4.3. Other possible uses of photometry

Photometers are often used in combination with other devices. They are often used in conjunction with chromatographic equipment in which the sample leaving the column is conducted through a flow cell and the absorbance of the solution is detected continuously. Plotting the measured absorbance against time will yield a curve called a chromatogram. If we use a diode-array detector, we can measure the absorbance of the conducted sample at multiple wavelengths simultaneously and can create a series of photometric spectra.

Another common practice is to measure the absorbance of not just one but multiple (tens or hundreds of) samples at a time by using a so-called plate reader (Figure 4.4). Plates holding 6, 12, 24, 48, 96 or 384 samples can be placed in such devices. Depending on the type of the plate, the volume of a sample can be between 10 µL and 10 mL. The most common type of plate has 96 wells with a maximal individual volume of 200 µL.

Plate reader with a 96-well plate

Figure 4.4. Plate reader with a 96-well plate