LC/MS/MS Analysis of Pesticide Residues in Pistachios on the Ascentis^® Express RP-Amide Column after QuEChERS Extraction

sample/matrix

5 g ground pistachios spiked with pesticides at 10 ng/g

extraction process

add 10 mL water and 10 mL acetonitrile; shake for 1 hour at 2500 rpm; add contents of Supel QuE citrate extraction tube; shake for 1 minute; centrifuge at 5000 rpm fo 5 minutes; draw off supernatant.

clean-up tube

Supel QuE Z-Sep + (55408-U)

clean-up process

transfer 1 mL of extract to 2 mL tube containing 75 mg Z-Sep+; shake for 1 minute; centrifuge at 5000 rpm for 3 minutes; draw off supernatant.

sample preparation

Dilute 100 μL of cleaned extract to a final volume of 1 mL in 5 mM ammonium formate/0.1% formic acid in water. Transfer diluted sample to vial for LC/MS/MS analysis

column

Ascentis Express RP-Amide, 10 cm x 2.1 mm I.D., 2 μm particles (51576-U)

mobile phase

[A] 5 mM ammonium formate + 0.1% formic acid in water; [B] 5 mM ammonium formate + 0.1% formic acid in 95:5 acetonitrile:H2O

gradient

95% A from 0 to 1 min; to 100% B in 13 min; held at 100% B for 1.5 min; to 95% A in 0.5 min; held at 95% A for 1.5 min

flow rate

0.4 mL/min

column temp.

30 °C

detector

MS, ESI (+), MRM

injection

5 μL

extraction tube

PK50 Supel QuE Citrate (EN) Tube (55227-U)