الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
Carbon monoxide (CO) is produced during the incomplete combustion of carbonaceous materials. Natural sources of CO include: forest fires and photochemical dissociation of carbon dioxide (CO2)’ Man-made sources of CO include: mobile sources such as motor vehicles; and stationary sources as industrial processes, burning of refuse, indoor heating and tobacco smoking. Carbon human being monoxide has an adverse health effect on due to the reversible reaction of CO with heamoglobien and other haem-containing compounds competing with oxygen. The affinity of haemoglobin for CO is about 230 times greater than that for oxygen. Persons exposed to CO for long periods suffer from some behavioural changes, difficulty in performing physical work and functional heart disturbance. Numerous measurements of CO levels in ambient air have been reported, the majority having been made near heavy traffic streets. For example, CO levels in 7 cities in the UK were found to be below 10 ppm, but peaks of up to 114 ppm were recorded. In Saudia Arabia (1977), concentrations near Dhahran (a coastal area) were 0.3 ppm, while in Riyadh the levels near downtown were in excess of 50 ppm. In Egypt a study showed that during heavy traffic in downtown Cairo CO concentration has reached 150 ppm, while in residential areas the results ranged from 10-39 ppm. In Alexandria, the average concentration at weekdays was 5.4 ppm while at weekends the concentration was 3.4 ppm. 11 Several chemical and physical methods have been studied by different investigators to determine CO in air. The chemical methods include, red mercuric oxide method, pyrotannic acid method, cacotheleine reagent method and combustion method. The physical methods include chromatographic and infrared techniques. In most developing countries the direct reading instruments are not available due to lack of economic considerations so thepresence of substituted methods for determination of CO in air is very urgent. This study is a trial to accomplish this purpose. The selected methods were leucocrystal violet method, iodine pentoxide method, combustion method, and MIRAN-IA analyzer as an infrared technique. For conducting this study, known concentrations of CO have been prepared in cylinders. Carbon monoxide has been prepared by the reaction between hot concentrated sulfuric acid and formic acid and injecting a known volume of pure CO gas in the evacuated cylinder. Dry air has been further comperessed in the cylinder at 80 poundsjinch2. The known concentrations of CO have been measured by the selected methods. The leucocrystal violet method (colorimetric method), depends on the reaction between CO and leucocrystal violet absorbing solution. known volumes of known concentrations of CO have been injected in separating funnels containing the absorbing solution. After shaking for 30 minutes the produced pink color has been measured spectrophotometrically. Different factors were found to affect the response of the absorbing solution. These factors include, air temperature, time of shaking and ptf of the absorbing solution. The iodine pentoxide (Oxidation reduction) method depends on the ability of CO to reduce heated iodine pentoxide crystals. This was done by passing the air sample through a reaction tube containing iodine pentoxide crystals which was heated in an oil bath at 140-150-oC. The liberated iodine vapor was trapped on potassium iodide solution and determined both volumetrically (titration against standard sodium thiosulfate) , and spectrophotometrically. The combustion method used is based on passing the air sample through certain heater containing platinum wire (catalyst for combustion) and trapping the liberated carbon dioxide in excess standard barium hydroxide solution Ba(Otf)2. The unreacted portion of Ba(Otf)2 has been determined volumetrically by titration against standard hydrochloric acid tfCl. j j A MIRAN-IA spectrophotometer has been used for studying the infrared techniques for determination of CO in air. With this technique carbon monoxide absorbs infrared radiation at 4.62511m. The absorbance of the gas has been detected and compared with a calibration curve which is drawn by injection of different known concentrations of CO in the closed loop of the instrument. To determine the corresponding absorbances. To compere the different methods under the same conditions, different known concentrations of carbon monoxide were prepared in a stainless steel chamber under atmospheric pressure. All the previous methods except leucocrystaI violet method, were used at the same time for determination of each concentration of CO in the chamber. For the leucocrystal violet method, known volumes of pure CO were injected directly into the separating funnels. To compare the different methods for ambient air determination, three positions in the street were selected for sampling CO from atmosphere. These positions were at 1,5 and 10 meters far from an exhaust pipe of motor vehicle. Samples of air were collected in plastic bags, and CO level was determined by all the previous methods. The optimum conditions for leucocrystal violet method was found to be 20-25°c and pt! of 3.1-3.12. This m’ethod is sensitive, accurate, reliable, reproducible, and precise for levels of CO higher than (40 ppm inside the separating funnels). It is not recommended for ambient levels of CO. Iodine pentoxide method is specific, sensitive, accurate, reliable, reproducible and precise for any level of CO in air. The accuracy of volumetric technique is higher for lower concentrations (ambient air level), while in spectrophotometric technique the accuracy levels appear to be higher for concentrations of 10 ppm and above. This methods is only suitable for grab samples. Combustion method is also specific, accurate, reliable, reproducible and precise for any level of CO above 10 ppm, and it is suitble for both grab and continuous samples. All the previous methods are not suitable for the instantaneous measurement of CO. While, MIRAN-IA as an infrared instrument is a portable analyzer that can be used for instantaneous measurement in the field. Also, the technique of measurement is very simple, sensitive, specific, accurate, reliable, reproducible and precise for concentrations of 10 ppm and above. Other types of MIRAN analyzer may give higher accuracy levels at lower concenrations.^leng