CN103018359B - Method for measuring content of oxalic acid in food or vegetables - Google Patents
Method for measuring content of oxalic acid in food or vegetables Download PDFInfo
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Abstract
The invention relates to a method for measuring a content of oxalic acid in food or vegetables, and particularly relates to a method for rapidly measuring the content of the oxalic acid in the food or the vegetables by using a headspace gas chromatography. The method comprises the following steps of (1) preparing a standard solution; (2) establishing a standard curve; (3) carrying out sample pretreatment; (4) using a headspace-gas chromatography to detect; and (5) calculating a result. The method for measuring the content of the oxalic acid in the food or the vegetables provided by the invention has the beneficial effects convenience and rapidness of operation, high detection sensitivity, accurate detecting result, and strong anti-jamming capability.
Description
Technical field
The present invention relates to a kind of oxalic acid content assay method, is a kind of method of utilizing headspace gas chromatography to measure food and vegetables mesoxalic acid content specifically, belongs to food analysis field.
background technology
Oxalic acid is also referred to as ethane diacid, is one of the simplest organic dibasic acid.It is extensively present in occurring in nature, particularly animal vegetable tissue, is mainly to exist with the form of free state (potassium oxalate and sodium oxalate) and calcium oxalate crystal.In our daily edible a lot of food and vegetables, be rich in oxalic acid, such as spinach, three-coloured amaranth, celery, beans, chocolate, strawberry, grape and tea etc.
From the angle of ecotoxicology and food science, oxalic acid is a kind of environmental toxin and ANFs.Oxalic acid is not easy oxidized decomposition in human body, and the product forming after metabolism belongs to acidic materials, can cause potential of hydrogen out of trim in human body, and too much eating also can be poisoning.The long-term edible high vegetables of oxalic acid content easily cause the diseases such as arthritis, low blood calcium, vesical calculus and kidney stone.In view of oxalic acid can produce certain harm to human body, the method that many researchers attempt to set up fast, accurate, low cost is measured food and vegetables mesoxalic acid content.
The assay method of oxalic acid mainly contains titrimetry, colourimetry, red, orange, green, blue, yellow (ROGBY) and enzyme process etc. at present, and these methods cut both ways.Wherein, titrimetry is still a kind of classical way in food analysis so far, but its sensitivity is lower, operation is more loaded down with trivial details and consuming time.Colourimetry is highly sensitive and cheap, but complex operation and repeatability are poor.Red, orange, green, blue, yellow (ROGBY) comprises two kinds of high performance liquid chromatography and chromatography of ions, and it is easy and simple to handle, quick, highly sensitive and reproducible, but in mensuration process, other material disturbs more serious.It is easy to be quick that enzyme process detects oxalic acid, and highly sensitive, selectivity is good, but testing cost is higher.Therefore a kind of set up more easy, with low cost, quick, Accurate Determining food and vegetables mesoxalic acid content method has realistic meaning.
Summary of the invention
The object of the present invention is to provide a kind of method of measuring food and vegetables mesoxalic acid content, overcome the existing drawback of method of present analysis food and vegetables mesoxalic acid content.Measuring principle of the present invention is based on oxalate and sodium bromate generation chemical reaction generation carbon dioxide under acid condition, then adopts Headspace-Gas Chromatography Analysis to measure the amount of carbon dioxide producing, thereby calculates the content of sample mesoxalic acid.Can realize Fast Measurement according to the method, simple to operate and easily grasp, its analysis result accuracy is high, has certain practicality.
The present invention is achieved by the following technical solutions, specifically comprises the following steps:
A method of measuring food or vegetables mesoxalic acid content, comprises the steps:
(1) preparing standard solution: take appropriate sodium oxalate in volumetric flask, add deionized water and be settled to volumetric flask scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adopt head-space sampler, in multiple different head space sample bottles, add respectively the sodium bromate aqueous solution of same volume and the aqueous sulfuric acid of same volume, and sealed sample bottle, then in different head space sample bottles, add the different described sodium oxalate standard solution of measuring successively, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, according to gas chromatography signal peak area and add the corresponding relation between the amount of oxalate to obtain a typical curve;
(3) sample pretreatment: testing sample is ground to form to homogenate or powder, then add hydrochloric acid under heating condition, to carry out extracting, the cooling rear deionized water constant volume of using, gets solution after appropriate constant volume and carries out centrifugally, and its supernatant liquid obtains sample after pre-service with 0.22 μ m membrane filtration;
(4) sample detection: get sample after appropriate pre-service, it is added to head-space sampler in the headspace sample bottle having sealed and sodium bromate solution and sulfuric acid solution are housed, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample;
(5) result is calculated: step (4) gained gas chromatography peak area and step (2) typical curve are compared, by calculating the content of sample mesoxalic acid.
Further optimize, described volumetric flask is 1000mL volumetric flask.
Further optimize, described in step (1), the concentration of sodium oxalate standard solution is 0.01 ~ 0.05mol/L.
Further optimize, the sodium bromate concentration of aqueous solution adding described in step (2) is 0.5 ~ 1.5mol/L, and volume is 1.0 ~ 3.0mL, and aqueous sulfuric acid concentration is 1.0 ~ 2.0mol/L, and volume is 1.0 ~ 2.0mL.
Further optimize, the volume of the oxalic acid standard solution adding described in step (2) is 0.0 ~ 0.6mL.
Further optimize, the operating conditions of the head-space sampler described in step (2) and (4) is: 50 ~ 80 ℃ of injector furnace temps; Equilibration time 5.0 ~ the 20.0min of head space bottle in baking oven.
Further optimize, in step (2) and (4), the operating conditions of gas chromatography is: column temperature is 40 ~ 70 ℃; Carrier gas is high pure nitrogen, and its flow velocity is 3.0 ~ 3.5mL/min; Detecting device is thermal conductivity detector (TCD) (TCD), and detector temperature is 200 ~ 250 ℃.
Further optimize, described in step (3), concentration of hydrochloric acid is 1.0 ~ 3.0mol/L, and pretreatment temperature is 80 ~ 100 ℃, and the reaction time is 20 ~ 60min, and centrifugal rotational speed is 5000 ~ 10000r/min, and centrifugation time is 10 ~ 30min.
Further optimize, described in step (4), after appropriate pre-service, the volume of sample is 0.5 ~ 2.0mL.
Further optimize, the method for said determination food or vegetables mesoxalic acid content specifically comprises step:
(1) preparing standard solution: accurately take 6.7 g(and be accurate to 0.0001g) sodium oxalate in 1000mL volumetric flask, add deionized water and be settled to scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adding respectively 1mL concentration at a series of headspace sample bottle is that sodium bromate solution and the 1mL concentration of 0.5mol/L is 1mol/L sulfuric acid solution, and sealed sample bottle, then toward adding successively 0,0.1,0.2,0.3,0.4,0.5 in different head space sample bottles, the sodium oxalate standard solution of 0.6mL, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, gained gas chromatography signal peak area and add between the amount of oxalate and can obtain a typical curve;
(3) sample pretreatment: accurately take sample, be ground into homogenate or powder, then adding concentration is hydrochloric acid solution extracting 20 ~ 30min at 80 ~ 100 ℃ of 2mol/L, coolingly be settled to 100mL with deionized water afterwards, get solution after 20mL constant volume through the centrifugal 10 ~ 20min of 5000 ~ 8000r/min, its supernatant liquid obtains pretreatment sample with 0.22 μ m membrane filtration.
(4) sample detection: accurately measure 0.5 ~ 2.0mL pretreatment sample, it is added to and has been sealed with injector, and the sodium bromate solution and the 1mL concentration that 1mL concentration is housed is 0.5mol/L are in the headspace sample bottle of 1mol/L sulfuric acid solution, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample.
(5) result is calculated: step (4) gained peak area and step (2) typical curve are compared, by calculating the content of sample mesoxalic acid.
Further optimize, described in step (5), the computing formula of oxalic acid content is:
In formula,
cfor the content of sample mesoxalic acid after the pre-service being obtained by typical curve;
vfor the overall solution volume after step (3) sample extracting constant volume; M is testing sample oven dry weight, and in the time that testing sample is solution, m is by testing sample volume V
1replace.
Owing to adopting technique scheme, compared with prior art, the advantage having and good effect are in the present invention:
(1) measure sample size used less;
(2) sensitivity of the method is higher, minimumly oxalic acid content 0.40 μ g can be detected;
(3) mensuration process time is short;
(4) antijamming capability is strong, and other the organic existence in sample can not impact measuring;
(5) easy and simple to handle and easily grasp;
(6) reaction system is simple, has reduced error at measurment;
(7) detecting reagent can preserve at normal temperatures.
Accompanying drawing explanation
Fig. 1 is gas chromatography signal peak area in example-add oxalate typical curve.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail.The present invention is not limited to following embodiment.Embodiment is only for explaining the present invention, and unrestricted the present invention all should belong to protection scope of the present invention for relating to simple change of the present invention.
embodiment 1 measures the content of solid food mesoxalic acid
(1) preparing standard solution: accurately take 6.7 g(and be accurate to 0.0001g) sodium oxalate in 1000mL volumetric flask, add deionized water and be settled to scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adding respectively 1mL concentration at a series of headspace sample bottle is that sodium bromate solution and the 1mL concentration of 0.5mol/L is 1mol/L sulfuric acid solution, and sealed sample bottle, then in different head space sample bottles, add successively 0, 0.02, 0.04, 0.06, 0.1, 0.2, 0.3, 0.4, 0.5, the sodium oxalate standard solution of 0.6mL, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, gained gas chromatography signal peak area and add between the amount of oxalate and can obtain a typical curve, as shown in Figure 1.The operating conditions of head-space sampler and gas chromatography as hereinbefore.
(3) sample pretreatment: accurately take 2 ~ 3g solid food sample, be ground into powder, then adding 30mL concentration is hydrochloric acid solution extracting 30min at 100 ℃ of 2mol/L, coolingly be settled to 50mL with deionized water afterwards, get solution after 20mL constant volume through the centrifugal 15min of 8000r/min, its supernatant liquid obtains pretreatment sample with 0.22 μ m membrane filtration.
(4) sample detection: accurately measure 2mL pretreatment sample, it is added to and has been sealed with injector, and the sodium bromate solution and the 1mL concentration that 1mL concentration is housed is 0.5mol/L are in the headspace sample bottle of 1mol/L sulfuric acid solution, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample.
(5) result is calculated: step (4) gained peak area and step (2) typical curve are compared, and by calculating the content of sample mesoxalic acid, its computing formula is:
In formula,
cfor the content of sample mesoxalic acid after the pre-service being obtained by typical curve;
vfor the cumulative volume of constant volume after sample extracting; M is working sample oven dry weight.
(6) measurement result:
embodiment2
measure the content of vegetables mesoxalic acid
(1) preparing standard solution: accurately take 6.7 g(and be accurate to 0.0001g) sodium oxalate in 1000mL volumetric flask, add deionized water and be settled to scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adding respectively 1mL concentration at a series of headspace sample bottle is that sodium bromate solution and the 1mL concentration of 0.5mol/L is 1mol/L sulfuric acid solution, and sealed sample bottle, then in different head space sample bottles, add successively 0, 0.02, 0.04, 0.06, 0.1, 0.2, 0.3, 0.4, 0.5, the sodium oxalate standard solution of 0.6mL, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, gained gas chromatography signal peak area and add between the amount of oxalate and can obtain a typical curve, as shown in Figure 1.
(3) sample pretreatment: accurately take 3 ~ 4g vegetable sample, be ground into homogenate, then adding 30mL concentration is hydrochloric acid solution extracting 30min at 90 ℃ of 2mol/L, coolingly be settled to 50mL with deionized water afterwards, get solution after 20mL constant volume through the centrifugal 15min of 6000r/min, its supernatant liquid obtains pretreatment sample with 0.22 μ m membrane filtration.
(4) sample detection: accurately measure 2mL pretreatment sample, it is added to and has been sealed with injector, and the sodium bromate solution and the 1mL concentration that 1mL concentration is housed is 0.5mol/L are in the headspace sample bottle of 1mol/L sulfuric acid solution, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample.
(5) result is calculated: step (4) gained peak area and step (2) typical curve are compared, and by calculating the content of sample mesoxalic acid, its computing formula is:
In formula,
cfor the content of sample mesoxalic acid after the pre-service being obtained by typical curve;
vfor the cumulative volume of constant volume after sample extracting; M is working sample oven dry weight.
(6) measurement result:
embodiment 3 measures the content of beer mesoxalic acid
(1) preparing standard solution: accurately take 6.7 g(and be accurate to 0.0001g) sodium oxalate in 1000mL volumetric flask, add deionized water and be settled to scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adding respectively 1mL concentration at a series of headspace sample bottle is that sodium bromate solution and the 1mL concentration of 1mol/L is 1 mol/L sulfuric acid solution, and sealed sample bottle, then in different head space sample bottles, add successively 0, 0.02, 0.04, 0.06, 0.1, 0.2, 0.3, 0.4, 0.5, the sodium oxalate standard solution of 0.6mL, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, gained gas chromatography signal peak area and add between the amount of oxalate and can obtain a typical curve, as shown in Figure 1.
(3) sample detection: accurately measure 1mL beer sample, it is added to and has been sealed with injector, and the sodium bromate solution and the 1mL concentration that 1mL concentration is housed is 0.5mol/L are in the headspace sample bottle of 1mol/L sulfuric acid solution, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample.
(4) result is calculated: step (3) gained peak area and step (2) typical curve are compared, and by calculating the content of sample mesoxalic acid, its computing formula is:
In formula,
cfor the content of sample mesoxalic acid after the pre-service being obtained by typical curve;
vfor the cumulative volume of constant volume after sample extracting; V
1for testing sample volume.
(5) measurement result:
Claims (7)
1. a method of measuring food or vegetables mesoxalic acid content, is characterized in that, comprises the steps:
(1) preparing standard solution: take appropriate sodium oxalate in volumetric flask, add deionized water and be settled to volumetric flask scale and obtain sodium oxalate standard solution;
(2) Criterion curve: adopt head-space sampler, in multiple different head space sample bottles, add respectively the sodium bromate aqueous solution of same volume and the aqueous sulfuric acid of same volume, and sealed sample bottle, then in different head space sample bottles, add the different described sodium oxalate standard solution of measuring successively, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, according to gas chromatography signal peak area and add the corresponding relation between the amount of oxalate to obtain a typical curve; The described sodium bromate concentration of aqueous solution adding is 0.5 ~ 1.5mol/L, and volume is 1.0 ~ 3.0mL, and aqueous sulfuric acid concentration is 1.0 ~ 2.0mol/L, and volume is 1.0 ~ 2.0mL; The operating conditions of described gas chromatography is: column temperature is 40 ~ 70 ℃; Carrier gas is high pure nitrogen, and its flow velocity is 3.0 ~ 3.5mL/min; Detecting device is thermal conductivity detector (TCD) (TCD), and detector temperature is 200 ~ 250 ℃;
(3) sample pretreatment: testing sample is ground to form to homogenate or powder, then add hydrochloric acid under heating condition, to carry out extracting, the cooling rear deionized water constant volume of using, gets solution after appropriate constant volume and carries out centrifugally, and its supernatant liquid obtains sample after pre-service with 0.22 μ m membrane filtration; Described concentration of hydrochloric acid is 1.0 ~ 3.0mol/L, and pretreatment temperature is 80 ~ 100 ℃, and the reaction time is 20 ~ 60min, and centrifugal rotational speed is 5000 ~ 10000r/min, and centrifugation time is 10 ~ 30min;
(4) sample detection: get sample after appropriate pre-service, it is added to head-space sampler in the headspace sample bottle having sealed and sodium bromate solution and sulfuric acid solution are housed, ready headspace sample bottle is positioned on sample stage, then carry out head space-gas chromatographic detection, record the gas chromatography peak area of sample; The operating conditions of described gas chromatography is: column temperature is 40 ~ 70 ℃; Carrier gas is high pure nitrogen, and its flow velocity is 3.0 ~ 3.5mL/min; Detecting device is thermal conductivity detector (TCD) (TCD), and detector temperature is 200 ~ 250 ℃;
(5) result is calculated: step (4) gained gas chromatography peak area and step (2) typical curve are compared, by calculating the content of sample mesoxalic acid.
2. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that described volumetric flask is 1000mL volumetric flask.
3. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that: described in step (1), the concentration of sodium oxalate standard solution is 0.01 ~ 0.05mol/L.
4. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that: the volume of the oxalic acid standard solution adding described in step (2) is 0.0 ~ 0.6mL.
5. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that: the operating conditions of the head-space sampler described in step (2) and (4) is: 50 ~ 80 ℃ of injector furnace temps; Equilibration time 5.0 ~ the 20.0min of head space bottle in baking oven.
6. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that: described in step (4), after appropriate pre-service, the volume of sample is 0.5 ~ 2.0mL.
7. the method for mensuration food according to claim 1 or vegetables mesoxalic acid content, is characterized in that: described in step (5), the computing formula of oxalic acid content is:
In formula,
cfor the content of sample mesoxalic acid after the pre-service being obtained by typical curve;
vfor the overall solution volume after step (3) sample extracting constant volume; M is testing sample oven dry weight, and in the time that testing sample is solution, m is by testing sample volume V
1replace.
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| CN103336073B (en) * | 2013-06-28 | 2015-04-15 | 宁夏启元药业有限公司 | Measuring method of mesoxalic acid in tetracycline filter liquor |
| CN103698437B (en) * | 2014-01-13 | 2015-04-08 | 福建农林大学 | Method for quickly detecting starch coated amount in modified calcium carbonate filler through headspace gas chromatography |
| CN104991979B (en) * | 2015-07-09 | 2019-03-01 | 熊贝贝 | Laboratory data processing method and processing system |
| CN110208410B (en) * | 2019-06-06 | 2021-05-14 | 华南理工大学 | Automatic headspace gas chromatography method for rapidly determining deacetylation degree of chitosan |
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