Spherical C18-functionalized ordered mesoporous silica packed on micro-solid phase extraction cartridges for simultaneous determination of twenty-three alkaloids in flower extract supplements

Abstract

A spherical ordered mesoporous silica functionalized with octadecylsilane ligand (SM-C18) was successfully synthesized and characterized, showing 647 m²/g of surface area, 45 Å of pore size, 4–6 μm of particle diameter and 0.37 mmol/g of functionalization degree. 1.5 mg of SM-C18 were packed into EPREP micro-solid phase extraction (µSPEed) cartridges for use with a handheld programmable digital analytical syringe (digiVOL®) to develop a sample preparation protocol for the analysis of two tropane (TAs) and twenty-one pyrrolizidine (PAs) alkaloids. The SM-C18 demonstrated greater retention capacity compared with commercial C18/hydrophilic amorphous silica sorbent. The optimized extraction conditions were as follows: 100 µL of methanol (2 cycles) and 100 µL of H₂O (2 cycles) for conditioning, 100 µL of H₂O-reconstituted sample (10 cycles), for a total of 1 mL of sample loaded, and 100 µL of methanol (2 cycles) for elution, followed by subsequent analysis by UHPLC-MS/MS. The method was successfully validated, showing good recoveries ranging between 91 and 97 %, low quantification limits and absence of matrix effect for the twenty-tree alkaloids. Additionally, cartridges packed with SM-C18 material allow for better reusability compared to the commercial material, as it has been demonstrated that they can be used for at least 75 extractions. This significantly enhances the method's sustainability. Finally, it was applied to 25 samples of flower extract supplements (FES). In two different batches of the sample obtained from Convolvulus arvensis flowers (FES4a and FES4b), atropine and scopolamine were quantified.