Hand sanitizers are probably one of the most common commodities used today. However, not all hand sanitizers are created equal, and their effectiveness and safety depend on several factors. One of the most crucial factors to consider is their pH level, which refers to the measure of acidity or alkalinity in a solution.

Most hand sanitizers have a pH range between 5.5 and 8.0, which is considered safe and effective for their intended use. A higher or lower pH level can cause skin irritation, damage or even decrease the sanitizer's effectiveness in killing germs. Therefore, it is important to keep the pH level of hand sanitizers in mind before using them.

Source: Mettler Toledo

Measuring pH of hand sanitizer

Most of the hand sanitizers are usually alcohol-based and contains components such as active ingredients, humectants and excipients. This makes it challenging to measure their pH using a standard sensor. Some of the key challenges are as following:

Complex sample matrix: Hand sanitizers often contain other chemicals such as fragrances or moisturizers, which can interfere with the sensor's readings. These other chemicals can react with the sensor and create false readings, making it difficult to obtain accurate pH measurements.

Varying temperatures: pH is temperature dependent. Therefore, you need to make sure that temperature is constant, or you need to do parallel of pH measurement a temperature measurement.

Sensor design: A sensor must be of certain design and need to withstand the high levels of alcohol that is often found in the hand sanitizers. It must have fast electrolyte outflow, robust shaft and membrane material.

Sensor maintenance: As hand sanitizer contains alcohol, besides typical maintenance like calibration and washing it with deionized water after each sample, it is also important to regularly replenish the membrane for 2 minutes in pH buffer 4.00.

Choosing the right sensor

As the hand sanitizers have a gel-like structure and contain alcohol, it is important that the sensor used in the measurement has a robust glass membrane and have a glass shaft, instead of a plastic shaft. METTLER TOLEDO’s InLab Max Pro ISM has been specially designed for pH samples like hand sanitizers. Its robust pH sensitive membrane and fast outflow of electrolyte from the sleeve junction helps obtaining a reliable pH measurement every time.

If the alcohol content is above 85%, then the best electrode to use is InLab Science Pro ISM as in this electrode the user can change the outer electrolyte to LiCl in ethanol. This is important for measuring pH in high alcohol as it will form precipitate if 3M KCl is used.

As temperature compensation is one of the key factors in the measurement process, the sensor comes with an integrated temperature probe.

Additionally, the sensor has an intelligent sensor management (ISM) technology that allows maximum data traceability and security.

To sum it up, the right pH range is crucial for safety and effectiveness of the hand sanitizers. While it can be tricky to measure the pH of hand sanitizers, using the right sensor can help us get accurate results. METTLER TOLEDO provides a wide variety of specialized pH electrodes and probes, including temperature probes and ISM technology, to ensure accurate readings for laboratory and field applications. Find the right sensor for your wide range of applications.

Also, check out the Expert Library to learn more about how to measure pH and conductivity in different samples.

To contact the author of this article, email pHmatters@mt.com