Characterising the amount and the purity of nucleic acid is an important step in state of the art polymerase chain reaction (PCR). In most cases, the analysis is done by stand-alone equipment. For the measurement, a small amount out of the PCR-process has to be removed. Furthermore, the evaluation of the measured spectra occurs only at three wavelengths (230 nm, 260 nm, 280 nm). Therefore, it should be possible to monitor the PCR-process in situ. We demonstrate an illumination unit with three UV-LEDs (245 nm, 265 nm and 280 nm). Every LED is collimated by two lenses. Two longwave-pass filters merge the optical axes of the different wavelength. Lenses and filters are commercial available. The illumination unit is available with and without fiber coupling. The optical behavior of the illumination unit will be shown and discussed. Further, we investigate the observed peak position of the supporting points in dependence of the impurity concentration of an example solution.
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