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.