Question

Briefly explain what information you obtained from the calibration plot and why we needed it. Be specific. How did you use it to find the concentration of the unknown?

Answer 1

For any instrument, say it a uv-vis, ion chromatography, atomic absorption spectrometer etc., where we determine the unknown concentration of the sample a calibration or the standard curve is required which is usually a linear graph. It is defined as the response generated by the instrument in the form of a signal for the known standards which we give as an input with which we determine the unknown without which analysing samples is utter waste. For eg: Consider UV-Vis to determine the concentration of unknown , we first prepare standards of known concentration and check the instrument response for the known sample and the instrument will generate the calibration curve. Taking this into consideration when the unknown samples are analysed , the absorbance for the unknown lies in the calibration curve range and by using y=mx+c equation we will find out the concentration of the sample. where y stands for the response the instrument generated (absorbance in case of UV-Vis), m is the slope, x is for the concentration to be calculated, and b for the intercept. A good calibration graph has a correlation coefficient has 0.999.