CN106680358A - Inductively coupled plasma mass spectrometry method for determining content of chrome, arsenic, cadmium and lead in soil - Google Patents

Abstract

The invention discloses the determination of the content of chromium, arsenic, cadmium and lead in soil by inductively coupled plasma mass spectrometry, which mainly includes the following steps: 1) digestion of soil samples; 2) dilution and constant volume filtration of the digestion solution; 4) result analysis: calculate the content of chromium, arsenic, cadmium and lead in the soil sample according to the weight of the soil sample taken by weighing and the concentration of the detected digestion solution: the detection method of the present invention is simple, fast, and the analysis speed is fast, and the detection limit Low, the detection limit of chromium is 0.0127mg/kg, the detection limit of arsenic is 0.0147mg/kg, the detection limit of cadmium is 0.0048mg/kg, the detection limit of lead is 0.0039mg/kg, and the recovery rate of addition is 89%～113 %, the relative standard deviation is less than 4.5%; the measurement dynamic linear range is wide, and it can detect multiple metal elements in the soil at the same time, which greatly improves the work efficiency.

Description

Determination of Chromium, Arsenic, Cadmium and Lead in Soil by Inductively Coupled Plasma Mass Spectrometry

technical field

The invention relates to the technical field of soil environmental protection detection, in particular to the determination of chromium, arsenic, cadmium and lead contents in soil by inductively coupled plasma mass spectrometry.

Background technique

At present, the detection methods of metal content in soil include atomic absorption method, atomic fluorescence method, ICP-AES method and ICP-MS method. The atomic absorption spectrometer radiates light with the characteristic spectral lines of the element to be measured from the light source, and is absorbed by the ground state atoms of the element to be measured in the vapor when it passes through the sample vapor, and the light of the characteristic spectral line of the radiation is weakened to measure the light to be measured in the sample. Measure the content of elements. The detection sensitivity of the atomic absorption method is low, and the sensitivity of the elements tested by the atomic fluorescence method is 2-3 orders of magnitude higher than that of the atomic absorption flame method, but like the atomic absorption method, multiple elements cannot be detected at the same time, and the detection efficiency is low.

ICP as the ionization source of MS is one of the fastest-growing inorganic trace analysis techniques since the 1990s, and its detection limit can reach ng/ml level, especially for some heavy metals, the detection limit is higher than that of common ICP- AES is 2 to 3 orders of magnitude lower; it is also suitable for simultaneous analysis of multiple elements; compared with the line-rich atomic emission spectrum of heavy elements, the spectral lines of mass spectrometry are much less, so spectral line interference is relatively not an important problem; capable of isotope analysis. ICP-MS is currently a research hotspot in the analysis of metals in different media, and it will obviously be an important direction for future development.

In soil, especially in environmental soil, the content of metal pollution elements is generally low. In this respect, ICP-MS method can especially show its superiority. At the same time, ICP-MS method greatly expands the types of elements that can be detected in soil, and realizes Simultaneous analysis improves work efficiency.

Contents of the invention

The present invention aims at the problem that the metal content detection method in the soil cannot detect multiple elements at the same time and the detection efficiency is low in the prior art, and provides a simple, fast, fast analysis speed, low detection limit, and wide dynamic linear range of measurement. It is a detection method that can detect multiple metal elements in soil at the same time.

The technical solution of the present invention is: the content of chromium, arsenic, cadmium and lead in soil is measured by inductively coupled plasma mass spectrometry, mainly comprising the following steps:

1) Digestion of soil samples: Weigh about 0.05g of air-dried soil samples passed through a 200-mesh sieve into a 50ml polytetrafluoroethylene beaker, add 8ml of nitric acid and 1ml of hydrofluoric acid, shake well, and digest in an electric digestion apparatus at 150°C for 20-24 hours , then heat up the electrothermal digestion apparatus to 180°C to drive out the acid until about 1ml of the digestion solution remains;

2) Dilute and constant-volume filtration of the digestion solution: wash out the digestion solution in the polytetrafluoroethylene beaker with ultrapure water into a 15ml plastic centrifuge tube, set the volume to 14.0ml, and filter the digestion solution with a 0.45 μm cellulose acetate membrane. Take 2.0ml of the filtered digestion solution and dilute to 10.0ml with ultrapure water;

3) Use an inductively coupled plasma mass spectrometer to detect:

a) Preparation of standard solution: take the mixed standard stock solution and dilute it step by step with 0.5% nitric acid solution to the standard working solution with concentrations of 0.1, 0.2, 0.5, 1.0, 10.0, 20.0, 50.0, 100.0ppb;

b) Use an inductively coupled plasma mass spectrometer to detect the standard working solution and the sample solution after digestion and filtration to a constant volume;

4) Result analysis: Calculate the content of chromium, arsenic, cadmium and lead in the soil sample according to the weight of the soil sample taken and the concentration of the detected digestion solution;

W is the metal content of the soil sample, mg/kg;

c is the metal concentration in the digestion solution, μg/kg;

V is the constant volume of the digestion solution, mL;

m is the mass of the soil, g.

Further, in the above scheme, the preparation of the standard working solution in the step 3): the concentration of the standard working solution selected when detecting chromium, arsenic and lead is 1.0, 10.0, 20.0, 50.0, 100.0ppb; the standard working solution selected when detecting cadmium The working solution concentration is 0.1, 0.2, 0.5, 1.0, 10.0ppb.

Further, in the above scheme, the main working parameters of the inductively coupled plasma mass spectrometer in step 3) are: peristaltic pump speed: 40rpm, number of scans: 50 times, number of repeated measurements: 2 times, sample lifting time: 50s, Cleaning time: 10s, mist chamber temperature: 2.7°C, atomizer flow rate: 1.03l/min, plasma torch power: 1548.6W, cooling air flow rate: 14l/min, cooling water flow rate: 3.5l/min.

Compared with the prior art, the beneficial effects of the present invention are: the detection method of the present invention is simple and fast, the analysis speed is fast, the detection limit is low, the detection limit of chromium is 0.0127mg/kg, the detection limit of arsenic is 0.0147mg/kg kg, the detection limit of cadmium is 0.0048mg/kg, the detection limit of lead is 0.0039mg/kg, the recovery rate of addition is 89%-113%, and the relative standard deviation is less than 4.5%. The dynamic linear range of measurement is wide and can be detected at the same time A variety of metal elements in the soil greatly improve work efficiency.

detailed description

Get certain field soil after air-drying of crossing 200 mesh sieves, weigh 1g, be divided into 20 parts on average, be recorded as A1, A2, A3, A4...A20 respectively, use the inductively coupled plasma mass spectrometry method of the present invention to measure chromium in soil respectively The content of arsenic, cadmium and lead mainly includes the following steps:

1) Digestion of soil samples: Weigh about 0.05g of air-dried soil samples passed through a 200-mesh sieve into a 50ml polytetrafluoroethylene beaker, add 8ml of nitric acid and 1ml of hydrofluoric acid, shake well, and digest in an electric digestion apparatus at 150°C for 20 hours, then Heat up the temperature of the electrothermal digestion instrument to 180°C to drive out the acid until about 1ml of the digestion solution remains;

2) Dilute and constant-volume filtration of the digestion solution: wash out the digestion solution in the polytetrafluoroethylene beaker with ultrapure water into a 15ml plastic centrifuge tube, set the volume to 14.0ml, and filter the digestion solution with a 0.45 μm cellulose acetate membrane. Take 2.0ml of the filtered digestion solution and dilute to 10.0ml with ultrapure water;

3) Use an inductively coupled plasma mass spectrometer to detect:

a) Preparation of standard solution: take the mixed standard stock solution and dilute it step by step with 0.5% nitric acid solution to the standard working solution with concentrations of 0.1, 0.2, 0.5, 1.0, 10.0, 20.0, 50.0, 100.0ppb;

The concentration of the standard working solution used when detecting chromium, arsenic and lead is 1.0, 10.0, 20.0, 50.0, 100.0ppb; the concentration of the standard working solution used when detecting cadmium is 0.1, 0.2, 0.5, 1.0, 10.0ppb;

b) Use an inductively coupled plasma mass spectrometer to detect the standard working solution and the sample solution after digestion and filtration to a constant volume;

The main working parameters of the inductively coupled plasma mass spectrometer are: peristaltic pump speed: 40rpm, number of scans: 50 times, number of repeated measurements: 2 times, sample lifting time: 50s, cleaning time: 10s, spray chamber temperature: 2.7°C, atomization The flow rate of the device is 1.03l/min, the power of the plasma torch: 1548.6W, the flow rate of cooling air: 14l/min, the flow rate of cooling water: 3.5l/min;

4) Result analysis: According to the weighed soil sample weight and the detected concentration of the digestion solution, calculate the content of chromium, arsenic, cadmium and lead in the soil sample according to the following formula;

W is the metal content of the soil sample, mg/kg; c is the metal concentration in the digestion solution, μg/kg; V is the constant volume of the digestion solution, mL; m is the weight of the soil, g.

The results are shown in Table 1:

Table 1 uses the method of the present invention to the detection result of 20 parts of soil samples

The actual content results of metal elements in the soil samples are shown in Table 2:

Table 2 The actual content of metal elements in the soil samples

Each group of metal types Chromium (mg/kg) Arsenic (mg/kg) Cadmium (mg/kg) Lead (mg/kg) content 0.01674 0.02867 0.0095 0.00840

From the comparison of the results in Table 1 and Table 2 above, it can be seen that the deviation between the data detected by the method of the present invention and the actual value is very small, and the accuracy rate is as high as 99.88%.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (3)

1. Inductively coupled plasma mass spectrometry measures the content of chromium, arsenic, cadmium and lead in soil, and is characterized in that, mainly comprises the following steps: 1) Digestion of soil samples: Weigh about 0.05g of air-dried soil samples passed through a 200-mesh sieve into a 50ml polytetrafluoroethylene beaker, add 8ml of nitric acid and 1ml of hydrofluoric acid, shake well, and then digest them in an electric digestion apparatus, and drive the acid to the digestion solution About 1ml remains. 2) Dilute and constant-volume filtration of the digestion solution: wash out the digestion solution in the polytetrafluoroethylene beaker with ultrapure water into a 15ml plastic centrifuge tube, set the volume to 14.0ml, and filter the digestion solution with a 0.45 μm cellulose acetate membrane. Take 2.0ml of the filtered digestion solution and dilute to 10.0ml with ultrapure water. 3) Use an inductively coupled plasma mass spectrometer to detect: a) Preparation of standard solution: take the mixed standard stock solution and dilute it step by step with 0.5% nitric acid solution to the standard working solution with concentrations of 0.1, 0.2, 0.5, 1.0, 10.0, 20.0, 50.0, 100.0ppb; b) Use an inductively coupled plasma mass spectrometer to detect the standard working solution and the sample solution after digestion and filtration to a constant volume; 4) Result analysis: Calculate the content of chromium, arsenic, cadmium and lead in the soil sample according to the weight of the soil sample taken and the concentration of the detected digestion solution; $\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; 1000</span>}\mathrm{<span\; class="notranslate">\; m</span>}}$ W is the metal content of the soil sample, mg/kg; c is the metal concentration in the digestion solution, μg/kg; V is the constant volume of the digestion solution, mL; m is the mass of the soil, g. 2. as claimed in claim 1, inductively coupled plasma mass spectrometry measures the content of chromium, arsenic, cadmium and lead in soil, it is characterized in that, described step 3) in the preparation of standard working fluid: select when detecting chromium, arsenic and lead The concentration of the standard working solution is 1.0, 10.0, 20.0, 50.0, 100.0ppb; the concentration of the standard working solution used when detecting cadmium is 0.1, 0.2, 0.5, 1.0, 10.0ppb. 3. as claimed in claim 1, the inductively coupled plasma mass spectrometry measures the content of chromium, arsenic, cadmium and lead in soil, it is characterized in that, described step 3) in inductively coupled plasma mass spectrometer main operating parameter is: peristaltic pump speed : 40rpm, number of scans: 50 times, number of repeated measurements: 2 times, sample lifting time: 50s, cleaning time: 10s, spray chamber temperature: about 2.7°C, atomizer flow rate 1.03l/min, plasma torch power: 1548.6 W, cooling air flow: 14l/min, cooling water flow: 3.5l/min.