This article is a short, but very important comment to the often used humification index (HIX), assumed to indicate the degree of biochemical degradation of dissolved organic matter in water samples. HIX is commonly calculated by dividing the fluorescence intensity detected at longer wave lengths by the intensity detected at shorter wavelengths.

However, we found typos in the original article that affect the used equation directly and thus the results. We compared the different ways to calculate HIX and found a strong correlation between all results. Nevertheless, we recommend to use only equation 1, especially if data from different studies should be compared.