Characterization of an ultraviolet irradiation chamber to monitor molecular photodegradation by Raman spectroscopy

Abstract

ABSTRACTA homemade ultraviolet chamber is reported to induce photochemical changes with characterization by Raman spectroscopy. The equipment has compartments for ultraviolet-A (UV-A) (8 lamps of 8 W) and for UV-A + ultraviolet-B (UV-B) irradiation (4 lamps of 26 W and 1 lamp of 15 W). The irradiance was measured 3, 5, and 10 cm from the light sources. The maximum irradiance was obtained at 3 cm (UV-A: 2.66 mW/cm2 and UV-A + UV-B: 4.30 mW/cm2). The chamber internal temperature was stabilized at 30°C after 1 hr of operation with an internal relative humidity of approximately 45%. 10% Collagen was irradiated with UV-A at 2.0 mW/cm2 for 3 hr with changes in Raman peaks at 1253, 1271, 1453, and 1660 cm−1 indicating changes in conformation. 5% Atenolol was irradiated with UV-A + UV-B at 4.30 mW/cm2 for 8 hours with changes to Raman peaks at 822, 1186, 1206, 1248, and 1618 cm−1. A commercial insect repellent was irradiated with UV-A + UV-B at 4.30 mW/cm2 for 8 hr and decreases in Raman intensity were observed at 526, 690, 1003, and 1606 cm−1 due to degradation of N, N-diethyl-m-toluamide. The results demonstrate proper operation of the irradiation chamber with Raman spectroscopic monitoring.