George J. Kallos

Investigations of the Formation of Bis-Chloromethyl Ether in Simulated Hydrogen Chloride-Formaldehyde Atmospheric Environments

The vapor phase reaction of formaldehyde and hydrogen chloride in air has been studied for the formation of bis-chloromethyl ether. At relatively high concentrations of these reactants (500 to 3000 ppm) bis-chloromethyl ether was produced at a low parts-per-billion level. It was found that bis-chloromethyl ether does not form in detectable amounts when formaldehyde and hydrogen chloride coexist in air at concentrations of a few parts per million. Even at concentrations higher than the threshold limit values off these materials-for example, at 100 ppm each-bis-chloromethyl ether is not formed at a detection limit of 0.1 ppb. The vapor phase mixing of formaldehyde and hydrogen chloride was done at ambient room temperature and relative humidity, and the mixture was allowed to stand for more than 14 hours before analysis.

Study of Aqueous HCI and Formaldehyde Mixtures for Formation of Bis (Chloromethyl) Ether

The reaction of aqueous HCI and formaldehyde at concentrations up to 2000 ppm were carried out at ambient temperature for 18 hours to investigate the possible formation of bis(chloromethyl)ether. Bis(chloromethyl)ether was not observed either in the aqueous phase or the gas phase above the reaction mixture, with detection limits of 9 ppb and 1 ppb, respectively. Strong inferential evidence shows that bis(chloromethyl)ether cannot be present at even a much lower level than 9 ppb in aqueous solution.

STABILITY STUDIES OF ALKOXYSILANES IN AQUEOUS MEDIA

In order to correlate hydrolysis rates under physiological conditions to differences in toxicity of trimethoxysilane, tetramethoxysilane, and methyltrimethoxysilane, the rates of hydrolysis of these compounds were studied in deionized water, sodium phosphate buffer solution at pH 7.4, and 10% rat serum in sodium phosphate buffer at 37.4 degrees C. A strong surface effect was observed on the hydrolysis rates of tetramethoxysilane in different reactors in the following decreasing order: quartz greater than soft glass (I) greater than stainless steel greater than Teflon greater than soft glass (II). By using the soft glass (II) reactor as the reaction vessel for hydrolysis experiments, trimethoxysilane and tetramethoxysilane were found to be very unstable in 0.15 M sodium phosphate buffer (pH 7.4) and 10% rat serum (0.15 M sodium phosphate buffer, pH 7.4) with similar rates of hydrolysis at greater than 3.0 min-1 (t 1/2 less than 0.23 min). Under similar conditions, however, the rate of hydrolysis for tetramethoxysilane in deionized water was measured to be considerably slower (k = 0.022 min-1; t 1/2 = 32 min) than that of trimethoxysilane (k greater than 8.1 min-1, t 1/2 less than 0.09 min). However, the rates of hydrolysis for methyltrimethoxysilane in water, sodium phosphate buffer at pH 7.4, and 10% rat serum were measured to be 0.03 min-1 (t 1/2 = 24 min), 0.10 min-1 (t 1/2 = 6.7 min), and 0.08 min-1 (t 1/2 = 8.6 min), respectively.

Reactive adsorbent derivative collection and gas chromatographic determination of chloromethyl methyl ether in air

A method has been developed and validated for the derivatization and collection of chloromethyl methyl ether (CMME) on a reactant-coated solid adsorbent tube. Following sampling, the CMME derivative is desorbed into methanol, cleaned up with aqueous KOH, extracted into hexane, and analyzed by gas chromatography with electron capture detection. Air containing the CMME is pulled through an air sampling tube containing 1.5% potassium 2,4,6-trichlorophenate on modified 120/140 mesh GLC-110 as the adsorbent. A derivative is formed by the reaction: The procedure is designed for industrial hygiene monitoring to give an accurate 4-hour time-weighted-average of the exposure level. Yields were found to be 56±10% (2σ) while recoveries independent of yield were 96±6% (2σ) for CMME concentrations in the range of 6 ppb (v/v) to 900 ppb (v/v) in air. Breakthrough concentrations, humidity and storage effects and other parameters were also investigated.