Graphene solid phase extraction (SPE) of synthetic antioxidants in complex food matrices

Synthetic phenolic antioxidants such as propyl gallate (PG) and butylated hydroxyanisole (BHA) are food additives whose levels in foodstuff must be controlled. The purpose of this study is to evaluate, for the first time, the usefulness of graphene as sorbent for the isolation of PG and BHA from complex food sample matrices, by a solid phase extraction (SPE) method. The influence of the eluent type and volume, amount of graphene, sample volume and concentration of antioxidants in the extraction process has been evaluated. Once the process was optimized, extraction yields of 81 and 95% were obtained for PG and BHA respectively. Quantification of the antioxidants was carried out by RP-HPLC with detection at 290 nm, in isocratic mode, using acetonitrile/1% H3PO4 (60/40 v/v) as mobile phase. The proposed method was applied to the quantification of both antioxidants in pre-cooked spaghetti and hard bouillon cube samples. In the spaghetti matrix, which contains both antioxidants, PG and BHA levels were found to be below established legal limits. The hard bouillon cubes, free from both antioxidants, were spiked with different amounts of PG and BHA, and recoveries very close to 100% were attained.