Validation protocol for the determination of copper in plant samples by isotope dilution inductively coupled plasma mass spectrometry

Copper determination in plant material was carried out by isotope dilution inductively coupled plasma mass spectrometry. The samples (copper standard solution and Four CRM of plant origin) were spiked with Cu-65 enriched standard solution and decomposed by pressurized microwave digestion in the HNO3-H2O2 mixture. In order to eliminate possible spectroscopic interferences originating from matrix elements, copper was separated from sample digests by adsorption on chelating ion-exchange resin Chelex 100 and elution with diluted HNO3. Performance parameters such as LOD, LOQ, selectivity, measurement ruggedness, precision and trueness were evaluated. LOD and LOQ were 57 and 138 ng g(-1), respectively. Repeatability of copper determination was 20 ng g(-1). The influences of sample weight and volume of spike solution on sensitivity and uncertainty of analysis were estimated. Results of copper determination in CRM were in good agreement with certified values.