An accurate and stable method for determining mercury in water by ICP-MS

Abstract

The present invention relates to an accurate and stable ICP-MS method for determining mercury in water, and belongs to the technical field of determination of mercury in water. Gold and L-cysteine ​​are combined with mercury to form a stable complex, so that mercury will not remain in the pipeline, and excess L-cysteine ​​is masked by thioethylene glycol, and excess thioethylene glycol does not affect the determination of mercury. The advantages are that the problem of unqualified linear coefficient of calibration curve is solved, and the accuracy and precision of data in the sample determination process are guaranteed; the digestion is carried out by electric hot plate, which greatly saves digestion time; it is suitable for application in the environmental field, food field, and medical field.

Description

Technical Field

[0001] The invention belongs to the technical field of mercury determination in water quality, and particularly relates to an accurate and stable thiocyanate determination method. Background Art

[0002] Mercury is a persistent heavy metal pollutant with extremely strong biological toxicity in the environment. It is difficult to be excreted after entering the organism, which seriously threatens human health. At present, the determination of mercury in water widely adopts atomic fluorescence method (HJ 694-2014 "Determination of mercury, arsenic, selenium, bismuth and antimony in water quality by atomic fluorescence method") and cold atomic absorption spectrophotometry (HJ 597-2011 "Determination of total mercury in water quality by cold atomic absorption spectrophotometry"), both of which require the use of multiple reagents and the preparation process is cumbersome, which will not only introduce large errors, but also easily produce mercury pollution. At the same time, it is also necessary to eliminate the spectral interference and various physical interferences caused by other metal elements, which seriously affects the work efficiency of testers.

[0003] Due to the strong adsorption effect and instability of mercury, it is difficult to measure mercury. In particular, once the atomic fluorescence is fed with a high-concentration sample, the entire sampling system will be contaminated, and a lot of time is needed to flush the pipeline, affecting work efficiency. With the gradual popularization of inductively coupled plasma mass spectrometers (ICP-MS), ICP-MS is less used in mercury measurement and there are fewer literatures. The main reason is that the problem of mercury residue has not been solved. Therefore, it is of great practical significance to develop a method for measuring total mercury in water using ICP-MS. Summary of the invention

[0004] The invention provides an accurate and stable ICP-MS method for determining mercury in water, so as to solve the problem that ICP-MS cannot accurately determine mercury due to mercury residue.

[0005] The technical solution adopted by the present invention comprises the following steps:

[0006] Step 1: According to the mercury content in the sample, measure 10mL~50mL of sample and dilute to 50mL, transfer to a 250mL beaker, add 2~4mL of aqua regia, shake well, add 5mL of 2mg / L gold solution, place on a hot plate, control the temperature of the hot plate between 250℃-300℃, digest for 45 minutes, remove and cool slightly;

[0007] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate between 60°C and 80°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0008] Step 3: Transfer the digestion solution cooled to room temperature into a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, and let it stand for 10 minutes before measuring;

[0009] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0010] Step 4: Blank the entire procedure with the sample;

[0011] Step 5, ICP-MS determination of samples;

[0012] Step 6: Calculate the concentration of thiocyanate in the water sample according to the following formula:

[0013]

[0014] Where: C——mercury concentration in water sample, ug / L;

[0015] C1——the concentration of mercury found from the standard curve, ug / L;

[0016] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0017] V——fixed volume during volume adjustment, mL;

[0018] V0——sampling volume of the sample, mL.

[0019] In the step 1, the aqua regia preparation method is: 3 volumes of hydrochloric acid and 1 volume of nitric acid are mixed.

[0020] In the step 1, the preparation method of 2 mg / L gold solution is as follows: 2 mL of the commercially available gold standard solution of 1000 μg / ml is pipetted into a 100 ml volumetric flask, fixed to volume, and shaken well; 10 mL of a diluent with a concentration of 20 μg / ml is pipetted into a 100 ml volumetric flask, fixed to volume, and shaken well.

[0021] In the step 2, the preparation method of L-cysteine ​​is: weigh 100 mg of L-cysteine ​​and dissolve it in 1000 mL of water.

[0022] In the step 3, the preparation method of thioethylene glycol is: weigh 100 mg of thioethylene glycol and dissolve it in 1000 mL of water.

[0023] Beneficial effects of the present invention:

[0024] 1) At present, the linear coefficient of the calibration curve of ICP-MS mercury measurement cannot meet the requirements of use, and the extreme difference in the accuracy and precision of the measured samples is also the main reason why ICP-MS mercury measurement has not been promoted. The present invention solves the problem of unqualified linear coefficient of the calibration curve. It also solves the accuracy and precision of the data in the sample measurement process.

[0025] 2) The problem of mercury residue in the test instrument pipeline is the main reason for the poor accuracy and precision of data during the sample measurement process. The present invention uses gold and L-cysteine ​​to combine with mercury to form a stable complex, uses less reagents, is accurate and fast, so that mercury will not remain in the pipeline, and the excess L-cysteine ​​is masked by thioethylene glycol. The excess thioethylene glycol does not affect the determination of mercury, which greatly improves the accuracy of ICP-MS mercury measurement. It meets the requirements of GB 3838-2002 "Surface Water Environmental Quality Standard" that the standard limit of Class I and Class II water is 0.05μg / L. At the same time, mercury-containing samples with higher concentrations can be measured.

[0026] 3) A more convenient, accurate and quick digestion method can be selected. Currently, the only digestion methods used for solid samples and liquid samples are water bath heating or microwave heating. Due to the instability of mercury, these two digestion methods are time-consuming, labor-intensive and inconvenient to operate. The present invention solves this problem because mercury forms a stable complex that can withstand high temperatures, and then an electric heating plate is used for digestion, which greatly saves digestion time.

[0027] 4) There is a great demand for mercury measurement in the fields of environment, food, and medicine. The present invention can provide better technical solutions to related fields and solve some problems related to people's livelihood. Mercury above 0.01 PPb can be accurately measured, which is impossible for instruments such as atomic fluorescence. DETAILED DESCRIPTION

[0028] In the following examples, aqua regia was prepared by mixing 3 volumes of hydrochloric acid and 1 volume of nitric acid.

[0029] Preparation method of 2mg / L gold solution: Commercially available gold standard solution is 1000ug / mL. Pipette 2mL of gold standard solution 1000ug / mL into a 100mL volumetric flask, dilute to volume, shake well, and pipette 10mL of diluted solution with a concentration of 20ug / mL into a 100mL volumetric flask, dilute to volume, and shake well.

[0030] The preparation method of L-cysteine ​​is as follows: weigh 100 mg of L-cysteine ​​and dissolve it in 1000 mL of water.

[0031] The preparation method of thioethylene glycol is as follows: weigh 100 mg of thioethylene glycol and dissolve it in 1000 mL of water.

[0032] Example 1

[0033] Step 1: Measure 50 mL of sample, transfer to a 250 mL beaker, add 4 mL of aqua regia, shake well, add 5 mL of 2 mg / L gold solution, place on a hot plate, control the temperature of the hot plate at 300 ° C, digest for 45 minutes, remove, and cool slightly;

[0034] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate at 60°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0035] Step 3: Transfer the digestion solution cooled to room temperature to a 50mL volumetric flask, add 5mL of 100mg / L thioethylene glycol, add double distilled water to make up to 50mL, shake well, let stand for 10 minutes and then measure;

[0036] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0037] Step 4: Blank the entire procedure with the sample;

[0038] Step 5: ICP-MS determination of samples. The mercury concentration was found to be 0.020 μg / L from the calibration curve; at the same time, the concentration of the blank sample was determined to be 0.000 μg / L;

[0039] The concentration of mercury in the water sample was calculated as follows:

[0040]

[0041] Where: C——mercury concentration in water sample, ug / L;

[0042] C1——the concentration of mercury found from the standard curve, ug / L;

[0043] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0044] V——fixed volume during volume adjustment, mL;

[0045] V0——sampling volume of the sample, mL.

[0046] The calculated mercury concentration is 0.020ug / L.

[0047] Example 2

[0048] Step 1: Measure 30 mL of sample and dilute to 50 mL with double distilled water, transfer to a 250 mL beaker, add 3 mL of aqua regia, shake well, add 5 mL of 2 mg / L gold solution, place on a hot plate, control the temperature of the hot plate at 280 ° C, digest for 40 minutes, remove, and cool slightly;

[0049] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate at 70°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0050] Step 3: Transfer the digestion solution cooled to room temperature into a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, and let it stand for 10 minutes before measuring;

[0051] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0052] Step 4: Blank the entire procedure with the sample;

[0053] Step 5: ICP-MS was used to measure the sample, and the mercury concentration was 5.00 μg / L from the calibration curve; at the same time, the concentration of the blank sample was 0.002 μg / L;

[0054] The concentration of mercury in the water sample was calculated as follows:

[0055]

[0056] Where: C——mercury concentration in water sample, ug / L;

[0057] C1——the concentration of mercury found from the standard curve, ug / L;

[0058] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0059] V——fixed volume during volume adjustment, mL;

[0060] V0——sampling volume of the sample, mL;

[0061] The calculated mercury concentration is 10.00ug / L.

[0062] Example 3

[0063] Step 1: Measure 10 mL of sample and dilute to 50 mL with double distilled water, transfer to a 250 mL beaker, add 2 mL of aqua regia, shake well, add 5 mL of 2 mg / L gold solution, place on a hot plate, control the temperature of the hot plate at 250 ° C, digest for 30 minutes, remove and cool slightly;

[0064] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate at 80°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0065] Step 3: Transfer the digestion solution cooled to room temperature into a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, and let it stand for 10 minutes before measuring;

[0066] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0067] Step 4: Blank the entire procedure with the sample;

[0068] Step 5: ICP-MS determination of samples. The mercury concentration was 9.85.00 μg / L from the calibration curve; at the same time, the concentration of the blank sample was 0.002 μg / L;

[0069] The concentration of mercury in the water sample was calculated as follows:

[0070]

[0071] Where: C——mercury concentration in water sample, ug / L;

[0072] C1——the concentration of mercury found from the standard curve, ug / L;

[0073] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0074] V——fixed volume during volume adjustment, mL;

[0075] V0——sampling volume of the sample, mL.

[0076] The calculated mercury concentration was 49.2ug / L.

[0077] The present invention is further described below through experimental examples.

[0078] Experimental Example 1: The standard value of standard sample GSB07-3173-2014202051 was measured: 11.2±1.3.

[0079] Step 1: Measure 25 mL of sample and dilute to 50 mL with double distilled water, transfer to a 250 mL beaker, add 2 mL of aqua regia, shake well, add 5 mL of 2 mg / L gold solution, place on a hot plate, control the temperature of the hot plate at 280 ° C, digest for 45 minutes, remove, and cool slightly;

[0080] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate at 80°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0081] Step 3: Transfer the digestion solution cooled to room temperature into a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, and let it stand for 10 minutes before measuring;

[0082] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0083] Step 4: Blank the entire procedure with the sample;

[0084] Step 5: ICP-MS was used to measure the sample, and the mercury concentration was 5.63 μg / L from the calibration curve; at the same time, the concentration of the blank sample was 0.00 μg / L;

[0085] The concentration of mercury in the water sample was calculated as follows:

[0086]

[0087] Where: C——mercury concentration in water sample, ug / L;

[0088] C1——the concentration of mercury found from the standard curve, ug / L;

[0089] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0090] V——fixed volume during volume adjustment, mL;

[0091] V0——sampling volume of the sample, mL.

[0092] The calculated mercury concentration is 11.30ug / L.

[0093] Experimental Example 2: The standard value of standard sample GSB07-3173-2014202052 was measured: 3.73±0.54.

[0094] Step 1: Measure 50 mL of sample, transfer to a 250 mL beaker, add 3 mL of aqua regia, shake well, add 5 mL of 2 mg / L gold solution, place on a hot plate, control the temperature of the hot plate at 280 ° C, digest for 35 minutes, remove, and cool slightly;

[0095] Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate at 60°C, and digest for 15 minutes. After digestion, remove and cool to room temperature;

[0096] Step 3: Transfer the digestion solution cooled to room temperature into a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, and let it stand for 10 minutes before measuring;

[0097] Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100 ml volumetric flask. Add 5 ml of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve;

[0098] Step 4: Blank the entire procedure with the sample;

[0099] Step 5: ICP-MS measured the sample and found the mercury concentration of 3.73 μg / L from the calibration curve; at the same time, the concentration of the blank sample was determined to be 0.002 μg / L;

[0100] The concentration of mercury in the water sample was calculated as follows:

[0101]

[0102] Where: C——mercury concentration in water sample, ug / L;

[0103] C1——the concentration of mercury found from the standard curve, ug / L;

[0104] C2——The concentration of mercury in the blank sample is obtained from the standard curve, ug / L;

[0105] V——fixed volume during volume adjustment, mL;

[0106] V0——sampling volume of the sample, mL.

[0107] The calculated mercury concentration is 3.73ug / L.

Claims

1. An accurate and stable ICP-MS method for determining mercury in water, characterized in that: The following steps are involved: Step 1: According to the mercury content in the sample, take 10 mL to 50 mL of the sample and dilute it to 50 mL. Transfer it to a 250 mL beaker, add 2 to 4 mL of aqua regia mixed with 3 volumes of hydrochloric acid and 1 volume of nitric acid, shake well, add 5 mL of 2 mg / L gold solution, place it on a hot plate, control the temperature of the hot plate between 250℃-300℃, digest for 45 minutes, remove it, and cool it slightly. Preparation method of 2 mg / L gold solution: 2 mL of commercially available gold standard solution 1000 μg / ml was pipetted into a 100 ml volumetric flask, fixed to volume, and shaken well. 10 mL of diluent with a concentration of 20 μg / ml was pipetted into a 100 ml volumetric flask, fixed to volume, and shaken well. Step 2: Add 5 mL of 100 mg / L L-cysteine, control the temperature of the hot plate between 60°C and 80°C, and digest for 15 minutes. After digestion, remove and cool to room temperature, wherein: The preparation method of L-cysteine ​​is as follows: weigh 100 mg of L-cysteine ​​and dissolve it in 1000 mL of water; Step 3: Transfer the digestion solution cooled to room temperature to a 50 mL volumetric flask, add 5 mL of 100 mg / L thioethylene glycol, add double distilled water to make up to 50 mL, shake well, let stand for 10 minutes and then measure: The preparation method of thioethylene glycol is as follows: weigh 100 mg of thioethylene glycol and dissolve it in 1000 mL of water; Step 4: Prepare a standard series of mercury concentrations of 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, and 10.00 μg / L, respectively, and prepare them in a 100-ml volumetric flask. Add 5 mL of 4 mg / L gold to each bottle of the standard series, where the gold content in each bottle of the standard series is 200 μg / L, and draw a calibration curve; Step 4: Blank the entire procedure with the sample; Step 5, ICP-MS determination of samples; Step 6: Calculate the concentration of mercury in the water sample according to the following formula: ； Where: C ——Concentration of mercury in water sample, ug / L; C 1——The concentration of mercury is obtained from the standard curve, ug / L; C 2——The concentration of mercury in the blank sample is found from the standard curve, ug / L; V ——The fixed volume during the fixed volume period, mL; V 0——The sampling volume of the sample, mL.

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