Czaja T, Wójcik K, Grzeszczuk M, Szostak R. Polypyrrole⁻Methyl Orange Raman pH Sensor.
Polymers (Basel) 2019;
11:E715. [PMID:
31010147 PMCID:
PMC6523554 DOI:
10.3390/polym11040715]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/15/2019] [Accepted: 04/16/2019] [Indexed: 11/28/2022] Open
Abstract
An easy-to-prepare pH sensor based on electrochemically obtained polypyrrole doped with methyl orange ions is described. It enables the determination of a pH value in the 3-13 range for volumes below 1 µL. In a wide pH range, resonance and pre-resonance methyl orange Raman spectra, excited with the 514.5 nm line of an Ar+ laser, changed noticeably in function of H+ concentration. Two types of measurements were performed. In the first case, Raman spectra of the analyzed solutions were collected for samples placed on the sensor surface using a confocal microscope equipped with a 10x objective. Next, measurements were conducted for the same samples without the sensor. On the basis of these spectra, partial least-squares models were elaborated and validated. Relative standard errors of prediction for calibration, validation, and test samples were found to be in the 3.7%-3.9% range. An analogous model build using spectra registered without the sensor was characterized by slightly worse parameters.
Collapse