Browsing by Author "Tian, Kang"
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Item Industrial applications of flow injection analysis(Texas Tech University, 2000-08) Tian, KangFlow injection analysis (FIA) is characterized by its ease of automation, high throughput, simple instrumental requirements, and wide applicability. These unique features make FIA a very useful analytical tool in industrial applications. In this dissertation, FIA systems, operating both in liquid and gas phase, were used to solve some challenging industrial analytical problems. At first, multi-channel FIA systems with thermometric, conductivity, and photometric detectors were designed to simultaneously determine hydroxide, chloride, hypochlorite, and chlorate ions that exist in Chlor-Alkali cell effluents in concentrations ranging from sub-millimolar to several molar concentrations. A negative bleaching method and a positive absorbance iodiometric method were studied and optimized for this purpose. The methods are reliable, simple, fast, and capable of a throughput rate of -100 samples per hour. A liquid phase FIA system was developed for automated measurement of hydroperoxides in oil, fat, and polyol samples. Lipid peroxidation has received much attention because of toxicities, bitter tastes, and off flavors produced during lipid oxidation. The method is based on the oxidation of Fe(II) to Fe(III) by peroxides in organic medium, followed by the colorimetric detection of the latter as the thiocyanate complex. The system exhibits a wide dynamic range and good linearity (e.g., linear r^2, 0.9943 for 0.1 -120 meq/kg cottonseed oil hydroperoxides) with a good throughput rate (up to 60 samples/h). Oxidative stability determination of various materials containing fats and oils is an important process in food, feed, and related industries. It is also a difficult parameter to measure. An attractive gas phase FIA method was developed for the stability evaluation. In the method, the rate of oxygen consumption of samples are measured at discrete temperatures. For all samples studied, log(oxygen consumption) is linearly related to the reciprocal of the absolute temperature. This makes it possible to extrapolate the temperature-dependent data to predict the stability of the samples at other temperatures, e.g., typical ambient storage temperatures, at which the direct determination of oxidative stability would be too slow for most samples. Compared with existing methods, not only is the developed method reliable, but also its sample throughput rate is an order of magnitude faster.Item The development and application of preconcentration/preelution ion chromatography methods for the detection of trace perchlorate in difficult matrices(2005-08) Cañas, Jaclyn E.; Anderson, Todd; Smith, Philip N.; Tian, Kang; Hooper, Michael J.Perchlorate originates as a contaminant in the environment from the use of solid salts in the manufacture of solid rocket fuels and munitions. As a result of perchlorate occurrence and persistence, there has been much debate over what level of perchlorate is safe for daily consumption and USEPA recently set a reference dose for perchlorate. Ion chromatography (IC) is one of the most widely used methods for perchlorate determination because of its availability. However, analysis of biological samples by IC is often difficult because matrix components often interfere with low level detection. A preconcentration/ preelution ion chromatography method (PC/PE) was developed in our laboratory to address such interferences in high salinity samples and was proposed to have potential application for other matrices. In this study, the ability of the method to remove interferences and lower sample background was determined for gastrointestinal tract, kidney, liver, zebrafish, quail egg, lettuce, milk, urine, citrus, and soil matrices. The PC/PE method was applicable to the analysis of kidney, liver, zebrafish, quail egg, lettuce, and urine samples. Operating conditions were optimized for each matrix and there appeared to be no significant effect of prewash solution concentration on background. The range of optimal wash volumes, regardless of matrix, was shorter with a 15 mM NaOH prewash solution than a 10 mM solution. Optimal injection durations varied with matrix type, but recoveries were excellent for most matrices at injection periods greater than 60s. The method was capable of reducing background when compared to EPA Method 314.0 which resulted in detection limits, with the exception of zebrafish and urine, that were 2-fold lower those achieved by common IC. PC/PE was applicable to the remaining matrices, but poor recovery in the cleanup process hindered further investigation of the gastrointestinal tract and citrus matrices. Previously published methods for milk were determined to be better than the methodology developed here. Finally, there was no difference in soil background when analyzed by PC/PE compared to EPA Method 314.0. Therefore, an extraction method for perchlorate from soil with analysis by EPA Method 314.0 is presented here.Item The development and application of preconcentration/preelution ion chromatography methods for the detection of trace perchlorate in difficult matrices(Texas Tech University, 2005-05) Cañas, Jaclyn E.; Anderson, Todd; Smith, Philip N.; Tian, Kang; Hooper, Michael J.Perchlorate originates as a contaminant in the environment from the use of solid salts in the manufacture of solid rocket fuels and munitions. As a result of perchlorate occurrence and persistence, there has been much debate over what level of perchlorate is safe for daily consumption and USEPA recently set a reference dose for perchlorate. Ion chromatography (IC) is one of the most widely used methods for perchlorate determination because of its availability. However, analysis of biological samples by IC is often difficult because matrix components often interfere with low level detection. A preconcentration/ preelution ion chromatography method (PC/PE) was developed in our laboratory to address such interferences in high salinity samples and was proposed to have potential application for other matrices. In this study, the ability of the method to remove interferences and lower sample background was determined for gastrointestinal tract, kidney, liver, zebrafish, quail egg, lettuce, milk, urine, citrus, and soil matrices. The PC/PE method was applicable to the analysis of kidney, liver, zebrafish, quail egg, lettuce, and urine samples. Operating conditions were optimized for each matrix and there appeared to be no significant effect of prewash solution concentration on background. The range of optimal wash volumes, regardless of matrix, was shorter with a 15 mM NaOH prewash solution than a 10 mM solution. Optimal injection durations varied with matrix type, but recoveries were excellent for most matrices at injection periods greater than 60s. The method was capable of reducing background when compared to EPA Method 314.0 which resulted in detection limits, with the exception of zebrafish and urine, that were 2-fold lower those achieved by common IC. PC/PE was applicable to the remaining matrices, but poor recovery in the cleanup process hindered further investigation of the gastrointestinal tract and citrus matrices. Previously published methods for milk were determined to be better than the methodology developed here. Finally, there was no difference in soil background when analyzed by PC/PE compared to EPA Method 314.0. Therefore, an extraction method for perchlorate from soil with analysis by EPA Method 314.0 is presented here.