in EU
Measurement of Hydrogen Content in Water
Why measure the hydrogen content in water?
Measurement Methods
1. Gas Chromatography
The reputable International Hydrogen Standards Association recommends using gas chromatography.
Gas chromatography (GC) is an expensive method, so its use is typically limited to specialized laboratories, scientific institutions, and manufacturers who require high-precision measurements and can afford investments in equipment and maintenance. How much does a gas chromatograph cost? Manufacturers of methylene blue test drops with colloidal platinum usually calibrate and check their characteristics using GC.
Gas chromatography is a method used to separate compounds in mixtures by analyzing the interaction between a gas (mobile phase) and a polymer material (stationary phase) contained in a long tube called a column.
The column is used to separate individual components of the sample. Although GC can measure many other gases and compounds in a sample, we will consider hydrogen gas (H2).
The test sample is injected into the GC injection port, and the hydrogen dissolved or contained in microbubbles is removed from the water by heat. The evaporated gas is then forced into the column using compressed inert carrier gas (usually argon or nitrogen). As the gas travels along the length of the column, it passes through a thermal conductivity detector (TCD), where its presence affects the electrical characteristics of a tungsten-rhenium filament. The detector's response will be proportional to the concentration of dissolved hydrogen gas in the sample solution, leading to a small but measurable change in voltage drop. By comparing the detector response over time with a stored calibration standard, GC can determine the unknown concentration of hydrogen present in the sample. This method shows hydrogen both dissolved in water and from bubbles.
Pros:
- High accuracy
- Ability to measure hydrogen from microbubbles
Cons:
- High equipment cost
- Used only in specialized laboratories and scientific institutions
2. Methylene blue drops with colloidal platinum
An affordable method for measuring hydrogen concentration by titration is widely used by manufacturers and allows the measurement of hydrogen in microbubbles.
On January 24, 2012, an article titled “A convenient method for determining the concentration of hydrogen in water: use of methylene blue with colloidal platinum” was published by Japanese scientists in the scientific journal Medical Gas Research. The article proposed measuring the amount of hydrogen by titration (sequential addition of drops until the solution changes color).
“The method for determining hydrogen concentration in water is highly desirable, especially if it is simpler and cheaper than the current method involving expensive electrochemical gas sensors. Accordingly, we investigated a simple oxidimetry method, which includes the redox reaction of the oxidizer methylene blue (MB) in the presence of a colloidal platinum (Pt) catalyst. It is well known that MB reacts with an equimolar amount of hydrogen in the presence of Pt or palladium to form the colorless reduced (leucomethylene blue, leuco MB) as follows: MB (blue) + 2H+ + 2e- → leucoMB (colorless),” the article states. Based on this methodology, many manufacturers produce the drops.
The measurement is performed by titration - adding drops of the blue solution and counting the number of drops until the solution changes color from blue to clear.
Pros:
- Simplicity and Convenience: The method is straightforward and easy to perform.
- Independence from pH: The measurement is not affected by the pH value of the solution.
- Effective for Microbubbles: Capable of measuring hydrogen in microbubbles in hydrogen water devices that produce ultra-high concentrations.
Cons:
- Hydrogen Loss: Some hydrogen escapes during the measurement process, resulting in a slightly lower reading than the actual concentration.
3. ORP-Based Hydrogen Measurement Devices
Oxidation-Reduction Potential (ORP) of a liquid indicates whether it can oxidize something, giving a positive ORP, or if it will be oxidized itself, resulting in a lower ORP.
Hydrogen can be oxidized, which lowers the ORP.
Important: However, many harmful substances also have a negative ORP – for example, organic matter in an old aquarium or motor oil. This doesn't mean that these liquids are beneficial to health.
Until 2018, devices like Trustlex were used in the market of hydrogen water generators to measure hydrogen content.
Now, inexpensive alternatives to these devices have appeared.
The principle of their operation is the measurement of the oxidation-reduction potential (ORP) of the solution and the automatic conversion into hydrogen concentration. Indeed, there is a correlation between hydrogen concentration and ORP.
This is the Nernst equation for the "molecular hydrogen - hydrogen ion" pair. It shows that the higher the concentration of molecular hydrogen (H₂ in square brackets), the more negative the ORP becomes.
However, the same equation shows that the concentration of hydrogen ions (H+) affects the ORP much more significantly—it is squared. Hydrogen ions (H+) determine acidity, or pH.
Conclusion: Even slight changes in pH affect ORP much more than hydrogen content. A minor shift in pH from the value the device is calibrated for leads to significant distortions.
Influencing Factors:
- ORP can be affected by many factors, not just hydrogen and its ions. For example, if an aquarium is not cleaned for a long time, the water will also have a negative ORP. Motor oil also has a negative ORP.
- Devices like Trustlex and its analogs, which measure hydrogen concentration based on ORP, are non-selective. They may indicate the presence of hydrogen even when there is none.
Limitations:
- This method does not account for hydrogen contained in microbubbles, which is particularly well absorbed by the body. This is especially relevant for ultra-high concentration hydrogen water generators.
- It does not provide reliable results, and for this reason, is not recommended by the International Hydrogen Standards Association (IHSA).
Pros:
- Simplicity of use
Cons:
- Inaccuracy due to the influence of pH and other factors
- Inability to account for hydrogen in microbubbles
4. Measurement of Hydrogen Concentration Using Gas Analyzers with Selective Electrodes
The principle of operation for these hydrogen measurement devices: The electrodes are immersed in an electrolyte solution separated by a membrane from the analyzed medium. The membrane is permeable to hydrogen but impermeable to water vapors and liquids. Hydrogen diffuses from the analyzed medium through the membrane into the electrolyte layer between the membrane and the anode. An electrochemical reaction involving hydrogen occurs on the surface of the anode.
As a result, the sensor begins to generate a DC signal, the magnitude of which is proportional to the concentration of hydrogen dissolved in the analyzed media. This signal is then converted into data. Scientifically, this is called an "amperometric sensor operating on the principle of a closed polarographic cell."
Pros:
- Independence from pH of the solution
Cons:
- Insensitivity to hydrogen in microbubbles
