Some laboratory technicians face difficulties with testing thick, aqueous based samples for pH. This is unfortunate and hereby we provide some tips.
ISFET Technology: Sensor and Reference Electrode
The principle of the pH ISFET (ion-sensitive field-effect transistor) technology is that when the Hydrogen (H+) activity changes, the current driven voltage will change and a different pH value is measured accordingly. To complete the electrical circuit, the ISFET sensor (also called the indicator electrode) needs a reference electrode. For any change in the analyte concentration, the potential of the reference electrode will remain virtually constant and so the change of potential will only be caused by the indicator electrode.
The pH probes of Wellinq are equipped with these components and so the user only has to take care that both the sensor and the reference diaphragm are in the same sample. Moreover, Wellinq has a broad experience in the development and manufacture for the circuitry and reference electrodes and offers tiny, stable, OEM designs compatible with medical and food safety standards.
From Aqueous to Thick, Viscous Samples
Fast, reproducible results are easily achieved as long as good contact between the sample, the ISFET sensor and the reference electrode diaphragm is made. Without a proper fluid (or semi-solid) connection between the entire sensor area and the reference diaphragm, no (stable) measurement can be performed. A good rule of thumb is to have at least the first millimeters from the probe tip to be immersed during measurements and calibrations.
For testing thick or viscous samples it requires a little stirring of the sample with the pH probe or placing the sample material directly onto the probe tip. A wooden toothpick will not damage the sensor.
Wellinq Sensor Solutions Webshop
Wellinq is an innovative company for development and manufacturing of high-quality medical devices. Moreover, the company provides design and produce sensor technology solutions for both the medical and non-medical market.
Wellinq leverages many years of experience to develop and produce high quality miniature sensors. Among others, the portfolio consists of glass-free pH ISFET (ion-sensitive field-effect transistor) sensors and differential Wheatstone bridge pressure sensors. Thanks to specific know-how of die attaching, wire bonding, encapsulating, steering and compensating the sensor, the company can provide successful R&D engineering projects. It is ISO 13485:2016 certified. The REACH and RoHS compliance declaration can be found at the website. It has a clean room facility for development, manufacture, product testing, and qualification services of sensors, assemblies and meters. These are meant for the determination of physical and chemical measured values in the engineering field.
