E3S Web of Conferences , 03004 (2021) https://doi.org/10.1051/e3sconf/202124503004 AEECS 2021 Rapid determination of iodine content in drinking water by isopropyl sensitization and inductively coupled plasma mass spectrometry (ICP-MS) Yanxia Zeng1,2, Xiashi Zhu1* 1Department of Chemical Engineering, Yangzhou University,Yangzhou City, Jiangsu Province漓225009漓China 2Institute of Marine Resource Development漓Jiangsu Ocean University, Lianyungang City, Jiangsu Province漓222005漓China) Abstract. A subject for the rapid determination of iodine content in drinking water by isopropyl sensitization and ICP-MS was established. The samples were dissolved in 1% ammonia solution,127I was selected as the mass number to be measured and 159Tb as an internal standard. At the same time, 4% (V/V) isopropanol was used to enhance aerosol gasification efficiency, 2% NH3·H2O was used to effectively eliminate memory effects of iodine by cleaning sample for 180 seconds. The results show that, the detection limits of iodine in this method are 0.007 mg·kg-1 and it is superior to other literature.The standard curve has a good linear relationship and the recovery rates of testing rusults range are from 96.00% to 112.3%. The content of iodine in standard substance water samples was determined by ICP-MS method. The iodine content in water samples from seven drinking water sources in Lianyungang area was analyzed between 14~21 μg·L-1. It was in line with the allowable value of 10~300 μg·L-1 of the sanitary standard for drinking water, suggesting that the iodine content of drinking water resources in Lianyungang area was in a safe range. and arsenic is somewhat high, such as the first ionization of iodine. It can be 10.45 eV, and there is only about 1 Introduction 25% ionization in the instrument, but compared with other analytical methods, it still has a relatively high Odine is closely related to the growth and metabolism of [9] the human body. It is one of the trace elements with sensitivity . At present, ICP-MS determination of important biological effects. Lack, excessive or iodine is mostly used to detect biological samples. For example, Vanhoeet al[10] determine milk powder samples, unbalanced intake of iodine can cause physiological [11] [12] abnormalities and lead to diseases.[1,2] The iodine that the Larsen et al determine food samples, Cox et al determine vegetable samples, Buchert et al[13] determine human body needs mainly comes from food and [14] water[3].Although most areas of the country are short of milk samples, and Baumann et al determine fresh milk, etc., but there are only a few reports on the detection of iodine or moderate in iodine, there are still about 30 [15] million people in 11 provinces living in high water iodine in water . iodine environment[4].At present, the commonly used This experiment established for the first time the method for determining water iodine content is cerium method of alkalization of ammonia water medium sulfate catalytic spectrophotometry[5], but the detection combined with isopropanol sensitization signal, and range is narrow and the limitations are strong. There are inductively coupled plasma mass spectrometry to many methods for measuring total iodine in water directly determine trace iodine in drinking water sources. samples, most of which have a narrow detection range The iodine of water samples of seven drinking water and cannot meet the requirements of high-iodine or low- sources in Lianyungang area was analyzed with iodine areas[6,7]. Lack of standard materials, low content, satisfactory results. easy contamination of the matrix, and active and easy oxidation of iodine are the main difficulties in the determination of trace ultra-trace iodine in water. Inductively coupled plasma mass spectrometry (ICP- MS) is currently recognized as the best multi-element simultaneous analysis technology[8], although the first ionization energy of non-metals such as bromine, iodine, *Corresponding author’s e-mail: [email protected]; [email protected] © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences , 03004 (2021) https://doi.org/10.1051/e3sconf/202124503004 AEECS 2021 2 Experimental part water (purchased by Lotte Mart, Cangwu Road, Xinpu District, Lianyungang); nitric acid (merk nitric acid, Germany); iodine standard solution (purchased from the 2.1 Instruments and reagents National Standard Material Center); ammonia (excellent electronic balance BS210S (Beijing Sartorius Balance grade pure, Sinopharm Chemical Reagent Co., Ltd.) Co., Ltd.); ICP-MS inductively coupled plasma mass spectrometer (ICP-MS) (Bruker ICP-MS M90); Sc 2.2 Instrument standard solution (purchased from the National Standard Material Center); The working conditions of the inductively coupled Iodine standard solution (purchased from the plasma mass spectrometer are shown in Table 1. National Standard Material Center); Watsons distilled Table 1. Working parameter of ICP-MS. Working parameter set value Working parameter value Plasma flow 16.5 Sampling depth / mm 6.5 velocity/L/min Auxiliary gas flow 2.00 Peristaltic pump rate/ rpm 4 velocity/L/min Protective gas flow 0.20 Stable delay time/s 10 velocity/L/min Atomizer 1.00 residence time/ ms 10000 velocity/L/min Scanning times Sample interval cleaning 50 60 /times time/s Analysis element 127I Total acquisition time/s 20 Radiofrequency 1.40 power/ kW 2.3 Water sample collection and processing 2.3.1 Acidification treatment. Accurately pipette Water samples from water sources were taken in cities 98.00 mL of filtered water sample and add nitric acid to and towns surrounding Lianyungang City. The locations a 100.00 mL PE volumetric flask to be tested. The final of the sampling points are shown in Table 2. Use a water water sample contains 2% nitric acid. collector to take a water sample from below the water 2.3.2 Alkalization treatment. Accurately pipette surface, put it into a 500mL plastic bottle, and bring it 99.00 mL of filtered water sample and add ammonia back to the laboratory refrigerator for storage. Before use, water to a 100.00 mL volumetric flask to be tested. The the original water sample is centrifuged and filtered, and final water sample contains 1% ammonia water. then acidified or alkalized. 2.3.3 Direct treatment. Take 100 ml of filtered water for testing. Table 2. Coordinates of sampling Points. Waterworks of Waterworks of Waterworks of place Qiantan West Ganyu Dayangzhuang Siying Maokou Haizhou City coordinate 119°13'7.93"E 119°13'7.84"E 119°13'7.05"E 119°13'7.47"E 119°13'7.47"E 119°13'7.47"E s 34°36'45.39"N 34°36'44.82"N 34°36'45.77"N 34°36'44.63"N 34°36'44.63"N 34°36'44.63"N signal intensity and RSD% in the water sample were used as indicators, and ammonia water and nitric acid 3 Results and discussion were used as the media respectively to compare the effects of the two media on the iodine signal in the water. 3.1 Sample medium selection The results are shown in Figure 1. The signal intensity of iodine in the water sample is related to the medium. In the experiment, the iodine 2 E3S Web of Conferences , 03004 (2021) https://doi.org/10.1051/e3sconf/202124503004 AEECS 2021 Fig.1 signal value of iodine in1%NH3·H2O vs 2%HNO3 medium It can be seen from the figure that the signal intensity of 127I in the ammonia medium is almost double the 3.2 sensitization value of nitric acid. The RSD% value of the water sample in 1% ammonia medium is between 0% and 5%, According to the literature report, adding a certain while the RSD% value in the 2% nitric acid medium is amount of ethanol to the solution by ICP-MS can between 20% and 41%. The results indicate the signal enhance the signal of iodine. The signal enhancement of stability and the signal sensitivityof iodine are better in iodine by methanol, ethanol and isopropanol in the ammonia medium than in nitric acid medium. concentration range of 1%~5% was investigated in the presence of 1% ammonia with the iodine signal value of the concentration of 20μg·L-1 127I as an index.The results are shown in figure 2. Fig.2 Signal value of 20μg·L-1 iodine under different alcohols media 3 E3S Web of Conferences , 03004 (2021) https://doi.org/10.1051/e3sconf/202124503004 AEECS 2021 As can be seen from the diagram, adding a small 3.4 optimization of cleaning media and cleaning amount of methanol, ethanol, isopropanol can improve time the signal sensitivity of iodine. Compared with several alcohols, the signal increase of isopropanol was the most Some problems, such as serious memory effect, great obvious change with the concentration, and the iodine fluctuation of Analytical Signal, poor accuracy and signal value was the largest when the content of precision, often occur in the determination of iodine in isopropanol increasd to 4% (V/V) . samples by ICP-MS.When iodine is determined in the form of iodide in HNO3 medium, the analytical error can be as high as 750%.[16] The main reason is that the 3.3 selection of internal standard determination of iodine by ICP-MS is complicated by the different forms of iodine, volatility and pollution. In If the sample contains internal standard elements, it will order to reduce the memory effect of iodine, we tried to interfere with the calibration of the analysis results,and if choose a suitable cleaning solution to clean the injection the concentration of internal standard elements is system.