Permeation of Limonene through Disposable Nitrile Gloves in the Robot Hand Whole Glove and ASTM Closed Loop Models
The ultimate purpose was to assess if a whole glove dextrous robotic hand model provided results that differed from the reference modified closed-loop ASTM F739-99/12 glove permeation technique. The candidate compounds were low volatile solvents to minimize the influence of volatilization as a confounding factor. After preliminary closed-loop studies with 2-ethoxyethanol and 2-butoxyethanol showed the breakthrough times for purple nitrile disposable gloves were too short to be compared in the dextrous robotic hand model, limonene was selected to compare the permeation parameters of different disposable nitrile exam gloves (blue, purple, sterling, and lavender) In the modified closed-loop ASTM permeation model four 1-inch diameter standard permeation cells (3 cells with solvent as challenge and one air blank) were used with water as the collection solvent at 35oC. Samples were analyzed by capillary gas chromatography-mass spectrometry and the internal standard method (4-bromophenol). For the static and moving whole glove model, a Yeager robotic hand and assembled. A circulating water system transferred water from between the outer test glove and the inner chemically protective glove of the doubly gloved robot hand in an incubator at 35.0±0.5 o C. The observed scheduled breakthrough time (SBRT) for blue, purple, sterling, and lavender glove specimens in the ASTM system was 70 ± 10 min, 30 ± 10 min, 15 ± 5 min, and 5 ± 5 min respectively. The two robot hand models showed similar SBRTs: 5 ± 5 min for lavender, 15 ± 5 min for sterling and purple, and 30 ± 10 min for blue gloves. The SBRTs for the blue and purple gloves for the robotic hand were significantly shorter than for the ASTM technique (P≤0.05). The average post-permeation thicknesses (before re-conditioning) for all glove materials for the moving and still robotic hand were more than 10% of the pre-permeation ones (P≤0.05) except for the blue gloves, although this was not so on reconditioning. The average steady state permeation rate (SSPR) for lavender glove for the static robotic hand was 0.423 ± 0.031 µg/cm2/min significantly higher (1.43 times) than for the ASTM method (0.295 ± 0.028 µg/cm2/min [P≤0.05]). Lavender gloves showed a significantly higher SSPR when the moving robotic hand was used (0.490 ± 0.031) compared to a non-moving one (P≤0.05). Although the respective SSPR for other gloves samples (blue, purple, and sterling) with the moving hand experiment appeared more than the static hand, the difference was not significant (P≤0.05). Here the exposed surface area was held constant as was temperature to assess if motion alone caused differences in permeation parameters. This suggests a thickness threshold for hand motion differences. The lavender, sterling, and purple gloves failed the Kimberly Clark Professional permeation breakthrough time criteria and Ansell's criteria for use, and therefore they should not be used as personal protective equipment for exposure to limonene, even for short exposure periods. Although blue gloves provided the highest performance against limonene compared to other gloves, they are safe for less than 20 minutes. Compared to the ASTM F739-99/12 model, the robotic hand permeation model is more sensitive and stringent in defining gloves' efficacy since it better simulates grip motions in the workplace.