Background
Cadmium and lead are heavy metals that people often come into contact with in their lives. GB2762-2022 (limit of pollutants in food safety national Standard food) clearly specifies that the limit of lead in milk and dairy products (raw milk, pasteurized milk, sterilized milk) is 0.02mg/L, and the limit of lead in milk and dairy products (prepared milk, fermented milk) is 0.04mg/L.
Currently, the method for measuring cadmium and lead in food mainly comprises large-scale instruments and equipment, for example: graphite Furnace Atomic Absorption Spectrometry (GFAAS), inductively coupled plasma mass spectrometry (ICP-MS) and the like, the detection result of the method is accurate, the stability is high, the reliability is strong, but the method has the problems that the whole flow is complicated, the operation of professionals with abundant experience is needed, expensive large-scale instruments and equipment are needed, the detection cost is high, and the method is difficult to popularize on a base layer in a large area.
The electrochemical method for detecting heavy metal content is based on electrochemical properties of substances and change rules thereof, and the change of electric signals is measured by utilizing parameters such as potential, conductivity, current, electric quantity and the like to analyze the heavy metal content in the to-be-detected object. Common methods include stripping voltammetry, polarography, and potentiometric stripping. The electrochemical test method has the advantages of small equipment, small sample consumption, simple operation, low cost and the like, and the electrochemical analysis system has the advantages of low requirements on user technology and operation environment and diversified modification materials, and in general, the electrochemical analysis method is very suitable for outdoor on-site analysis, can be widely applied to heavy metal detection in the fields of environmental monitoring, food industry, medicine and the like, and has good development prospect.
Patent application document with publication number CN110361438A, named as extraction technology of heavy metal lead in milk and dairy products and on-site rapid high-sensitivity detection method, discloses that the milk and dairy products are leached by acid in the first step, pH is regulated by alkali in the second step, prepared magnetic nano particles containing rich carboxyl are adopted, the magnetic nano particles are absorbed, vortex oscillation and uniform mixing are carried out, and standing is carried out until the magnetic nano particles are completely absorbed, and tube supernatant of a second centrifuge tube is removed; then dilute nitric acid is added, vortex oscillation is carried out fully, and then standing is carried out until the magnetic nano particles are completely adsorbed, clear liquid is taken to be detected, and the detection is carried out through a portable electrochemical heavy metal detector. However, the processing steps before detection in the technical scheme are complicated, and the magnetic nanoparticles are inconvenient to use and increase the cost when being analyzed outdoors on site.
The publication No. CN103592356B, chinese patent document entitled method for rapidly detecting lead and cadmium by adopting a scanning anode stripping voltammetry, discloses a mercury pre-plating method, wherein the rapid scanning anode stripping voltammetry is used as a basic principle of detection, a mercury membrane electrode conduction terminal is connected with an independently developed electrochemical workstation through a wire, and a data acquisition and processing system comprising the electrochemical workstation, a computer and a software system is used for detecting whether a sample to be detected contains lead and cadmium and the content of ultra trace lead and cadmium. However, high-concentration perchloric acid and nitric acid are needed to be added in pretreatment of the sample to be detected for microwave digestion for 20min, residual acid is needed to be removed after digestion, and the pretreatment time is long and potential safety hazards exist.
Therefore, it is necessary to provide a method for detecting heavy metal cadmium and lead, so as to solve the problems that the prior art has complicated steps and long pretreatment time, and can not quickly detect cadmium and lead in milk and dairy products on site.
Disclosure of Invention
In view of the above, the invention provides a method for simultaneously and rapidly detecting cadmium and lead in milk and dairy products, which realizes the rapid detection of high stability and low quantitative limit of cadmium and lead in milk and dairy products.
In order to achieve the above purpose, the invention provides a method for simultaneously and rapidly detecting cadmium and lead in milk and dairy products, which comprises the following steps:
(1) Sample pretreatment: sampling milk and dairy products, adding an extracting solution, and carrying out oscillation extraction to obtain a sample solution to be detected;
(2) Detecting a sample: immersing a disposable screen printing electrode in a working buffer solution, activating the electrode, adding the sample solution to be detected, and detecting by an anodic stripping voltammetry, wherein the working buffer solution is a mixed solution of 20-120ppm mercury standard solution, 0.001-0.010mol/L iodine chloride solution and 0.2-1.2mol/L ammonium acetate solution; the ink carbon-based material of the electrode is ACHESON carbon paste PR406.
According to the technical scheme provided by the invention, the working buffer solution is matched with the special ink carbon-based material, the mercury standard solution, the iodine chloride and the ammonium acetate solution are mixed, so that on one hand, the total amount of ions in the solution is increased, the conductivity is enhanced, and on the other hand, substances in the mixed solution are adsorbed on the ink carbon-based material on the surface of the electrode, so that the electrochemical activity of cadmium and lead is influenced while the surface of the electrode is protected, the cadmium and the lead generate more obvious response on the surface of the electrode, the sensitivity of the electrode to the cadmium and the lead is enhanced, and the stability of the detection method is ensured. The technical scheme provided by the invention has short extraction time, and can realize rapid detection by matching with a special working buffer solution and a carbon-based material of a working electrode.
Optionally, the disposable screen printing electrode comprises a PET bottom plate, and an auxiliary electrode, a working electrode and a reference electrode are sequentially arranged on the PET bottom plate, and the working electrode is square.
Optionally, the extracting solution comprises one or a combination of more than two of hydrochloric acid solution, nitric acid solution and sulfuric acid solution.
Optionally, the concentration of the extracting solution is 6-18%.
The extracting solution adopted by the technical scheme provided by the invention is low-concentration acid, so that the operation safety is higher, and acid removal after extraction is not needed.
Optionally, the volume ratio of the mass of the sample to the extract is 0.8-1:1g/ml.
Optionally, the ratio of the mass of the sample to the volume of the extraction solution is 1:1g/ml.
Optionally, the parameters extracted by oscillation include: 1000-1400 times/min, and oscillating for 1-5min.
Optionally, the parameters extracted by oscillation include: 1200 times/min, and oscillating for 3min.
Optionally, the detection parameters are deposition potential-1.3V, deposition time 240s, scanning initial potential-0.9V, termination potential-0.5V, potential increment 0.004V, amplitude 0.025V and frequency 25Hz.
Optionally, the method comprises the following steps: (1) sample pretreatment: sampling milk and dairy products, adding 10% hydrochloric acid solution, oscillating at 1200 times/min, and extracting for 3min to obtain sample liquid to be detected; (2) detecting a sample: immersing a disposable screen printing electrode in a mixed solution of 60ppm mercury standard solution, 0.005mol/L iodine chloride solution and 0.6mol/L ammonium acetate solution to activate the electrode, and adding the sample solution to be detected to detect, wherein the detection parameters are deposition potential-1.3V, deposition time 240s, scanning initial potential-0.9V, termination potential-0.5V, potential increment 0.004V, amplitude 0.025V and frequency 25Hz.
The technical scheme of the invention at least comprises the following beneficial effects:
According to the technical scheme provided by the invention, a special working buffer solution is adopted, so that a mercury standard solution, iodine chloride and ammonium acetate solution are mixed and are shared with ACHESON carbon paste PR406 ink carbon-based material, on one hand, the total amount of ions in the solution is increased, the conductivity is enhanced, and on the other hand, substances in the mixed solution are adsorbed on the ink carbon-based material on the surface of the electrode, so that the electrode surface is protected, meanwhile, the electrochemical activity of cadmium and lead is influenced, the cadmium and lead generate more obvious response on the electrode surface, the sensitivity of the electrode to the cadmium and the lead is enhanced, and the stability of a detection method is ensured. The technical scheme provided by the invention has the advantages that the extraction time is short, the use of additives such as magnetic nano particles and the treatment waiting time of the additives are not needed by matching with a special working buffer solution and a carbon-based material of a working electrode, the strong sensitivity can be realized, the detection result can be obtained quickly, and the high stability and the quantitative limit are as low as 0.010mg/L; the method is simple, quick and efficient, and is suitable for large-scale production and application on the base layer.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to fig. 1 to fig. 9 of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the invention.
In the invention, a plurality of kinds of milk and dairy products are selected as specific detection objects. The portable electrochemical heavy metal detector, the disposable screen printing electrode, the milk and dairy product samples used in the invention are provided by Wuhan Qianxing Jinjin technology Co., ltd, and are purchased from the under-flag brand of the commercial inner Mongolian cow milk industry (group) Co., ltd.
Wherein the concentration of the marked cadmium in the pure milk is as follows in sequence: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L; the concentration of the marked lead in the pure milk is as follows: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/.
The cadmium adding concentrations of the yoghourt and the chocolate milk are as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L; the concentration of the marked lead in the yoghurt and the chocolate milk is as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L.
Wherein the concentration of the marked cadmium in the soymilk is as follows in sequence: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L; the concentration of the marked lead in the soymilk is as follows: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L.
Wherein the concentration of the marked cadmium in the milk powder is as follows in sequence: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L; the concentration of the marked lead in the soymilk is as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L.
Other conventional reagents and equipment used in the present invention are commercially available unless otherwise specified.
Example 1
Sample pretreatment: 1.0g of pure milk is weighed, wherein the cadmium adding standard concentration is as follows in sequence: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L; the lead addition concentration is as follows in sequence: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L and 0.080mg/L, respectively placing the materials into a 10mL plastic cover centrifuge tube, adding 1mL10% hydrochloric acid solution, placing the solutions on an oscillator for oscillation extraction, wherein the oscillation frequency is 1200 times/min, and the extraction time is 3min; and after the extraction is finished, obtaining the sample liquid to be detected.
Detecting a sample: accurately transferring 800 mu L of a solution containing 60ppm of mercury standard solution, 0.005mol/L of iodine chloride and 0.6mol/L of ammonium acetate into a 700 sample cup by using a micropipette, inserting a disposable screen printing electrode (cadmium and lead) into an electrode plug, pressing the electrode plug to enable an electrode working area to be completely immersed in the solution, clicking a working button at the interface of a portable electrochemical heavy metal detector, activating the electrode, wherein the working electrode 3 is square, and a carbon-based material in the working electrode 3 is ACHESON carbon slurry PR406; after the activation is finished, 400 mu L of the pure milk sample liquid to be detected is added, a working button of an interface of a portable electrochemical heavy metal detector is clicked to detect, the portable electrochemical heavy metal detector adopts an electrochemical anode stripping voltammetry, and the parameters are set as follows: the corresponding redox current is recorded, the corresponding redox current is taken as an abscissa, the concentration value of cadmium or lead in pure milk serving as a standard sample is taken as an ordinate, and Excel is utilized to draw a standard working curve of cadmium and lead in the pure milk, so that fig. 2 and 3 are obtained.
According to the technical scheme provided by the invention, a special working buffer solution is adopted, so that a mercury standard solution, iodine chloride and ammonium acetate solution are mixed and are shared with ACHESON carbon paste PR406 ink carbon-based material, on one hand, the total amount of ions in the solution is increased, the conductivity is enhanced, and on the other hand, substances in the mixed solution are adsorbed on the ink carbon-based material on the surface of the electrode, so that the electrode surface is protected, meanwhile, the electrochemical activity of cadmium and lead is influenced, the cadmium and lead generate more obvious response on the electrode surface, the sensitivity of the electrode to the cadmium and the lead is enhanced, and the stability of a detection method is ensured. The technical scheme provided by the invention has the advantages that the extraction time is short, the use of additives such as magnetic nano particles and the like and the treatment waiting time of the additives are not needed by matching with a special working buffer solution and a carbon-based material of a working electrode, the high sensitivity can be realized, the detection result can be obtained quickly, and the high stability and the quantitative limit are as low as 0.010mg/L. The method is simple, quick and efficient, and is suitable for large-scale production and application on the base layer.
Example 2
Sample pretreatment: 1.0g of yoghourt is weighed, wherein the cadmium adding standard concentration is as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L; the lead addition concentration is as follows in sequence: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L, then respectively placing the materials into a 10mL plastic cover centrifuge tube, adding 1mL12% hydrochloric acid and nitric acid mixed solution, placing the solutions on an oscillator for oscillation extraction, wherein the oscillation frequency is 1000 times/min, and the extraction time is 5min; and after the extraction is finished, obtaining the sample liquid to be detected.
Detecting a sample: accurately transferring 800 mu L of a sample containing 100ppm of mercury standard solution, 0.008mol/L of iodine chloride solution and 1mol/L of ammonium acetate solution into a 700 sample cup by using a micropipette, inserting a disposable screen printing electrode (cadmium and lead) into an electrode plug, pressing the electrode plug to enable an electrode working area to be completely immersed in the solution, clicking a working button at the interface of a portable electrochemical heavy metal detector to activate the electrode, wherein the working electrode 3 is square, and a carbon-based material in the working electrode 3 is ACHESON carbon slurry PR406; after the activation is finished, 400 mu L of the yoghurt sample liquid to be detected is added, a working button of an interface of a portable electrochemical heavy metal detector is clicked to detect, the portable electrochemical heavy metal detector adopts an electrochemical anode stripping voltammetry, and the parameters are set as follows: the corresponding redox current is recorded, the corresponding redox current is taken as an abscissa, the concentration value of cadmium or lead in the standard yoghurt is taken as an ordinate, and Excel is utilized to draw a standard working curve of cadmium and lead in the yoghurt, so that fig. 4 and 5 are obtained.
Example 3
Sample pretreatment: 1.0g of chocolate milk is weighed, wherein the cadmium adding standard concentration is as follows in sequence: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L; the lead addition concentration is as follows in sequence: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L, then respectively placing the materials into a 10mL plastic continuous cover centrifuge tube, adding 1mL16% hydrochloric acid and sulfuric acid mixed solution, placing the solutions on an oscillator for oscillation extraction, wherein the oscillation frequency is 1400 times/min, and the extraction time is 5min; and after the extraction is finished, obtaining the sample liquid to be detected.
Detecting a sample: accurately transferring 800 mu L of a sample containing 120ppm of mercury standard solution, 0.01mol/L of iodine chloride solution and 1.2mol/L of ammonium acetate solution into a 700 sample cup by using a micropipette, inserting a disposable screen printing electrode (cadmium and lead) into an electrode plug, pressing the electrode plug to enable an electrode working area to be completely immersed in the solution, clicking a working button at the interface of a portable electrochemical heavy metal detector to activate the electrode, wherein the working electrode 3 is square, and a carbon-based material in the working electrode 3 is ACHESON carbon slurry PR406; after the activation is finished, 400 mu L of the sample liquid to be tested of the chocolate milk is added, a working button of an interface of a portable electrochemical heavy metal detector is clicked to detect, the portable electrochemical heavy metal detector adopts an electrochemical anode stripping voltammetry, and the parameters are set as follows: the corresponding redox current is recorded, the corresponding redox current is taken as an abscissa, the concentration value of cadmium or lead in chocolate milk is taken as an ordinate, and the Excel is utilized to draw a standard working curve of cadmium and lead in chocolate milk, so that fig. 6 and 7 are obtained.
Example 4
The only difference compared to example 1 is that the sample was soymilk with the following marked cadmium concentrations in order: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L; the concentration of the marked lead in the soymilk is as follows: 0.005mg/L, 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L.
Example 5
The only difference compared with example 2 is that the sample is milk powder with the concentration of cadmium marked in sequence as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L; the concentration of the marked lead in the soymilk is as follows: 0.010mg/L, 0.020mg/L, 0.040mg/L, 0.080mg/L and 0.160mg/L.
Example 6
The difference compared to example 1 is that the sample was pure milk only with cadmium and lead addition levels of 0.02mg/L, respectively.
Comparative example 1
The difference from example 6 is only that the working electrode 3 is rectangular in shape.
Comparative example 2
The only difference compared to example 6 is that the working electrode 3 is circular in shape.
Comparative example 3
The only difference compared to example 6 is that the working electrode 3 is elliptical in shape.
Comparative example 4
The only difference compared to example 6 is that the carbon-based material of the working electrode 3 is the broadleaf set GC-810-1.
Comparative example 5
The only difference compared to example 6 is that the carbon-based material of the working electrode 3 is edike C-1011-6.
Comparative example 6
The only difference compared to example 6 is that the carbon-based material of the working electrode 3 is emei CI-2018.
Comparative example 7
The only difference compared to example 6 is that the carbon-based material of the working electrode 3 is Morita Capiton-CI.
Comparative example 8
The only difference compared to example 6 is that the carbon-based material of the working electrode 3 is ten CH-8MOD2 in japan.
The effect of each cadmium and lead current signal was determined by performing 7 replicates of comparative examples 1-8, respectively, for example 6, and the data are shown in tables 1, 8, 9.
TABLE 1 cadmium and lead current signals for example 6 and comparative examples 1-8
As is clear from table 1 and fig. 8, the difference between example 6 and comparative examples 1 to 3 is that the shape of the working electrode 3 is different, the square working electrode is used in example 6, the coefficient of variation of the influence on the cadmium current signal is 6.3%, the coefficient of variation of the influence on the lead current signal is 4.9%, but the rectangular working electrode, the circular working electrode and the elliptical working electrode are respectively used in comparative examples 1 to 3, the coefficients of variation of the influence on the cadmium current signal are respectively 10.4%, 12%, 12.2%, and the coefficient of variation of the influence on the cadmium current signal is more than 6.3% and is nearly doubled; the coefficients of variation affecting the lead current signal were 9.4%, 11.8% and 13.3%, respectively, and exceeded the coefficient of variation of example 6 by 4.9% by a factor of two. The square working electrode is helpful to reduce the cadmium current signal and the influence of the lead current signal, and has positive effect on improving the detection stability of the working electrode to cadmium and lead.
As can be seen from Table 1 and FIG. 9, the difference between the working electrode 3 and the carbon-based material of example 6 and comparative example 4-8 is that the carbon-based material of example 6 was ACHESON carbon paste PR406, the coefficient of variation of the effect on the cadmium current signal was 6.3%, the coefficient of variation of the effect on the lead current signal was 4.9%, but the coefficients of variation of the effect on the cadmium current signal were 10.2%, 13.7%, 8.4%, 11% and 10% which were far greater than the coefficient of variation of 6.3 in example 6, respectively, using Guangyi GC-810-1, edic C-1011-6, emei CI-2018, morita Capiton-CI and Japanese ten CH-8MOD 2; the coefficients of variation on the lead current signal effect were 9.2%, 12.7%, 10.5%, 12.4% and 9.7%, respectively, and the coefficients of variation were far greater than the coefficient of variation of 4.9% of example 6, demonstrating that carbon-based material ACHESON carbon paste PR406 greatly helps to improve the detection sensitivity and stability of the working electrode for detecting lead and cadmium.
As can be seen from table 1, fig. 8 and fig. 9, the coefficient of variation of the influence of example 6 on the cadmium current signal is 6.3%, and the coefficient of variation of the influence on the lead current signal is 4.9%; the coefficient of variation of the influence of comparative example 4 on the cadmium current signal is 10.2%, and the coefficient of variation of the influence on the lead current signal is 9.2%; the coefficient of variation of the influence of comparative example 6 on the cadmium current signal is 8.4%, and the coefficient of variation of the influence on the lead current signal is 10.5%; from comparison of comparative example 4 and comparative example 6, the difference between them is only that the carbon-based material is different, and it is understood that the cadmium current signal effect is reduced but the lead current signal effect is increased when the carbon-based material is changed from the broad-set GC-810-1 to the exemestane CI-2018. Therefore, the current signal influence of different carbon-based materials on cadmium and lead is not consistent, each carbon-based material has certain characteristics, and the carbon-based material ACHESON carbon paste PR406 selected by the invention has synergistic effect with the working buffer solution, the shape of the working electrode and various parameters, so that the influence on the cadmium and lead current signals can be reduced simultaneously.
As can be seen from fig. 2-7, the correlation R2 in the detection standard curves of pure milk, yoghurt and chocolate milk provided by the technical scheme of the invention is above 0.999, and the stability is strong.
Verification experiment
According to the technical scheme, pure milk (6 parts of each concentration) with the mixed standard concentration of cadmium and lead of 0.010mg/L, 0.020mg/L and 0.040mg/L is respectively added; the method comprises the steps of respectively adding yoghourt and chocolate milk with the mixed standard concentration of cadmium and lead of 0.020mg/L, 0.040mg/L and 0.080mg/L, wherein each concentration of each sample is 6 parts; each operating according to the detection method of the embodiment 1, and reading and recording the detection result of the instrument; pure milk (6 parts per concentration) with mixed standard concentration of 0.010mg/L, 0.020mg/L and 0.040mg/L of added cadmium and lead, yoghurt with mixed standard concentration of 0.020mg/L, 0.040mg/L and 0.080mg/L of added cadmium and lead and chocolate milk (6 parts per concentration of each sample) are detected by a graphite oven atomic absorption spectrometry, the method for detecting cadmium by GFAAS is referred to GB5009.15-2023 "determination of cadmium in food safety national standard food", the method for detecting lead is referred to GB5009.12-2023 "determination of lead in food safety national standard food", and corresponding detection results are recorded, and specific detection results are shown in Table 2.
TABLE 2 comparison of electrochemical rapid quantification method and atomic absorption spectrometry of graphite furnace
As can be seen from the results shown in Table 2, the method for rapidly detecting cadmium and lead in milk and dairy products provided by the invention has the detection result basically similar to the GFAAS detection result, the recovery rate is within 100-108%, the average relative standard deviation of cadmium detection in pure milk is less than or equal to 7.6%, the average relative standard deviation of cadmium detection in pure milk is less than or equal to 3.3%, the average relative standard deviation of lead detection is less than or equal to 6.2%, and the average relative standard deviation of lead detection in pure milk is less than or equal to 2%; the average relative standard deviation of cadmium detection in the yoghurt is less than or equal to 5.1 percent, can reach less than or equal to 2.1 percent, and the average relative standard deviation of lead detection is less than or equal to 4.8 percent, can reach less than or equal to 2.7 percent; the average relative standard deviation of cadmium detection in chocolate milk is less than or equal to 6 percent, can be less than or equal to 3 percent, and the average relative standard deviation of lead detection is less than or equal to 5.6 percent, can be less than or equal to 3.1 percent, so the method for rapidly and simultaneously detecting cadmium and lead in milk and dairy products provided by the invention meets the requirement of rapidly and quantitatively detecting cadmium and lead on site.
Quantitative limit experiment of cadmium and lead in milk and milk products
Repeating the test for 10 blank pure milk, yoghurt and chocolate milk samples by adopting the parameter method in the embodiment 1, taking 3 times of the standard deviation of the cadmium current signal value multiplied by the slope of the pure milk or yoghurt or chocolate milk cadmium standard curve as a cadmium detection Limit (LOD) and 10 times as a cadmium quantitative Limit (LOQ); the lead detection Limit (LOD) is 3 times of the standard deviation of the lead current signal value multiplied by the lead standard curve slope of pure milk or yoghurt or chocolate milk, and the lead quantification Limit (LOQ) is 10 times. The specific result data are shown in Table 3.
TABLE 3 limit of cadmium and lead and ration in milk and milk products
As can be seen from the results in Table 3, the quantitative limits of cadmium and lead in pure milk are 0.008mg/L and 0.007mg/L, respectively; the quantitative limit of cadmium and lead in the yoghourt is 0.008mg/L and 0.008mg/L respectively; the quantitative limits of cadmium and lead in chocolate milk are respectively 0.009mg/L and 0.009mg/L. The technical scheme provided by the invention can be used for detecting and quantifying cadmium and lead in milk and milk products to be less than 0.010 mg/L.
The foregoing is a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.