Heike Borcherding ; Thomas Thiele ; Uwe Schedler ; Ute Resch-Genger
• 刊名：Analytical Chemistry
• 出版年：2011
• 出版时间：June 15, 2011
• 年：2011
• 卷：83
• 期：12
• 页码：4970-4974
• 全文大小：790K
• 年卷期：v.83,no.12(June 15, 2011)
• ISSN：1520-6882

文摘

We present a novel, simple, and fast colorimetric method to quantify the total number of carboxy groups on polymer microparticle and nanoparticle surfaces. This method exploits that small divalent transition metal cations (M²⁺ = Ni²⁺, Co²⁺, Cd²⁺) are efficiently bound to these surface functional groups, which allows their extraction by a single centrifugation step. Remaining M²⁺ in the supernatant is subsequently quantified spectrophotometrically after addition of the metal ion indicator pyrocatechol violet, for which Ni²⁺ was identified to be the most suitable transition metal cation. We demonstrate that the difference between added and detected M²⁺ is nicely correlated to the number of surface carboxy groups as determined by conductometry, thereby affording a validated measure for the trueness of this procedure. The variation coefficient of 5% found in reproducibility studies underlines the potential of this novel method that can find conceivable applications for the characterization of different types of poly(carboxylic acid)-functionalized materials, e.g., for quality control by manufacturers of such materials.