I want to know the physicochemical basis of selecting compound like KCl, K2Cr2O7, Toluene, Holmium oxide for calibration of various parameters of a UV Spectrophotometer.
there are two point standardization procedures available. The single-point procedure involves the measurement of the absorbance of a sample solution and of a standard solution of the reference substance. The standard and sample solutions are prepared in a similar manner. Ideally, the concentration of the standard solution should be close to that of the sample solution. A 'two-point bracketing' standardization is therefore required to determine the concentration of the sample solutions. The concentration of one of the standard solutions is greater than that of the sample while the other standard solution has a lower concentration than the sample.
Rather i will refer you to http://www.pharmainfo.net/reviews/various-uv-spectrophotometric-simultaneous-estimation-methods here you can find much more than what you have asked.
One more paper you can read that is Noui et al 2202 in
Chemical Engineering and Processing
Development of a high resolution UV spectrophotometer for at-line monitoring of bioprocesses
These compounds are chosen for calibration for several reasons:
1. They are easy to obtain in pure form and not expensive.
2. They are stable and not very hazardous.
3. They have well-defined absorbance characteristics.
Number 3. is the most important. For wavelength calibration, it is best if you have a sharp absorbance band (narrow in terms of wavelength spread). This allows you to measure the peak very easily, and use it for checking calibration. Sometimes solvent and/or pH are also specified.
For example, benzene in the vapor state (put a small drop in the cell and let it evaporate) has five very sharp absorbance bands at known wavelengths. These are called the "benzene fingers" because of the appearance of the bands.
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i want know the universal compound for calibration of various parameters of a UV Spectrophotometer
There is not a single universal compoound that is used for all calibration experiments. Each compound has its own use. For example, KCl is used to measure light scattering, holmium oxide is used for wavelength calibration.