Robert Clifford (1), Jeff Dahl (1); (1) Shimadzu Scientific Instruments, Columbia, MD, U.S.A.
Pesticides and other crop protection agents may be applied to hops (Humulus lupulus)
to increase yield; however, if improperly applied, they may result in
harmful levels of chemical residues reaching the final brewed product.
Sensitive detection of chemical residues in hops requires liquid
chromatography coupled with tandem mass spectrometric detection. In the
present work, a method was developed for analysis of 200 pesticides in
dried hop cones and hop pellets using a QuEChERS-style sample
preparation followed by dSPE sample cleanup and LC-MS-MS detection.
Matrix-matched calibration curves were prepared for quantitative
analysis, and a market survey of five dozen varieties of dried hop cones
or hop pellets was carried out. Detection limits ranged from less than
10 ppb to ppm levels; however, most analytes could be quantified at or
below the 50 ppb level. This rapid method has an LCMS run time of just
15 min and provides robust and effective detection of potentially
harmful chemical residues.
Robert Clifford received his bachelor’s degree from Glassboro
State College, now Rowan University, in New Jersey, his master’s degree
from Villanova in Pennsylvania, and his Ph.D. degree from George
Washington University in Washington, DC. He has published and presented
over 100 papers in the fields of food, pharmaceutical, environmental,
energy, geology, material science, photonics, and marijuana. However,
his true love is foods and beverages. His first chemistry job was as a
summer intern at the Campbell Soup Company, where he was hired as a
full-time employee. After he went back to graduate school he took
another job as an intern at the FDA, where he was also hired as a
full-time employee. After graduating with his Ph.D. degree he left the
FDA for Shimadzu, where he has worked for the last 25 years. His current
title is marketing manager of food and consumer products.