UPLC-MS/MS Determination of 3 Gelsemium Alkaloids in Putrefied Human Blood with Pretreatment by QuEChERS

Three of the gelsemium alkaloids in putrefied whole blood were pretreated by the QuEChERS approach and determined by UPLC-MS/MS. In the QuEChERS, 1.00 mL of the blood sample was extracted by swirly shaking for 20 s with 2 mL of acetonitrile and 50 mg of NaCl, and the shaking was continued for 10 min, and the mixture was centrifuged for 10 min at a rate of 8 000 r·min^-1. The supernatant was taken and treated by the dispersed-matrix SPE using 20 mg of C₁₈ as adsorbent and the mixture was shaken and centrifuged in the same way as described above. The supernatant was separated and used for UPLC and MS/MS analysis as described in the instrumental working conditions. The chromatographic column of ZORBAX Eclipse Plus C₁₈ was selected as stationary phase, and mixtures of (A) acetonitrile and (B) 5 mmol·L^-1 ammonium formate (containing φ 0.1% of formic acid) in various ratios were used as mobile phase in gradient elution, to have the 3 gelsemium alkaloids well-separated. In the MS/MS determinations, electrospray positive ion source and mode of multi-reaction monitoring were adopted in MS/MS. Linear relationships were obtained between values of peak areas and mass concentrations of the 3 gelsemium alkaloids in definite ranges, with detection limits (3S/N) in the range of 0.005-0.1 μg·L^-1. Recovery tests were made by addition mixed standard solutions of the 3 gelsemium alkaloids to a blank sample as matrix and then determined by the proposed method, giving values of recovery in the range of 90.5%-110%, and values of RSDs (n=6) in the range of 2.1%-5.1%.