page_title: Variable pathlength cell
section_title: Background subtraction
hierarchical_section_title: Variable pathlength cell / Background subtraction
caption_attribution_description: English: example of slope spectroscopy baseline plot vs. no baseline
context_page_description: A variable pathlength cell is a sample holder used for ultraviolet–visible spectroscopy or infrared spectroscopy that has a path length that can be varied to change the absorbance without changing the sample concentration.
context_section_description: Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorbtivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary. The image on the right is a linear plot showing both the background corrected data and the raw data.
  This shows that the absorbance values on the plot are offset by an equal amount and the slope of the two plots are equal. Thus, the concentration calculated from the two plots is equal. Other scalar components that contribute to the absorbance of a given sample like contaminants on the cuvette or a different cuvette material also are averaged out during the slope measurement.
  The technique is also applicable for in line measurements for TFF and chromatography applications.
caption: Base line no base line
exif: {}