CN106290630B - The measuring method of methoxyl content in a kind of pectin - Google Patents
The measuring method of methoxyl content in a kind of pectin Download PDFInfo
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- CN106290630B CN106290630B CN201610630817.6A CN201610630817A CN106290630B CN 106290630 B CN106290630 B CN 106290630B CN 201610630817 A CN201610630817 A CN 201610630817A CN 106290630 B CN106290630 B CN 106290630B
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
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Abstract
The invention belongs to analysis detection fields, disclose a kind of method for measuring methoxyl content in pectin, more particularly to a kind of method using methoxyl content in phase inversion combination Headspace-Gas Chromatography measurement pectin, it the steps include: the preparation of (1) standard solution；(2) foundation of standard curve；(3) sample is pre-processed；(4) it is analyzed using HS GC；(5) result calculates.The advantages that this method has measurement result accurate using the content of methoxyl group in above method measurement pectin, simple and efficient to handle, and detection sensitivity is high.
Description
Technical field
The present invention relates to a kind of measuring methods of methoxyl content in pectin, specifically a kind of to utilize phase-inversion technologies knot
The content for closing methoxyl group in Headspace Gas Chromatography pectin, belongs to analysis detection field.
Background technique
Pectin is the natural additive by extracting in fruit, is a kind of using galacturonic acid as the poly of basic unit
High-molecular compound, molecular weight are about 1000~40000.Pectin is present among all green plantss tissue, has good
Gelatine and stable emulsifying effect, are widely used in food industry, in cosmetics and medicine.Pectin as food gelling agent,
Emulsifier and stabilizer depend primarily on the content of polygalacturonase and methoxyl group in molecular structure.Methoxyl group in pectin
Absolute theoretical value 16.3%.Therefore, the content of methoxyl group is also measure pectin solution and its gel characteristic one extremely heavy
The parameter wanted.For the characteristic for identifying and understanding pectin, it is necessary to the content of methoxyl group in accurate analysis pectin.
The method of tradition measurement pectin methoxyl group has volumetric method (titration) and spectrophotometry (colorimetric method).Volumetric method is
First the pectin after a small amount of ethanol wet is dissolved in not carbonated water, few drops of phenolphthalein are added dropwise, are titrated with concentrated sodium hydroxide
After obtain initial titration value.Then saponification occurs with quantitative concentrated sodium hydroxide and pectin, places after a certain period of time, is added
With the hydrochloric acid of sodium hydroxide equivalent, acutely shake until pink color disappeared.Sodium hydroxide titration is finally used, endpoint titration is obtained
Value.Although volumetric method is widely used in laboratory and industry, there is also cumbersome, the larger disadvantages of error.Colorimetric method is
Methanol being generated after pectin piptonychia ester, oxidizer reacts to obtain formaldehyde, due to formaldehyde and many substance energy reaction solutions, and its
Absorbance is directly proportional to the content of formaldehyde, therefore can measure the content of pectin methoxyl group.Colorimetric method is due to that need to add special reagent
And measurement result is unstable, poor repeatability, is rarely employed now.Therefore it is a kind of easy to operate, at low cost, quick, accurate to establish
The method for measuring methoxyl content in pectin has realistic meaning.
Summary of the invention
The purpose of the present invention is to provide a kind of methods of methoxyl content in measurement pectin, overcome in present analysis pectin
Drawback present in the method for methoxyl content.Quick, accurate detection, the easy to operate and easy palm may be implemented according to this method
It holds, analysis result accuracy is high.The purpose of the present invention is achieved through the following technical solutions.
The method of methoxyl content, includes the following steps: in a kind of measurement pectin
(1) preparation of methanol standard solution: suitable methanol (gas chromatography standard product) is measured in volumetric flask, adds distillation
Water is settled to volumetric flask scale and obtains methanol standard solution；
(2) different amounts of step (1) successively the foundation of standard curve: is added into the different headspace sample bottles sealed
Ready headspace sample bottle is placed on sample stage by the methanol standard solution, then carries out HS GC inspection
It surveys, a standard curve is obtained according to the corresponding relationship between gas-chromatography signal peak area and the amount of addition methanol；
(3) sample pretreatment: accurately weighing sample, and sodium hydroxide or potassium hydroxide solution is then added under ultrasound condition
It is handled, sample after after treatment is pre-processed with distilled water constant volume；
(4) sample detection: sample after appropriate pretreatment is taken, it is added with microsyringe to the headspace sample sealed
In bottle, ready headspace sample bottle is placed on sample stage, HS GC detection is then carried out, records sample
Gas-chromatography peak area；
(5) result calculates: gas-chromatography peak area obtained by step (4) being compared with step (2) standard curve, is passed through
The content of methoxyl group in pectin sample is calculated.
It advanced optimizes, the concentration of methanol standard solution described in step (1) is 0.20~5.00g/L.
It advanced optimizes, the methanol standard solution volume of addition described in step (2) is 0~0.05mL.
It advanced optimizing, the concentration of the sodium hydroxide of addition described in step (3) or potassium hydroxide solution is 0.5~
5.0mol/L。
It advanced optimizing, ultrasonic treatment temperature described in step (3) is 20~50 DEG C, and the processing time is 5~120min,
Ultrasonic power is 200~500W.
It advanced optimizes, the operating condition of headspace sampling in step (2) and (4) are as follows: sample injector furnace temp 100~
130℃；1.0~the 10.0min of equilibration time of ml headspace bottle in an oven.
It advanced optimizes, gas-chromatography operating condition described in step (2) and (4) are as follows: column temperature is 35-90 DEG C；It carries
Gas is helium, and flow velocity is 6.0~10.0mL/min；Detector is flame ionization detector (FID), and detector temperature is
190~250 DEG C.
It advanced optimizes, suitable sample to be tested is taken described in step (4), volume is 0.01~0.04mL.
The calculation formula of methoxyl content described in step (5) are as follows:
In formula, C is the content of methanol in sample after the pretreatment obtained by standard curve；V is step (3) sample treatment
Overall solution volume after constant volume；M is sample to be tested oven dry weight, and 31 be the molecular weight of methoxyl group；32 be the molecular weight of methanol.
Compared with prior art, the advantages and positive effects of the present invention are as follows:
(1) easy to operate and easy grasp；
(2) sensitivity of this method is higher；
(3) reaction system is simple, and measurement result is accurate, and evaluated error can reduce 70%；
(4) the continuous mode time is short.
Specific embodiment
Below with reference to embodiment, invention is further described in detail.The invention is not limited to following implementation.
The examples are only for explaining the invention, is not intended to limit the present invention, and should belong to the present invention for the simple change for being related to of the invention
Protection scope.
Embodiment 1 measures the content of methoxyl group in high methoxy pectin
(1) preparation of methanol standard solution: accurately measuring the methanol (gas chromatography standard product) of 0.800g in volumetric flask,
Add distilled water to be settled to 1000mL and obtains methanol standard solution；
(2) foundation of standard curve: successively into the different headspace sample bottles sealed be added 0,0.005,0.01,
0.015, ready headspace sample bottle is placed on sample stage, then by the methanol standard solution of 0.02,0.03,0.04mL
HS GC detection is carried out, wherein the operating condition of head-space sampler are as follows: 110 DEG C of furnace temp；Ml headspace bottle is in baking oven
In equilibration time 5.0min, gas-chromatography operating condition are as follows: column temperature be 35 DEG C；Carrier gas is helium, flow velocity 6.0mL/
Min, detector temperature are 250 DEG C.Then according to the corresponding relationship between gas-chromatography signal peak area and the amount of addition methanol
Obtain a standard curve；
(3) sample pretreatment: accurately weighing five parts of samples, and it is 1.0mol/L sodium hydroxide or hydroxide that concentration, which is then added,
Potassium solution handles 20min under 30 DEG C of ultrasound conditions with 500W power, and after treatment is pre-processed with distilled water constant volume
Sample afterwards；
(4) sample detection: it is added with microsyringe to having sealed sample after the accurate pretreatment for measuring 0.02mL
Headspace sample bottle in, ready headspace sample bottle is placed on sample stage, then carry out HS GC detection,
Record the gas-chromatography peak area of sample；
(5) result calculates: gas-chromatography peak area obtained by step (4) being compared with step (2) standard curve, is passed through
The content of methoxyl group in pectin sample is calculated, measurement result is as shown in table 1.
Table 1
Embodiment 2 measures the content of methoxyl group in low methoxy pectin
(1) preparation of methanol standard solution: accurately measuring the methanol (gas chromatography standard product) of 0.200g in volumetric flask,
Add distilled water to be settled to 1000mL and obtains methanol standard solution；
(2) foundation of standard curve: successively into the different headspace sample bottles sealed be added 0,0.005,0.01,
0.015, ready headspace sample bottle is placed on sample stage, then by the methanol standard solution of 0.02,0.03,0.04mL
Carry out HS GC detection, the operating condition of head-space sampler are as follows: 110 DEG C of furnace temp；Ml headspace bottle is in an oven
Equilibration time 5.0min, gas-chromatography operating condition are as follows: column temperature is 35 DEG C；Carrier gas is helium, flow velocity 6.0mL/min, inspection
Surveying device temperature is 250 DEG C.Then one is obtained according to the corresponding relationship between gas-chromatography signal peak area and the amount of addition methanol
Standard curve；
(3) sample pretreatment: accurately weighing sample, and it is that 0.5mol/L sodium hydroxide or potassium hydroxide are molten that concentration, which is then added,
Liquid handles 10min, sample after after treatment is pre-processed with distilled water constant volume under 30 DEG C of ultrasound conditions with 300W power
Product；
(4) sample detection: it is added with microsyringe to having sealed sample after the accurate pretreatment for measuring 0.04mL
Headspace sample bottle in, ready headspace sample bottle is placed on sample stage, then carry out HS GC detection,
Record the gas-chromatography peak area of sample；
(5) result calculates: gas-chromatography peak area obtained by step (4) being compared with step (2) standard curve, is passed through
The content of methoxyl group in pectin sample is calculated, measurement result is as shown in table 2.
Table 2
Claims (9)
1. a kind of method of methoxyl content in measurement pectin, which comprises the steps of:
(1) it is molten that different amounts of methanol standard successively the foundation of standard curve: is added into the different headspace sample bottles sealed
Ready headspace sample bottle is placed on sample stage by liquid, HS GC detection is then carried out, according to gas-chromatography
Corresponding relationship between signal peak area and the amount that methanol is added obtains a standard curve；
(2) sample pretreatment: accurately weighing sample, and sodium hydroxide then is added or potassium hydroxide solution carries out under ultrasound condition
Processing, treatment temperature are 20~50 DEG C, and the processing time is 10~20min, and after treatment is pre-processed with distilled water constant volume
Sample afterwards；
(3) sample detection: sample after appropriate pretreatment is taken, it is added with microsyringe to the headspace sample bottle sealed
In, ready headspace sample bottle is placed on sample stage, HS GC detection is then carried out, records sample
Gas-chromatography peak area；
(4) result calculates: gas-chromatography peak area obtained by step (3) being compared with step (1) standard curve, passes through calculating
Obtain the content of methoxyl group in pectin sample.
2. the method according to claim 1, wherein the concentration of methanol standard solution described in step (1) is
0.20~5.00g/L.
3. the method according to claim 1, wherein the body of the methanol standard solution of addition described in step (1)
Product is 0~0.05mL.
4. the method according to claim 1, wherein in step (1) and (3) headspace sampling operating condition are as follows:
100~130 DEG C of furnace temp；1.0~the 10.0min of equilibration time of headspace sample bottle in an oven.
5. the method according to claim 1, wherein in step (1) and (3) gas-chromatography operating condition are as follows:
Column temperature is 35~90 DEG C；Carrier gas is helium, and flow velocity is 6.0~10.0mL/min；Detector is flame ionization detector, inspection
Surveying device temperature is 190~250 DEG C.
6. the method according to claim 1, wherein sodium hydroxide or potassium hydroxide solution described in step (2)
Concentration be 0.5~5.0mol/L.
7. method described in any one according to claim 1~6, which is characterized in that in step (2) ultrasonic power be 200~
500W。
8. the method according to the description of claim 7 is characterized in that the volume of sample is after pre-processing described in step (3)
0.01~0.04mL.
9. the method measured according to claim 7, which is characterized in that the calculation formula of methoxyl content described in step (4)
Are as follows:
In formula, C is the content of methanol in sample after the pretreatment obtained by standard curve；V is step (2) sample treatment constant volume
Overall solution volume afterwards；M is sample to be tested oven dry weight, and 31 be the molecular weight of methoxyl group；32 be the molecular weight of methanol.
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| WO2012040318A2 (en) * | 2010-09-23 | 2012-03-29 | University Of Miami | Compositions, methods and kits for detecting melanoma and margins of melanoma |
| CN104931608A (en) * | 2015-05-26 | 2015-09-23 | 华南理工大学 | Method for rapidly and accurately measuring content of carbonyl groups in lignin |
-
2016
- 2016-08-01 CN CN201610630817.6A patent/CN106290630B/en active Active
Patent Citations (3)
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| WO2012040318A2 (en) * | 2010-09-23 | 2012-03-29 | University Of Miami | Compositions, methods and kits for detecting melanoma and margins of melanoma |
| CN102384951A (en) * | 2011-08-19 | 2012-03-21 | 华南理工大学 | Method by utilizing all-volatility headspace gas chromatography to measure content of alkoxy |
| CN104931608A (en) * | 2015-05-26 | 2015-09-23 | 华南理工大学 | Method for rapidly and accurately measuring content of carbonyl groups in lignin |
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| Gas Chromatographic Methods for the Assay of Pectin Methylesterase，Free Methanol,and Methoxy Groups in Plant Tissues;Linda G 等;《J. AGR. FOOD CHEM.》;19721231;第20卷(第2期);第262-266页 |
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