Flow Cells

The flow cell is integrated into a flow loop. Chemosensors containing luminescent dye indicators are embedded in a matrix and held inline by the flow cell. The sample travels through the flow cell, passing over the chemosensor. A fiber optic cable is fed into the top of the flow cell, which transmits light between the chemosensor and the fiber optic sensor.

The sensor emits a red light (orange-red at a wavelength of 610-630 nm), exciting the chemosensors which show luminescence in the near infrared region (NIR, 760-790 nm). Depending on the molecules present in the solution, the amount of luminescence changes. The sensor measures this phase shift which is then calculated into the relevant parameter.

The chemosensor contains both a pH-sensitive indicator and a pH-insensitive reference dye.

At higher pH levels, the pH indicator dye is de-pronated. When the deprotonated chemosensor is excited via red light transmitted from the fiber optic sensor, the luminescence of the pH-sensitive indicator is quenched and only the NIR emission is measured. As the pH lowers, the sample becomes more acidic and the pH indicator becomes protonated. In this state, when the sensor emits red light, the indicator emits bright NIR luminescence.

This chemosensor contains an oxygen-sensitive indicator. 

When the sensor emits red light, the indicator shows bright luminescence in the NIR range. At low concentrations of dissolved oxygen, there is less collision between oxygen molecules and the indicator dye, allowing for a brighter emission of NIR light. As the oxygen concentration increases, the rate of collision also increases. This collision quenches the luminescence of the oxygen-sensitive indicator, reducing the intensity of NIR-emission.