Determination of heavy metals in aerial part of hyssop [Hyssopus officinalis L.] using high performance ion chromatography with the aid of a linear and non-linear weighted least-squares regression model

Heavy and transition metals are of special importance from the ecotoxicological point of view, both because of the high toxicity of compounds containing in these metals and because of their accumulation in various organisms. Information on their content in plants and animals is of great botanical, nutritional and environmental interest. Some of the heavy and transition metals are toxic when their concentrations exceed certain values. After applying a microwave-assisted high pressure digestion system, a highly sensitive analytical technique based on ion chromatography under isocratic eluent flow-rate conditions (0.3 mL/min) was used. A bifunctional ion-exchange column (IonPac CS 5A, Dionex, Sunnyvale, CA, US A) together with PDCA (pyridine-2.6 dicarboxylic acid) eluent was applied. Detection of all metal ions was carried out by UVVis spectrophotometry (at 530 nm) after a post-column derivatization reaction applying 4-(2-pyridylazo) resorcinol (PAR). The selected method of digestion of plant sample and the application of the optimized chromatographic system to heavy metal analysis of Hyssopus officinalis L. are presented in this work. Linear and non-linear calibration curves for all ions were constructed using a weighted least-squares (WLS) regression model in order to estimate properly detection and quantitation limits obtained during the analysis on IonPac CS 5A column. The LO Ds for all the chromatographic tests were determined using Hubaux-Vos’ method.