CN117269295A - Method for detecting calcium content in emulsion - Google Patents
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- CN117269295A CN117269295A CN202311273273.9A CN202311273273A CN117269295A CN 117269295 A CN117269295 A CN 117269295A CN 202311273273 A CN202311273273 A CN 202311273273A CN 117269295 A CN117269295 A CN 117269295A
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- 239000000839 emulsion Substances 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 39
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910052791 calcium Inorganic materials 0.000 title claims abstract description 38
- 239000011575 calcium Substances 0.000 title claims abstract description 38
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 46
- 238000009616 inductively coupled plasma Methods 0.000 claims abstract description 11
- 239000011259 mixed solution Substances 0.000 claims description 8
- 235000020247 cow milk Nutrition 0.000 claims description 5
- 238000001514 detection method Methods 0.000 abstract description 44
- 238000000120 microwave digestion Methods 0.000 abstract description 14
- 239000002253 acid Substances 0.000 abstract description 11
- 230000029087 digestion Effects 0.000 abstract description 11
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 abstract description 7
- 238000004186 food analysis Methods 0.000 abstract description 2
- 229960005069 calcium Drugs 0.000 description 29
- 239000000523 sample Substances 0.000 description 29
- 235000013336 milk Nutrition 0.000 description 25
- 210000004080 milk Anatomy 0.000 description 25
- 239000008267 milk Substances 0.000 description 24
- 238000011084 recovery Methods 0.000 description 18
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 15
- 229910001424 calcium ion Inorganic materials 0.000 description 11
- 239000012086 standard solution Substances 0.000 description 9
- 239000000126 substance Substances 0.000 description 6
- 239000012895 dilution Substances 0.000 description 5
- 238000010790 dilution Methods 0.000 description 5
- 229910021645 metal ion Inorganic materials 0.000 description 5
- 239000007788 liquid Substances 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000003908 quality control method Methods 0.000 description 3
- 229910052706 scandium Inorganic materials 0.000 description 3
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000004448 titration Methods 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 2
- 238000004993 emission spectroscopy Methods 0.000 description 2
- 238000000705 flame atomic absorption spectrometry Methods 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 2
- 238000010813 internal standard method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- MKJXYGKVIBWPFZ-UHFFFAOYSA-L calcium lactate Chemical compound [Ca+2].CC(O)C([O-])=O.CC(O)C([O-])=O MKJXYGKVIBWPFZ-UHFFFAOYSA-L 0.000 description 1
- 229960002401 calcium lactate Drugs 0.000 description 1
- 239000001527 calcium lactate Substances 0.000 description 1
- 235000011086 calcium lactate Nutrition 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000012470 diluted sample Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010812 external standard method Methods 0.000 description 1
- 235000020604 functional milk Nutrition 0.000 description 1
- 235000020251 goat milk Nutrition 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/626—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using heat to ionise a gas
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
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- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention belongs to the technical field of food analysis, and particularly relates to a method for detecting calcium content in emulsion. The detection method comprises the following steps: (1) Mixing the emulsion with nitric acid to obtain a sample to be detected, wherein the concentration of the emulsion in the sample to be detected is 1g/1000mL; (2) And detecting the sample to be detected by using an inductively coupled plasma mass spectrometer. Compared with an inductively coupled plasma mass spectrometry detection method based on a microwave digestion method and a pressure tank digestion method, the detection method omits the steps of microwave digestion or pressure tank digestion, shortens the whole time by about 2 hours, and is simpler and more convenient to operate and less in acid consumption; and the detection accuracy is not affected.
Description
Technical Field
The invention belongs to the technical field of food analysis, and particularly relates to a method for detecting calcium content in emulsion.
Background
Calcium is a necessary nutrient element for human body, the emulsion is one of important ways for obtaining calcium source, and the calcium in the emulsion is natural calcium which is easy to absorb, for example, the absorption rate of the calcium in fresh milk by human body is as high as 70%, which is far higher than that of other common calcium sources, 2.15 times of calcium carbonate, 1.75 times of calcium lactate and 5.5 times of shell calcium, so the calcium content is one of important indexes for evaluating the quality of the emulsion.
At present, four detection methods are described in the detection standard of calcium GB 5009.92-2016: (1) flame atomic absorption spectrometry, (2) EDTA titration, (3) inductively coupled plasma emission spectrometry, and (4) inductively coupled plasma mass spectrometry. The EDTA titration method is a chemical titration method for judging an endpoint by utilizing color, and has larger error and is rarely adopted; flame atomic absorption spectrometry, inductively coupled plasma emission spectrometry, and inductively coupled plasma mass spectrometry are currently relatively common methods, particularly inductively coupled plasma mass spectrometry with higher accuracy.
The inductively coupled plasma mass spectrometry French standard GB5009.268-2016 specifies that pretreatment is required for a detection sample, the pretreatment method comprises a microwave digestion method and a pressure tank digestion method, and the microwave digestion method and the pressure tank digestion method both require longer digestion time, so that the detection time is longer, operation steps are added, and the efficiency is not high when the sample is sent for detection in case of emergency; in addition, the microwave digestion can also lead nitric acid to form acid gas, and pollute the air.
Therefore, it is necessary to develop a method for detecting calcium content in emulsion which is simple to operate, free from air pollution and short in detection time.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a method for detecting the calcium content in emulsion, which is characterized in that nitric acid is directly used for mixing with emulsion samples, and then detection is carried out based on inductively coupled plasma mass spectrometry, so that the detection time can be shortened to a great extent, the operation is simple and the acid consumption is small.
In order to achieve the above purpose, the present invention may adopt the following technical scheme:
in one aspect, the invention provides a method for detecting calcium content in an emulsion, comprising the following steps: (1) Mixing the emulsion with nitric acid to obtain a sample to be detected, wherein the concentration of the emulsion in the sample to be detected is less than or equal to 1g/1000mL; (2) And (3) detecting the sample to be detected in the step (1) by using an inductively coupled plasma mass spectrometer.
Preferably, the emulsion may be cow's milk.
Preferably, in the step (1), it may include: mixing the emulsion and nitric acid to a constant volume of 1g/100mL, and shaking to obtain a mixed solution; and then mixing the mixed solution with nitric acid to a constant volume of 1mL/10mL, and shaking to obtain a sample to be detected.
More preferably, the shaking is performed using a vortex oscillator.
Preferably, in the step (1), the mass fraction of the nitric acid may be 2% -8%.
More preferably, in the step (1), the mass fraction of the nitric acid may be 5%.
The beneficial effects of the invention at least comprise: compared with an inductively coupled plasma mass spectrometry detection method based on a microwave digestion method and a pressure tank digestion method, the detection method provided by the invention has the advantages that steps of microwave digestion or pressure tank digestion are saved, the whole time is shortened by about 2 hours, the operation is simpler and more convenient, and the acid consumption is reduced; and the detection accuracy is not affected.
Detailed Description
The examples are presented for better illustration of the invention, but the invention is not limited to the examples. Those skilled in the art will appreciate that various modifications and adaptations of the embodiments described above are possible in light of the above teachings and are intended to be within the scope of the invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. Unless the context clearly differs, singular forms of expression include plural forms of expression. As used herein, it is understood that terms such as "comprising," "having," "including," and the like are intended to indicate the presence of features, numbers, operations, materials, or combinations. The terms of the present invention are disclosed in the specification and are not intended to exclude the possibility that one or more other features, numbers, operations, materials or combinations thereof may be present or may be added. As used herein, "/" may be interpreted as "and" or "as appropriate.
The embodiment of the invention provides a method for detecting the content of calcium in emulsion, which comprises the following steps: (1) Mixing the emulsion with nitric acid to obtain a sample to be detected, wherein the concentration of the emulsion in the sample to be detected is less than or equal to 1g/1000mL; (2) And (3) detecting the sample to be detected in the step (1) by using an inductively coupled plasma mass spectrometer.
In the present invention, "1g/1000mL" means 1g of emulsion in 1000mL, but the present invention is not limited to this unit limitation, and the mass and volume may be converted according to international units; such as 1mg/1mL or 1kg/1L, etc.
In the invention, the inductively coupled plasma mass spectrometer is used for measuring the calcium ions in the emulsion, so that the calcium elements in the emulsion can be converted into the calcium ions through inductively coupled plasma, and then the calcium ions are detected; in the prior art, the purpose of pretreatment by digestion with microwaves or a pressure tank is to convert calcium element in the emulsion into calcium ions and digest organic matters in the emulsion so as to prevent the pollution and damage of the emulsion to instruments; according to the invention, through the steps of reducing microwave or pressure tank digestion, and using nitric acid to directly fix the volume of the emulsion to the concentration less than or equal to 1g/1000mL, then performing on-machine detection, so that the detection value of calcium ions is in a standard curve based on an inductively coupled plasma mass spectrometer measurement method, (the calcium content in milk is about 90 mg/hundred grams to 120 mg/hundred grams, the standard range is 0.4 mg/L to 20 mg/L according to GB5009.268-2016, and the maximum concentration of the standard curve is 0.5 mg/L according to PE instrument manufacturer), and more importantly, through long-term practice, the invention does not accelerate the pollution and damage of an instrument, thereby influencing the detection accuracy value (the early communication with the instrument manufacturer indicates that the instrument is not greatly influenced by damaging the instrument so as to influence the detection accuracy). Based on the method, compared with a detection method based on microwave or pressure tank digestion, the method provided by the invention has the advantages that the time is saved, the operation is simpler and more convenient, the detection efficiency is greatly improved, and especially the aging problem of samples needing urgent detection and the detection pressure of samples which are not concentrated in multiple batches are solved.
It should be noted that the purpose of directly fixing the volume of the emulsion to the concentration less than or equal to 1g/1000mL is to prevent the organic matters in the emulsion from polluting and damaging the instrument, and meanwhile, the concentration of calcium ions is within a standard curve, so that the detection accuracy is high; when the concentration of other metal ions is less than or equal to 1 per mill, the metal ions fall near the zero point of the standard curve infinitely, and the accuracy of the result is not ensured in consideration of detection errors; therefore, not all metal ions are suitable for the invention, and if other metal ions want to have detection values above the standard curve, the concentration of the emulsion needs to be increased, but if the concentration of the emulsion is more than 1g/1000mL, the instrument is polluted to influence the detection accuracy. Therefore, the method is only suitable for detecting calcium ions in the emulsion.
In the detection method of the present invention, nitric acid is used, but the detection method is not heated, and no acid gas is generated to pollute the air; and the acid recovery after the nitric acid is used is lower in cost than the tail gas treatment after the acid gas is generated.
In some embodiments, the concentration of the emulsion in the sample to be tested may preferably be 1g/1000mL. At this concentration, the detection accuracy is higher and the instrument is not damaged.
In some embodiments, the emulsion may be goat milk or cow milk, especially cow milk, which may be fresh cow milk or uniform composite milk.
Since the detection object in the present invention is required to be in a uniform liquid state, the solid product is not suitable for this method, and is difficult to dissolve sufficiently because of the high dilution factor.
It should be further noted that, the content of calcium ions in the diluted sample of the solution to be tested should be higher than the lowest point of the standard curve by 0.1mg/kg and not higher than the highest point of the standard curve by 0.5mg/kg, so that the concentration of the diluted emulsion is preferably between 0.1g/1000mL and 1g/1000mL, and the content of calcium ions in the diluted emulsion is above the standard curve of calcium ions. In addition, for functional milk, conversion can be performed according to the milk ratio, and then the multiple of the dilution of the emulsion is selected.
In some embodiments, in the step (1), the method includes: mixing the emulsion and nitric acid to a constant volume of 1g/100mL, and shaking to obtain a mixed solution; and then mixing the mixed solution with nitric acid to a constant volume of 1mL/10mL, and shaking to obtain a sample to be detected.
The sample to be detected can be emulsion and nitric acid with a constant volume of 1g/1000mL at a time, or can be repeatedly constant volume of 1g/1000mL, such as twice constant volume of 1g/1000mL. Specifically, in order to prevent the dilution multiple from being too high, the primary volume metering is inaccurate, the volume metering can be carried out for a plurality of times, preferably twice, after the volume metering is carried out for twice, the sample to be detected with relatively accurate concentration can be basically obtained, the volume metering times are too many, the emulsion is easy to lose, and the operation time is prolonged.
It is to be noted that mixing the emulsion and nitric acid to a constant volume of 1g/100mL means that 1g of the emulsion is added with nitric acid to 100mL, and so on, the unit is not limited, and only the unit conversion accords with the international standard; mixing the mixed solution and nitric acid to a constant volume of 1mL/10mL means that the mixed solution of 1mL and nitric acid are added to a constant volume of 10mL, and the like, and the unit is not limited, so long as the unit conversion accords with the international standard.
In some embodiments, in step (1) above, the shaking is performed using a vortex oscillator. In the present invention, since the dilution ratio is high, the shaking is required to be uniform, and the shaking effect by using the vortex oscillator is better than that by using other shaking devices, the shaking speed is preferably 1000RPM, the shaking time is preferably 10 minutes, and the emulsion and the nitric acid can be uniformly mixed in the shortest time under the shaking parameters.
In some embodiments, in the step (1), the mass fraction of the nitric acid may be 2% -8%. It should be noted that the mass fraction of nitric acid has a certain influence on the detection accuracy, preferably 2% -8%, more preferably 5%, and when the concentration is 5%, the standard adding recovery rate is closest to 100%, and the accuracy is highest.
For a better understanding of the present invention, the content of the present invention is further elucidated below in connection with the specific examples, but the content of the present invention is not limited to the examples below.
In the embodiment of the invention, the standard adding recovery rate requirement of the GB/T27404-2008 laboratory quality control specification on the sample is specifically specified as shown in the following table 1.
Table 1 GB/T27404-2008 laboratory quality control Specification requirements for sample addition recovery
| Content of measured component mg/kg | Recovery range% |
| ＞100 | 95-105 |
| 1-100 | 90-110 |
| 0.1-1 | 80-110 |
| ＜0.1 | 60-120 |
In the embodiment of the invention, the relation between absolute difference values and arithmetic average values of two independent detection results specified in GB5009.268-2016 is specifically shown in the following table 2.
Table 2 GB5009.268-2016 provides a relationship between absolute difference and arithmetic average of two independent measurements
| Content of measured component mg/kg | Relative deviation% |
| ＞1 | ≤10 |
| 1-0.1 | ≤15 |
| ≤0.1 | ≤20 |
In the embodiment of the invention, the method for detecting the calcium content in the milk is carried out according to the following steps:
(1) Firstly, weighing 1.0+/-0.1 g of a milk liquid sample in a 100mL volumetric flask, and fixing the volume by nitric acid;
(2) Placing the volumetric flask after volume fixing on a vortex oscillator, and shaking at 1000RPM for 10min;
(3) Sucking 1mL of sample liquid in the volumetric flask after shaking by a pipetting gun into another 10mL volumetric flask, and fixing the volume by nitric acid;
(4) Placing the volumetric flask after the volume is fixed again on a vortex oscillator, and shaking at 1000RPM for 10min;
(5) And (3) directly detecting the liquid to be detected in the volumetric flask after the volume is determined again by using a platinum elmer inductively coupled plasma mass spectrometer.
1. Different nitric acid dissolution recovery rates
Kangmei nuclear flower milk (called Kangmei nuclear flower milk 7.3 for short) produced by Kangmei Dai of Chongqing, md.S. Limited, 2023, 7 and 5 days is detected according to the method for detecting the calcium content in the milk, and (3) respectively selecting 2%, 5% and 8% of nitric acid by mass fraction in the step (1) and the step (3), respectively treating the nitric acid, and detecting the nitric acid.
In addition, samples treated by 2%, 5% and 8% nitric acid are respectively parallel twice, and each sample is provided with an external standard recovery sample, namely, an external standard method is used for adding a standard; adding 50 mug of calcium standard solution into a labeled sample, and simultaneously treating the sample according to a microwave digestion method specified in GB5009.268-2016, wherein the sample is also two parallel samples and one labeled recovery sample; the standard solutions were prepared at concentrations of 0.1mg/kg, 0.2mg/kg, 0.3mg/kg, 0.4mg/kg and 0.5mg/kg, respectively, and the results of the measurements are shown in Table 3 below.
TABLE 3 detection of different mass fractions after nitric acid treatment
| Sample of | Calcium content (mg/kg) |
| Standard solution 1 | 0.10 |
| Standard solution 2 | 0.20 |
| Standard solution 3 | 0.32 |
| Standard solution 4 | 0.42 |
| Standard solution 5 | 0.49 |
| Blank space | 0.02 |
| Blank space | 0.01 |
| Kangmei nuclear flower milk 7.5+2% nitric acid | 352.63 |
| Kangmei nuclear flower milk 7.5+2% nitric acid | 348.60 |
| Kangmei nuclear flower milk 7.5+2% nitric acid+50 calcium | 398.19 |
| Kangmei nuclear flower milk 7.5+5% nitric acid | 356.25 |
| Kangmei nuclear flower milk 7.5+5% nitric acid | 350.80 |
| Kangmei nuclear flower milk 7.5+5% nitric acid+50 calcium | 405.16 |
| Kangmei nuclear flower milk 7.5+8% acid | 350.72 |
| Kangmei nuclear flower milk 7.5+8% acid | 346.80 |
| Kangmei nuclear flower milk 7.5+8% acid+50 calcium | 401.25 |
| Kangmei nuclear flower milk 7.5 (microwave digestion) | 357.23 |
| Kangmei nuclear flower milk 7.5 (microwave digestion) | 351.69 |
| Kangmei nuclear flower milk 7.5 (microwave digestion) +50 calcium | 403.23 |
Next, the average value and the standard recovery rate of each sample in Table 1 above were calculated as shown in Table 4 below.
TABLE 4 conditions of labeled recovery for samples of different nitric acid concentrations
As can be seen from Table 4 above, the absolute deviation (GB 5009.268-2016) and the standard recovery (GB/T27404-2008) of the four groups of samples tested both meet the standard specifications. Because the specified calcium content of the detected product is between 300mg/kg and 400mg/kg, four groups of results are satisfactory, so that the method for directly measuring the constant volume without pretreatment can be proved to be feasible, and the results are accurate. Meanwhile, the recovery rates of the four groups of results are compared, the national standard method of the second group (5% acid constant volume) and microwave digestion is closest to 100%, and the relative deviation meets the standard requirement. Therefore, a number of experiments were subsequently performed in the present invention using the mass fraction constant volume sample to verify the stability of the method.
2. Batch sample detection
37 samples (test samples 090316 to 090343) produced by Daiyou Co., ltd.2023, 3, 16 in Chongqing, are detected according to the method for detecting the calcium content in milk, wherein the nitric acid with the nitric acid mass fraction of 5% in the steps (1) and (3) is treated, and then the standard adding recovery rate is detected and calculated; and an internal standard method is adopted for verification (scandium element (45) with the atomic weight similar to that of calcium element (43) is used as an internal standard substance, the internal standard substance is provided by platinum Elmer company, the content is 10mg/L, 50 times of dilution is carried out on-machine detection, and the concentration of the internal standard substance is 0.2 mg/L), and the detection results are shown in the following table 5.
TABLE 5 batch test of different samples
From the above table 5, it can be known that the content of the internal standard substance is 0.2mg/L, the internal standard addition recovery rate of 37 samples is between 80% and 110%, the detection result meets the requirement of laboratory quality control standard in GB/T27404-2008 on the addition recovery rate of the samples, and the stability is good.
3. Detection of different metal ions
According to the method for detecting the calcium content in the milk, different milks (see table 1) are diluted to 1g/1000mL to obtain samples to be detected; and a mixed standard solution (containing scandium (Sc), germanium (Ge) and bismuth (Bi) internal standard) was prepared, and standard curves (0.005 mg/kg, 0.010mg/kg, 0.015mg/kg, 0.020mg/kg, 0.025 mg/kg) were obtained, while the sample to be tested and the mixed standard solution were examined on-machine, and the examination results are shown in table 6 below.
TABLE 6 recovery of different metals
As can be seen from Table 6, the recovery rates of Sc (scandium), ge (germanium) and Bi (bismuth) by the internal standard method are all over the range of 80% -110% specified in GB/T27404-2008 (the content of the internal standard substance is 0.2mg/L, and the recovery rate is controlled to be 80-110%), which indicates that the method of the invention using the direct volumetric method of nitric acid and then performing the detection is not suitable for the detection of lead, chromium, arsenic and mercury.
In addition, it should be noted that, according to the specification of GB5009.268-2016, microwave digestion is performed for a batch of samples with a simple digestion time of 50 minutes, taking into account data of temperature reduction and exhaust gas, it usually takes about 2.5 hours to complete from starting up to obtaining a sample to be detected, but only about 30 minutes is needed in the present invention, which can save about 2 hours, and the subsequent time for detection by the inductively coupled plasma mass spectrometer is consistent, so that the present invention can save about 2 hours compared with microwave digestion.
In summary, the detection method of the present invention is only suitable for detecting calcium ions in emulsion, and is not suitable for other metal elements. When detecting the calcium element, the method has the advantages of high accuracy, short detection time and simple operation, and has important significance for detecting the calcium content in emulsion, especially milk.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.
Claims (7)
1. A method for detecting the calcium content in an emulsion, comprising the steps of: (1) Mixing the emulsion with nitric acid to obtain a sample to be detected, wherein the concentration of the emulsion in the sample to be detected is less than or equal to 1g/1000mL; (2) And (3) detecting the sample to be detected in the step (1) by using an inductively coupled plasma mass spectrometer.
2. The method for detecting calcium content in an emulsion according to claim 1, wherein the emulsion is cow's milk.
3. The method for detecting the calcium content in an emulsion according to claim 1 or 2, wherein in the step (1), it comprises:
mixing the emulsion and nitric acid to a constant volume of 1g/100mL, and shaking to obtain a mixed solution; and then mixing the mixed solution with nitric acid to a constant volume of 1mL/10mL, and shaking to obtain a sample to be detected.
4. A method for detecting calcium content in an emulsion according to claim 3, wherein the shaking is performed using a vortex oscillator.
5. The method for detecting calcium content in emulsion according to claim 1, 2 or 4, wherein in step (1), the mass fraction of nitric acid is 2% -8%.
6. The method for detecting calcium content in emulsion according to claim 3, wherein in the step (1), the mass fraction of nitric acid is 2% -8%.
7. The method for detecting calcium content in an emulsion according to claim 1, 2, 4 or 6, wherein in the step (1), the mass fraction of nitric acid is 5%.
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| CN202311273273.9A CN117269295A (en) | 2023-09-28 | 2023-09-28 | Method for detecting calcium content in emulsion |
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2023
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