The ion analyzer mainly uses ion-selective electrode measurement method to achieve accurate detection. The electrodes on the instrument: fluorine, sodium, potassium, ionized calcium, magnesium, and reference electrode. Each electrode has an ion-selective membrane, will be measured with the corresponding ions in the sample to produce a reaction, the membrane is an ion exchanger, and the ionic charge reacts and changes the membrane potential, you can detect the liquid, the sample and the potential between the membrane. The difference between the two potentials detected on both sides of the membrane generates a current, the sample, the reference electrode, the reference electrode liquid constitutes the "loop" on one side, the membrane, the internal electrode liquid, the internal electrode for the other side.
The difference in ion concentration between the internal electrode fluid and the sample generates an electrochemical voltage on both sides of the membrane at the working electrode, which is routed through the highly conductive internal electrode to the amplifier, and the reference electrode to the amplifier site. A calibration curve is obtained by assaying a precise standard solution of known ion concentration, thus detecting the ion concentration in the sample.
Ion migration occurs within the aqueous layer of the ion-selective electrode matrix when the measured ion in solution contacts the electrode. The change in charge of the migrating ions exists as a potential, thus changing the potential between the membrane surfaces and creating a potential difference between the measuring electrode and the reference electrode.
Generally used electrode structure:
Electrode characteristics: Fluorine electrode is a glass capillary electrode is used to determine the concentration of sodium ions in liquid samples,
Main structure: electrode cover: transparent plastic.
Measuring capillary: sodium sensitive glass.
Electrode chamber : Sealed and filled with sodium electrode solution.
Electrode core : Ag, Agcl
Sodium electrode characteristics:
Sodium electrode is a glass capillary electrode used to determine the concentration of sodium ions in liquid samples,
Main structure : Electrode sleeve : Transparent plastic.
Measuring capillary: sodium sensitive glass. Electrode chamber : Sealed and filled with sodium electrode solution.
Electrode core : Ag, Agcl Potassium electrode features : Potassium electrode is a membrane electrode plate, also used to measure the concentration of potassium ions in the sample. Main structure: Electrode sleeve: transparent plastic. Measuring capillary: potassium ion sensitive membrane.
Electrode chamber: sealed and filled with K+ liquid. Electrode core: Ag/Agcl
Features of reference electrode: The reference electrode is a device that connects the sample and the signal ground.
Main structure: the reference electrode consists of two parts: the reference electrode sleeve and the reference electrode core. The reference liquid in the reference sleeve forms a salt bridge between the reference core and the sample. At the beginning of each measurement, the reference liquid is injected into the reference sleeve, and at the same time, a small portion of the reference liquid seeps into the measurement chamber through the glass capillary tube, thus forming a salt bridge between the sample and the reference core, which forms a circuit between the electrical signal ground and the reference liquid.
Measurement process: Ion selective electrode, the electrode contains a known ion concentration of the electrode liquid, through the ion selective electrode membrane and the corresponding ions in the sample interpenetration, thus generating a membrane potential on both sides of the membrane, the concentration of ions in the sample does not use, the size of the potential signal generated is also different, through the measurement of the size of the potential signal can be measured to know the concentration of ions in the sample.
The difference in ion concentration between the liquid in the electrode and the sample generates an electrochemical potential in the electrode membrane, which can be taken out by the electrode and transferred to the input of the amplifier, and the other input of the amplifier is connected to the reference electrode and grounded, and the electrode voltage can be further amplified. A voltage difference is formed which determines the ion concentration of the sample being measured.
Study process:
Ion migration occurs within the aqueous layer of the ion-selective electrode membrane matrix when the measured ion in the electrode solution contacts the electrode. A potential exists for the change in charge of the migrating ion, thus causing a change in potential between the membrane surfaces; a potential difference is generated between the measuring electrode and the reference electrode. Ideal ion-selective electrode for the solution of the ions to be measured in the potential difference, should be consistent with the Nernst (Nernst) equation: E = E0 + log10a (x) E: measured potential E0: standard electrode potential (constant) R: gas constant T: absolute temperature Z: ionic valence F: Faraday's constant a (x): the activity of the ion
See the measured electrode potential and the "X" ions. "X" the logarithm of the activity of the ion is proportional, when the activity coefficient is kept constant, the electrode potential and the logarithm of the concentration of ions (C) is also proportional to find out the activity or concentration of ions in solution.
Currently the production of fluoride ions, nitrate, PH, water hardness (Ca 2 +, Mg 2 + ions), K +, Na + multi-parameter (a number of) Ion Analyzer manufacturers are fewer domestic manufacturers, the representative manufacturers are: Shenzhen Hangchuang Medical Equipment Co.