| Inductively coupled plasma atomic emission spectrometry (ICP-AES) has become a widely used powerful tool for trace elemental analysis in many laboratories around the world due to its excellent sensitivity, reliability, and relative ease of operation since its first introduction into the field of analytical atomic spectrometry. For laboratories that require rapid results or have high sample throughput, analysis speed is paramount. To meet this requirement, the development of ICP spectrometric instrumentation has gone through from single channel sequential scanning spectrometer, multichannel direct-reading spectrometer to recently developed simultaneous spectrometer employing echelle grating and prism (commonly used) as light dispersion system, and two dimensional CCD (commonly used) array as detector. The emerging of simultaneous ICP spectrometer has been regarded as a milestone of the development of ICP-AES. Such trends embody the common developing process of atomic emission spectrometer, and indicate that atomic emission spectrometry is going forward to the "ideal multielement method of analysis". Similarly, the development of newly developed and commercialized MPT-AES spectrometer (Changchun Jilin University-Little Swan Instruments Co. Ltd, Changchun, China) should also go through the same way. That is, it should also develop from single channel sequential scanning systems to simultaneous multielement determination systems. Duan had made many efforts on the miniaturization of the MPT instrument, but what he had done was focused on the air particulate monitoring. Up to now, no miniature simultaneous MPT spectrometer for solution analysis has been commercialized. In this work, a novel unique miniature simultaneous MPT-AES system for solution analysis has been developed by Professor Jin's group in China. The analytical figures of merit including detection limits and precisions of this new spectrometer have reached the same level of 510 model MPT spectrometer. Such a simultaneous spectrometer has advantages of determining multi-elements at the same time, saving sample and time. We solved some problems in the course of development: (1) we have developed a new miniature total internal microwave power generator and a new controllable circuit of microwave power generator. The coaxial cable was replaced by rigid wave-guide parts of an apparatus and the magnetron was cooled with water. (2) The sample introduction and desolvation system used in this work is the same as commonly used system in commercialized MPT spectrometer and had been described in previous work. A pneumatic concentric nebulizer was used to generate sample aerosols. The carrier gas flow was regulated by means of a mass flow controller, Model D07-7A/ZM (Jianzhong Instrument Factory, Beijing, China), taking the importance of carrier gas flow rate and stability to generate fine aerosols into account. Since MPT was operated at low power, the volume of the plasma was small and the temperature was not high enough to desolvate, atomize and excite the wet aerosols efficiently, therefore, sample desolvation is a must in MPT-AES. Spray chamber, heating tube, water condenser and concentrated H2SO4 cell together composed the desolvation system. It was shown that about 99.7 % of the total mass of water leaving the spray chamber was removed by such a desolvation system. (3) In this work, the radiation emitted from the MPT plasma was transferred to the light dispersion and detection system through a 2 meters single-strand silica-core and silica-clad optical fiber. Since the diameter of the fiber is only 600 μm, if use it to collect directly the radiation beam from the MPT plasma source, the solid angle of beam collection is quite small. With such an optical arrangement, the signal magnitude and stability would all be very poor. To solve this problem and increase the beam collection efficiency, a lens and a concave mirrorfocusing assembly was developed to enlarge the beam collection solid angle and, therefore, to enhance the instrument sensitivity and signal stability. A 7.5 centimeter-focal-length lens was positioned between the plasma and fiber head, the distance between the plasma and lens was more than twice the focal length to ensure that a clear minimized solid image was obtained at the fiber head. At the opposite side a 5 cm focal-length concave mirror is placed to further increase the signal strength. The sensitivity of this assembly with the concave mirror was increased at least two times as compare with the single lens assembly. (4) An integrated, small modular spectrometer, HR2000 high-resolution miniature fiber optic spectrometer (Ocean Optics Inc. USA) is being used for optical beam dispersing and signal measurement. A Sony ILX511 linear CCD array detector with 2048 element pixels was installed for simultaneous measurements of analytical lines. It sends an analog signal consisting of a stream of voltage levels that are proportional to the light hitting on each pixel of the detector. The spectrometer has a small well depth. It can be used to record emission intensity up to as much as 4096 AD counts. (5) A self-developed Windows 9X based 32-bit software was used for all the spectrum display, system control and data analysis. The spectrum for the whole wavelength range could be recorded simultaneously with the software. So the background subtraction could be done easily. With this system multielements and/or multi-wavelengths could be measured at the same time, which enhances the reliability of the analysis results and increases the sample throughput dramatically. Finally, the analytical figures of merit about the newly developed simultaneous MPT spectrometer including detection limits, simultaneous multielement detectability, dynamic linear range, long-term stability and so on were determined systematically. And the results were satisfactory. In this work, the analytical figures of merit of some sample introduction methods were determined systematically. (1) A novel flow injection system with on-line preconcentration was developed for the determination of Al, Cu, Fe, Mn and Zn in drinking water by using a simultaneous microwave plasma touch-atomic emission spectrometer (MPT-AES). The preconcentration columnwas packed with 717-anion exchange resin under alkalic conditions. The operating parameters were studied and optimized. The detection limits are 17, 0.27, 2.0, 4.3, 9.8 μg/L for Al, Cu, Fe, Mn and Zn, respectively, and the relative standard deviations are less than 5 % (n=7). The new system was successfully applied to the analysis of lab-made water and tap water samples. (2) An on-line standard addition method for simultaneous determination of Ca, Cu, Fe, Mg and Mn in grains by FI-MPT-AES was established in this paper. Three different smple pretreatment methods were compared. Under optimized conditions, the samples of American Standard Material (1567, 1568) were analyzed, and the results obtained were in good agreement with the certified values. The detection limits for Ca, Cu, Fe, Mg and Mn were shown to be 3.9, 18, 31, 6.4 and 69 ng/mL, respectively, and RSDs were all less than 5.5 %. The recoveries were shown to be in the range of 95.1%~114.1%. (3) The sample system of MPT-AES is a pneumatic nebulization system, but its efficiency is not good. This thesis has designed a new-built injector pump-ultrasonic nebulizer combination sample system. Its performance is tested and compared with the pneumatic nebulization system. We can draw the conclusion that the new-built sample introduction system can increase the spectral line intensity and decrease the detection limits. The spectral line intensity of the new-built sample system are about 2-3 times of that of the original one and the detection limits are decreased 2-10 times. Moreover, this new-built system can reduce the time for washing the sample cell from 30 minutes or so to about 10 minutes, thereby improves the efficient. (4) The development of a novel procedure for the direct determination of Mg, Cu and Fe in lubricating oil using this simultaneous microwave plasma torch spectrometer with an improved electrothermal vaporization device (ETV-MPT) was described. The ETV device consists of a tantalum coil in a glass apparatus. Background emission and spectral interferences caused by tantalum ablation were reduced by coating the coil with tantalum carbide. The operating parameters were studied and optimized. The detection limits were shown to be 0.6, 0.9 and 7.6 μg/L for Mg, Cu and Fe, respectively, and the relative standard deviations were less than 5 % (n=6). The new system was successfully applied to the analysis of lubricating oil, and therecoveries of the tested elements were in the range of 89.0 % to 112 % The argon inductively coupled plasma (Ar-ICP) fulfills many of the analytical needs within an inorganic analysis laboratory. Unfortunately, alkali metals typically yield maximum emission intensities at very low observation region (5-7 mm above the load coil) in the plasma (owing to their extremely low ionization potentials). Because in commercial ICP spectrometer, the torch position is either fixed or adjusted to monitor higher regions (12-20 mm above the load coil) of the plasma where most transition metals exhibit maximum intensity. The sensitivity for these elements of the Ar-ICP decreases with decreasing ionization potential. Even with the decreased sensitivity of the alkali metals vs the transition metals, Li, Na, and K are routinely determined by Ar-ICP, while Rb and Cs are best determined by flame photometry or ion chromatography, owing to the extremely poor response of these elements in the Ar-ICP. Therefore, to develop a method that can determine Li, Na, K, Rb and Cs simultaneously is of value. In this study, the microwave power and argon flow utilized to sustain the Ar-MPT were optimized for the determination of Li, Na, K, Rb and Cs ions in solution. The utilization of low power level (60-100 W) facilitates the direct introduction of aqueous aerosols into the plasma. Spectral profiles, relative emission intensities and sensitivities, as well as detection limits obtained with the Ar-MPT are compared with those acquired with argon inductively coupled plasma (Ar-ICP). And spectral and matrix interference effects are studied in some detail. Presently, quite a number of data proved that many microelements are not casually consisting in the frond, but are the indispensable substance for the botanic growth. Some metalline ions (Fe2+, Cu2+, Zn2+, Co2+ and Mo2+) in many biological macromolecules including nucleic acid, protein, enzyme and incretion have differential physiological function. They are catalysts of cell's natural metabolism. So, people are interested in the relation of botanic abioelement to curative effect. In this part, we had carried through a preliminary study for the abioelement in the Chinese traditional medicine by using the miniature simultaneous MPT spectrometer. (1) Important... |
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