Nano-zirconium-silicate solid-phase extraction method for the rapid quantification of pyrrolizidine alkaloids from plant extracts by UHPLC-QTOF-MS

Abstract

The aim of this work was to develop and validate a rapid dispersive-solid-phase extraction method for the quantification of pyrrolizidine alkaloids (PA) from plant extracts. The method was focused on the significant removal of the intricate matrix to ensure good sensitivity for the subsequent instrumental analysis of PA. This was achieved by employing nano-zirconium silicate (NZS) as a dispersive-SPE sorbent. The specific affinity of NZS for PAs allowed for the effective removal of a substantial portion of the complex matrix, thereby significantly improving the sensitivity of the method, compared to the common methods, were no specific enrichment of the PAs on the SPE sorbent is achieved. Ultra-high-performance liquid chromatography coupled to high resolution time-of-flight mass spectrometry (UHPLC/TOF MS) was used for the qualitative and quantitative analysis of PA. The procedure demonstrated high recoveries for the standard compounds spiked into a blank verbena extract at different concentrations. Recovery rates of 72–95 % for PA, and 30–70 % for their respective N-oxides (PANO) could be obtained. The method was compared to the most commonly used C18 SPE sorbent, and demonstrated a significant lower limit of quantification (LOQ) of 0.64–4.5 ng mL⁻¹ as compared to 4.98–25.7 ng mL⁻¹. The method was validated in accordance with ICH guidelines. PA standards had a linear response between 5 and 150 ng mL ⁻¹ and demonstrated a co-efficient of variance below ± 3 % with a % relative error below ± 15. The presented analytical approach was also tested for the determination of PA from contaminated Verbenae herba extract with success. The presented scheme improves the clean-up efficacy of the already used stationary phases for PA analysis and provides a great alternative analytical tool for the isolation of PAs from plant extracts.