色谱/原子吸收联用系统中卧管式微火焰原子化离子化同步检测器的研究与应用

Abstract：Gas chromatography/atomic absorption spectroscopy(GC/AAS) is a good me thod for the species analysis of organometallic compounds. But the traditi o nal atomizers are not very suitable for this technology and all of them response only to one kind of signal - the conc e ntration of the metallic atoms of the ground state. They can not give any info r mation about the organic group of organometallic compounds and organic compound s which coexist with the former. For GC/AAS we want to design and manufacture a n ew kind of detector which is much more sensitive and has a much smaller dead vol ume and will sensitively and synchronousl y response to the atomization signal of organometallic compound and ionization s ignal of organic compound. The authors have noticed that the atomization of o r ganometallic compound and ionization of organic compound have been existing in t he same hydrogen flame. The question is how to gain and exchange and output the two signals which are completely different in characters. For this purpose we de signed and manufactured a new type of horizontal pipe mini-flame atomization an d ionization synchronous detector. The key part is a T type glass tube (80 mm× 13 mm×10 mm i.d.) w hich covers horizontally on the jet of the mini-flame atomizer and a long p i pe stainless steel collector (70 mm×9.5 mm o.d.×9 mm i.d.) is tightly ins erted in the tube. The light beam of the hollow cathode lamp passes through the hydroge n flame along the axial center of the glass tube and the ground state metallic at o ms in the flame diffuses to both ends of the tube along the axial center of the g lass tube too. This process enriches the depth of the light absorption and then increases the sensitivity of atomization. At the same time the long pipe collec t or can enrich the collection efficiency of the ionization and increases the sens itivity and widens the linear range. So the detector can synchronously and sens itively detect the organometallic and organic compounds. The detection li mit for atomization of the organometallic compound(diethylmercury) is 2.5×10^-11g^.s^-1 and for ionization of the organic compound (benzene) is 1.0×10^-11g^.s^-1. The linear range is 7.0×10² for atomization of diethylmercury (r=0.9 98 9) and 2 .5×10⁵ for ionization of benzene (r=0.999 2). The selectivity of the detector t o the organic solvent under the optimum operating condition of atomization i s 10⁴-10⁷. The relative standard deviation (RSD,n=11) of the peak area in the optimum operating conditions of atomization for the organometallic compound (die thylmercury) and of ionization for the organic compound (benzene) is 1.8% and 1 .5% respectively. Under the same operating condition, the atomization and the i onization can not reach the optimum performance at the same time. If the atomiz a tion is in the optimum performance state, the performance for ionization is like a chromatographic thermal conductivity detector(TCD). The opti m um performance of the atomization and ionization can be quickly adjusted by chan ging the flow rates of the corresponding gases such as H₂,N₂ and air.
Keywords：horizontal pipe mini-flame atomization and ionization sync hronous detector; gas chromatography and atomic absorption spectrometer; organometallic compound