Measuring principle
The basic principles by which the measurements are performed are moving boundary electrophoresis for sampling, capillary zone electrophoresis for separation and conductivity detection for detection. The disposable chips contain a glass portion 3 cm long and 1.5 cm wide with which the liquid droplet is contacted during measurement. This glass strip in particular has an injection point, measuring electrodes and 2 micro-channels, the sample channel and the separation channel. The diameter of the channel is 5 times smaller than a hair. The channels are perpendicular to each other and are filled with a solution. After the start of the measurement the electric field makes sure that the ions in the liquid are sucked into the separation channel, where the components are then extracted by differences in the affinity with the wall. One ion takes longer for the journey than another. This is what shows their identity. By measuring the conductivity it is possible to recover the lithium concentration. The measured concentration is placed on the display after measurement and saved in the memory of the Multireader.
The measurement principle in 5 steps:
Step 1 - Sampling: A drop of blood is inserted into the sample reservoir at the end of the sample channel.
Step 2 - Injection: An electric field is placed on the sample channel. As a result, the positive particles from the blood are drawn toward the opposite end of the sample channel, where the negative electrode is located.
Step 3 - Separation: After this an electric field is placed across the separation channel. Through this positive ions migrate to the junction of the two channels at the end of the separation channel. The different speeds of migration of the ions and the length of the channel the ions are completely separated from each other.
Step 4 - Analysis: The conductivity across the width of the separation channel changes when the ions reach it. The conductivity sensors over the channel measure these changes. Because the migration speeds of the various ions are known, it is also known which peaks in conductivity belong to which ions. It is therefore possible to calculate the concentration of the specific substances and pass the measured value through the display to the user, for example: your lithium is 0.30 mmol per liter.