Doehlert matrix for the optimization of ultrasound dispersive liquid?liquid microextraction of melatonin in Argentine and Brazilian wine samples

ANGELICA F. CARNEIRO; CANDICE N. CARNEIRO; GOMEZ, FEDERICO J. V.; SPISSO, ADRIAN; M. FERNANDA SILVA; LUCAS A.C. MINHO; WALTER N.L DOS SANTOS; DE SOUZA DIAS, FABIO

MICROCHEMICAL JOURNAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 159

0026-265X

In the present work, a method based on the Ultrasound-dispersive liquid?liquid microextraction (US-DLLME) forthe preconcentration of melatonin in Brazilian and Argentinian wine samples prior to the determination byreverse phase high performance liquid chromatography with diode array detector HPLC-DAD was developed.Sample prep optimization was carried out in two stages. First, a full factorial design was executed to evaluate thevariables significance. The second step consisted of significant variables optimization (pH, extraction volume,sonication time, centrifugation time) using a Doehlert matrix to determine the critical values. Optimal USDLLMEextraction conditions were as follows: pH of 4.5, sonication time of 6.8 min, centrifugation time of2.5 min, extractor volume of 250 μL and 5.0 mL of sample. The organic phase was retrieved with a microsyringeto a glass tube, dried and diluted with the mobile phase prior injection. The method presented a limit of detection(LOD) of 0.23 μg L−1 and a limit of quantification (LOQ) of 0.70 μg L−1. The precision expressed asrelative standard deviation (R.S.D.) was 0.8% and 1.9% at 10.0 and 1.0 μg L−1, respectively. Accuracy wasconfirmed by comparison of the results found by the proposed methods with an alternative method, and spiketests with recuperations ranging from 92 to 103%. The analyzed samples showed concentrations varying from2.2 to 5.0 μg L−1.