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Updated: Aug 6, 2026

UV-Vis Spectroscopic Characterization of Nanomaterials in Aqueous Media
Published on: October 25, 2021
Rapid spectrophotometric pH measurements based on the dual-wavelength technique
P A Johansson1, G Ostling, J Drakenberg
1Astra Pharmaceutical Production AB, Analytical Control, S-151 85 Södertälje, Sweden.
Abstract:
A spectrophotometric method for the measurement of pH in solutions of lidocaine hydrochloride (Xylocaine) for injection is presented. 4-Nitrophenol is used as an indicator for determinations of pH in the range 6.5-7.0. The method was found to be faster than the conventional potentiometric method, mainly due to the utilization of a computer-controlled photodiode array spectrophotometer for the measurements. A further advantage with the spectrophotometric method is that errors arising from varying liquid junction potentials are avoided.
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