title: Quantitative pH assessment of small-volume samples using a universal pH indicator.
abstract: We developed a hue-based pH determination method to analyze digital images of samples in a 384-well plate after the addition of a universal pH indicator. The standard error of calibration for 69 pH standards was 0.078 pH units, and no sample gave an error greater than 0.23 units. We then used in-solution isoelectric focusing to determine the isoelectric point of Wnt3A protein in conditioned medium and after purification and applied the described method to assess the pH of these small-volume samples. End users may access our standard to assay the pH of their own samples with no additional calibration.
authors.affiliation: Department of Biology, University of Portland, Portland, OR 97203, USA. Electronic address: brownje@up.edu.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Brown
authors.affiliation: Department of Biology, University of Portland, Portland, OR 97203, USA.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Bell
authors.affiliation: Department of Chemistry, University of Portland, Portland, OR 97203, USA.
authors.forename: Victoria
authors.initials: V
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Portland, Portland, OR 97203, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Cantrell
mesh_terms: D000818:Animals; D002138:Calibration; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing / Q000379:methods*; D057230:Limit of Detection
keywords: Isoelectric focusing; Wnt; pH determination; pH indicator