Related Experiment Video
Updated: Jul 9, 2026

Qualitative Identification of Carboxylic Acids, Boronic Acids, and Amines Using Cruciform Fluorophores
Published on: August 19, 2013
Determination of 4-aminophenol using the quartz crystal microbalance sensor
Nikolaos G Karousos1, Subrayal M Reddy
1School of Biomedical and Life Sciences, University of Surrey, Guildford, UK.
Abstract:
In this paper we report a method for the determination of 4-aminophenol (4-AP) in solution using a quartz crystal microbalance (QCM) sensor. 4-AP reacts with (para-unsubstituted) phenols to form hydrophobic indophenol dye species that precipitate out and adsorb to the surface of the crystal to produce a shift in the crystal resonant frequency. This frequency change, due to in-situ indophenol mass adsorption, can be related to the initial 4-AP concentration. A range of phenols (namely o-cresol, 1-naphthol, resorcinol, catechol and 8-hydroxyquinoline) and their reaction with 4-AP were tested. Ammonium persulfate (APS) and potassium periodate were used as initiators to improve the speed of the reaction and the rate of formation of the precipitate. APS elicited improved signal in terms of response times and frequency shifts compared with KIO4. Of the phenols studied, resorcinol gave the best response time of 6 min for 4-AP determination. The reaction of resorcinol with 4-AP gave extended response times and signal size with decreasing concentration of 4-AP (in the range 2-5 mM).
More Related Videos
07:11Dissipative Microgravimetry to Study the Binding Dynamics of the Phospholipid Binding Protein Annexin A2 to Solid-supported Lipid Bilayers Using a Quartz Resonator
Published on: November 1, 2018
08:21Sample Preparation in Quartz Crystal Microbalance Measurements of Protein Adsorption and Polymer Mechanics
Published on: January 22, 2020
Related Concept Videos
Precipitation Titration: Endpoint Detection Methods
In the Volhard method, a standard excess of AgNO3 is first added to the...
Washing, Drying, and Ignition of Precipitates
Mass Analyzers: Common Types
Atomic Absorption Spectroscopy: Lab
Solutions containing organic solvents, such as low-molecular-mass alcohols, esters, or ketones, enhance absorbances by increasing nebulizer...
Determination of Crystal Structures