The concept of elemental form is the development of modern materials and life sciences. If only the total amount of elements in the system is studied, it is not enough to study the physiological and toxicological effects of this element in the system. The behavioral effects of an element do not depend on the total amount of the element. A particular element can only act on living systems and organisms within a specific concentration range and a certain form of existence. Different elemental forms have different properties. For example, the toxicity of organic arsenic compounds is generally less than that of inorganic arsenic; As (III) is more toxic than As (V), and alkylated mercury and lead are much more toxic than their corresponding inorganic states. . According to the IUPAC definition: the morphology of an element is the expression or distribution of that element in different classes of compounds: morphological analysis is the qualitative and quantitative analysis of one or more chemical forms of an element in a sample. Elemental morphological analysis is performed using modern analytical techniques. In-situ, in-line, micro-area, and transient high-sensitivity and high-resolution analysis, and analysis tasks such as arsenic and mercury are difficult to perform with a single instrument or technology. After the 1980s, the detection of mercury and arsenic has reached the ppt level, especially the ICP-MS can accurately determine the total arsenic and mercury content. However, ICP-MS analysis method also difficult to complete the morphology of the metal elements of research, combined with technical analysis is an important means of modern scientific research, since 1980, first proposed by the hyphenated techniques Hirschfeld, combined with various means of rapid development, which Efficient Liquid chromatography ( HPLC ) and inductively coupled plasma mass spectrometry (ICP-MS) are one of the most well-developed technologies. Currently, this technology has been widely used in the morphological analysis of elements in materials and life science samples. Because the toxicity of different forms of Hg is quite different, at the same time, their migration in the environment and the transformation and toxicity in animals and plants are directly related to their morphology. The morphological analysis of Hg in environmental and ecological research is increasingly causing people. s concern. For example, Jackie Moron et al. applied a simple sample processing method to extract the morphology of different Hg in hair samples. In their research, it was found that although HPLC-ICPMS can reach the detection limit of the sub-ppb level when analyzing the morphology of different Hg, only 0.1 milligrams of methyl mercury and H reach about 500 ng in 0.1 g hair samples. g can be detected clearly, but the results of these morphological analyses become unreliable when the sample volume is insufficient or the Hg is low. This study further expanded the detection ability of Hg morphology by HPLC-ICPMS, so that the detection limit of different Hg morphology reached the sub-ppt level, which makes the method applicable to the analysis of actual hair samples and seawater.
1 Interface technology for HPLC and ICP-MS As shown in Figure 1, the Agilent 1100 series high performance liquid chromatography pump system and Agilent 7500a ICP-MS are connected through A~lent's proprietary interface system. The interface system directs the effluent from the HPLC column through a grounded PEEK tube (0.1 mm inside diameter) to the ICP-MS Nebulizer. The interface system also features the simultaneous startup of HPLC and ICP-MS. The ICP-MS system is equipped with a PFA micro atomizer and a Shield Torch high sensitivity device. ICP. When the MS is working, it is tuned with liquid phase mobile phase containing 1ppb Bi. The sensitivity of Bi is adjusted to zoi high, about 25×10 CPS/ppb. The signal of Bi is also detected during the analysis, and analyzed in 10 hours. In the process, it was found that the signal stability of Bi was better than 5%, so the internal standard was not used in this test.
2 Test results and discussion Prepare 1ppb methylmercury, inorganic mercury, ethylmercury (in terms of Hg) with pure water, and prepare three kinds of Hg form mixing standards, HPLC-ICP. The Hg (202) selected ion spectrum of MS is shown in Fig. 2, the injection volume is 20 l, and the flow rate is 0.4 ml/min. The single-form standard injection test determined that the retention time of methylmercury was 2.77min, the retention time of inorganic mercury was 3.71min, and the retention time of ethylmercury was 8.02min. Figure 2 is automatically integrated using the chromatographic software installed on the Agilent 7500a instrument. The integration results are shown in Table 1.
It can be seen from Table 1 that the integrated peak area of ​​methylmercury is approximately the same as the integrated peak area of ​​ethylmercury, which is consistent with the principle that the detection of ICP-MS is independent of the molecular structure of the compound. However, their peak area is about twice the peak area of ​​inorganic mercury. Throughout the test, including high concentration standards (100ng / l) to low concentration standards (10ng / l), large injection volume (1000 ~ 1) to small injection volume (20μ1), mobile phase flow rate 0.4ml / Min to 0.5ml/min, this ratio remains unchanged. Since Hg2+ is formulated by common inorganic mercury standards, it is possible that the Hg in this standard is not all Hg2+, and other forms of Hg may exist. For example, Hg+ may also be inaccurate due to the inaccurate concentration of the original inorganic mercury.
Prepare a series of standard working curves for three forms of Hg, and use HPLC-ICP. MS analysis, the integrated peak area list is shown in Table 2. Taking the logarithm of the working curve of Table 2 as shown in Figure 3, it can be seen that the linear working curve range of this technique is greater than 4 orders of magnitude.
The seawater sample was simulated with 3% NaC1 solution, and 100 ng/l of three Hg standard solutions were added and filtered. Direct injection was compared with the spectrum of pure water as shown in Fig. 4. From the results of the integrated peak area, the spiked recoveries of the three Hg morphological analyses in simulated seawater ranged from 90% to 110%.
In the above test, the flow rate of the liquid phase mobile phase was 0.4 ml/min, and the volume of the injection loop was 20 il1. Analysis of a polymorphic Hg sample takes about 10 minutes. By increasing the volume of the injection loop to 100~1 and accelerating the flow rate to 0.5ml/min, the sensitivity can be further improved and the analysis time can be shortened, as shown in Figure 5-7. For 1000ng/l. The 100 ng/l, 10 ng/l, 0 ng/l standard working curve series was analyzed and the peaks were superimposed, and the analysis time was shortened to about 8 min. The integrated peak area is about 5 times that of 20μl injection, and the pure water background is shown in Figure 5.
When further increasing the injection loop to 1000 μl, 10 ng/l mixed standard HPLC-ICP. The sensitivity of MS analysis was further improved, but the peak retention time and background spectrum of pure water analysis changed, as shown in Figure 8.
When applying the spectral subtraction technique, the HPLC-ICP-MS spectrum of 10 ng/l 3 Hg forms is shown in Fig. 9. Its integrated peak area is also about 10 times that of 100μ injection. The signal-to-noise ratio of the 10 ng/l standard spectra from 100 μl and 1000 μl can be concluded. HPLC-ICP-MS can be used to analyze three forms of mercury up to a single ng/l or even ng. /l magnitude.
3 Conclusions In this work, the high sensitivity of Shield Torch technology provides sufficient sensitivity for the morphological analysis of multiple Hg on the order of ppt. Since the mobile phase of the liquid phase contains 5% methanol, high organic loading may cause instability of the ICP-MS analysis signal, especially the carbon powder produced by methanol decomposition may cause clogging of the ICP-MS cone, resulting in Hg and internal The gradual drop of the standard Bi signal even disappears completely. In this test, the signal of Bi internal standard is always stable, which is attributed to the control of a large channel of 5 ° C in a two-channel mist chamber to remove a large amount of organic vapor and 1550W high power ICP to completely decompose the sample matrix. Through this study, it is proved that the morphological analysis of Hg of ppt and even sub-ppt is fast and feasible.
references
[1] Wang Xiaoru, Sun Dahai, Zhuang Yuxia, discussion on major scientific issues in the complex system of traditional Chinese medicine. Xiamen: Xiamen University Press, 1998, 62
[2] Agata K, Jacek N, Trends in Arialytical Chemistry, 2000, 19 (2+3): 69
[3] Hirsehfeld T, Ana1. Chem. , 1980, 52: 297A
[4] Jaekie M, Vikki AC, Philip HEG, J. Ana1. At. Spectrom. , 2002, 17: 377 - 38l
1 Interface technology for HPLC and ICP-MS As shown in Figure 1, the Agilent 1100 series high performance liquid chromatography pump system and Agilent 7500a ICP-MS are connected through A~lent's proprietary interface system. The interface system directs the effluent from the HPLC column through a grounded PEEK tube (0.1 mm inside diameter) to the ICP-MS Nebulizer. The interface system also features the simultaneous startup of HPLC and ICP-MS. The ICP-MS system is equipped with a PFA micro atomizer and a Shield Torch high sensitivity device. ICP. When the MS is working, it is tuned with liquid phase mobile phase containing 1ppb Bi. The sensitivity of Bi is adjusted to zoi high, about 25×10 CPS/ppb. The signal of Bi is also detected during the analysis, and analyzed in 10 hours. In the process, it was found that the signal stability of Bi was better than 5%, so the internal standard was not used in this test.
2 Test results and discussion Prepare 1ppb methylmercury, inorganic mercury, ethylmercury (in terms of Hg) with pure water, and prepare three kinds of Hg form mixing standards, HPLC-ICP. The Hg (202) selected ion spectrum of MS is shown in Fig. 2, the injection volume is 20 l, and the flow rate is 0.4 ml/min. The single-form standard injection test determined that the retention time of methylmercury was 2.77min, the retention time of inorganic mercury was 3.71min, and the retention time of ethylmercury was 8.02min. Figure 2 is automatically integrated using the chromatographic software installed on the Agilent 7500a instrument. The integration results are shown in Table 1.
It can be seen from Table 1 that the integrated peak area of ​​methylmercury is approximately the same as the integrated peak area of ​​ethylmercury, which is consistent with the principle that the detection of ICP-MS is independent of the molecular structure of the compound. However, their peak area is about twice the peak area of ​​inorganic mercury. Throughout the test, including high concentration standards (100ng / l) to low concentration standards (10ng / l), large injection volume (1000 ~ 1) to small injection volume (20μ1), mobile phase flow rate 0.4ml / Min to 0.5ml/min, this ratio remains unchanged. Since Hg2+ is formulated by common inorganic mercury standards, it is possible that the Hg in this standard is not all Hg2+, and other forms of Hg may exist. For example, Hg+ may also be inaccurate due to the inaccurate concentration of the original inorganic mercury.
Prepare a series of standard working curves for three forms of Hg, and use HPLC-ICP. MS analysis, the integrated peak area list is shown in Table 2. Taking the logarithm of the working curve of Table 2 as shown in Figure 3, it can be seen that the linear working curve range of this technique is greater than 4 orders of magnitude.
The seawater sample was simulated with 3% NaC1 solution, and 100 ng/l of three Hg standard solutions were added and filtered. Direct injection was compared with the spectrum of pure water as shown in Fig. 4. From the results of the integrated peak area, the spiked recoveries of the three Hg morphological analyses in simulated seawater ranged from 90% to 110%.
In the above test, the flow rate of the liquid phase mobile phase was 0.4 ml/min, and the volume of the injection loop was 20 il1. Analysis of a polymorphic Hg sample takes about 10 minutes. By increasing the volume of the injection loop to 100~1 and accelerating the flow rate to 0.5ml/min, the sensitivity can be further improved and the analysis time can be shortened, as shown in Figure 5-7. For 1000ng/l. The 100 ng/l, 10 ng/l, 0 ng/l standard working curve series was analyzed and the peaks were superimposed, and the analysis time was shortened to about 8 min. The integrated peak area is about 5 times that of 20μl injection, and the pure water background is shown in Figure 5.
When further increasing the injection loop to 1000 μl, 10 ng/l mixed standard HPLC-ICP. The sensitivity of MS analysis was further improved, but the peak retention time and background spectrum of pure water analysis changed, as shown in Figure 8.
When applying the spectral subtraction technique, the HPLC-ICP-MS spectrum of 10 ng/l 3 Hg forms is shown in Fig. 9. Its integrated peak area is also about 10 times that of 100μ injection. The signal-to-noise ratio of the 10 ng/l standard spectra from 100 μl and 1000 μl can be concluded. HPLC-ICP-MS can be used to analyze three forms of mercury up to a single ng/l or even ng. /l magnitude.
3 Conclusions In this work, the high sensitivity of Shield Torch technology provides sufficient sensitivity for the morphological analysis of multiple Hg on the order of ppt. Since the mobile phase of the liquid phase contains 5% methanol, high organic loading may cause instability of the ICP-MS analysis signal, especially the carbon powder produced by methanol decomposition may cause clogging of the ICP-MS cone, resulting in Hg and internal The gradual drop of the standard Bi signal even disappears completely. In this test, the signal of Bi internal standard is always stable, which is attributed to the control of a large channel of 5 ° C in a two-channel mist chamber to remove a large amount of organic vapor and 1550W high power ICP to completely decompose the sample matrix. Through this study, it is proved that the morphological analysis of Hg of ppt and even sub-ppt is fast and feasible.
references
[1] Wang Xiaoru, Sun Dahai, Zhuang Yuxia, discussion on major scientific issues in the complex system of traditional Chinese medicine. Xiamen: Xiamen University Press, 1998, 62
[2] Agata K, Jacek N, Trends in Arialytical Chemistry, 2000, 19 (2+3): 69
[3] Hirsehfeld T, Ana1. Chem. , 1980, 52: 297A
[4] Jaekie M, Vikki AC, Philip HEG, J. Ana1. At. Spectrom. , 2002, 17: 377 - 38l
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