pH Family FAQS
1. What's the lifetime of a pH probe?
The expected lifetime of a correctly used and maintained pH probe is around one to three years. Some factors such ashigh temperature and measuring at extreme pH values contribute to a reduction of the lifetime even for probes that have been well maintained and properly stored. When a meter starts performing poorly, it may be possible to regenerate the pH-sensitive glass membrane and restore the electrode to its previous level of performance.
2. How do you select the correct pH probe?
For optimal pH measurement it is crucial to choose the right pH probe for each application. The most important sample criteria are: chemical composition, homogeneity, temperature, process pressure, pH range and container size (length and width restrictions). The choice of sensor becomes of particular importance for non-aqueous, low conductivity, protein-rich and viscous samples where general purpose glass electrodes are subject to various sources of error. The response time and accuracy of an electrode is dependent on a number of factors. Measurements at extreme pH values and temperatures, or low conductivity may take longer than those of aqueous solutions at room temperature with a neutral pH value.
3. Howshould you maintain/clean a probe?
Regular maintenance is very important for prolonging the lifetime of any pH probe. Probes with liquid electrolyte need the electrolyte to be topped-up when the level threatens to become lower than the level of the sample solution. This maintenance prevents a reflux of thesample into the probe. The complete reference electrolyte should also be regularly changed, approximately once a month. This ensures that the electrolyte is fresh and that no crystallization occurs due toevaporation from the open filling port during measurement. It is important not to get any bubbles on the inside of the probe, especially near the junction. If this happens the measurements will be unstable. To get rid of any bubbles, gently shake the probe in a vertical motion as with a fever thermometer.
To clean the probe, rinse it with deionized water after each measurement but never wipe it with a tissue. The surface of the paper tissue can scratch and damage the pH-sensitive glass membrane, removing the gel-layer and creating an electrostatic charge on the electrode. This electrostatic charge causes the measured signal to become very unstable. Special cleaning procedures may be necessary after contamination with certain samples.
Every application has specific demands which is why METTLER TOLEDO has a measurement solution for every need. Whether your process is at a very high temperature, in a sterile environment or in a hazardous area we have an analog or digital meter that will provide accurate, dependable measurements.
Our range of in-line pH probes and meters include
In applications where very precise measurements are important, refillable pH and ORP probes deliver high accuracy and long lifetime.
Sterilizable and hygienic design combined with high measurement accuracy. Ideal for pharmaceutical as well as food and beverage applications.
pH probes with liquid or polymer electrolyte that are highly resistant to poisoning. For harsh chemical and industrial wastewater applications.
pH probes for pure and ultrapure water applications measure reliably in low-conductivity waters.
In industries such as food where product safety is paramount, non-glass, ISFET, hygienic design probes provide exceptional reliability.
The innovative design of the pH meter allows its optimum use in a whole variety of applications. Suitable for laboratory and industrial-scale use.
ISM accessories such as software, data logger or transmission solution allow you to take full advantage of ISM technology.