The Development Of Oxygen-sensitive Membrane And Its Application In Organic Solvents

In this paper, a sensitive method was developed to determine trace amount of dissolved oxygen in organic solvents based on the characteristic of fluorescence quenching of ruthenium complex by molecular oxygen . two new types of oxygen-sensitive membrane were developed. The precursors or carrier, the oxygen sensitive dictator and the optimum condition to prepara the oxygen-sensitive copolymer membrane were studied. A new method to determine dissolved oxygen in organic solvents by flow injection analysis was established. The main research contents are as follows:1. the study of siloxane copolymer precursor for the oxygen sensorThe choice of preparation conditions for oxygen sensitive membrane: The sol-gel process as well as the effect of film of trimethoxysilane (MTOS), tetramethyl silane (TMOS), tetraethoxy silane (TEOS) and dimethyl ethoxy silicane (DDS) as siloxane coupling agent were studied. We found when the above precursors were used alone,it can not get ideal Sol and it also can not form a complete membrane. Further study shows that, When the methyl trimethoxysilane (MTOS) and four-ethoxy silane (TEOS) mixed in 3:1(v/v), the effect of film was best , Through optimization experiments, the paper selected oxygen sensitive membrane preparation conditions are as follows: alcohol-water ratio is 2:1 (v/v), silane ratio (MTOS: TEOS) is 3:1 (v/v), Water-Silicon ratio is 1:1(v/v), pH = 6, N, N-dimethylformamide (DMF) as the toughening agent, silicone oil with ether as dispersing agent and polyester film as oxygen sensitive membrane carrier.The choice of oxygen-sensitive indicator: We added a certain concentration of indictatas such as 8-hydroxyquinoline - Aluminum (AIq3), bipyridine ruthenium Ru(bpy)3Cl2 , 4,7 - diphenyl-1,10 - phenanthroline ruthenium(Ⅱ) dichloride complex Ru(dpp)3Cl2 to the incorporation of the siloxane aging liquid sol, coating film after a certain period of aging time. The results show that the film added to Ru(bpy)3Cl2 was the best.The optimum of dissolved oxygen determination conditions: At the maximum excitation wavelength of oxygen-sensitive membrane (465nm), The effect of temperature, pump flow rate and membrane thickness on the sensitivity were studied. Under the optimized determination conditions, Dissolved oxygen in 1,3-butanediol, 1,2-glycerol , propylene glycol and PEG-400 were determined . The results show that their response time was less than 30s. Their linear range of dissolved oxygen are 0～73.58mg/L,0～116.43 mg/L,0～205.68 mg/L and 0~165.03 mg/L respectively, and RSD(n=6) are 3.5%,5.4%,2.8% and 1.0% respectively.2. the study of organic macromolecule polymer materials as carrier for the oxygen sensorThe choice of organic macromolecule polymer material: The phenylpropanoid milk, styrene-acrylic emulsion, polyvinyl chloride (PVC) and polyvinyl butyral (PVB) for the preparation as the carrier of the membrane were studied respectively. The results show that for the phenylpropanoid milk emulsion , it can form uniform film after coated to polyester film alone; but after adding oxygen-sensitive indicator [AIq3, Ru(bpy)3Cl2, Ru(dpp)3Cl2] , the emulsion with varying degrees of cohesion; The film coated by styrene-acrylic emulsion dissolved in acetic acid 2% (w/w) is transparent, uniform with higher sensitivity when used to determine dissolved oxygen in organic solvents , but the quality of the film is light, crisp, drifting or cracking easily with the flow of solvents by flow injection analysis system resulting fluorescence signal instability; We dissolved PVC with tetrahydrofuran to form a transparent solution, after coating to glasses we can get uniform and transparent film with good toughness, but the oxygen sensitive indicator spread unevenly in it; The PVB emulsion can form a uniform transparency, good toughness film, and the oxygen sensitive indicator spread evenly in it. so PVB was chosen as carrier for oxygen sensor.The choice of oxygen sensitive indicator: Adding AIq3, Ru(dpp)3Cl2and Ru(bpy)3Cl2 to the PVB emulsion respectively, we found the AIq3, Ru(dpp)3Cl2 in the emulsion distribution were uneven with minor degree of curd;the solvent added Ru(bpy)3Cl2 spreaded evenly, after coated to glasses and drying for a certain time we can get orange, transparent, tough film.So Ru(bpy)3Cl2 was choosed as indictator.The optimum of dissolved oxygen determination conditions: the PVB membranes with Ru(bpy)3Cl2 were used to determine dissolved oxygen in organic solvents. The results showed that the oxygen-sensitive membrane has a faster response time (<30s) to oxygen, a good response reversibility (the values of I0/I remain almost constant within 30min, and the relative standard deviation (RSD ) are 2.4% and 4.4% for nitrogen saturated solution and oxygen saturated solution, respectively). It reveals that the oxygen-sensitive film has excellent reversibility to dissolved oxygen. Moreover, it indicates that the oxygen-sensitive film has high stability ( the value of I0/I unchanged after 180d), The proposed method is applied to determine the concentration of dissolved oxygen in 1,3 - butanediol, 1,2-glycerol , propylene glycol and PEG-400. Their linear range of dissolved oxygen are 0～72.11mg/L,0～69.12 mg/L, 0～200.19 mg/L and 0～109.54 mg/L respectively. and RSD(n=6) are 11.4%,2.0%,7.85 % and 1.76% respectively.