Lasihelmipohjaisten

Lasihelmipohjaisten, literally “glass electrode‐based”, refers to a class of electrochemical sensors that utilize a glass membrane as the active sensing element. The glass surface is selective to specific ions or ion pairs, most commonly hydrogen ions, and it generates a voltage that is proportional to the ionic activity in the surrounding solution. The most well‑known example of a lasihelmipohjaisten device is the pH meter, in which a glass electrode measures the proton activity of a liquid and converts the potential difference to a pH value.

The functional principle is based on the Donnan equilibrium, whereby the glass–solution interface establishes a potential that depends logarithmically on the ion concentration. The glass alters its surface charge in response to changes in the ionic environment, and this produces the measurable voltage. The sensor is typically part of a two‑electrode system, with a reference electrode that provides a stable potential against which the glass electrode is compared.

Glass electrodes are prized for their non‑smearing, low wear, and long life. They work in a wide range of pH values, usually from about 1 to 13, and can be used in both laboratory and industrial settings. Modern advances include chemicallymodified glass membranes that extend sensitivity to other ions such as potassium, sodium, or certain heavy metals. Because the electrodes are robust and cost‑effective, they form the backbone of routine analytical methods in environmental monitoring, biochemistry, and pharmaceuticals.

Applications of lasihelmipohjaisten cover food quality control, water testing, clinical diagnostics, and research. Their operation requires regular calibration with standards and occasional blank corrections to maintain accuracy. The simplicity of the device, coupled with its reliable performance, has made glass‑based electrochemical sensing a core technology in analytical chemistry.