University of Hertfordshire

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Original languageEnglish
JournalJournal of Pharmacy and Pharmacology
Early online date31 May 2017
Publication statusE-pub ahead of print - 31 May 2017


Objectives: A method was developed to analyze St John's wort (Hypericum perforatum L.) herb and preparations using inductively coupled plasma-optical emission spectroscopy (ICP-OES) to determine the quantity of 11 elements (Al, B, Ba, Ca, Cu, Fe, Mg, Mn, Ni, Sr and Zn). Methods: This study includes the evaluation of digestion acids and calibration methods, as well as instrumental parameters such as choice of nebulizer and emission wavelength. Key findings: Two nebulizers (Conikal and SeaSpray) performed similarly for most elements, and two optimum wavelengths were determined for each element. Five acids were evaluated for the digestion of the Polish Certified Reference Material Tea Leaves (INCT-TL-1), while three were taken forward to use for the different St John's wort formulations (i.e. herb, capsule and tablet). A simple protocol using 5 ml HNO3 was sufficient in most cases; however, variability was observed for elements often bound in silicates (e.g. Al, Fe and Zn). An external weighted calibration was also found to be preferential over unweighted, and the use of standard addition affected some concentration values up to 20%. Conclusions: Therefore, this paper presents the development and optimized method parameters to be used with ICP-OES that will allow the analysis of 11 key elements present in St John's wort herb and preparations.


This is the peer reviewed version of the following article: Owen, J. D., Evans, S. J., Guirguis, A., Kellett, K. and Stair, J. L. (2017), 'Method development for the determination of elements in Hypericum perforatum L. (St John's wort) herb and preparations using inductively coupled plasma–optical emission', which has been published in final form at doi: 10.1111/jphp.12742 . Under embargo. Embargo end date: 31 May 2018. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

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