以石墨式原子吸光法測定土壤中汞之研究

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Title:	以石墨式原子吸光法測定土壤中汞之研究
Other Titles:	a study on the determination of mercury in soil by graphite-furnace atomic absorption spectrophotometry
Authors:	鄭翰鈞
Contributors:	郭茂松 Kuo, Mao-Sung 東海大學環境科學與工程學系
Keywords:	汞;石墨式原子吸光法;土壤;部分萃取;王水全量消化 mercury;gfaas;soil
Date:	2000
Issue Date:	2011-07-26T03:52:05Z (UTC)
Abstract:	摘要環境中微量汞的分析方法以原子吸收光譜法（atomic absorption spectrometry，AAS）應用最廣。以石墨式原子吸光法（graphite-furnace atomic absorption spectrometry，GFAAS）測定時，當選用適當的基質修飾劑以提高汞在石墨管內的熱穩定性。當汞的濃度低於儀器的偵測極限時，必須藉由濃縮的方式來提高汞的濃度，使其能被偵測到。本研究以兩種方法：部分萃取法與全量消化法將土壤中的汞盡量移出，與2,3-dimercaptopropane-1-sulfonate（DMPS）形成複合物後，以GFAAS測定汞的含量。由實驗所得的結果，作為探討此兩種方法對於測定土壤中汞的可行性。 1. 部分萃取法在每25 mL萃取液中，含有1.0 mL 1.0 M醋酸鈉緩衝溶液（pH=6.0）與400 µL 1.2×10-3 M DMPS。取0.20 g土壤樣品，加入8.0 mL萃取液，以超音波震盪器在室溫（25-30℃）萃取1.5 h，共進行八次，將土壤中的汞萃取出與DMPS形成複合物，以離心方式將固液分離後，濾液流經兩個串聯的Sep-Pak C18 cartridge，將汞-DMPS複合物滯留於C18 cartridge後，各以甲醇沖洗出並定量至2.00 mL。混合均勻後，取出50 µL注入GFAAS測定汞的含量，所得的回收率約為84-91%。以標準添加法測得東海土壤中汞的含量為0.029 µg/g，屬於低含量；檢量線之線性範圍為10-100 ng，偵測極限為1.7 ng。 2. 全量消化法取0.20 g土壤樣品加入1.0 mL王水，在70℃加熱1.0 h後，以NaOH（1.0 M和0.10 M）調整pH值至約6.0，經抽氣過濾後，濾液部分先流經一個C18 cartridge，用以移除土壤基質中的一些干擾物，然後加入1.0 mL 1.0 M醋酸鈉緩衝溶液（pH=6.0）與300 µL 1.2×10-3 M 之DMPS與汞反應約1 h後，流經兩個串聯的C18 cartridge，將汞-DMPS複合物滯留於C18 cartridge上，各以甲醇沖洗出並定量至2.00 mL。混合均勻後，取出50 µL注入GFAAS測定汞的含量，所得回收率約為64-97%。仍需進一步研究探討，使回收率能達理想之結果。 Abstract Two approaching methods for the determination of total mercury content in soil were attempted in this thesis. The first method was multiplication-extraction (totally, eight times) by adding 8.0 mL of an extracting solution (containing 2,3-dimercaptopropane-1-sulfonate (DMPS) 0.48 µmol, and sodium acetate buffer (0.32 mmol, pH=6.0)) to a Tunghai soil sample (0.20 g) and spiked mercury soil sample (10-100 ng Hg2+ or CH3Hg+), respectively. In each extraction, the mixture was sonicated at room temperature (25-30℃) for about 1.5 h. The mercury extracted by DMPS in the solution formed Hg(DMPS)2 or CH3Hg(DMPS) complex which was concentrated on two Sep-Pak C18 cartridges in series. Each cartridge was eluted with methanol (2.00 mL). A portion (50 µL) was introduced into a graphite cuvette and was atomized according to a temperature program by using a graphite-furnace atomic absorption spectrophotometry (GFAAS). The amount of mercury in each extraction was determined from its peak height absorbance. The content of total mercury in Tunghai soil was obtained as 0.029 µg/g form the standard addition method. The recoveries were 84-91% and the method detection limit (MDL) was 1.7 ng. The second method was digestion with aqua regia by adding 0.75 mL conc. HCl and 0.25 mL conc. HNO3 into the Tunghai soil (0.20 g) or the spiked mercury soil sample (10 -100 ng of Hg2+ or CH3Hg+), respectively. The mixture was digested at 70℃for 1.0 h. After cool to room temperature, the pH of the mixture was adjusted to about 6.0 with NaOH. After filtration, the filtrate was passed through a Sep-Pak C18 cartridge to remove some impurities, and then sodium acetate buffer (1.0 mmol, pH=6.0) and DMPS (0.36 µmol) were added to form complexes with mercury (Hg2+ or CH3Hg+). The same concentration procedure and volume introduced into GFAAS as mentioned above were performed. Recoveries were 64-97%. Further investigation is still needed in order to obtain better recoveries.
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