The provided code is designed to calculate nitrate concentrations measured with the UV-hyperspectral photometer (OPUS) manufactured by the company TriOS (Germany). It also applicable on the former UV-spectrophotometer ProPS. Based on the absorption spectra obtained by the instrument, the nitrate concentrations of a sample are calculated, taking temperature and salinity into account to correct the absorption spectrum. Values have to be provided using an external sensor. Furthermore, CDOM is addressed. A manual how to use the Matlab code and its example data is given in the "HowTo_CalculateNO3.pdf". Within the document, also publications are cited dealing with the topic of optical nitrate detection. There are two zip-files available, one for the UV spectro photometer OPUS and one for the ProPS (former version of OPUS). The uploaded files contain Matlab codes and an example dataset collected during Heincke cruise HE545 in the German Bight (November 2019): - Matlab code "ImportData_OPUS" as well as "ImportData_ProPS" - Matlab code "ImportData_TS" - Matlab code "CalculateNO3" - Example dataset of absorption spectra"HE545_absorptionOPUS" as well as "HE545_absorptionProPS" - Example dataset of external measured temperature and salinity including nitrate concentrations of wet chemical analyses "TS_NitrateLab" - Example reference spectra "ReferenceNitrate" and "ReferenceSalinity"

Example dataset to run the Matlab code attached.