title: Simple colorimetric method for quantification of surface carboxy groups on polymer particles.
abstract: 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 (M(2+) = Ni(2+), Co(2+), Cd(2+)) are efficiently bound to these surface functional groups, which allows their extraction by a single centrifugation step. Remaining M(2+) in the supernatant is subsequently quantified spectrophotometrically after addition of the metal ion indicator pyrocatechol violet, for which Ni(2+) was identified to be the most suitable transition metal cation. We demonstrate that the difference between added and detected M(2+) 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.
authors.affiliation: BAM-Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse 11, D-12489 Berlin, Germany. andreas.hennig@bam.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Hennig
authors.forename: Angelika
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Heike
authors.initials: H
authors.lastname: Borcherding
authors.forename: Thomas
authors.initials: T
authors.lastname: Thiele
authors.forename: Uwe
authors.initials: U
authors.lastname: Schedler
authors.forename: Ute
authors.initials: U
authors.lastname: Resch-Genger
mesh_terms: D002104:Cadmium / Q000737:chemistry; D002264:Carboxylic Acids / Q000032:analysis*; D002412:Cations / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003124:Colorimetry / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D002412:Cations; D011108:Polymers; D028561:Transition Elements; D002104:Cadmium; D003035:Cobalt; D009532:Nickel