Determination of Anthraquinone in Technical Material, Formulations, and Lettuce by High Performance Liquid Chromatography

Abstract

Foraging on lettuce seeds and seedlings by horned larks (Eremophila alpestris) causes millions of dollars in losses to the California lettuce crop annually. Anthraquinone (AQ; 9,10-anthracenedione) has been shown to deter pest birds from consuming the seeds and seedlings of several plant species and was evaluated as a repellent to horned larks when applied to lettuce seedlings. A set of analytical methods using simple liquid extraction followed by high-performance liquid chromatography analysis were developed for the quantitation of AQ as technical material, as an active ingredient in a commercial formulation, and as a residue in lettuce plants. The methods were easy, reliable, and repeatable. AQ recoveries from control formulation fortified to concentrations of either 24 or 600 mg g(-)(1) were 99 (+/-1.2%) and 98% (+/-1.2%), respectively, with a control formulation method limit of detection (MLOD) of 0.50 mg g(-)(1). Control lettuce tissues from three growth stages were AQ-fortified to concentrations of 0.50 and 500 microg g(-)(1). The resulting AQ recoveries for the two fortification levels were 99 (+/-8.5) and 89% (+/-1.5%) for 11 day old seedlings, 95 (+/-2.6%) and 86% (2.1%) for 16 day old plants, and 92 (+/-1.4%) and 93% (+/-1.1%) for adult head lettuce cover leaves, respectively. The MLODs for the same three lettuce tissues were 0.055, 0.058, and 0.077 microg g(-)(1), respectively. These methods were used to quantify AQ residues from field-grown, treated lettuce and associated fortified quality control samples.