How to Calibrate a Spectrophotometer with Potassium dichromate Video
Learn how to calibrate a UV VIS spectrophotometer using potassium dichromate calibration filters. I’m going to turn on our spectrophotometer and let it heat up for 45 minutes. Let’s go ahead and choose a wavelength to calibrate. For potassium dichromate there are four different wavelengths you can choose. I’m going to set our machine to test 235nm. Now we have to insert the perchloric acid blank that came with our potassium dichromate kit. When we insert the blank we’re going to get a reading, so we have to blank the machine now with the blank still in the cuvette holder. When the machine is reading zero we can insert one of the potassium dichromate filters. Let’s go with the 20 mg/L filter. Now we’ll check the reading against the certificate of calibration. Let’s go ahead and test 40 mg/L at 235 nm. When you switch to different wavelengths, you have to insert the blank and blank the machine. The reason we use a blank is because we only want to measure the absorbance of the potassium dichromate and not the cuvette or the perchloric acid. The blank accounts for the percholic acid and the cuvette so when we zero the machine we are eliminating these factors and leaving us only with the potassium dichromate.