LC/MS/MS Analysis of Pesticide Residues in Pistachios on the Ascentis® Express RP-Amide Column after QuEChERS Extraction
Materials
analytical column
SPE tube or plate
accessory
Certified Vial Kit, Low Adsorption (LA), 2 mL, pk of 100
volume 2 mL, amber glass vial (with marking spot), natural PTFE/silicone septa (with slit), thread for 9 mmCONDITIONS
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)
Description
Analysis Note
The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method can be used to analyze multiple pesticide residues found in pistachios. Because they contain a significant amount of fat, a cleanup step should be used as part of the QuEChERS method. In this study, QuEChERS extraction and cleanup using Z-Sep+ was used for the analysis of pesticide residues of interest in pistachios. Average recoveries obtained for replicate samples spiked at 10 ng/g were in the range of 70-120% for 23 of the 25 pesticides analyzed. .
Other Notes
Freeze whole pistachios (with shells) using liquid nitrogen, and grind.
Legal Information
Ascentis is a registered trademark of Merck KGaA, Darmstadt, Germany