氧化-原子发射光谱快速测定油田水中微量碘

Rapid Determination of Trace Iodine in Oilfield Brine Based on Oxidation-Atomic Emission Spectrometry

柴达木盆地西部的南翼山地区油田水中碘资源丰富,有极大的开发利用价值。该油田水盐度高,组成复杂,现有碘的分析方法难以满足研究工作的需求,建立准确分析南翼山油田水中碘浓度的方法是开展相关研究工作的基础和关键。电感耦合等离子体原子发射光谱(ICP-AES)具有分析快速、线性范围宽、样品基体影响小等优势。然而,由于碘属于高电离能元素,ICP-AES直接测定碘的灵敏度低、检出限高,不能满足样品中微量碘的分析要求。借助自行设计加工的用于ICP-AES集进样、化学反应和气液分离三种功能为一体的进样装置(其具有组成合理、结构紧凑的优点),将碘离子氧化为碘单质导入ICP-AES中测定,在提高有效进样量的同时降低了样品基体对碘测定的影响,从而大幅降低了碘的检出限,建立了ICP-AES快速测定油田水中微量碘的方法。优化了氧化碘离子为碘单质所用酸和氧化剂的浓度,最佳反应试剂为10 mmol·L^(-1) NaNO_(2)和1 mol·L^(-1) HNO_(3)。I 178.276 nm处的检出限为1.65μg·L^(-1),一次测定所需时间三分钟。采用部分因子实验设计详细研究了南翼山油田水中主要共存离子(如钾、钠、钙、镁、锂、锶、铵)及它们之间的交互作用对碘分析的影响。在95%置信水平下,发现钙对碘的测定存在显著性影响。通过对样品进行适当的稀释可以消除钙和其他组分对碘准确测定的影响。采用标准曲线法将建立方法应用于南翼山不同蒸发浓缩阶段实际油田水中碘的分析,测定结果表明加标回收率为90%~104%。实验建立的分析方法具有简便快速、基体干扰小、准确度高等优点,为油田水中微量碘的测定提供了一种新的方法,对于卤水碘基础数据的获得和碘分离提取工艺具有重要意义。

The oilfield brine in Nanyi Mountain,located in the west of Qaidam Basin China,is rich in iodine,which is valuable to exploit.The accurate determination of iodine is very difficult because of the high salinity and complicated composition of the oilfield brine.Inductively coupled plasma atomic emission spectroscopy(ICP-AES)has the advantages of fast,wide linear range,low interference.ICP-AES exhibits low sensitivity and high detection limit for direct determination of iodine due to its high ionization energy,resulting in hardly meet the analysis requirements of trace iodine in hypersaline water.A device integrating sampling,chemical reaction and gas-liquid separation was designed so that the iodide ion could be oxidized to iodine and then imported into ICP-AES for determination.The effective injection volume was increased,and the sample matrix’s influence was reduced to reduce the detection limit,and a rapid detection method for trace iodine in oilfield brine with ICP-AES was established.Better conditions of oxidation were 10 mmol·L^(-1) NaNO_(2) and 1 mol·L^(-1) HNO_(3).The detection limit at I178.276 nm was 1.65μg·L^(-1),and measurement could be completed in three minutes.Partial factor experiments were designed to investigate the interference of main coexisting ions(such as potassium,sodium,calcium,magnesium,lithium,strontium,ammonium).Results indicated that calcium had a significant effect on the determination of iodine at the 95%confidence level.This interference could be eliminated by appropriate dilution.The iodine contents in practical oilfield brine of different evaporative concentration stages were determined with a standard curve,and the recoveries were in the range of 90%~104%.This method was characterized by simple operation,low matrix interference and high accuracy.It will be a promising technique for detecting iodine in oilfield brine samples in the future,which can provide basic data for the extraction technology of iodine.