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Three Birds with One Fe3O4 Nanoparticle: Integration of Green and Rapid Microwave Digestion, Solid Phase Extraction and Magnetic Separation for Sensitive Determination of Arsenic and Antimony in Fish Samples Yun Jia, Huimin Yu, Li Wu, Xiandeng Hou, Lu Yang, and Chengbin Zheng Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.5b00712 • Publication Date (Web): 12 May 2015 Downloaded from http://pubs.acs.org on May 13, 2015

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Analytical Chemistry

Three Birds with One Fe3O4 Nanoparticle: Integration of Green and Rapid Microwave Digestion, Solid Phase Extraction and Magnetic Separation for Sensitive Determination of Arsenic and Antimony in Fish Samples Yun Jia†, Huimin Yu†, Li Wu‡, Xiandeng Hou†, ‡, Lu Yang§, 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

§

Chemical Metrology, Measurement Science and Standards, National Research Council Canada,

Ottawa, Canada, K1A 0R6

*Address correspondence to: Fax: +86 28 85412907; Phone: +86-28-85415180 E–mail: [email protected] (C. B. Zheng) Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

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ABSTRACT An environment friendly and fast sample treatment approach integrating accelerated microwave digestion, solid phase extraction and magnetic separation into a single step, was developed for the determination of As and Sb in fish samples by using Fe3O4 magnetic nanoparticles. Compared to conventional microwave digestion, the consumption of HNO3 was reduced significantly to 12.5%, and the digestion time and temperature were substantially decreased to 6 min and 80 oC, respectively. This is largely attributed to Fe3O4 magnetic nanoparticles being a highly effective catalyst for rapid generation of oxidative radicals from H2O2 as well as an excellent absorber of microwave irradiation. Moreover, potential interferences arising from sample matrices were eliminated because the As and Sb species adsorbed on the nanoparticles were efficiently separated from the digests with a hand-held magnet prior to analysis. Limits of detection for As and Sb were in the range of 0.01–0.06 μg g-1 and 0.03-0.08 μg g-1 by using hydride generation atomic fluorescence spectrometry, respectively, and further improved to 0.002–0.005 μg g-1 and 0.005-0.01 μg g-1 when inductively coupled plasma mass spectrometry was used as the detector. Precisions of replicate measurements (n=9) were better than 6% by analyzing 0.1 g test sample spiked with 1 μg g-1 As and Sb. The proposed method was validated by analysis of two Certified Reference Materials (DORM-3 and DORM-4) with good recoveries (90-106%).

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INTRODUCTION Complete digestion of sample matrices is one of the fundamental steps of modern elemental analysis, because organic matrix constituents frequently cause severe interferences on the trace element determination.1 Attributed to its advantages in improving digestion efficiency and minimizing analyte loss, microwave digestion (MWD) has been the most recommended technique for digestion of various samples.1-3 However, concentrated mineral acids are needed in most cases of MWD. These concentrated acids especially HNO3 influence the subsequent measurements using hydride generation (HG) atomic spectrometry.4 It is worth noting that much time is required to cool the pressurized vessel to room temperature, though the time used for MWD is significantly reduced compared to conventional digestion techniques.1,3 In this regard, combustion methods combined with diluted acid extraction have been regarded as ideal digestion techniques to obtain simultaneously rapid digestion and minimization of concentrated acids consumption.5,6 Unfortunately, these methods tend to lose of some volatile and semi-volatile elements (As, Sb, Se and Hg) prior to instrumental analysis. In order to minimize the consumption of mineral acid and avoid loss of analytes in samples, enzymatic digestion methods have been developed to gently digest sample at room temperature.7,8 Recently, Yan et al.9 reported that Fe3O4 MNPs retained peroxidase-like activity and could catalytically produce powerful oxidative radicals of •OH from H2O2. Subsequently, Fe3O4 MNPs was widely used to determine H2O2, glucose and other biological molecules10 and to develop a heterogeneous Fenton-like reaction for the decomposition of organic pollutants11,12, allowing recyclable use of the catalyst and reducing unrecyclable sludge. Because of the peroxidase-like activity of Fe3O4 MNPs, the MNPs could be used as alternative to enzymes for gentle digestion of sample. However, the Fe3O4 MNPs based heterogeneous Fenton-like reaction is too weak to quickly degrade some stable organic compounds.13 After examining 150 substances, Walkeiwicz et al.14 found magnetite beads were the best absorbers to microwave irradiation, suggesting MNPs might be used as efficient absorbers to increase the rate of heating and thus improve the performance of conventional MWD. Based on this capacity of Fe3O4 MNPs, Chen15 and Zhang et al.16 accomplished accelerated microwave digestion of protein by immobilizing enzyme onto the MNPs, thereby reducing the time required from hours to 15 seconds. Considering the characters of Fe3O4 MNPs both on adsorption of microwave irradiation and activation of H2O2, it is expected that the digestion time and temperature as well as the consumption of mineral acid would be significantly reduced when Fe3O4 MNPs are employed in MWD. Moreover, Fe3O4 MNPs has also been identified as an efficient adsorbent of solid phase extraction (SPE) for preconcentration of As.17 3



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Based on the capacities of Fe3O4 MNPs, the aim of this work was to develop a simple and rapid sample treatment method for the sensitive determination of As and Sb in fish samples by integrating the novel Fe3O4 MNPs accelerated MWD, SPE and magnetic separation into a single step.

 EXPERIMENTAL SECTION Instrumentation. A microwave oven (Master 40, Shanghai Sineo Microwave Chemistry Technology Co., China) equipped with an accurate temperature control system was used for the Fe3O4 MNPs accelerated MWD. A commercial HG non-dispersive atomic fluorescence spectrometer (AFS, Model AFS-2202, Beijing Haiguang Instrument Co., Beijing, China) was used for the AFS detection. A water bath (HH-s6, Yuhua Instrument Co., Gongyi, China) was also used to digest fish samples. A 1020A total organic carbon (TOC) analyzer (OI Analytical Company, America) was used for the determination of the residual carbon content. The ICP-MS analysis was performed with an Agilent 7700 ICP-MS (Agilent Technologies, USA). The Optimized instrumental parameters of HG-AFS and ICP-MS are summarized in Table S1 of the Supporting Information (SI). Reagents and Materials. All the reagents were of analytical grade or better. All solutions were prepared using 18.2 MΩ-cm deionized water (DIW) produced by a water purification system (Chengdu Ultrapure Technology Co., China). 1000 mg L-1 stock solutions of As(III) and Sb(III) were obtained from National Research Center of China (NRCC, Beijing, China). Other chemicals were purchased from Kelong Chemical Reagents Co. High-purity argon (Ar) and nitrogen (N2) were supplied by Qiaoyuan Gas Co. (Chengdu, China). Fe3O4 MNPs with different sizes were prepared according to a reported co-precipitation method.18 Sample collection and preparation. Two fish samples obtained from local market were used as test samples and two Certified References Materials (CRMs, DORM-3 and DORM-4) from the National Research Council Canada (NRC, Ottawa, Canada) were used to validate the accuracy of this method. Other samples bought from local markets were employed to evaluate the universality of the Fe3O4 MNPs accelerated MWD. The scales, skin and bones of fish were removed. Then, the residual soft tissues were homogenized by mechanical blending and freeze-dried using liquid nitrogen. The dried fish tissue samples were successively triturated, then transferred to polyethylene bottles and sealed with plastic seals. The samples were kept in a refrigerator at 4 oC prior to use. Digestion and Analytical Procedure. The digestion and analytical procedure is shown in Figure S1 in the SI. About 0.1 g of sample was accurately weighed and blended with 8 mg of 30 nm Fe3O4 MNPs in an agate mortar to obtain an even mixture. This mixture was then transferred 4


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into precleaned Teflon vessels using 15 mL of DIW and spiked with various concentrations of As(III) and Sb(III). Six ml of 30% (m/v) H2O2 and 100 μL of concentrated HNO3 were then added. Three sample blanks were processed along with samples. The vessels were sealed and heated in the microwave oven at 80 oC for 6 min. Owing to this low digestion temperature, the caps could be removed immediately after digestion. The digests were then transferred to precleaned 50 mL polyethylene tubes. Consequently, the As and Sb species adsorbed on the Fe3O4 MNPs were separated from the digests with a permanent hand-held magnet. The MNPs were dissolved with 2 mL HCl and diluted with DIW and 1% (m/v) of thiourea solution to a final volume of 20 mL prior to the HG-AFS determination. Two mL of the digested solution was directly pumped to mixed with 1.5% (m/v) KBH4 for the generation of As and Sb hydrides, which were separated from liquid phase by Ar carrier gas and further transported to an Ar-H2 flame atomizer for the AFS determination. In order to avoid the interference of 40Ar35Cl+ on the determination of

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As+, 2 mL HNO3 was used as alternative to digest the MNPs in the case of

ICP-MS detection. For the validation of the proposed digestion method, conventional MWD was also used to digest the samples prior to ICP-MS detection. The conventional MWD was summarized in Sections 3 of the SI.

 RESULTS AND DISCUSSION Possible Mechanism of Fe3O4 MNPs Accelerated MWD. Digestion of 0.1 g fresh fish sample was carried out at 80 oC by using 8 mg of 30 nm Fe3O4 MNPs, 150 µL HNO3 and 6 mL H2O2, as shown in Figure 1A. Interestingly, the fish slurry solution turned clear and transparent within 16 min thus significantly improving the sample throughput, whereas 30-60 min was needed in conventional MWD. According to previous works,19 the TOC values of the digests were measured to accurately evaluate the digestion efficiency and summarized in Figure 1B-a. About 8% of the TOC remained in the digest after 16 min of digestion. Moreover, the consumption of inorganic acid and digestion temperature required in the proposed method were significantly reduced compared to conventional MWD. Two experiments were designed to understand the roles played by microwave radiation and Fe3O4 MNPs in this digestion, respectively. One was use of a temperature controlled water bath as an alternative to microwave to digest the fish sample at 80 oC (Figure 1B-b), the other was digestion of the fish sample with microwave in absence of Fe3O4 MNPs (Figure 1B-c). The results show the TOC of the digests cannot decline to 10% in these two cases, even with the digestion time as long as 80 min, indicating that both microwave and Fe3O4 MNPs act as important roles to accelerate this digestion. 5



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In order to differentiate whether this rapid MWD is due to the dissolved Fe(II) from Fe3O4 MNPs, the free iron ions in the leaching solution was determined by ICP-OES after removing the Fe3O4 MNPs, and found to be 0.5 mM. Therefore, 0.5 mM FeSO4 was used as an alternative of Fe3O4 MNPs to digest the fish sample. From Figure 1B-d, it is clear that the TOC of the sample solution is still higher than 20% after 60 min of digestion, while this digestion is faster than that without using any catalyst (Figure 1B-c). Base on these observations and the previous works9, 10,12, we speculate that the digestion activity provided by the MNPs is mainly attributed to the iron active sites (≡Fe2+/≡Fe3+) on the surface of the MNPs, rather than just the dissolved Fe(II). Therefore, this accelerated MWD may consist of a dominant digestion arising from the surface of Fe3O4 MNPs, and a subsidiary digestion occurring in the leaching solution, which are described in Figure S3 and further discussed in Section 4 of the SI. According to the previous works15,16, we further speculate that the MNPs in this rapid digestion not only just appear as catalysts but also act as absorbers to efficiently adsorb microwave irradiation. Thus, the temperature around Fe3O4 MNPs was thus sharply increased and the digestion occurred on the surface of Fe3O4 MNPs is accelerated. To support this hypothesis, the temperatures of 20 mL DIW incubated with and without 8 mg Fe3O4 MNPs were measured after 25 s microwave irradiation at 400 W, respectively. The results show the temperature obtained using Fe3O4 MNPs (79 ± 4 oC) was much higher than that without using MNPs (60 ± 2 oC). Subsequently, the MNPs were coated with SiO2 to eliminate the effect from the ≡Fe2+/≡Fe3+ and used for digestion of the fish sample. The results (Figure 1B-e) show that this digestion is obviously more efficient than the case using 0.5 mM Fe2+ (Figure 1B-c) or without using any catalyst (Figures 1B-d) but much slower compare to the case using Fe3O4 MNPs. These observations confirm the capability of Fe3O4 MNPs on adsorption of microwave irradiation and indicate the main fish tissue was digested on the MNPs surface due to the presence of large amounts of ≡Fe2+/≡Fe3+ and elevated temperature. Experimental Conditions for Fe3O4 MNPs Accelerated MWD. About 0.1 g of fish sample and 8 mg of 30 nm Fe3O4 MNPs were blended for 10 min before MWD. As shown in Figure 1B-f, it is evident that the digestion is further improved compared to the initial experiment (Figure 1B-a). This is because that the Fe3O4 MNPs are evenly dispersed on the fish tissues, thereby alleviating the decrease of catalytic activity arising from the aggregation of Fe3O4 MNPs. The effect of the diameter of Fe3O4 MNP is described in Figure S4 (see Section 5 of the SI) and shows that digestion time increased with increase in the diameter. This is probably because more ≡Fe2+/≡Fe3+ are available when surface-to-volume of nanoparticles is increased. The effects of the concentration of Fe3O4 MNPs, H2O2 and HNO3 as well as acidity and reaction temperature 6


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are summarized in Figure 2 and discussed in details in Section 5 of the SI. The complete digestions of milk, lean beef and pork were also obtained within 10 min (see Figure S5 in Section 6 of the SI), showing the good universality of the proposed method. Experimental Conditions for Fe3O4 MNPs Based SPE and HG. The chemicals used for sample digestion especially HNO3 and H2O2 can suppress HG efficiency. Therefore, separation of As and Sb from the digest prior to HG should increase their HG efficiencies. Fe3O4 MNPs are excellent adsorbents which can be used conveniently to concentrate/separate As and Sb from sample matrix with a permanent hand-held magnet.13 Therefore, the experimental conditions for SPE of As and Sb were optimized by using a fish sample solution spiked with As(III) and Sb(III). The effect of pH on the adsorption efficiencies of As and Sb is shown in Figure 2f. In order to avoid Fe3O4 MNPs dissolution and eliminate tedious pH adjustment, the SPE of As and Sb was directly carried out in digestion solution because its value (pH=2) was within the optimum range. The results show that the adsorption equilibriums were rapidly attained within 1 min, suggesting the adsorption must be synchronized with the digestion. Therefore, no additional adsorption time was needed. According to our previous work,13 2% (m/v) KBH4 dissolved in 0.5% (m/v) KOH was used to efficiently convert As(III) and Sb(III) to their corresponding hydrides after complete dissolution of Fe3O4 and 20 min of pre-reduction using 1.0% (m/v) thiourea. Analytical Performance. The analytical performance of the proposed method was evaluated under optimum conditions. Linear coefficients (R2) of these curves are better than 0.99. Precisions (RSDs, n=9) are better than 6% for analysis 0.1 g tested sample spiked with 1 μg g1 As and Sb. The LODs defined as three times of the standard deviation of 11 measurements of a blank solution divided by the calibration curve slope for each of the tested fish samples and CRMs, were in the range 0.01–0.06 μg g-1 and 0.03-0.08 μg g-1 for As and Sb using HG-AFS, respectively. The LODs were improved to 0.002–0.005 μg g-1 and 0.005-0.01 μg g-1 for As and Sb, respectively, when ICP-MS was used as a detector. It should be noted that the LODs and the sensitivity may be further improved if As and Sb adsorbed on Fe3O4 MNPs were dissolved and diluted to a smaller final volume or a higher sample mass was used. The figures of merit characterizing the current methodology and comparison of performance with other similar digestion methods are summarized in Table 1. It is evident that the consumption of HNO3, the digestion time and temperature are significantly reduced compared to the conventional MWD. Although Fe3O4 MNPs are still needed, they are low toxic and easily prepared. Therefore, the proposed method is more environmentally friendly and inexpensive than the conventional techniques. 7



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Sample Analysis.The accuracy of the proposed method was evaluated by analyzing two CRMs (DORM-3 and DORM-4). The proposed method was also applied for the determination of As and Sb in two fresh fish samples. Table 2 summarizes the results obtained by the proposed method using external standard calibration. The results show that the determined values of DORM-3 and DORM-4 are in good agreement with the certified ones, confirming the accuracy of the proposed method. Spike recoveries for As and Sb were found to be in the range of 90-106%. For further evaluation of the accuracy, both the fish samples and the CRMs were digested with conventional MWD and determined by ICP-MS. The analytical results are also summarized in Table 2. The t-test showed that the analytical results obtained by the proposed method were not significantly different from those values achieved by conventional microwave digestion ICP-MS at the confidence level of 95%. 

CONCLUSION It is demonstrated for the first time that Fe3O4 MNPs can significantly accelerate microwave

digestion of fish samples. The MNPs retain several functions in this approach, including catalytic generation oxidative radicals from H2O2, absorption of microwave irradiation for rapidly increasing the digestion temperature, concentration and separation of trace As and Sb from matrices. Owing to these functions, an approach integrating accelerated microwave digestion, solid phase extraction and magnetic separation in to a single step was thus developed for sample treatment. Compared to convention methods, the proposed method is more rapid and environmentally friendly. It is expected that the performance of Fe3O4 accelerated MWD will be significantly improved and extended to rapid digestion of other environmental and biological samples since the catalytic capability of Fe3O4 MNPs can be further improved through changing its diameter and shape. 

ACKNOWLEDGEMENTS The authors gratefully acknowledge the National Nature Science Foundation of China (Nos.

21128006 and 21275103) for financial support. C. B. Zheng is grateful for the financial support by Ministry of Education of China through the Grant NCET-11-0361. 

ASSOCIATED CONTENT

Supporting Information. Additional information as noted in text. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

1. Capelo-Martínez, J. L.; Ximénez-Embún, P.; Madrid, Y.; Cámara, C. TrAC, Trend. Anal. Chem. 2004, 23, 331−340. 2. Chen, L. G.; Song, D. Q.; Tian, Y.; Ding, L.; Yu, A. M.; Zhang, H. Q. TrAC, Trend. Anal. Chem.2008, 27, 151-159. 3. Keith, L. H.;Gron, L. U.; Young, J. L. Chem. Rev.2007, 107, 2695–2708. 4. Zheng, C. B.; Yang, L.; Sturgeon R. E.; Hou, X. D. Anal. Chem.2010, 82, 3899–3904. 5. Flores, E. M. M.; Muller, E. I.; Duarte, F. A.; Grinberg, P.; Sturgeon, R. E. Anal. Chem.2013, 85, 374–380. 6. Mesko, M. F.; Pereira, J. S. F.; Moraes, D. P.; Barin, J. S.; Mello, P. A.; Paniz, J. N. G.; Nóbrega, J. A.; Kor, M. G. A.; Flores E. M. M. Anal. Chem. 2010, 82, 2155–2160. 7. Fredriksson, S.; Artursson, E.; Bergström, T.; Östin, A.; Nilsson, C.; Åstot, C. Anal. Chem. 2015, 87, 967–974. 8. Taverna, D.; Norris, J. L.; Caprioli, R. M. Anal. Chem. 2015, 87, 670–676. 9. Gao, L. Z.; Zhuang, J.; Nie, L.; Zhang, J. B.; Zhang, Y.; Gu, N. W.; Feng, J.; Yang, D. L.; Perrett, S.; Yan, X. Y. Nat. Nanotechnol.2007, 2, 577−583. 10. Wei, H.; Wang, E. K. Chem. Soc. Rev. 2013, 42, 6060-6093. 11. Zeng, T.; Zhang, X. L.; Wang, S. H.; Ma, Y. R.; Niu, H. Y.; Cai, Y. Q. Chem. Eur. J. 2014, 20, 6474-6481. 12. Luo, W.; Zhu, L. H.; Wang, N.; Tang, H. Q.; Cao, M. J.; She, Y. B. Environ. Sci. Technol. 2010, 44, 1786–1791. 13. Ai, X.; Wu, L.; Zhang, M. N.; Hou, X. D.; Yang, L.; Zheng, C. B. J. Agric. Food Chem. 2014, 62, 8586−8593. 14. Walkeiwicz, J. W.; Clark, A. E.; Mcgill, S. L. Miner. Metall. Proc. 1988, 124, 247-252. 15. Chen, W. Y.; Chen, Y. C. Anal. Chem. 2007, 79, 2394-2401. 16. Lin, S.; Yao, G. P.; Qi, D. W.; Li, Y.; Deng, C. H.; Yang P. Y.; Zhang, X. M. Anal. Chem. 2008, 80, 3655–3665. 17. Prucek, R.; Tuč ek, J.; Kolař ík, J.; Filip, J.; Maruš ák, Z.; Sharma, V. K.; Zboř il, R. Environ. Sci. Technol. 2013, 47, 3283−3292. 18. Ai, X.; Wang, Y.; Hou, X. D.; Yang, L.; Zheng, C. B.; Wu, L. Analyst 2013, 138, 3494–3501. 9



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19. Pichler, U.; Haase, A.; Knapp, G. Anal. Chem. 1999, 71, 4050-4055. 20. Yang, K. X.; Swami, K. Spectrochim. Acta Part B 2007, 62, 1177-1181. 21. Manjusha, R.; Dash, K.; Karunasagar, D. Food Chem. 2007, 105, 260-265. 22. Florian, D.; Knapp G. Anal. Chem. 2001, 73, 1515-1520. 23. Mesko, M. F.; Flores, E. M. M. J. Anal. At. Spectrom. 2015, 30, 260-266. 24. Capelo, J. L.; Lavilla, I.; Bendicho, C. Anal. Chem. 2001, 73, 3732-3736. 25. Allen, L. B.; Siitonen, P. H.; Thompson, Jr. H. C. J. Agric. Food Chem. 1997, 45, 162-165.

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Table 1. Comparison of performance with other similar digestion methods Digestion method

sample

Conventional MWD

Digestion reagents

Digestion time and temperature 0

Detection

LOD, μg g-1

reference

ICP-MS

As, 0.016; Sb, 0.017

20

Oyster muscle or DORM-2 (dogfish

HNO3, 2 mL; HF, 0.3

Ramped to 110 C, 20 min; Hold, 5 min;

muscle), 0.15 g

mL; H2O2, 2 mL

Cooling, about 1 hour; Ramped to 200 0C,10 min;

UV digestion

Food or vegetable, 0.25 g

H2O2,1 mL; HNO3 , 7

Irradiation at 65 oC, 1 hour

ET-AAS

Se, 0.035-0.04

21

UV assisted MWD

Milk powder, 0.075 g

Irradiation at 250-280 oC, 30 min

ICP-AES

-

22

As, 0.005;

23

Hold, 10 min; Cooling, about 1 hour

mL HNO3, 50

μL;

HCl:

50μL; H2O2,1 mL Antarctic seaweeds, 0.5-0.8 g

HNO3,10 mL

GF-AAS Irradiation at 250 oC,10 min;

ICP-MS

Cooling: 20 min

Cd, 0.001; Pb, 0.012

Ultrasonic extraction

Sediment or plant, 0.05-0.1g

HCl, 15 mL

Irradiation (90% amplitude), 5 min;

HG-AAS

As, 0.19-2.8

24

ICP-AES

Pb, 0.02;

25

centrifugation: 10 min; irradiation at a 60% amplitude, 15-60 min Open vessel digestion using

Sucrose or Corn syrups,

HNO3,1 mL; H2O2, 9

hot plate

4 mL

mL; 1% HNO3, 10 mL

Fish samples, DORM-3 or DROM-4,

HNO3, 100 μL; H2O2, 6

0.1 g

mL

Heating at 90 °C, Several hours

Cu, 0.007; Cd, 0.008

Fe3O4 MWD

MNPs

accelerated

Irradiation at 80 oC, 6 min

HG-AFS

HG-AFS:

This

ICP-MS

As, 0.01-0.06;

method

Sb, 0.03-0.08. ICP-MS: As, 0.002-0.005; Sb, 0.005-0.01 ET, Electrothermal; AAS, atomic absorption spectrometry; AES, Atomic emission spectrometry.

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Table 2. Analytical results of As and Sb in fish samples and CRMs sample

Found a (b), μg g-1

Certified, μg g-1

Added, μg g-1

As

-

-

2.00

Sb

-

-

4.00

As

-

-

2.00

Sb

-

-

4.00

6.88 ± 0.30

2.00

-

4.00

6.80± 0.64

2.00

-

4.00

Element

Fish 1

Fish 2

As DORM-3 Sb

As DORM-4 Sb a

6.66±0.05 (6.75±0.08) 6.53 ±0.07 (6.64±0.06) -

Found after addition a,

Recovery，

μg g-1

%

2.04 ± 0.02

102

(2.02± 0.03) b

(101) b

3.89±0.08

97

(3.96 ± 0.02) b

(99) b

2.12 ± 0.01

106

(2.03 ± 0.05)

b

3.90±0.06

98

(3.98 ± 0.05)

b

8.52 ± 0.10 (8.54±0.09)


(90) b 90

b

8.49 ± 0.06

(95) b 98

b

(95) b

3.63±0.07

91

(3.80±0.08) b

(95) b

(8.53±0.07)

Mean and standard deviation (n = 3). bDetected by ICP-MS after microwave digestion.

12

(100) b 93

b

3.60±0.05 (3.80±0.05)

(101) b

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Figure Captions

Figure 1. A, Pictures of digestion of 0.1 g fish samples using 8 mg of Fe3O4 MNPs, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave irradiation at different time; B, TOC values of digests obtained from different digestion conditions: (a) 8 mg of Fe3O4 MNPs, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave irradiation; (b) 8 mg of Fe3O4 MNPs, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, water bath; (c) 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave digestion; (d) 0.5 mM FeSO4, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave digestion; (e) 8 mg of Fe3O4 MNPs coated with SiO2, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave irradiation; and (f) dispersion of 8 mg of Fe3O4 on fish tissues, 6 mL H2O2, and 150 μL HNO3, 80 oC of digestion temperature, microwave irradiation.

Figure 2. Effects of experimental conditions on the Fe3O4 MNPs accelerated microwave digestion. (a) effect of the concentration of Fe3O4; (b) effect of the volume of HNO3; (c) effect of the volume of H2O2; (d) effect of the digestion temperature; and (e) effect of the digestion time. Error bars indicate standard errors of the mean (n = 5). And (f) effect of pH of sample solution on the adsorption efficiencies of As(III) and Sb(III).

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Figure 1.

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Figure 2.

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for TOC only

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Three Birds with One Fe3O4 Nanoparticle ... - ACS Publications

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