Ultrasonic–microwave synergistic liquid–liquid microextraction based on solidified floating organic droplets for extraction of histamine in beer and fish and exploration of the extraction process

It is important to detect the presence of histamine (His) for indicating food quality. To improve the precision and accuracy of histamine detection, this study developed a novel ultrasonic–microwave synergistic liquid–liquid microextraction based on solidified floating organic droplets (UMS-SFO-LLME) to determine His in beer and fish combined with visible spectrophotometry. Through single-factor experiments and response surface Box–Behnken design, the key extraction conditions affecting UMS-SFO-LLME were systematically optimized. The results for the extraction kinetics and thermodynamics indicated that UMS-SFO-LLME is a spontaneous endothermic diffusion extraction process. The linear range of this method in combination with visible spectrophotometry for the determination of His in beer and fish is 0.3–15 mg L−1 and 1–300 mg kg−1, limit of detection is 0.1 mg L−1 and 0.3 mg kg−1, the intra-day precision is 0.86%–1.22% and 0.98%–2.11%, and the inter-day precision is 0.81%–1.75% and 1.45%–2.32%, respectively. UMS-SFO-LLME is an efficient, green and economical sample pretreatment method for determination of His in beer and fish samples.