Determination of Formaldehyde Yields in E-Cigarette Aerosols: An Evaluation of the Efficiency of the DNPH Derivatization Method

Recent reports have suggested that (1) formaldehyde levels (measured as a hydrazone derivative using the DNPH derivatization method) in Electronic Nicotine Delivery Systems (ENDS) products were underreported because formaldehyde may react with propylene glycol (PG) and glycerin (Gly) in the aerosol to form hemiacetals; (2) the equilibrium would shift from the hemiacetals to the acetals in the acidic DNPH trapping solution. In both cases, neither the hemiacetal nor the acetal would react with DNPH to form the target formaldehyde hydrazone, due to the lack of the carbonyl functional group, thus underreporting formaldehyde. These reports were studied in our laboratory. Our results showed that the aerosol generated from formaldehyde-fortified e-liquids provided a near-quantitative recovery of formaldehyde in the aerosol, suggesting that if any hemiacetal was formed in the aerosol, it would readily hydrolyze to free formaldehyde and, consequently, form formaldehyde hydrazone in the acidic DNPH trapping solution. We demonstrated that custom-synthesized Gly and PG hemiacetal adducts added to the DNPH trapping solution would readily hydrolyze to form the formaldehyde hydrazone. We demonstrated that acetals of PG and Gly present in e-liquid are almost completely transferred to the aerosol during aerosolization. The study results demonstrate that the DNPH derivatization method allows for an accurate measurement of formaldehyde in vapor products.

Improvement of sub-level caving mining methods during high-grade iron ore mining

Purpose. To improve of the sub-level caving mining methods during mining of deposits of high-grade iron ores by applying a rational mode and intensifying the ore drawing. Methodology. It included an analysis of scientific literature, design documentation and the practice of mining of deposits of high-grade iron-ores in complex geomechanical conditions of deep horizons of mines, to establish the formation of fundamentally new foundations of scientific-and-design solutions for the rational extraction of minerals; numerical (application a special computer software package PFC 3D) and physical (based on the application of volumetric physical models and equivalent materials) modeling of ore drawing, aimed at identifying regularities of recovery process depending on the mining-geological and mining conditions of the mining of deposits, and also the physical- and-mechanical properties of the loosened ore mass. Findings. Regularities of changes in the qualitative and quantitative recovery percentages depending on the intensity of the ore drawing and physical-and-mechanical properties of the ore have been established using numerical and physical simulation. The obtained regularities made it possible to substantiate the rational parameters of the structural elements of the technological scheme for drawing and delivery of ore. A linear-alternating condition of ore drawing was developed, which will ensure an increase in the extraction of pure ore up to 10% and, as a result, up to 4.6% of quantitative and up to 5.2% of qualitative indicators of ore percentages, as well as up to 1.5% of absolute quality of mined ore mass. Originality. Power-law dependencies of the change in the angle of ore tapping on the intensity of the ore drawing and the ultimate strength of the ore for uniaxial compression have been established as well as dependencies of the increase in the volume of the tapping figure, when a linear-alternating condition of ore drawing is applied, on the intensity of the ore drawing, the height of the collapsed ore layer and the ultimate strength of the ore for uniaxial compression. Practical value. A linear-alternating condition of ore drawing has been developed, the implementation of which in practice makes it possible to increase the qualitative and quantitative recovery percentages and eliminate the human factor while observing the ore drawing planograms.