Short advice on dilutions for spectroscopy

I noticed today that many of you assumed that the dilutions needed to obtain a reliable standard curve for Crystal Violet determinations, were far too great. In the experiments last week we used a much more concentrated stock of dye, hence the large dilutions necessary to obtain absorbances of less than 1. This week however, the stock dye was diluted in advance and so smaller dilutions were required. When carrying out similar experiments, it is good practice to make a dilution that will give you a reasonable level of colour: not too dark and not too weak. Measure the absorbance and use this measurement to inform the range of dilutions needed to obtain a standard curve with absorbance values between 0.1 and 0.8.

Key words: Absorbance, standard curve, cuvettes, spectroscopy