I have been conducting liquid phase adsorption experiments of xylene and toluene using activated carbon. I made solutions at 2 concentrations (200ppm and 400ppm) of individual components of toluene and xylene in methanol, as a solvent. Initially, the plan was to use Gas Chromatography to determine the concentrations of the solutions to see how much of the toluene and xylene were adsorbed with time. After several weeks of struggling and calibrating the GC, I was not able to get good/repeatable results. The values output were not consistent and were varying up to 30% using standard solutions! So I'm switching to UV-Vis spectroscopy but I have some doubts which I would like to clear. The plastic cuvette's that fit in the machine can hold up to about 1.5mL of liquid, but since I've only withdrawn 1mL of my adsorption experimental samples (at different times) will it be possible to dilute it and get results on the UV-Vis? Is it correct to take 100μL of my sample and diluting it with 900μL of Methanol then multiplying by a factor of 9 to obtain the actual concentration? These are the steps I will follow when using the UV-Vis: 1) I will fill a cuvette with methanol only and use that as a blank 2) I will calibrate with standard solutions of toluene and xylene of known concentrations of 200ppm and 400ppm. 3) Use my adsorption samples (diluting as mentioned above) Are there any equations which I should use to determine the concentrations based on the components I have or can I use the Beer-Lambert Law? Also are there any other methods I can investigate that can be used to determine the concentrations of my samples?