A new and feasible analytical method using reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for further determination of Nickel in hydrogenated vegetable fat.

A new and simple method for Ni determination in hydrogenated vegetable fat (HVF) has been developed using a RP-DLLME sample preparation procedure for further determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrophotometry (GFAAS). The RP-DLLME procedure includes simultaneous microextraction and preconcentration of Ni in HVF, using 5.0 g of HVF preheated (75 °C) and diluted in 5.0 mL of xylene, with the addition of a dispersant/extractant mixture (n-propanol/dilute HNO3). The sample was manually stirred and centrifuged and the aqueous phase was collected for further Ni determination by FAAS and GFAAS. RP-DLLME was carried out using only 700 µL of n-propanol and 300 µL of 2.0 mol L-1 HNO3. The recovery varied from 93.3% to 101.5% for HVF. The LODs and LOQs were 40 and 90 ng g-1 for FAAS, and 0.41 and 1.36 ng g-1 for GFAAS. The proposed analytical method is viable and this is the first application of RP-DLLME to solid fat samples, with Ni determination as an example of application. This method consumes small amounts of reagents, with lower toxicity as compared to microwave decomposition. Furthermore, the key features of the RP-DLLME method include simplicity of operation, high sample mass, reduced reagent consumption, and use of diluted HNO3 as an extractant.