Volume: 5, 2026
5th International PhD Students’ Conference at the University of Life Sciences in Lublin, Poland:
ENVIRONMENT – PLANT – ANIMAL – PRODUCT
Abstract number: F001
DOI: https://doi.org/10.24326/ICDSUPL5.F001
Published online: 22 April 2026
Moisture content evaluation of herbal dietary supplements
Petra Bajt*1, Iva Dragun2, Jelena Kovačić2, Ana Mornar Turk2 and Daniela Amidžić Klarić2
1 Center for Translational Research and Innovations in Pharmacy, Faculty of Pharmacy and Biochemistry, University of Zagreb, 1 A. Kovačića St., 10 000 Zagreb, Croatia
2 Department of Pharmaceutical Analysis, Faculty of Pharmacy and Biochemistry, University of Zagreb, 1 A. Kovačića St., 10 000 Zagreb, Croatia
* Corresponding author: pbajt@pharma.hr
Determination of moisture, including water, in herbal dietary supplements is important, because it can affect product quality and safety. A commonly used method for moisture determination is loss on drying (LOD), a gravimetric method that measures water and other volatile compounds, while the specific method for measuring total water content is the Karl Fischer (KF) volumetric method.
This study assessed moisture and water content in 22 dietary supplements (hard capsules or bulk form) containing turmeric, Indian frankincense, green chiretta, and/or black pepper by LOD and KF. Pharmacopeial acceptable limits for moisture content, which can also apply to water content, for these herbs, were determined depending on whether they contained dry extracts or herbal drugs. Limits for dry extracts were 7% for turmeric, 5% for Indian frankincense and green chiretta, and 2% for black pepper. Herbal drugs limits were 10% for turmeric and green chiretta,12% for Indian frankincense and 13% for black pepper. Results showed that LOD values were up to 34.95% and that six samples were above the limits, while KF values were up to 7.83% and four samples exceeded the limits. Of these, three hard capsules values were above limits in both methods. Most samples were slightly above the limit by up to 2.3%, except for one multi-herbal hard capsule sample in LOD exceeding limit by 29.9%. This sample, which contained all examined herbs, showed the highest moisture, probably due to its high content of hyaluronic acid ingredient. Comparing results in both methods, they were similar within ±3.91%, except for the sample with the highest moisture content (33.6%). These differences are probably because of their different measurement principles. In addition, a positive correlation was observed between LOD and KF results (r=0.79) after excluding outlier.
These findings highlight the importance of stricter regulatory control of these dietary supplements and the need to use both methods to obtain comprehensive information about their moisture profile.
This work has been supported by the European Regional Development Fund (FarmInova; grant number KK.01.1.1.02.0021).
Keywords: herbal dietary supplements; Karl Fischer method; loss on drying
How to cite
Bajt P., Dragun I., Kovačić J., Mornar Turk A., Amidžić Klarić D., 2026. Moisture content evaluation of herbal dietary supplements. In: 5th International PhD Students’ Conference at the University of Life Sciences in Lublin, Poland: Environment – Plant – Animal – Product. https://doi.org/10.24326/ICDSUPL5.F001