Answer Posted / tanu bhardwaj

when we prepare a solution for UV-vis spectroscopy, we prepare it in a solvent, to remove the absorption effects due to solvent, we keep that solvent into blank, so that when the two rays coming out of two cuvettes are subtracted, then we get only the absorption due to solute, not due to solvent. if we prepare sample in water, then water is used as blank.

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My question about gas chromatography sulfur chemiluminsecence detector. I test unknown sample gas by GC-SCD (calibrated ) and the result of *H2S is 279 PPM , *but when I test the same sample with the GC-TCD (calibrated ) the value of *H2S is 2500 PPM . I'd like to inform you that both GCs are calibrated and have very good operation conditions with stable parameters . the question is if the sample gas with higher H2S over detection limits of SCD detector (1000 ppm). why the result it 279 ppm Best regards

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