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