Supporting Information (SI) Simultaneous Determination of Hg, Fe, Ni and Co by Miniaturized Optical Emission Spectrometry Integrated with Flow Injection Photochemical Vapor Generation and Point Discharge Shu Zhang, Hong Luo, Mengting Peng, Yunfei Tian, Xiandeng Hou,, Xiaoming Jiang, * and Chengbin Zheng,* Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China Analytical & Testing Center, Sichuan University, Chengdu, Sichuan 610064, China *Address correspondence to: Fax: +86 28 85412907; Phone: +86-28-85415180 E mails: abinscu@scu.edu.cn (C. B. Zheng) or jiangxm@scu.edu.cn (X. M. Jiang) Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. S1 /S12
Table of Contents 1. The Cross-Sectional View of the PD Device 2. Preparation of DORM-3 and DORM-4 3. Experimental Setup, Experimental Conditions and Spectral Characteristics of PVG-DBD-OES 4. Background Correction Method 5. Optimization of PVG Experimental Conditions for Tested Elements 6. Potential for Determination of C, I and Se by PVG-PD-OES S2 /S12
1. The cross-sectional view of the PD Device Figure S1. The cross-sectional view of the PD S3 /S12
2. Preparation of DORM-3 and DORM-4 Sample preparation was undertaken according to previous work 1. Aliquotes ofsamples of 0.35 g of DORM-3 or DORM-4 were weighed into precleaned Teflon vessels and 6 ml of HNO 3 and 2 ml of H 2 O 2 were then added. A sample blank was processed along with the samples. The vessels were sealed and heated in a microwave oven (Master 40, Shanghai Sineo Microwave Chemistry Technology Co., China) operated under the following conditions: 15 min at 130 C and 2200 W; 20 min at 150 C and 2200 W; 20 min at 180 C and 2200 W. The caps were removed after cooling. The digests were transferred to pre-cleaned volumetric flasks, diluted to 50 ml with DIW and stored at 4 o C prior to analysis. S4 /S12
3. Experimental Setup, Experimental Conditions and Spectral Characteristics of PVG-DBD-OES The PVG-DBD-OES consisted of the PVG reactor, a cylindrical DBD and the miniaturized CCD Spectrometer. According to our previous work 2, the DBD device was made using a quartz tube (50 mm 3.0 mm i.d. 5.0 mm o.d.) and two separated copper wires, which served as electrodes, both tightly wrapped around the outside of the tube evenly and inserted into the tube. The electrodes were connected to a compact ac ozone generation power supply (YG.BP105P, Electronic Equipment Factory of Guangzhou Salvage, Guangzhou, China). A transformer (TPGC2J-1, Shanghai Pafe Electronic Equipment Ltd. Co., Shanghai, China) was used to connect to the power supply for convenient adjustment of the DBD power. The optimized operating conditions used for PVG-DBD-OES are summarized in Table S1. The optical emission spectra obtained by using an argon DBD microplasma are shown in Figure S1. Table S1. Experimental conditions for the determination of Hg, Fe, Co and Ni by PVG-DBD-OES Experimental conditions Value Formic concentration, %(v/v) 50 UV irradiation time, s 200 Discharge voltage, V 45 Ar flow rate, ml min -1 400 S5 /S12
Figure S2. Optical emission spectra obtained with an Ar DBD microplasma. a, blank; b, sample solution,1, Co 228.62 nm; 2, Ni 231.60 nm; 3, Co 241.41 nm; 4, Hg 253.65 nm; 5, Ni 300.25 nm; 6, Ni 341.48 nm; 7, Ni 349.30 nm; and 8: Ni 361.94 nm. S6 /S12
4. Background Correction Method A background correction method was used to improve the stability by simultaneously recording the responses of Hg 253.65 nm, Fe 248.64 nm, Co 228.62 nm and Ni 231.60 nm, and the background emission intensities at 254.0 nm and 228.0 nm at the same time. The responses obtained by deducting the responses at 228.0 nm from 228.64 nm and 231.60 nm from blank and sample solution were used as background and sample signal of Co and Ni, respectively. In the same way, the background and sample signals of Hg and Fe were obtained by deducting the responses at 254.0 nm from 253.65 nm and 248.64 nm from blank and sample solution. The net emission intensities of Hg 253.65 nm, Fe 248.64 nm, Co 228.62 nm and Ni 231.60 nm are derived by deducting the background signals from the sample signals. S7 /S12
5. Optimization of PVG Experimental Conditions for Tested Elements Previous reports 3,4 found that the PVG efficiencies of Hg, Co and Ni were significantly dependent on the type and concentration of low molecular weight (LWM) organic acid. Although many LWM organic acids, including formic, acetic and propionic acids could convert Hg (II), Ni(II) and Co(II) to their corresponding volatile species with UV irradiation, the most efficient medium for all the tested analytes was formic acid. Therefore, only the effect of formic acid concentration was carefully investigated. The results are summarized in Fig. S3a and show that the response from Ni was significantly increased throughout the range of 50-80% (v/v), followed by a plateau at higher concentrations. However, the stable and maximum responses of Hg and Co can be obtained beyond 10% (v/v) and 20% (v/v), respectively. Finally, a concentration of 50% (v/v) of formic acid was used for all subsequent experiments. Previous work reported that the optimum PVG irradiation time was determined by the LWM organic acid used and the type of element. For example, only several seconds is enough for generation of volatile species of I or Hg while vapor generation of Fe or Ni requires more than 100 s of irradiation time. 3,4 Therefore, a standard solution containing 5 µg L -1 Ni(II), 20 µg L -1 Ni(II) and 200 µg L -1 Co(II) was used to evaluate the effect of UV irradiation time on response, as shown in Figure S3b. Results indicate that the response from both Ni(II) and Co(II) increased over the range of 0-3 min irradiation time and reach maximum signals when the higher irradiation time is used. In order to reduce analytical time and increase sample throughput, a 3 min of irradiation time was used in all subsequent experiments. In our previous work 5, the PVG efficiency of Fe was found to be strongly dependent on the ph of the test solution, with the optimum ph range being 2.0-3.0. Therefore, the effect of the ph on the response of Fe, Co and Ni from their standard solutions was investigated by adding various concentrations of ammonia. The ph values were measured by a ph meter. The results are summarized in Figure S3c and indicate that the response of Fe is significantly affected by the concentration of ammonia and the optimum response is obtained at 30% (v/v, ph=2.80). However, the effect of ph on the responses from Ni and Co is not obvious. These are similar to the results reported in our previous work. 30% (V/V) of ammonia was thus used in the following work. S8 /S12
Figure S3. Effect of experimental conditions on the PVG efficiencies of Hg, Fe, Co and Ni. (a) concentration of formic acid; (b) irradiation time; and (c) concentration of ammonia. S9 /S12
Figure S4 S10 /S12
6. Potential for Determination of C, I and Se by PVG-PD-OES Figure S5. Atomic emissions of I, C and Se obtained by PVG-PD-OES. S11 /S12
REFERENCES 1. Zheng, C. B.; Yang, L.; Sturgeon, R. E.; Hou, X. D. Anal. Chem. 2010, 82, 3899 3904. 2. Li, W.; Zheng, C. B.; Fan, G. Y.; Tang, L.; Xu, K. L.; Lv, Y.; Hou, X. D. Anal. Chem. 2011, 83, 5050 5055. 3. Zheng, C. B.; Li, Y.; He, Y. H.; Ma, Q.; Hou, X. D. J. Anal. At. Spectrom. 2005, 20, 746-750 4. Zheng, C. B.; Sturgeon, R. E.; Brophy, C.; Hou, X. D. Anal. Chem. 2010, 82, 3086 3093 5. Zheng, C. B.; Sturgeon, R. E.; Brophy, C. S.; He, S. P.; Hou, X. D. Anal. Chem. 2010, 82, 2996 3001. S12 /S12