Multiwalled Carbon Nanotubes-Dispersive Solid-Phase Extraction Coupled with UPLC–ESI-MS-MS for Simultaneous Determination of 10 Illegal Adulterants in Antihypertensive Functional Foods

A reliable method for simultaneous determination of 10 illegal adulterants including chlortalidone, hydrochlorothiazide, indapamide, metoprolol, nifedipine, nimodipine, nitrendipine, reserpine, triamterene and valsartan in antihypertensive functional foods by ultra-high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry is presented in this article. The target chemicals were extracted with acetonitrile ultrasonically and cleaned up using multiwalled carbon nanotubes-dispersive solid-phase extraction. The separation was performed on a Waters ACQUITY UPLC BEH C18 Column (2.1 × 100 mm, 1.7 µm) with acetonitrile, 0.1% formic acid and 10 mmol/L ammonium acetate solution as mobile phase at a flow rate of 0.2 mL/min. Multiple reaction monitoring was applied for detection and sildenafil was used as the internal standard. The correlation coefficients of the method were >0.995, with the limits of detection of 0.022-0.30 ng/mL and the limits of quantification of 0.075-0.99 ng/mL. The interday and intraday relative standard deviations were <9.77% and the recoveries were in the range of 85.8-109%. The established method has been applied for the analysis of real samples, and reserpine was detected in a tonic wine sample with a content of 60.1 ± 3.2 mg/L.