A method for rapid determination of total mercury in soil

Abstract

The present invention proposes a method for rapidly determining total mercury in soil, comprising the following steps: weighing an appropriate amount of soil sample into a stoppered colorimetric tube, adding a little water to moisten the soil sample, adding aqua regia and deionized water, shaking at room temperature, diluting to scale with deionized water, and taking the sample supernatant to be tested; preparing a series of mercury standard solutions with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8, and 1 μg / L respectively, the diluting solution is a 5% (v / v) hydrochloric acid solution, and performing standard blank treatment at the same time; respectively adding the supernatant of the sample to be tested, the sample blank, the standard series of mercury solutions, and the standard blank into the automatic sampler of a dual-channel atomic fluorescence photometer, setting the instrument analysis conditions for testing; the test method is the standard curve method, and the reading method is the peak area. The detection limit, accuracy, and precision of the method of the present invention are all superior to the existing test methods, and the operation is simple and convenient, the detection efficiency is higher, and it is suitable for the analysis and determination of total mercury in a large number of soils, and it is a relatively ideal analysis method.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical detection, and in particular to a method for rapidly determining total mercury in soil. Background Art

[0002] Mercury exists in environmental media in various forms such as elemental mercury, organic mercury, and inorganic mercury. It is a long-standing and mobile environmental pollutant that can enter the human body through the food chain and seriously damage human health. Regarding the determination of total mercury in soil, conventional methods include boiling water bath digestion-atomic fluorescence spectrometry (GB / T22105.1-2008), microwave digestion-atomic fluorescence spectrometry (HJ 680-2013), catalytic pyrolysis-cold atomic absorption spectrophotometry (HJ 923-2017), etc. However, the above methods require the use of water baths (pots) or electric heating plates, microwave digestion instruments, combustion catalytic furnaces and other pre-treatment equipment, which are cumbersome to operate, have low detection efficiency, and high costs. Summary of the invention

[0003] The present invention provides a method for rapidly determining total mercury in soil, which overcomes the shortcomings of the above-mentioned prior art and adopts a method for rapidly determining total mercury in soil by cold dissolution digestion at room temperature using reverse aqua regia (a mixture of concentrated hydrochloric acid and concentrated nitric acid in a ratio of 1:3)-atomic fluorescence spectrometry. The method does not require pre-treatment equipment such as a water bath or a hot plate, a microwave digestion instrument, a combustion catalytic furnace, etc. The operation is simple and fast, the detection efficiency is improved, and the detection cost is saved.

[0004] In order to achieve the above object, the present invention provides a method for quickly determining total mercury in soil, comprising the following steps:

[0005] 1) Sample preparation: Weigh an appropriate amount of soil sample into a stoppered colorimetric tube, add a small amount of water to moisten the soil sample, add aqua regia and deionized water, and shake well at room temperature. The mass ratio of aqua regia, deionized water and soil sample is (20-35): (15-25): 1;

[0006] Continue to add deionized water to the scale, shake well and let stand or pour into a centrifuge tube for centrifugation, take the sample supernatant for testing, and do sample blank treatment at the same time;

[0007] 2) Preparation of a series of mercury standard solutions: prepare a series of mercury standard solutions with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8, and 1 μg / L, respectively, with a constant volume solution of 5% (v / v) hydrochloric acid solution, and perform a standard blank treatment at the same time;

[0008] 3) Sample determination:

[0009] The supernatant of the sample to be tested, the sample blank, the mercury standard series solution and the standard blank were respectively added into the automatic sampler of the dual-channel atomic fluorescence photometer, and the instrument analysis conditions were set for testing; the test method was the standard curve method, and the reading method was the peak area.

[0010] The following are further optimizations and / or improvements to the above technical solutions:

[0011] The preparation of the reverse aqua regia is as follows: 3 volumes of nitric acid are mixed with 1 volume of hydrochloric acid, and stirred evenly to obtain the reverse aqua regia, wherein the reverse aqua regia is prepared half an hour before dissolving the soil sample.

[0012] In step 2), the preparation method of the mercury standard series solution is as follows: take 1 ml of 1000 mg / L Hg standard solution and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain an intermediate solution 1 with a concentration of 10 mg / L; take 1 ml of intermediate solution 1 and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain an intermediate solution 2 with a concentration of 100 μg / L; take 10 ml of intermediate solution 2 and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain a standard working solution with a concentration of 10 μg / L; take 1, 2, 4, 6, 8, and 10 ml of the standard working solution and add them to 5 100 ml volumetric flasks, dilute and fix the volume to obtain a mercury standard series solution with a concentration gradient of 0.1, 0.2, 0.4, 0.6, 0.8, and 1 μg / L.

[0013] In step 3), the conditions for measuring mercury are: negative high voltage is 300V, lamp current is 30mA, carrier gas flow rate is 400mL / min, shielding gas flow rate is 1000mL / min, and atomizer height is 10mm.

[0014] In step 3), the reading time during the test is 16S and the delay time is 1S.

[0015] In step 3), when tested by a dual-channel atomic fluorescence spectrophotometer, the reducing agent used is 0.5% (w / w) KBH4 + 0.25% (w / w) KOH.

[0016] In step 3), the test method using a dual-channel atomic fluorescence photometer includes the following steps: setting instrument parameters, standard curve concentration and dilution parameters, preheating the instrument for more than half an hour, and driving the reducing agent and the carrier liquid, measuring in the order of standard blank, mercury standard series solution, sample blank, and sample to be tested to obtain the mercury content in the sample solution to be tested.

[0017] In step 1), the soil sample is weighed to an accuracy of 0.0001 g.

[0018] The present invention has the following advantages:

[0019] The method of the present invention uses reverse aqua regia cold dissolution at room temperature to pre-treat soil samples, does not require any pre-treatment equipment such as water bath or electric hot plate heating, microwave digestion instrument and combustion catalytic furnace, reduces water bath heating, microwave heating digestion and combustion catalysis and other intermediate processing links, is simple to operate, effectively avoids contamination or loss during pre-treatment, improves work efficiency, saves experimental cost advantages, makes pre-treatment convenient and fast, and is suitable for large-scale sample detection. And the method has good detection limit, accuracy and precision, and fast determination speed.

[0020] The detection limit, accuracy and precision of the method of the present invention are better than those of the existing test methods, and the operation is simple and convenient, the detection efficiency is higher, and it is suitable for the analysis and determination of total mercury in large quantities of soil. It is a relatively ideal analysis method. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the standard curve of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in the following examples, but the present invention is not limited thereto.

[0023] Example 1

[0024] Preparation of reverse aqua regia: Mix 3 volumes of nitric acid with 1 volume of hydrochloric acid and stir evenly with a glass rod. The reverse aqua regia has the strongest oxidizing ability half an hour after preparation, so it should be prepared in advance, but it should not be left for a long time, as it will evaporate too much. Currently, reverse aqua regia is prepared about half an hour before processing the sample.

[0025] Preparation of mercury standard series solutions: Take 1ml of 1000mg / L Hg standard solution and add it to a 100ml volumetric flask, dilute it with 5% HCl (v / v) solution to obtain intermediate solution 1 with a concentration of 10mg / L. Take 1ml of intermediate solution 1 and add it to a 100ml volumetric flask, dilute it with 5% HCl solution to obtain intermediate solution 2 with a concentration of 100μg / L. Take 10ml of intermediate solution 2 and add it to a 100ml volumetric flask, dilute it with 5% HCl solution to obtain a standard working solution with a concentration of 10μg / L. Take 1, 2, 4, 6, 8, and 10ml of the standard working solution and add them to 5 100ml volumetric flasks, dilute and adjust the volume to obtain a series of mercury standard solutions with a concentration gradient of 0.1, 0.2, 0.4, 0.6, 0.8, and 1μg / L, and perform standard blank treatment at the same time.

[0026] Sample preparation: Weigh 0.2500g to 0.3000g (accurate to 0.0001g) of soil sample into a 25mL stoppered colorimetric tube, add a little water to moisten the sample, add 5mL of aqua regia and 5mL of deionized water, shake well at room temperature, immediately dilute to the scale with deionized water, shake well and let stand or pour into a centrifuge tube for centrifugation, take the supernatant and directly measure on the machine, and perform sample blank treatment at the same time.

[0027] Sample determination: add the supernatant of the sample to be tested, sample blank, mercury standard series solution and standard blank into the automatic sampler of the dual-channel atomic fluorescence photometer respectively, set the instrument parameters, standard curve concentration and dilution parameters, wait for the instrument to be preheated for more than half an hour, and drive the reducing agent and carrier liquid, determine in the order of standard blank, mercury standard series solution, sample blank, sample to obtain the mercury content in the sample solution to be tested.

[0028] During the test: Carrier liquid: 5% (v / v) hydrochloric acid;

[0029] Reducing agent: 0.5% (w / w) KBH4 + 0.25% (w / w) KOH.

[0030] The optimal working conditions of the instrument are: negative high voltage is 300V, lamp current is 30mA, carrier gas flow rate is 400mL / min, shielding gas flow rate is 1000mL / min, atomizer height is 10mm, reading mode is peak area, reading time is 16S, and delay time is 1S.

[0031] Calculation results:

[0032] The mercury content in soil is expressed as mass fraction w, in milligrams per kilogram (mg / kg), and is calculated according to formula (1).

[0033]

[0034] Where:

[0035] m—sample mass, in grams (g);

[0036] ρ1—Substitute the fluorescence intensity of the test solution into the regression equation to calculate the mass concentration of the test solution in nanograms per milliliter (ng / mL);

[0037] ρ0—Substitute the fluorescence intensity of the blank test solution into the regression equation to calculate the mass concentration of the test solution in nanograms per milliliter (ng / mL);

[0038] 25-The constant volume of the sample solution, in milliliters (mL)

[0039] 10 -3 -Conversion factor for converting mass values ​​in nanograms (ng) to mass values ​​in milligrams (mg).

[0040] Standard working curve:

[0041] The results showed that the curve of atomic fluorescence spectrometry had good linearity in the range of 0.0-1.0 μg / L, the slope of the standard curve was 3162, the intercept was -15.10, and the correlation coefficient was 0.9999. Figure 1 This is the linear regression of the standard curve, and its regression equation is: I=3162ρ-15.10.

[0042] Table 1 Mercury standard series mass concentration ρ (μg / L) and corresponding fluorescence intensity I

[0043]

[0044]

[0045] 1. Method accuracy

[0046] In order to verify the accuracy and reliability of the method, this experiment selected five national soil standard substances, coded GBW07448 (GSS-19), GBW07451 (GSS-22), GBW07452 (GSS-23), GBW07385 (GSS-29), and GBW07386 (GSS-30), for determination. At the same time, three actual samples were selected for separate determination, and a certain mass of national standard substances (coded GBW07451 (GSS-22), GBW07385 (GSS-29), and GBW07386 (GSS-30)) were added for determination. The operation was carried out according to the implementation method. The results showed (see Table 2 and Table 3): the relative errors of the measured values ​​of the five national soil standard substances were between 1.54% and 8.00%, and were all within the certified value range (see Table 2). The spiked recoveries of the three actual samples were 103.8%, 94.7%, and 99.8%, respectively (see Table 3).

[0047] Table 2 Standard values ​​of reference materials and determination results

[0048]

[0049] Table 3 Results of actual sample spike recovery determination

[0050]

[0051] 2. Precision and detection limit of the method

[0052] According to the above experimental method, the national standard substances GBW07448 (GSS-19), GBW07451 (GSS-22), and GBW07452 (GSS-23) were selected for 6 measurements to determine the relative standard deviation of the method. The relative deviations of the three standard substances were 6.69%, 4.51%, and 2.95%, respectively (see Table 4). At the same time, 12 blank solutions were prepared, and the detection limit of the method was calculated using three times the standard deviation (3S). The results (see Table 5) showed that the detection limit was 0.000113 mg / kg, which was lower than the boiling water bath digestion-atomic fluorescence spectrometry (GB / T 22105.1-2008, detection limit 0.002 mg / kg), microwave digestion-atomic fluorescence spectrometry (HJ680-2013, detection limit 0.002 mg / kg), catalytic pyrolysis-cold atomic absorption spectrophotometry (HJ 923-2017, detection limit 0.0002 mg / kg).

[0053] Table 4 Precision of the method

[0054]

[0055] Table 5 Detection limits of the method

[0056]

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for rapidly determining total mercury in soil, characterized in that: The steps include: 1) Sample preparation: Weigh an appropriate amount of soil sample into a stoppered colorimetric tube, add a small amount of water to moisten the soil sample, add aqua regia and deionized water, and shake well at room temperature. The mass ratio of aqua regia, deionized water and soil sample is (20-35): (15-25): 1; Continue to add deionized water to the scale, shake well and let stand or pour into a centrifuge tube for centrifugation, take the sample supernatant for testing, and do sample blank treatment at the same time; 2) Preparation of a series of mercury standard solutions: prepare a series of mercury standard solutions with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8, and 1 μg / L, respectively, with a constant volume solution of 5% (v / v) hydrochloric acid solution, and perform a standard blank treatment at the same time; 3) Sample determination: The supernatant of the sample to be tested, the sample blank, the mercury standard series solution and the standard blank are respectively added into the automatic sampler of the dual-channel atomic fluorescence photometer, and the instrument analysis conditions are set for testing; the test method is the standard curve method, and the reading method is the peak area; The preparation of the reverse aqua regia is as follows: 3 volumes of nitric acid and 1 volume of hydrochloric acid are mixed and stirred evenly to obtain the reverse aqua regia, wherein the reverse aqua regia is prepared half an hour before dissolving the soil sample; In step 3), when tested by a dual-channel atomic fluorescence spectrophotometer, the reducing agent used is 0.5% (w / w) KBH4 + 0.25% (w / w) KOH.

2. A method for rapidly determining total mercury in soil according to claim 1, characterized in that: In step 2), the preparation method of the mercury standard series solution is as follows: take 1 ml of 1000 mg / L Hg standard solution and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain an intermediate solution 1 with a concentration of 10 mg / L; take 1 ml of intermediate solution 1 and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain an intermediate solution 2 with a concentration of 100 μg / L; take 10 ml of intermediate solution 2 and add it to a 100 ml volumetric flask, dilute it with 5% HCl solution to obtain a standard working solution with a concentration of 10 μg / L; take 1, 2, 4, 6, 8, and 10 ml of the standard working solution and add them to 5 100 ml volumetric flasks, dilute and fix the volume to obtain a mercury standard series solution with a concentration gradient of 0.1, 0.2, 0.4, 0.6, 0.8, and 1 μg / L.

3. A method for rapidly determining total mercury in soil according to claim 1, characterized in that: In step 3), the conditions for measuring mercury are: negative high voltage is 300V, lamp current is 30mA, carrier gas flow rate is 400mL / min, shielding gas flow rate is 1000mL / min, and atomizer height is 10mm.

4. A method for rapidly determining total mercury in soil according to claim 1, characterized in that: In step 3), the reading time during the test is 16S and the delay time is 1S.

5. A method for rapidly determining total mercury in soil according to claim 1, characterized in that: In step 3), the test method using a dual-channel atomic fluorescence photometer includes the following steps: setting instrument parameters, standard curve concentration and dilution parameters, preheating the instrument for more than half an hour, and driving the reducing agent and the carrier liquid, measuring in the order of standard blank, mercury standard series solution, sample blank, and sample to be tested to obtain the mercury content in the sample solution to be tested.

6. A method for rapidly determining total mercury in soil according to claim 1, characterized in that: In step 1), the soil sample is weighed to an accuracy of 0.0001 g.

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