title: Digital image-based titrations.
abstract: The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H3PO4 in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H3PO4, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection.
authors.affiliation: Universidade Federal da Paraíba, CCEN, Departamento de Química, P. Box: 5093, 58051-970 João Pessoa, PB, Brazil.
authors.forename: Edvaldo da Nobrega
authors.initials: Eda N
authors.lastname: Gaiao
authors.forename: Valdomiro Lacerda
authors.initials: VL
authors.lastname: Martins
authors.forename: Wellington da Silva
authors.initials: Wda S
authors.lastname: Lyra
authors.forename: Luciano Farias
authors.initials: LF
authors.lastname: de Almeida
authors.forename: Edvan Cirino
authors.initials: EC
authors.lastname: da Silva
authors.forename: Mário César Ugulino
authors.initials: MC
authors.lastname: Araújo