以DCB法萃取土壤中游離氧化鐵之探討

The study of the free iron oxides in soil extracted by DCB method

呂惠靖(Hui-Jing Lu)

指導教授 ： 何聖賓

國立臺灣大學/生物資源暨農學院/農業化學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00148

摘要

傳統上土壤中的游離氧化鐵，包括無定形與結晶性鐵氧化物，皆採用次亞硫酸鈉-檸檬酸鈉-碳酸氫鈉法（Sodium Dithionite-Citrate- Bicarbonate，簡稱 DCB法）來移除及定量。但以 DCB 法溶出之含鐵溶液，由於其中含有大量的鈉鹽，在以原子吸光法來測定鐵時，常造成原子吸光儀之燃燒器阻塞或試樣溶液互相干擾的困擾，影響測定的精密度與準確度，測定時間亦會延長數倍之久。
本研究針對 DCB 法萃取游離氧化鐵在定量上的困擾，提出修正法，以銨鹽取代 DCB 試劑中大部分的鈉鹽，並以飽和氯化銨或聚丙烯醯 ( Polyacrylamide, PAM ) 取代飽和氯化鈉，探討其可行性。以原子吸光法，分光光度計法，感應耦合電漿原子發射光譜法測定溶液中鐵含量，藉以討論不同萃取法與測定方法之差異。共選擇十種台灣代表性土壤進行試驗，分別為初鹿土系 ( Cl )、台南土系 ( Tn )、老埤土系 ( Lo )、五魁寮土系 ( Wkl )、淡水土系 ( TTs )、蘆竹土系 ( Lc )、二林土系 ( Eh )、瑞穗土系 ( Js )、太康土系 ( Tk )、平鎮土系 ( Pc )。傳統之 DCB 法以 TS表示；僅以聚丙烯醯胺取代飽和氯化鈉之方法，以 TA表示。以檸檬酸銨取代檸檬酸鈉，碳酸氫銨取代碳酸氫鈉，飽和氯化銨或聚丙烯醯胺取代飽和氯化鈉之方法，則分別以 MS、MA 表示。
研究結果顯示，改良之 DCB 法的確可有效降低傳統 DCB 法測定上，鈉鹽含量過高之干擾。而在原子吸光法、分光光度計法及感應耦合電漿原子發射光譜法測定的結果中，改良之 DCB 法的測值與傳統之 DCB 法之值接近，並可降低萃取溶液中的鹽類濃度，進而改善鹽類含量過高所造成之干擾現象。

關鍵字

游離氧化鐵 ； DCB 法 ； 聚丙烯醯胺

並列摘要

The citrate-bicarbonate-dithionite (CBD) method is the most commonly used procedure to extract the total free iron oxides in soils. However, the high sodium salt content in the CBD extracts not only causes severe carry-over effect and tends to clog the burner head during atomic absorption spectrophotometric (AAS) analysis. Aspiration of deionized water or dilute acids for a longer period between samples is thus needed for accurate analysis. The objectives of this study were (i) to evaluate the effect of using ammonium salts and/or polyacrylamide (PAM) instead of sodium salts in the CBD reagent on the extraction of total free iron oxides in soils, (ii) to compare the results of using AAS, the colorimetric method of Fe2+-1,10-phenanthroline procedure, and the inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the determination of iron in the CBD extracts of soils. Ten representative agricultural soils in Taiwan were used in this study. The result showed that the amounts of total free iron oxides in soils extracted by the ammonium salts of citrate and bicarbonate in the CBD reagent was similar to those by the sodium salts after correcting the matrix interference by using any of the three methods for iron determination. The use of ammonium salts of CBD reagent for the extraction of total free iron oxides in soils and the use of PAM as the flocculating agent could effectively reduce the carry-over effect and avoid the clogging of the burner head during AAS analysis. The matrix interference in the determination of iron in the CBD extracts was most severe by the ICP-AES method, followed by the AAS and the colorimetric method of Fe2+-1,10-phenanthroline procedure was among the least interfered.

並列關鍵字

free iron oxides ； DCB method ； polyacrylamide

參考文獻

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