Bongbeen Yim | PubMed Health

PubMed2006

Badge-type diffusive sampler using 3-methyl-2-benzothiazolinone hydrazone for measuring formaldehyde in indoor air.

The evaluation of a badge-type diffusive sampler for measuring formaldehyde using 3-methyl-2-benzothiazolinone hydrazone (MBTH) was investigated. On average, the formaldehyde concentration in blanks was reduced by approximately 31% by cleaning procedures. The cleaning techniques did not significantly differ in effectiveness. The maximum sampling rate was 22.4 +/- 3.5 mL min(-1) at MBTH concentrations of 0.05%. The formaldehyde concentration in blanks did not appreciably increase over a period of about 1 month at room temperature, and was 0.36 +/- 0.03 microg, with a relative standard deviation of 8%. The diffusive sampler had good precision and accuracy for measuring formaldehyde in indoor environments. For a 24-h exposure time, the limits of detection and quantification calculated with the field blanks were 9.7 and 13.8 ppb, respectively. The minimum exposure times were calculated based on the measured and calculated limits of quantification, the sampling rate, and the atmospheric formaldehyde concentration. The capacity of the diffusive sampler with 0.5% MBTH was 3 ppm h(-1), approximately 1.5-times the capacity when the MBTH concentrations were 0.05%.

Air↗

PubMed2003

Sonolysis of alkylphenols in aqueous solution with Fe(II) and Fe(III).

The sonolytic degradation of alkylphenols (APs), such as butylphenol, pentylphenol, octylphenol, and nonylphenol (NP), in water was investigated at a sound frequency of 200 kHz with an acoustic intensity of 6 W cm(-2) under argon, oxygen, and air atmospheres. The sonolytic degradation rate of the APs under the conditions of the present study depended upon their alkyl chain length. The decrease in the degradation rate by the radical scavenging effect was in the range of about 48-82% for APs in the presence of 3 mM 2-methyl-2-propanol. The free radicals play a significant role in the sonolytic degradation process of the APs. In the presence of Fe(II) and Fe(III), the pseudo-first-order rate constants for the sonolytic degradation of 30 microM NP as a function of the concentration of Fe(II) and Fe(III) were estimated under argon and oxygen. The maximum rate constants were observed at 50 microM Fe(II) (0.139 +/- 0.008 min(-1)) and 100 microM Fe(III) (0.103 +/- 0.001 min(-1)) under oxygen. The total organic carbon concentration (TOC) was investigated under same conditions. TOC decreased in the range of about 50-70% during the sonication in the presence of Fe(II) and Fe(III) under argon and oxygen. The sonochemical effects by the addition of Fe(II) and Fe(III) as catalyst during the sonication under the proper atmosphere result in a remarkable enhancement of degradation and mineralization.

Argon↗