Microfluidic measurement with Lilian Labs

The European standard ISO 7393 – 2 describes the water quality in relation to the determination of free chlorine and total chlorine. This is the colourimetric detection method using N,N – dialkyl – 1,4 – phenylenediamine, better known under the abbreviation DPD for routine checks.

In public swimming pools, colourimeters, such as comparators or photometers, are usually used for detection. Almost all devices on the market are based on reagent tablets, powder packets or liquid reagents as indicator systems. Due to the relatively complex sample preparation, taking colour reaction times into account, a measurement cycle takes an average of around six to seven minutes and contains a number of potential analytical errors. Added to this is the subsequent cleaning of the sample containers (cuvettes), lids, stirring rods etc. in order to exclude carry-over errors in subsequent measurements.

This results in an additional time factor and labour costs in addition to the actual analysis. The LILIAN LABS Photometer Pro and Wave, on the other hand, have a unique selling point, as they work according to the principle of microfluidisation. What does this mean and what advantages does it have for the user compared to conventional methods? The central module is a high-precision disposable cuvette filled with DPD reagents. This module, known as SensoStick, contains several microchannels, comparable to the needles of a syringe. As soon as the photometer’s measuring process is activated, a pump integrated into the photometer draws the water sample through a small hole in the SensoStick into the microchannels, where it reacts with the indicators and produces the characteristic colour development. Less than 1 ml of sample volume is required for this process. Compared to conventional methods, approx. 40 times fewer reagents are required per measurement process. The analysis is then carried out photometrically as usual.

In summary, this concept has the following advantages for the user:

  • ISO 7393 – 2 and DIN 19 643 compliant measurement method
  • Simultaneous measurement of pH value, free, combined and total chlorine within only approx. 60 seconds
  • Highest precision, certified by an independent German institute
  • Significant time saving, as no sample preparation is required
  • No need to clean cuvettes, lids, stirring rods, …
  • Exact measurement results without prior chemical / technical knowledge of the user
  • Enormous savings in personnel resources for daily routine measurements, which are carried out several times a day per swimming & bathing pool.
  • Digital data processing of the measured values using free software