In my thesis, I have developed a method for determining vitamin D3 in dietary supplements using high-performing liquid chromatography.
I first optimized the method by determining the analytical conditions (temperature, type of mobile phases, wavelength, column, flow, volume of injection…) and determined the appropriate gradient method. This was followed by the preparation of different solutions of samples and standards with different concentrations, filming and analysing their chromatograms. I used the prepared solutions to validate the method. During the validation of the method, I checked its repeatability, linearity and the stability of the solutions. I also determined the LOQ and LOD (limit of quantification and limit of detection) for vitamin D3 and checked the quantification using the standard additive method. It turns out that the repeatability of the method is good, but that the stability of the prepared solutions is relatively is poor. The quantification using the standard additive method gave similar results to that of the external standard, that is why we can assume the accuracy of the method. The resulting LOQ and LOD indicate that vitamin D3 can be detected and quantified at very low concentrations.
I found out that the method for determining vitamin D3 using high-performance liquid chromatography is appropriate, but immediate injection is necessary after preparation of a sample containing vitamin D3, because if its not injected soon vitamin D3 starts to gradually decay.
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