In vivo Measurement Considerations

In vivo analysis is the direct measurement of chlorophyll in algal cells without extraction or chemical treatment. Since the measurements are direct, the chlorophyll can be measured using an in-situ instrument in discrete samples; through continuous flow monitoring; or by a submersible sensor. This is the advantage of in vivo measurements compared to doing an extractive analysis.

Discrete Cell Sampling of Chlorophyll
Discrete cell sampling can be done in the lab, or in the field using one of the Turner Designs family of fluorometers, see the Product Selection Guide. The sample of interest is contained in a sample cell or cuvette. The size of the sample cell affects the minimum detectable concentration. The larger the sample, the lower the concentration that can be read. Discrete sampling, also known as "hand sampling" or "grab sampling" can be used in all types of field studies.

Depending on the fluorometer, the sample cell may be a 10mm x 10mm cuvette or a 13mm or 25mm test tube. The 13mm tube is typically used when extracting chlorophyll using acetone to minimize the amount of solvent used.

Fluorometers that use 25mm tubes hold a larger measurement sample and the resulting longer pathlength will be better for low level chlorophyll measurements.

Continuous Flow Sampling of Chlorophyll
Continuous flow sampling allows for continuous sampling, (real-time monitoring) from a fixed location; or for horizontal profiling through installation on a ship. Water must be pumped through the fluorometer, and data can be logged at specified intervals, or transferred to an external logging system. Turner Designs has on-line fluorometers to enable remote/unattended monitoring of water, such as the AlgaeWatch shown here.

Submersible Fluorometers
Submersible fluorometers are ideal tools for profiling and moored applications. They can be placed directly in the water without the need for a pump, or sample cell.