Biomedical subjects
Publications and source records attributed to J L Monkman.
An analytical scheme was developed for vinyl chloride, which is applicable to ambient and in-plant atmospheres. Using computerized gas chromatographs equipped with automatic injection system and flow rate control, high reproducibilities are achieved in the ppb range. Samples from various sources have been analyzed.
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Substantial progress has been made in the last few years in the development of a rapid method for determining polycyclic aromatic hydrocarbons (PAH) in environmental samples. The three-step method consists of (i) a preliminary separation of PAH by solvent and/or column chromatography, (ii) identification by a combination of gas chromatography with quadrupole mass spectrometry and computer, and (iii) measurement by computerized gas chromatography using internal standards. Samples of industrial effluents, coke oven emissions, coal tar and airborne particulates have been investigated. The efficiencies of different gas chromatographic columns were evaluated during these investigations.
The volatility of two fungicidal seed dressings, Panogen 15 B liquid and Panogen PX powder, containing methyl mercuric dicyandiamide in equivalent amounts at the dosage used, was compared with that of triple distilled mercury. Tests were made in the absence and presence of cleaned Manitou wheat of 12.0% and 17.1% moisture content. The Panogen formulations were compared at the recommended and twice the recommended rate at different dosages, storage periods and storage temperatures. The Hg content of air samples was determined by the Corte-Monkman method, capable of determining 0.4 ng of Hg, which in a 1-L air sample is equivalent to 0.049 ppb (v/v). The volatility of the interstitial air expressed as mug of Hg vapor/m3 air depended on temperature, wheat moisture content and storage duration and ranged from 150 to 2,240 for metallic Hg, 21 to 350 for Panogen 15 B, and 31 to 380 for PX. In the absence of wheat the volatility of 15 B was greatest (395) at -17.5 degees C and least (75) at 4.5 degrees C, but increased rapidly thereafter with increased temperature. Volatility of metallic Hg after application to wheat of 12.0% and 17.1% moisture content was not significantly reduced after four days storage, but that of Panogen 15 B and PX was reduced considerably, particularly at the higher moisture level. Thus, volatility of mercurial seed dressings cannot be predicted from Hg content alone. Reduction of volatility through possible irreversible chemical bonding of Hg with seed components is suggested for more detailed investigation.
Airborne mercury from dental offices was selectively trapped by silber gauze elements in borosilicate glass obsorbers, followed by heat-desorption and spectrophotometric measurement at 2537A. As little as 0.4 ng of Hg could be accurately determined, which is equivalent to 49 ppt in a wone-L air sample on a v/v basis. Over 860 air samples were taken over a range of locations and working conditions at 88 different dental offices, and at the Dental Training Clinic of the University of Manitoba. The Hg vapor concentrations at the dental facilities ranged from 0.45 to 742 mug/m3 of air, 29% of the samples were within 0.45 to 5 mug; 37.8 were within 5.1 to 25mug;and 33.2% were above 25 mug. Mercury concentrations varied during the working day, depending on the time of sampling, the number of amalgams placed, and the interval between placements. The lowest concentrations were obtained in the morning. Disturbance of residual mercury droplets on floors or working areas by sweeping or dusting, or immediately after attempted clean-up of a mercury spill, sharply increased the amount of airborne mercury.
Instrumental development is now entering a more logical era, where the former artistic character of electronics is being replaced by cold technology. Because of this, one should be expect more reliability; however, there still exist many weak links in practical application. Digital readout systems and computer processing induce a false sense of security. In reality, it is the sample-measurement relationship that determines an instrument's credibility and not the number of digits on its meter. In describing three faulty practices that greatly influence an instrument's performance, it is hoped that measurement may be more closely related to the sample!
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