CN103399034A - Method for detecting purity of stearic acid - Google Patents
Method for detecting purity of stearic acid Download PDFInfo
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- CN103399034A CN103399034A CN2013103471740A CN201310347174A CN103399034A CN 103399034 A CN103399034 A CN 103399034A CN 2013103471740 A CN2013103471740 A CN 2013103471740A CN 201310347174 A CN201310347174 A CN 201310347174A CN 103399034 A CN103399034 A CN 103399034A
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Abstract
The present invention provides a kind of method for detecting purity of stearic acid. This method comprises: obtain the melting heat balance diagram spectrum of different quality stearic acid standard items respectively using differential scanning calorimeter,Using the quality m of stearic acid standard items as abscissa,Using stearic acid standard items, the peak height Y of stearic acid melting peak determines coordinate points as ordinate in melting heat balance diagram spectrum,Linear fit is carried out to it establishes the standard curve for passing through reference axis zero point,Calibration curve equation is formula (1): m=AY(1),Wherein A is regression coefficient; The melting heat balance diagram spectrum of sample to be tested is obtained under the same conditions; Bring the peak height Y1 of sample to be tested quality m1 and its stearic acid melting peak in melting heat balance diagram spectrum into formula
In obtain stearic purity in sample to be tested
The peak temperature that rises of stearic acid melting peak is 68-72 DEG C, and terminating temperature is 75-85 DEG C. Method provided by the invention is easy to operation, can purity of stearic acid in rapid determination of sample, and it is low in cost.
Description
Technical field
The present invention relates to a kind of method that detects stearic acid purity, belong to the detection technique field.
Background technology
Stearic acid, legal numbering INS(international number system) 570, EEC No.570, CAS[57-11-4], for white or yellowish white solid, be dissolved in alcohol and acetone, be soluble in ether, chloroform, benzene, phenixin, carbon disulphide, amyl acetate and toluene etc., 69.6 ℃ of fusing points are one of principal ingredients of grease.Stearic purposes is very extensive, and it can be used as the vulcanizing activator of natural gum, synthetic rubber (except butyl rubber) and latex; The raw material of plastic plasticizer and stabilizing agent; Also can be used for manufacturing cosmetics, candle, water-proofing agent, polisher etc.; Pharmaceutically can be used for preparing ointment, suppository etc.; In food industry, be used as the raw material of lubricant, defoamer and food additives etc., such as the raw material as glyceryl stearate, sorbitan monostearate, sucrose ester etc.
Commercial stearic acid product is a kind of potpourri, for the purposes difference, wherein the index such as stearic purity is different, stearic acid product specification both domestic and external is very many, for example 1801,1803,1805,1806,1809,1806,1835,1836,1837,1839,1840,1841,1842,1845,1850,1855,1865,1870,1885,1895,1896,1005,1205, stearic acid 200 and stearic acid 800 etc., one of key distinction of products of different specifications just is stearic acid purity difference.In general, when other index of stearic acid product was similar, stearic purity was higher, and the price of product is also just higher.
For the detection of stearic acid purity in commercialization stearic acid product, generally according to the regulation in " GB/T9104-2008 industry stearic acid test method ", adopt vapor-phase chromatography to measure at present.But the method sample pretreatment is loaded down with trivial details, the equipment operating complexity, and the detection of each sample is consuming time longer, in testing process, needs to use the multinomial consumptive materials such as methyl alcohol, sulfuric acid, ether, nitrogen, high-purity hydrogen and air simultaneously, and testing cost is higher.
Summary of the invention
The invention provides a kind of method that detects stearic acid purity, by simple and easy to do operation, determine fast the purity of sample, and detection method is with low cost.
Differential scanning calorimeter (Differential Scanning Calorimeter, DSC) is that a kind of detection sample absorbs or exothermic equipment in temperature changing process.Method choice for use DSC provided by the invention obtains the peak height of sample and standard items stearic acid melting peak in the melting heat flow curve, characterize stearic quality in sample, thereby stearic purity in the quantitatively characterizing sample, as an index estimating in actual applications stearic acid product quality quality.
Method of the present invention is usingd the stearic acid product as testing sample, detects wherein stearic quality, calculates the stearic acid purity that obtains product.The method according to this invention, comprise the following steps: utilize differential scanning calorimeter to obtain respectively the melting heat flow graph spectrum of the stearic acid standard items of different quality, take the quality m of described stearic acid standard items as horizontal ordinate, take the peak height Y of described stearic acid standard items corresponding stearic acid melting peak in described melting heat flow graph spectrum as ordinate, determine coordinate points, described coordinate points is carried out to linear fit, set up by the coordinate axis typical curve at zero point, and obtain the typical curve equation of formula (1):
M=AY (1), wherein A is regression coefficient;
Obtain under the same conditions the melting heat flow graph spectrum of testing sample;
Quality m by described testing sample
1Peak height Y with the stearic acid melting peak of described testing sample in melting heat flow graph spectrum
1Bring in following formula (2) and calculate stearic purity in testing sample
Wherein, a peak temperature of stearic acid melting peak is 68-72 ℃, and end temp is 75-85 ℃, and for example, the endothermic peak between 69.6-80.0 ℃ is the stearic acid melting peak take described stearic acid standard items or testing sample.
Above-mentioned " stearic acid standard items " are the stearic acid sterling, can be by being purchased or preparing voluntarily.In actual production, requirement to the stearic acid product purity there are differences according to application scenario is different, method provided by the invention can be carried out quantitatively characterizing to the purity of stearic acid product, the quality good or not of stearic acid product can be estimated in actual applications, as the reference of actual production according to the different application occasion.
The method according to this invention, also comprise that wherein the typical curve equation m=AY to formula (1) proofreaies and correct to obtain stearic corrected purity in testing sample
Step, be specially:
Use vapor-phase chromatography to characterize stearic purity in testing sample, obtain stearic purity ψ in testing sample;
Utilize stearic purity in above-mentioned gained testing sample
Stearic purity ψ calculates relative deviation C with the vapor-phase chromatography gained, by in the following formula of value substitution (3) of regression coefficient A and resulting relative deviation C, must proofread and correct regression coefficient A ':
A’=A（1+C） （3）
Adopt and proofread and correct regression coefficient A ' by stearic corrected purity in the described testing sample of following formula (4) acquisition
The method according to this invention, the method that obtains correction regression coefficient A ' can also be:
Obtain respectively stearic purity in a plurality of testing samples
And use vapor-phase chromatography to obtain respectively stearic purity ψ in each testing sample;
The purity of utilizing above-mentioned two kinds of methods to obtain
With ψ, calculate the mean relative deviation C ' of described a plurality of testing samples, and, by in itself and described regression coefficient A substitution formula (3), must proofread and correct regression coefficient A '.
The method according to this invention, while utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, initial temperature is lower than 50 ℃, and end temp is higher than 90 ℃.In a specific embodiment of the present invention, can select the sweep limit of 30-110 ℃.
The method according to this invention, while utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, scan with the heating rate of 2-20 ℃/min.
In the present invention, described setting heating rate can be generally 2-20 ℃/min with reference in known technology, using the heating rate of DSC when the said temperature scope scans, and in a specific embodiment of the present invention, for example can select 10 ℃/min.
The enforcement of technical solution of the present invention has following advantage at least:
1, method provided by the invention does not need sample is carried out to pre-service, and is simple and quick;
2, the consumptive material that uses in testing process of method provided by the invention is few, with low cost.
The accompanying drawing explanation
Stearic acid standard items melting heat flow curve schematic diagram in the method that Fig. 1 provides for the embodiment of the present invention.
The stearic acid typical curve schematic diagram that Fig. 2 obtains for the melting heat flow curve according to the different stearic acid standard items in Fig. 1.
Embodiment
Below in conjunction with specific embodiments and embodiment, the present invention is further elaborated, be intended to help the reader to understand better flesh and blood of the present invention, can not be interpreted as any restriction to the scope of the present invention.
Embodiment 1
The present embodiment uses DSC to obtain the peak height of testing sample and the melting peak of stearic acid standard items in the melting heat flow curve, and stearic quality in the sign testing sample, thereby stearic purity in the quantitatively characterizing testing sample, as an index estimating in actual applications stearic acid product quality quality.Concrete grammar is: accurately taking quality m is a plurality of stearic acid standard items of 0.1-10mg, be sealed in dry aluminum crucible, and use DSC(model Diamond DSC, Perkin Elmer, Shelton, CT, USA production) detect the melting heat flow curve of each stearic acid standard items, sweep limit is 30-110 ℃, and heating rate is 10 ℃/min, obtains the melting heat flow graph spectrum of stearic acid standard items.As shown in Figure 1, take the quality m of stearic acid standard items as horizontal ordinate, take the peak height Y of the corresponding melting peak of stearic acid standard items as ordinate, determine coordinate points, coordinate points is carried out to linear fit and set up by the coordinate axis typical curve at zero point, and obtain typical curve equation m=0.0763Y (1).
Some commercially available stearic acid product A, B and C of selection, then the stearic acid product that different stearic acid analogs are added in preparation at random are as testing sample, and its composition is as shown in table 1.
Table 1
*A, B and C represent respectively the stearic acid of three different brands, numeric representation stearic massfraction wherein in bracket.
*'-' representative is not added.
Under the same conditions testing sample is scanned, obtain the melting heat flow graph spectrum of testing sample, in the quality of sample and its melting heat flow graph spectrum, the peak height of stearic acid melting peak is in Table 2.
Table 2
| Sample number into spectrum | Sample quality (mg) | The peak height of melting peak (mW) |
| 1 | 2.34 | 18.2 |
| 2 | 3.35 | 20.3 |
| 3 | 3.47 | 28.6 |
| 4 | 2.96 | 22.5 |
| 5 | 4.74 | 32.8 |
| 6 | 4.28 | 34.1 |
| 7 | 3.22 | 13.2 |
| 8 | 3.54 | 2.92 |
| 9 | 3.38 | 14.4 |
| 10 | 3.27 | 14.9 |
| 11 | 4.32 | 29.1 |
| 12 | 4.36 | 6.46 |
| 13 | 3.84 | 27.0 |
| 14 | 2.85 | 20.1 |
| 15 | 4.43 | 34.3 |
The peak height Y of the stearic acid melting peak by sample between 69.6-80.0 ℃
1Bring in typical curve equation (1), and according to stearic purity in formula (2) calculation sample
It is as shown in table 3,
Wherein
For stearic purity (%) in testing sample, Y
1For the peak height (mW) of stearic acid melting peak in testing sample, m
1Quality (mg) for testing sample.
Simultaneously, the step according to described in GB " GB/T9104-2008 industry stearic acid test method ", adopt stearic purity ψ in above-mentioned 15 testing samples of gas chromatography determination.In the method that the present invention sets up and vapor-phase chromatography detection sample, stearic acid purity result is more as shown in table 3.
Table 3
The mean relative deviation C ' that is drawn detection method that the present invention sets up and vapor-phase chromatography result by table 2 is-(7.16 ± 4.41) %, and the method that the present invention sets up can quantitative response goes out the purity of sample, and easy to operation, and detection method is with low cost.
The present embodiment proofreaies and correct to reduce the value of mean relative deviation C ' to the result of gained in embodiment 1.Above-mentioned mean relative deviation C ' can proofread and correct by the regression coefficient A in formula (2), and concrete grammar is: by in the following formula of value substitution (3) of A and C ',
A’=A（1+C’） （3）
Must proofread and correct regression coefficient A ' is 0.0818, the corrected purity of sample
According to formula (5), calculate,
Wherein
For stearic corrected purity (%) in testing sample, Δ Y
SFor testing sample endothermic peak peak height (mW) between 69.6-80 ℃; M is the quality (mg) of testing sample.
Stearic corrected purity in the sample that the method for using the present invention to set up obtains
The comparative result that detects stearic purity ψ in the sample that obtains with vapor-phase chromatography is as shown in table 4.
Table 4
The above results shows, stearic corrected purity in the sample that the method for using the present invention to set up obtains
The mean relative deviation that detects stearic purity ψ in the sample that obtains with vapor-phase chromatography is-(0.52 ± 4.73) % to have reflected more accurately the purity of sample; And easy to operation, detection method is with low cost.
Finally it should be noted that: above each embodiment, only in order to technical scheme of the present invention to be described, is not intended to limit; Although with reference to aforementioned each embodiment, the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme that aforementioned each embodiment puts down in writing, or some or all of technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the scope of various embodiments of the present invention technical scheme.
Claims (5)
1. detect the method for stearic acid purity, comprise the following steps:
Utilize differential scanning calorimeter to obtain respectively the melting heat flow graph spectrum of different quality stearic acid standard items, take the quality m of described stearic acid standard items as horizontal ordinate, take the peak height Y of described stearic acid standard items corresponding stearic acid melting peak in described melting heat flow graph spectrum as ordinate, determine coordinate points, described coordinate points is carried out to linear fit, set up by the coordinate axis typical curve at zero point, and obtain the typical curve equation of formula (1):
M=AY (1), wherein A is regression coefficient;
Obtain under the same conditions the melting heat flow graph spectrum of testing sample;
Quality m by described testing sample
1Peak height Y with the stearic acid melting peak of described testing sample in melting heat flow graph spectrum
1Bring in following formula (2) and obtain stearic purity in testing sample
A peak temperature of described stearic acid melting peak is 68-72 ℃, and end temp is 75-85 ℃,
2. method according to claim 1, also comprise that wherein the typical curve equation m=AY to formula (1) proofreaies and correct to obtain stearic corrected purity in testing sample
Step, be specially:
Use vapor-phase chromatography to characterize stearic purity in testing sample, obtain stearic purity ψ in testing sample;
Utilize stearic purity in described testing sample
Stearic purity ψ calculates relative deviation C with the vapor-phase chromatography gained, by in the following formula of value substitution (3) of described regression coefficient A and resulting relative deviation C, must proofread and correct regression coefficient A ':
A’=A（1+C） （3）
Adopt and proofread and correct regression coefficient A ' by stearic corrected purity in the described testing sample of following formula (4) acquisition
3. method according to claim 2, wherein, the method that obtains to proofread and correct regression coefficient A ' can also be:
Obtain respectively stearic purity in a plurality of testing samples
And use vapor-phase chromatography to obtain respectively stearic purity ψ in each testing sample;
The purity of utilizing above-mentioned two kinds of methods to obtain
With ψ, calculate the mean relative deviation C ' of described a plurality of testing samples, and, by in itself and described regression coefficient A substitution formula (3), must proofread and correct regression coefficient A '.
4. the described method of according to claim 1-3 any one, wherein, while utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, initial temperature is lower than 50 ℃, and end temp is higher than 90 ℃.
5. the described method of according to claim 1-3 any one, wherein, while utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, scan with the heating rate of 2-20 ℃/min.
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| CN105424743A (en) * | 2015-12-02 | 2016-03-23 | 常州大学 | Method for rapidly determining purity of raw materials in process of producing polyglycolic acid |
| CN105784762A (en) * | 2016-04-29 | 2016-07-20 | 山东大学 | Quick purity testing and analyzing method for low-melting-point materials |
| CN105842277A (en) * | 2016-03-30 | 2016-08-10 | 北京彤程创展科技有限公司 | Testing method for detecting activity of vulcanizing activator |
| CN110174436A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A kind of method of glycerol in quick measurement tobacco juice for electronic smoke, content of propylene glycol |
| CN110174437A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A method of nicotine content in tobacco juice for electronic smoke is quickly measured according to differential scanning calorimetry heat enthalpy value |
| CN111189877A (en) * | 2018-11-15 | 2020-05-22 | 中国科学院大连化学物理研究所 | Sample purity measuring and calculating method based on adiabatic calorimetry |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111189877A (en) * | 2018-11-15 | 2020-05-22 | 中国科学院大连化学物理研究所 | Sample purity measuring and calculating method based on adiabatic calorimetry |
| CN110174436A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A kind of method of glycerol in quick measurement tobacco juice for electronic smoke, content of propylene glycol |
| CN110174437A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A method of nicotine content in tobacco juice for electronic smoke is quickly measured according to differential scanning calorimetry heat enthalpy value |
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