Dissolvable layered double hydroxide coated magnetic nanoparticles for extraction followed by high performance liquid chromatography for the determination of phenolic acids in fruit juices

• Magnetic nanoparticles (MNPs) were coated with dissolvable layered double hydroxide (LDHs) and the sorbent was used for the extraction of phenolic acids.
• The extraction method followed by HPLC-DAD was successfully applied for the determination of the selected phenolic acids in fruit juice.
• The method combined advantages of both MNPs and dissolvable LDHs.
• The method was inexpensive, fast, and simple which used no organic solvent for the extraction and desorption steps.

A magnesium–aluminum layered double hydroxide coated on magnetic nanoparticles was synthesized and used as a sorbent to extract some phenolic acids including p-hydroxy benzoic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid from fruit juices. After extraction, the elution step was performed through dissolving double hydroxide layers containing the analytes by changing the solution pH. The extracted phenolic acids were separated and quantified using high performance liquid chromatography-photodiode array detection. Experimental parameters such as sorbent amount, solution pH, desorption solvent volume and extraction time were studied and optimized. The linearity range of the method was between 2 and 500 μg L−1 with the determination coefficient (r2) higher than 0.991. Relative standard deviations for intra- and inter-day precision for the analytes at 100 μg L−1 were in the range of 4.3–9.2% and 4.9–8.6%, respectively. Batch-to-batch reproducibility at 100 μg L−1 concentration level was in the range of 7.8–11% (n = 3). The limits of detection were between 0.44 and 1.3 μg L−1. Relative recoveries higher than 81% with RSDs in the range of 4.2–9.7% were obtained in the analysis of fruit juice samples.