2.1. Setup and experimental design
HVACP system employs a transformer that converts an energy input of 120 VAC/60 Hz, into an energy output of 0-130 kV. This device has a dielectric barrier discharge configuration, as described elsewhere (Yepez & Keener, 2016). A plasma state is formed between two aluminum electrodes. Briefly, electrodes were positioned at the top and bottom of the plasma chamber, allowing the sample to receive a direct exposure of the electric field (Fig.1a, 1b). Dielectric layers (4mm thickness, polypropylene) were added to maintain a uniform glow, free from arcing. The box (polypropylene, 175 x 275 x 44 mm) used as a plasma chamber was flushed with hydrogen gas (common grade, 99.8% purity) for 5 min with a flow rate of 1 L/min to allow a uniform composition. Then, sealed with a high barrier film (Cryovac®, Sealed Air Corporation, NJ). The experiments were carried out inside a hood to extract and neutralize the reactive species generated through the HVACP treatment. A nitrogen gas blanket was adapted to cover the electrodes entirely and diminish the risk of flammability of hydrogen gas. All experiments were conducted at 80 kV.
Soybean oil was procured from a local store, and samples (15 g) were treated in a glass petri dish for 0, 2, 4, and 6 hours by triplicate. Treated samples were collected from 3 points of the plasma chamber: 1) Liquid, inside the petri dish; 2) Gel, outside the petri dish; and, 3) Solid, from the top of the plasma chamber (Fig. 1c). Samples were collected after treatment and maintained at -18°C for further analysis. A partially hydrogenated soybean oil was used as a reference for the comparison of the treated and untreated samples.
Fig. 1 – about here