CN115096985A - Method for simultaneously determining contents of multiple heavy metal elements in feed by graphite digestion-plasma mass spectrometer - Google Patents
Method for simultaneously determining contents of multiple heavy metal elements in feed by graphite digestion-plasma mass spectrometer Download PDFInfo
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Abstract
A method for simultaneously determining the contents of various heavy metal elements in feed by graphite digestion-plasma mass spectrometer comprises the following steps: step 1: drying a feed sample to be detected, and then grinding and sieving to obtain sample powder; and 2, step: mixing the sample powder with a digestion reagent, and then carrying out graphite digestion; the digestion reagent is a mixture of nitric acid and hydrofluoric acid; and step 3: then adding secondary water, covering and keeping the temperature at 140 ℃ and 160 ℃, heating for 8-12min, filtering to obtain filtrate, fixing the volume of the filtrate to 50mL, and shaking up to obtain a sample to be detected; and 4, step 4: preparing a standard working solution from the multiple metal element standard solution; and 5: and sequentially sucking the sample to be detected and the standard working solution into the plasma mass spectrometer, measuring the signal response values of the element to be detected and the internal standard element, and obtaining the concentration of the element to be detected in the test solution according to the standard curve. The nitric acid-hydrofluoric acid system graphite instrument digestion-plasma mass spectrometry established by the invention is an ideal method for simultaneously analyzing and detecting multiple heavy metal elements in the feed.
Description
Technical Field
The invention belongs to the technical field of heavy metal detection, and relates to a method for simultaneously determining the contents of various heavy metal elements in feed by graphite digestion-plasma mass spectrometry.
Background
Heavy metals in the feed are easy to accumulate in animals for a long time due to the enrichment effect, and finally enter human bodies through food chains, so that great threat is brought to human beings, and long-term market supervision is required.
The pretreatment method is a key influencing factor in heavy metal analysis, and currently, a dry ashing method, a microwave digestion method, a wet digestion method and a graphite digestion method are commonly used. The dry ashing method is a treatment method adopted in national feed detection standards, and achieves the purpose of digestion mainly through high-temperature calcination; the microwave digestion method is to add a certain amount of acid into a digestion tube weighed with a sample and carry out digestion under the action of closed microwaves and strong acid, and has the advantages of strong digestion capability, high digestion speed and the like; the wet digestion method generally completes the digestion of a sample by combining different acid liquor or alkali liquor systems under high-temperature heating conditions, and has complex and time-consuming operation.
Heavy metals in the feed are detected by adopting an atomic absorption spectrometer in the current national standard, and the working efficiency is lower during batch detection. Compared with other heavy metal measuring instruments, the plasma mass spectrometry (ICP-MS) has the advantages of high precision, low detection limit and the like, can simultaneously measure various metal elements in the feed, and has the working efficiency far higher than that of an atomic absorption spectrometer adopted in the current national standard.
For heavy metal detection in feed, the standard of multi-element simultaneous determination is not released at present, the existing standard is to use graphite furnace atomic absorption spectrometry to perform single element determination, and the provided pretreatment method is only a dry ashing method, which is basically a single element one-method one-standard method. If the measurement of multiple elements is required, pretreatment and instrument analysis need to be carried out one by one, the operation is complicated and time-consuming, the efficiency is relatively low, and the test efficiency is greatly limited when large-scale detection is carried out.
Disclosure of Invention
The invention aims to provide a method for simultaneously determining the contents of various heavy metal elements in feed by graphite digestion-plasma mass spectrometry.
In order to achieve the above objects and other related objects, the present invention provides the following technical solutions: a method for simultaneously determining the contents of various heavy metal elements in feed by graphite digestion-plasma mass spectrometer comprises the following steps:
step 1: drying a feed sample to be detected, and then grinding and sieving to obtain sample powder;
step 2: mixing the sample powder with a digestion reagent, and then carrying out graphite digestion; the digestion reagent is a mixture of nitric acid and hydrofluoric acid;
and step 3: then adding secondary water, covering and keeping the temperature at 140-160 ℃, heating for 8-12min, filtering to obtain filtrate, fixing the volume of the filtrate to 50mL, and shaking up to obtain a sample to be detected;
and 4, step 4: preparing the multiple metal element standard solution into standard working solution with mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L;
and 5: and sequentially sucking the sample to be detected and the standard working solution into the plasma mass spectrometer, measuring the signal response values of the element to be detected and the internal standard element, and obtaining the concentration of the element to be detected in the test solution according to the standard curve.
The preferable technical scheme is as follows: the volume ratio of the nitric acid to the hydrofluoric acid is as follows: 5-8: 1.
the preferable technical scheme is as follows: the procedure for graphite digestion was: heating for 15min to 120 ℃, and keeping for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 160, 180, 200 and 220 deg.C for 10min, respectively, and maintaining for 90, 120, 150 and 180 min.
Due to the application of the technical scheme, compared with the prior art, the invention has the advantages that:
the invention establishes a nitric acid-hydrofluoric acid system graphite instrument digestion-plasma mass spectrometry method which is an ideal method for simultaneously analyzing and detecting various heavy metal elements in the feed. The graphite digestion instrument realizes the integration of digestion and acid dispelling, and can effectively reduce the harm of reagents to experimenters. Meanwhile, according to the time consumption for detection and the difficulty degree of the process, the invention realizes rapid detection and high-efficiency detection.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
Example 1: method for simultaneously determining contents of multiple heavy metal elements in feed by graphite digestion-plasma mass spectrometer
1 materials and methods
1.1 materials and reagents
Taking 10-25g of feed sample, placing in a 90 ℃ oven for 9-10 hours, evaporating all water, completely drying, manually grinding by using a mortar, sieving by using a 1mm nylon sieve, uniformly mixing, drying and storing in dark place for later use.
The digestion reagents are superior pure if not specified, and the test water is secondary water. In order to avoid pollution caused by glassware, the glassware is soaked overnight in 20 percent nitric acid solution and washed by secondary water before use.
The mixed tuning liquid Li, Co, In and U are 10mg/L, and the content is U.S. O2 si; the standard solutions Cr, Cu, Cd, Pb, Ge, Rh and Re were all 1000 mg/L.
Multielement standard solutions (GSB 04-1767-2004). The multi-element standard solution is a mixed solution, is purchased from the national nonferrous metals and electronic material analysis and test center, is 100 mu g/mL, and can simultaneously detect the following heavy metal elements (Al, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, Li, Mg, Mn, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V and Zn).
Pig feed standard substance (GBW 10243).
1.2 instruments and devices
The instruments used for the tests were: an accurate temperature control electric heating digestion instrument (Nanjing Reneck DV4000), a numerical control high temperature electric furnace (TOPPER 31750A in the United states), an ultra-pure water machine (MERCK MILLIPORE Elix5+ Milli Q Element in Germany), an electronic balance (Japan island jin AYU220), a graphite digestion instrument (Guangzhou GDANA D-56) and a plasma mass spectrometer (ICP-MS) (Sammer flying X series II).
1.3 test methods
1.3.1 sample Pre-treatment
In order to determine the pretreatment conditions of the graphite digestion method, different digestion reagents, digestion temperatures and digestion times are respectively set for sample treatment research.
Accurately weighing 0.5g (accurate to 0.1mg) of sample, and respectively adding 8.0mL of HNO 3 ；②6.4mL HNO 3 +1.6mL H 2 O 2 ；③6.4mL HNO 3 +1.6mL HF (this procedure was performed in a fume hood) was used for graphite digestion. The mass concentration of hydrofluoric acid is 50%, and the mass concentration of nitric acid is 68%.
The specific digestion procedure was as follows: heating the temperature program for 15min to 120 ℃, and keeping the temperature for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 160, 180, 200 and 220 deg.C for 10min, respectively, and maintaining for 90, 120, 150 and 180 min.
After the digestion process is finished, adding 5mL of secondary water after cooling slightly, covering and keeping the temperature at 150 ℃ for heating for 10min, filtering again to fix the volume to 50mL, and shaking up to be tested. Each treatment was performed in parallel with 6 samples and a blank test was performed.
In the testing process, if the concentration of the sample exceeds the range of the standard curve, the high-concentration elements are correspondingly diluted, so that the concentration measurement value is continuously tested within the range covered by the standard curve, and the data accuracy is ensured.
1.3.2 preparation of Standard solution
Accurately sucking 1mL of a multi-element standard solution of 100 mu g/mL, metering the solution into a 10mL volumetric flask by using a 1% nitric acid solution, and shaking the solution uniformly for later use.
And transferring a proper amount of standard mixed solution into a 50mL volumetric flask to prepare standard working solution with the mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L.
1.3.4 measurement of sample solution
And sequentially sucking the digestion solution obtained by the pretreatment and the standard working solution into a plasma mass spectrometer, measuring the signal response values of the element to be detected and the internal standard element, measuring each solution for more than two times, and obtaining the concentration of the element to be detected in the test solution by using a standard curve.
1.4 data processing
Microsoft Office Excel 2010 was used to process the data and tabulate. The data used were all 6 replicates.
Of the test specimenThe content (X) of the element to be detected can be calculated by the following formula, and the unit of the result is mg.L -1 ：
Wherein C is the concentration of the sample solution (mg. L) read from the calibration curve - 1)；C 0 To read the concentration of the blank solution (mg. L) from the standard curve -1 ) (ii) a V is a constant volume (mL); m is the mass (g) of the sample; d is the dilution factor.
Recovery (%) (value determined by adding standard sample-value determined by sample)/standard addition × 100.
The pipetting rate of the instrument was ensured to be constant during the test.
2 results and analysis
2.1 determination of pretreatment conditions
In order to determine the pretreatment conditions of the graphite digestion method, different conditions were designed for the study, and 6 replicates were set for each sample.
2.1.1 Effect of digestion reagents on assay results
Different digestion reagent combinations were added to study the effect on assay results.
As can be seen from Table 1, the digestion result of the combination of the reagents is better, the digestion solution is transparent, the complete digestion is shown, and the detection result is in the range of the standard substance. When the digestion reagents are selected and combined, the experimental effects of the digestion reagents are similar to those of the digestion reagents, the digestion solutions are turbid, black residues are scattered in the pipes, the digestion is not complete, the parallelism of the samples is poor, and the detection result is obviously lower than that of the combination of the reagent and the detection result, so that the combination of the reagent and the detection result can be selected: 6.4mL HNO 3 +1.6mL of HF as digestion reagent for the feed.
TABLE 1 measurement results of different digestion reagents
2.1.2 Effect of digestion ceiling temperature on assay results
In order to study the influence of the digestion maximum temperature on the element content, the digestion maximum temperature of the sample is set to be 160 ℃, 180 ℃, 200 ℃ and 220 ℃, and the test results are shown in table 2.
TABLE 2 measurement results of different digestion maximum temperatures
As can be seen from Table 2, when the maximum digestion temperature of the sample was set at 160 ℃, the contents were lower than the standard values, and the digestion solutions were all turbid, indicating that digestion was incomplete. When set at 220 ℃, it was found that a part of the digestion solution in the sample tube was completely volatilized, resulting in failure of the experiment. When the temperature is set to be 180 ℃ and 200 ℃, the digestion effects of the two are similar, the digestion solutions are transparent, the digestion is complete, the detection result is within the range of the standard substance, the sample parallelism is good, and the RSD is within 10%. In view of equipment maintenance, it is appropriate to set the temperature to 180 ℃.
2.1.3 Effect of digestion time on assay results
In order to study the influence of the digestion maximum temperature time on the element content, the sample digestion maximum temperature holding time is respectively set to be 90 min, 120min, 150min and 180min, and the test results are shown in table 3.
TABLE 3 measurement results of various maximum temperature times
As can be seen from Table 3, when the maximum digestion temperature retention time of the sample was set to 90 and 120min, the element content was significantly lower than the standard value. When the highest digestion temperature is kept for 150min and 180min, the digestion effects of the two solutions are similar, the digestion solutions are transparent, the detection results are within the range of standard substances, the result parallelism is good, and the RSD is within 10%. In view of improving the digestion efficiency, it is preferable to set the time to 150 min.
Through the above tests, the digestion conditions of the graphite digestion method can be determined as follows: at 6.4mLHNO 3 And 1.6mLHF isAnd (4) decomposing the reagent, raising the temperature by a program, keeping the temperature for 150min when the highest digestion temperature reaches 180 ℃.
2.2 interference of ICP-MS
In the sample analysis process, the main interference of errors generated by the instrument is mass spectrum interference, and the interference caused by mass spectrum peak superposition and polyatomic composite ions in the mass spectrum interference is large. The mass spectrum interference can be effectively reduced by adjusting the resolution of the instrument and selecting the isotope of the measuring element. Collision reactions can also be used to eliminate different forms of interference. During measurement, 52Sc, 103Rh and 185Re elements are selected as internal standard elements.
2.3 Linear equation and correlation coefficient
And (3) obtaining a linear equation and a correlation coefficient of the digestion method, wherein the method has a good linear relation in a curve range of 0.00-200 mug/L, and the linear correlation coefficient is more than 0.999, which shows that the methods all meet the detection requirements, and the table 4 shows.
TABLE 4 Linear equation and correlation coefficient
2.4 detection Limit
And (3) respectively measuring 11 blank solutions processed by the digestion mode according to the selected optimal instrument parameters, taking 11 measurement results, and calculating a blank standard deviation(s) to obtain a detection limit (3s) of the method. From the results, it can be seen that the detection limit is far lower than the limit value level of metals in the feed sample, which indicates that the method is suitable for the determination of lead, cadmium, copper, chromium and nickel in the feed, and the results are shown in table 5.
TABLE 5 detection limits
2.5 accuracy and precision
In order to verify the accuracy of the digestion process, the results are compared by using a standard substance of the GBW10243 concentrated pig feed developed by Beijing northern great institute of measurement and technology and a standard adding mode of an actual sample.
The digestion assay was repeated 6 times and the assay results are shown in table 6. The experimental results obtained by processing are all within the uncertainty interval of the standard substance mark of the pig feed, and meet the relevant requirements of accuracy.
TABLE 6 measurement results of standard substances
And (3) performing a standard addition experiment, calculating the precision of the method, measuring that the recovery rate is 91.4-96.2%, and the RSD value is less than 10%, so that the method has better stability, meets the related requirements of the recovery rate, can be used as a method for detecting the metal content in the feed, and has the results shown in table 7.
TABLE 7 recovery and precision (n ═ 6)
2.6 comparison of the operating procedures of the different digestion methods
The analysis compares the operation processes of the graphite digestion method and the dry ashing method, and the operation processes are shown in the table 8.
The dry ashing method needs a muffle furnace and an electric heating plate, the sample weighing is large, the acid consumption is small, but the operation process is complicated, the time consumption is long, the power consumption is large, the sample amount processed in a single time is small, the pollution is easy to cause and the like, and because the acid is added on the electric heating plate for digestion, the dry ashing method needs personnel to keep guard all the time to prevent evaporation, and the working efficiency is low.
The wet digestion method adopts a microwave digestion instrument and an electric heating plate which are matched for use, feed is digested by a perchloric acid-nitric acid system, the perchloric acid shows strong oxidizing property under the condition of high temperature, but the wet digestion belongs to open digestion and high temperature digestion, so that loss of elements to be detected and pollution of exogenous substances are easily caused, and the method also needs to have richer experimental operation experience when being operated.
The digestion method of the nitric acid-hydrofluoric acid system graphite instrument established by the invention has the advantages of low cost, short digestion time, greatly increased experimental efficiency and easier popularization. The sample is heated uniformly in the digestion process, and the digestion and acid dispelling processes can be automatically completed without the need of keeping on by personnel, so that the single-time treatment of the sample has considerable volume, and the method is suitable for analysis and test of large-batch samples.
TABLE 8 comparison of different digestion procedures
| Item | Dry ashing process | Graphite digestion method |
| Main equipment | Muffle furnace and electric heating plate | Graphite digestion instrument |
| Sample weighing/g | 0.1-5 | 0.1-1 |
| Reagent | Nitric acid, hydrochloric acid | Nitric acid, hydrofluoric acid |
| Reagent dosage/mL | 5 | 8 |
| Time for digestion/h | 10-12 | 4-5 |
| Per batch digestion quantity/quantity | 12 | 56 |
| Degree of contamination of sample | Is easy to be polluted | Small |
2.7 actual sample analysis
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to specific embodiments below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The first embodiment is as follows:
detecting elements of a pig concentrated feed standard substance (GBW 10243):
1) sample weighing
Accurately weighing 0.5g (to 0.1mg) sample with ten-thousandth balance
2) Sample digestion
6.4mL of HNO were added separately 3 +1.6mL HF (this process was done in a fume hood) and graphite digestion was performed.
The specific digestion procedure was as follows: heating the temperature program for 15min to 120 ℃, and keeping the temperature for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 180 deg.C for 10min, and maintaining for 150 min.
After the digestion process is finished, adding 5mL of secondary water after cooling slightly, covering and keeping the temperature at 150 ℃ for heating for 10min, filtering again to fix the volume to 50mL, and shaking up to be tested. Each treatment was performed in parallel with 6 samples and a blank test was performed.
3) Preparation of Standard solution
Accurately sucking 1mL of 100 mu g/mL multielement standard solution, adding 1% nitric acid solution to a volumetric flask with a constant volume of 10mL, and shaking up for later use.
And transferring a proper amount of standard mixed solution into a 50mL volumetric flask to prepare standard working solution with the mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L.
4) Measurement of sample solution
And sequentially sucking the digestion solution obtained by the pretreatment and the standard working solution into a plasma mass spectrometer, measuring the signal response values of the element to be detected and the internal standard element, measuring each solution for more than two times, and obtaining the concentration of the element to be detected in the test solution by using a standard curve.
In the testing process, if the concentration of the sample exceeds the range of the standard curve, the high-concentration elements are correspondingly diluted, so that the concentration measurement value is continuously tested within the range covered by the standard curve, and the data accuracy is ensured.
Example two:
detecting the elements of a chicken concentrated feed standard substance (GBW 10244):
1) sample weighing
Accurately weighing 0.5g (to 0.1mg) sample with ten-thousandth balance
2) Sample digestion
6.4mL of HNO were added separately 3 +1.6mL HF (this process was done in a fume hood) and graphite digestion was performed.
The specific digestion procedure was as follows: heating the temperature program for 15min to 120 ℃, and keeping the temperature for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 180 deg.C for another 10min, and maintaining for 150 min.
After the digestion process is finished, adding 5mL of secondary water after cooling slightly, covering and keeping the temperature at 150 ℃ for heating for 10min, filtering again to fix the volume to 50mL, and shaking up to be tested. Each treatment was performed in parallel with 6 samples and a blank test was performed.
3) Preparation of standard solution
Accurately sucking 1mL of a multi-element standard solution of 100 mu g/mL, metering the solution into a 10mL volumetric flask by using a 1% nitric acid solution, and shaking the solution uniformly for later use.
And transferring a proper amount of standard mixed solution into a 50mL volumetric flask to prepare standard working solution with the mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L.
4) Measurement of sample solution
And (4) sequentially sucking the digestion solution and the standard working solution into a plasma mass spectrometer, measuring each solution for more than two times, and obtaining the concentration of the element to be measured in the test solution according to a standard curve.
In the testing process, if the concentration of the sample exceeds the range of the standard curve, the high-concentration elements are correspondingly diluted, so that the concentration measurement value is continuously tested within the range covered by the standard curve, and the data accuracy is ensured.
Example three:
detecting the elements of the shellfish compound feed sample:
1) sample weighing
Accurately weighing 0.5g (to 0.1mg) sample with ten-thousandth balance
2) Sample digestion
6.4mL of HNO were added separately 3 +1.6mL HF (this procedure was performed in a fume hood) was used for graphite digestion.
The specific digestion procedure was as follows: heating the temperature program for 15min to 120 ℃, and keeping the temperature for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 180 deg.C for another 10min, and maintaining for 150 min.
After the digestion process is finished, adding 5mL of secondary water after cooling slightly, covering and keeping the temperature at 150 ℃ for heating for 10min, filtering again to fix the volume to 50mL, and shaking up to be tested. Each treatment was performed in parallel with 6 samples and a blank test was performed.
3) Preparation of standard solution
Accurately sucking 1mL of a multi-element standard solution of 100 mu g/mL, metering the solution into a 10mL volumetric flask by using a 1% nitric acid solution, and shaking the solution uniformly for later use.
And transferring a proper amount of standard mixed solution into a 50mL volumetric flask to prepare standard working solution with the mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L.
4) Measurement of sample solution
And (4) sequentially sucking the digestion solution and the standard working solution into a plasma mass spectrometer, measuring each solution for more than two times, and obtaining the concentration of the element to be measured in the test solution according to a standard curve.
In the testing process, if the concentration of the sample exceeds the range of the standard curve, the high-concentration elements are correspondingly diluted, so that the concentration measurement value is continuously tested within the range covered by the standard curve, and the data accuracy is ensured.
Example four:
detecting elements of a pig compound feed sample:
1) sample weighing
Accurately weighing 0.5g (to 0.1mg) sample with ten-thousandth balance
2) Sample digestion
6.4mL of HNO were added separately 3 +1.6mL HF (this procedure was performed in a fume hood) was used for graphite digestion.
The specific digestion procedure was as follows: heating the temperature program for 15min to 120 ℃, and keeping the temperature for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 180 deg.C for 10min, and maintaining for 150 min.
And (4) ending the digestion program, adding 5mL of secondary water after slight cooling, covering and keeping the temperature at 150 ℃ for heating for 10min, filtering to fix the volume to 50mL, and shaking up to be tested. Each treatment was performed in parallel with 6 samples and a blank test was performed.
3) Preparation of standard solution
Accurately sucking 1mL of a multi-element standard solution of 100 mu g/mL, metering the solution into a 10mL volumetric flask by using a 1% nitric acid solution, and shaking the solution uniformly for later use.
And transferring a proper amount of standard mixed solution into a 50mL volumetric flask to prepare standard working solution with the mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L.
4) Measurement of sample solution
And (4) sequentially sucking the digestion solution and the standard working solution into a plasma mass spectrometer, measuring each solution for more than two times, and obtaining the concentration of the element to be measured in the test solution according to a standard curve.
In the testing process, if the concentration of the sample exceeds the range of the standard curve, the high-concentration elements are correspondingly diluted, so that the concentration measurement value is continuously tested within the range covered by the standard curve, and the data accuracy is ensured.
In order to verify the detection accuracy of the method, a mature standard test method, namely a dry ashing method (the atomic absorption spectrometry for measuring the content of lead in the GB/T13080-2018 feed, the method for measuring the content of cadmium in the GB/T13082-:
TABLE 9 test results of the samples of the examples and the national standard method
TABLE 10 test results of the second sample of example and the national standard method
TABLE 11 test results of the three samples of the example and the national standard method
TABLE 12 test results of the four samples of the example and the national standard method
As can be seen from tables 9-12, the accuracy of the detection method is not inferior to that of the traditional national standard method, and the test results of the standard substance samples are within the allowable range of the standard value, which indicates that the detection method is feasible.
In conclusion, the digestion-plasma mass spectrometry method of the nitric acid-hydrofluoric acid system graphite instrument established by the invention is an ideal method for simultaneously analyzing and detecting various heavy metal elements in the feed. The graphite digestion instrument realizes the integration of digestion and acid dispelling, and can effectively reduce the harm of the reagent to the experimenters. Meanwhile, according to the time consumption for detection and the difficulty degree of the process, the invention realizes rapid detection and high-efficiency detection.
Determining digestion conditions of a graphite digestion method as follows: at 6.4mLHNO 3 And 1.6mLHF is used as a digestion reagent, the temperature is programmed to rise, the highest digestion temperature is up to 180 ℃, and the temperature is kept for 150 min.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (3)
1. A method for simultaneously determining the contents of various heavy metal elements in feed by graphite digestion-plasma mass spectrometer is characterized by comprising the following steps: comprises the following steps:
step 1: drying a feed sample to be detected, and then grinding and sieving to obtain sample powder;
step 2: mixing the sample powder with a digestion reagent, and then carrying out graphite digestion; the digestion reagent is a mixture of nitric acid and hydrofluoric acid;
and step 3: then adding secondary water, covering and keeping the temperature at 140 ℃ and 160 ℃, heating for 8-12min, filtering to obtain filtrate, fixing the volume of the filtrate to 50mL, and shaking up to obtain a sample to be detected;
and 4, step 4: preparing the multiple metal element standard solution into standard working solution with mass concentration of 0, 0.5, 1, 5, 10, 50, 100, 200, 400 and 600 mug/L;
and 5: and sequentially sucking the sample to be detected and the standard working solution into the plasma mass spectrometer, measuring the signal response values of the element to be detected and the internal standard element, and obtaining the concentration of the element to be detected in the test solution according to the standard curve.
2. The method for simultaneously determining the contents of multiple heavy metal elements in the feed by using the graphite digestion-plasma mass spectrometer as claimed in claim 1, wherein the method comprises the following steps: the volume ratio of the nitric acid to the hydrofluoric acid is as follows: 5-8: 1.
3. the method for simultaneously determining the contents of multiple heavy metal elements in the feed by using the graphite digestion-plasma mass spectrometer as claimed in claim 1, wherein the method comprises the following steps: the graphite digestion procedure was: heating for 15min to 120 ℃, and keeping for 1 h; keeping the temperature for 30min at 10min to 150 ℃; heating to 160, 180, 200 and 220 deg.C for 10min, respectively, and maintaining for 90, 120, 150 and 180 min.
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