Browsing by Author "Lu, Chien-Wei"

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Analysis of metal ion impurities in liquid crystals using high resolution inductively coupled plasma mass spectrometry
(2012-11-01)
Hung, Huan-Yi
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Lu, Chien-Wei
;
Lee, Cheng-Yu
;
Hsu, Chain-Shu
;
Hsieh, You-Zung
We have developed a method, using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), to directly analyze metal ion impurities in liquid crystals (LCs). From measurements of resistivity, a commonly used technique for quality control of liquid crystal display (LCD) cells, we found that the resistivities of the LCs decreased significantly upon progressing through the different stages of the LCD cell manufacturing process. We determined the levels of metal ion impurities in the LCs through direct loading of diluted LC samples into the HR-ICP-MS system at a steady flow rate. Solutions featuring LC contents of 10% (v/v) were formed by dissolving each LC in isopropanol (IPA) containing acetone as a modifier. We quantified the trace metal ion impurities in the LC samples using a certified standard of metal ions diluted in IPA (external calibration) without the need for digestion pretreatment. Next, we compared the levels of metal ion impurities with the resistivities of the LCs at the different stages of the LCD cell manufacturing process. We confirmed that the resistivities of the LCs decreased as the total levels of metal ion impurities in the LCs increased. The total content of metal ion impurities added into the LC was higher in the siphoning process than in the one-drop filling process during the fabrication of LCD cells. The HR-ICP-MS method could, therefore, be used to directly measure metal ion impurities in LCs during the LCD cell manufacturing process, potentially replacing resistivity measurements of LCs as a means of quality control. We suggest setting 1400 ng L-1 as the limit of the total metal ion concentration in LCs used for LCD cell manufacturing. We used the HR-ICP-MS method to analyze a stained LCD panel to confirm that the content of metal ion impurities was indeed significantly greater in the stained area of the defected LCD. HR-ICP-MS appears to be a promising technique for the direct and effective analyses of metal ion impurities in LCs.
Analysis of metal ion impurity in tetraethyl orthosilicate by sector field inductively coupled plasma mass spectrometry
(2018-11-01)
Lu, Chien-Wei
;
Hung, Huan-Yi
;
Lin, Wen-Lung
;
Wu, Shu-Pao
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應用化學系
A sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) method was developed to directly analyze metal ion impurity in tetraethyl orthosilicate (TEOS). As trace metal ion impurity in TEOS can cause a damaging effect on wafer-product-based electronic devices, it is necessary to develop an efficient analytical method for quantifying the trace metal ions in TEOS for semiconductor manufacturing. The low metal ion content (nanogram per liter level) in a TEOS solution is difficult to be analyzed directly by SF-ICP-MS. Pretreatment such as acidic digestion and direct dilution results in lower concentrations of the metal ions down to picogram per liter level which reaches the instrumental limitation and is not suitable for analysis. In this study, simple liquid liquid extraction (LLE) was applied by adding isopropanol and deionized water to extract the metal ion in TEOS. The interfering compounds can be directly separated from the analyte by SF-ICP-MS with an appropriate resolution, thereby preventing any ambiguity in the identification of metal ions. The maximum concentration factor was 18.94. The applicability of the proposed method has also been validated by the analysis of three TEOS samples for different applications. The concentrations of metal ions with the range from nanogram per liter to microgram per liter can all be determined with good precision (RSD < 9.46%) and good accuracy (spike recoveries from 94% to 113%). This study demonstrates that SF-ICP-MS with LLE pretreatment is a promising approach for analyzing metal ion impurity in TEOS.
Total sulfur determination in petroleum fuels for routine quality control by sector field inductively coupled plasma mass spectrometry after dilution treatment
(2019-03-01)
Lu, Chien-Wei
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Hung, Huan-Yi
;
Sung, Hsin-Chen
;
Sheu, Yiong-Shing
;
Lin, Wen-Lung
Sulfur is found in petroleum fuels and is oxidized to create sulfur oxides during combustion, resulting in air pollution and acid rain. It is therefore important to monitor the trace sulfur content in petroleum fuels. An accurate, sensitive, and fast method is developed to determine the total sulfur content in petroleum fuels by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Gasoline-and diesel-type samples are directly introduced into the SF-ICP-MS system with a steady flow rate after 1000-fold dilution with isopropanol (IPA) and IPA containing 10% toluene, respectively. The concentration of sulfur in the petroleum fuels is quantified using a certified standard diluted in IPA or IPA-toluene solution as the external calibration system, without the need for any other pretreatments such as digestion or emulsion. The method detection limit values range from 0.12 to 0.17 ng g(-1) for different petroleum fuels. Fourteen petroleum fuels containing gasoline, ethanol-blended gasoline, diesel, and biodiesel obtained from the international proficiency testing program of the American Society for Testing and Materials and the Institute for Interlaboratory Studies are analyzed using the developed method. The Z-score values are in the range of -0.39 to 1.27 for all analytes, indicating good analytical accuracy for this method. Thirty petroleum fuels taken from refueling guns at petrol stations across Taiwan are analyzed directly using the developed method to demonstrate its practicality.