CN103399034B - Detect the method for purity of stearic acid - Google Patents
Detect the method for purity of stearic acid Download PDFInfo
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- CN103399034B CN103399034B CN201310347174.0A CN201310347174A CN103399034B CN 103399034 B CN103399034 B CN 103399034B CN 201310347174 A CN201310347174 A CN 201310347174A CN 103399034 B CN103399034 B CN 103399034B
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Abstract
The invention provides a kind of method detecting purity of stearic acid.The method comprises: utilize differential scanning calorimeter to obtain the melting heat flow graph spectrum of different quality stearic acid standard items respectively, with the quality m of stearic acid standard items for horizontal ordinate, with the peak height Y of stearic acid standard items stearic acid melting peak in melting heat flow graph spectrum for ordinate determination coordinate points, the typical curve of linear fit foundation by coordinate axis zero point is carried out to it, does is typical curve equation formula (1): m=AY? (1), wherein A is regression coefficient; Obtain the melting heat flow graph spectrum of testing sample under the same conditions; By testing sample quality m
1with the peak height Y of its stearic acid melting peak in melting heat flow graph spectrum
1bring formula into
in obtain stearic purity in testing sample
a peak temperature for stearic acid melting peak is 68-72 DEG C, and end temp is 75-85 DEG C.Method provided by the invention is easy to operation, can determine the purity of stearic acid in sample fast, and with low cost.
Description
Technical field
The present invention relates to a kind of method detecting purity of stearic acid, belong to detection technique field.
Background technology
Stearic acid, legal numbering INS(internationalnumbersystem) 570, EECNo.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., fusing point 69.6 DEG C is one of principal ingredient of grease.Widely, it can be used as the vulcanizing activator of natural gum, synthetic rubber (except butyl rubber) and latex to stearic purposes; 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.; Be used as the raw material of lubricant, defoamer and food additives etc. in the food industry, such as, as the raw material of glyceryl stearate, sorbitan monostearate, sucrose ester etc.
Commercial stearic acid product is a kind of potpourri, different for purposes, wherein the index such as stearic purity is different, stearic acid product specification both domestic and external is very many, such as 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 is just that purity of stearic acid is different.In general, when other index of stearic acid product is similar, stearic purity is higher, and the price of product is also higher.
At present for the detection of purity of stearic acid in commercialization stearic acid product, generally vapor-phase chromatography is adopted to measure according to the regulation in " GB/T9104-2008 industry stearic acid test method ".But the method sample pretreatment is loaded down with trivial details, equipment operating is complicated, and the detection of each sample is consuming time longer, and need to use the multinomial consumptive materials such as methyl alcohol, sulfuric acid, ether, nitrogen, high-purity hydrogen and air in testing process, testing cost is higher simultaneously.
Summary of the invention
The invention provides a kind of method detecting purity of stearic acid, by simple and easy to do operation, determine the purity of sample fast, and detection method is with low cost.
Differential scanning calorimeter (DifferentialScanningCalorimeter, DSC) is that a kind of sample that detects absorbs or exothermic equipment in temperature changing process.Method choice provided by the invention uses DSC to obtain the peak height of sample and standard items stearic acid melting peak in melting heat flow curve, stearic quality in characterizing sample, thus stearic purity in quantitatively characterizing sample, as the index evaluating stearic acid product quality quality in actual applications.
Method of the present invention, using stearic acid product as testing sample, detects wherein stearic quality, calculates the purity of stearic acid obtaining product.According to method of the present invention, comprise the following steps: utilize differential scanning calorimeter to obtain the melting heat flow graph spectrum of the stearic acid standard items of different quality respectively, with the quality m of described stearic acid standard items for horizontal ordinate, with the peak height Y of the stearic acid melting peak corresponding in described melting heat flow graph spectrum of described stearic acid standard items for ordinate determination coordinate points, linear fit is carried out to described coordinate points, set up the typical curve by coordinate axis zero point, and obtain the typical curve equation of formula (1):
M=AY(1), wherein A is regression coefficient;
Obtain the melting heat flow graph spectrum of testing sample under the same conditions;
By the quality m of described testing sample
1with the peak height Y of 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 for stearic acid melting peak is 68-72 DEG C, and end temp is 75-85 DEG C, and such as, with described stearic acid standard items or testing sample, the endothermic peak between 69.6-80.0 DEG C is stearic acid melting peak.
Above-mentioned " stearic acid standard items " are stearic acid sterling, by being purchased or preparing voluntarily.In actual production, the requirement of stearic acid product purity be there are differences according to application scenario difference, method provided by the invention can carry out quantitatively characterizing to the purity of stearic acid product, the quality good or not of stearic acid product can be evaluated in actual applications, as the reference of actual production according to different application occasion.
According to method of the present invention, wherein also comprise and the typical curve equation m=AY of formula (1) is corrected to obtain stearic corrected purity in testing sample
step, be specially:
Use vapor-phase chromatography to characterize purity stearic in testing sample, obtain stearic purity ψ in testing sample;
Utilize stearic purity in above-mentioned gained testing sample
calculate relative deviation C with the stearic purity ψ of vapor-phase chromatography gained, regression coefficient A and the value of the relative deviation C obtained substituted in following formula (3), must regression coefficient A ' be corrected:
A’=A（1+C）（3）
Correction regression coefficient A ' is adopted to obtain stearic corrected purity in described testing sample by following formula (4)
According to method of the present invention, obtaining the method correcting regression coefficient A ' can also be:
Obtain stearic purity in multiple testing sample respectively
and use vapor-phase chromatography to obtain stearic purity ψ in each testing sample respectively;
Utilize the purity that above-mentioned two kinds of methods obtain
calculate the mean relative deviation C ' of described multiple testing sample with ψ, and itself and described regression coefficient A are substituted in formula (3), must regression coefficient A ' be corrected.
According to method of the present invention, when utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, initial temperature is lower than 50 DEG C, and end temp is higher than 90 DEG C.In a specific embodiment of the present invention, the sweep limit of 30-110 DEG C can be selected.
According to method of the present invention, when utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, scan with the heating rate of 2-20 DEG C/min.
In the present invention, described setting heating rate can refer in known technology and uses the heating rate of DSC when said temperature scope scans, and is generally 2-20 DEG C/min, in a specific embodiment of the present invention, such as, can select 10 DEG C/min.
The enforcement of technical solution of the present invention, at least has following advantage:
1, method provided by the invention does not need to carry out pre-service to sample, simple and quick;
2, the consumptive material that uses in testing process of method provided by the invention is few, with low cost.
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.
Fig. 2 is the stearic acid typical curve schematic diagram obtained according to the melting heat flow curve of the different stearic acid standard items in Fig. 1.
Embodiment
Below in conjunction with specific embodiments and embodiment, the present invention is elaborated further, be intended to help reader to understand flesh and blood of the present invention better, any restriction to the scope of the present invention can not be interpreted as.
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 melting heat flow curve, and characterize stearic quality in testing sample, thus stearic purity in quantitatively characterizing testing sample, as the index evaluating stearic acid product quality quality in actual applications.Concrete grammar is: accurately take multiple stearic acid standard items that quality m is 0.1-10mg, be sealed in dry aluminum cup, and use DSC(model DiamondDSC, PerkinElmer, Shelton, CT, USA produces) detect the melting heat flow curve of each stearic acid standard items, sweep limit is 30-110 DEG C, and heating rate is 10 DEG C/min, obtains the melting heat flow graph spectrum of stearic acid standard items.As shown in Figure 1, with the quality m of stearic acid standard items for horizontal ordinate, with the peak height Y of the melting peak corresponding to stearic acid standard items for ordinate determination coordinate points, the typical curve of linear fit foundation by coordinate axis zero point is carried out to coordinate points, and obtains typical curve equation m=0.0763Y(1).
Stochastic choice some commercially available stearic acid product A, B and C, then preparation adds the stearic acid product of different stearic acid analog as testing sample, its composition is as shown in table 1.
Table 1
*a, B and C represent the stearic acid of three different brands respectively, numeric representation wherein stearic massfraction in bracket.
*'-' representative is not added.
Under the same conditions testing sample is scanned, obtains the melting heat flow graph spectrum of testing sample, the quality of sample and its melting heat flow graph compose in the peak height of stearic acid melting peak in table 2.
Table 2
| Sample number into spectrum | Sample quality (mg) | The peak height (mW) of melting peak |
| 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 |
By the peak height Y of the stearic acid melting peak of sample between 69.6-80.0 DEG C
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 purity (%) stearic in testing sample, Y
1for the peak height (mW) of stearic acid melting peak in testing sample, m
1for the quality (mg) of testing sample.
Meanwhile, according to the step described in GB " GB/T9104-2008 industry stearic acid test method ", stearic purity ψ in above-mentioned 15 testing samples of gas chromatography determination is adopted.The method that the present invention sets up and vapor-phase chromatography detect the more as shown in table 3 of purity of stearic acid result in sample.
Table 3
Show that the mean relative deviation C ' of the detection method that the present invention sets up and vapor-phase chromatography result is-(7.16 ± 4.41) % by table 2, the method that the present invention sets up can go out the purity of sample by quantitative response, and easy to operation, detection method is with low cost.
Embodiment 2
The present embodiment corrects to the result of gained in embodiment 1 value reducing mean relative deviation C '.Above-mentioned mean relative deviation C ' can by correcting the regression coefficient A in formula (2), and concrete grammar is: the value of A and C ' substituted in following formula (3),
A’=A（1+C’）（3）
Must correct regression coefficient A ' is 0.0818, the corrected purity of sample
calculate according to formula (5),
Wherein
for corrected purity (%) stearic in testing sample, Δ Y
sfor testing sample endothermic peak peak height (mW) between 69.6-80 DEG C; M is the quality (mg) of testing sample.
Stearic corrected purity in the sample that the method using the present invention to set up obtains
the comparative result detecting stearic purity ψ in the sample obtained 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 using the present invention to set up obtains
the mean relative deviation detecting stearic purity ψ in the sample obtained with vapor-phase chromatography is-(0.52 ± 4.73) %, reflects the purity of sample more accurately; And easy to operation, detection method is with low cost.
Last it is noted that above each embodiment is only in order to illustrate technical scheme of the present invention, be not intended to limit; Although with reference to foregoing embodiments to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein some or all of technical characteristic; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme.
Claims (3)
1. detect the method for purity of stearic acid, comprise the following steps: utilize differential scanning calorimeter to obtain the melting heat flow graph spectrum of different quality stearic acid standard items respectively, with the quality m of described stearic acid standard items for horizontal ordinate, with the peak height Y of the stearic acid melting peak corresponding in described melting heat flow graph spectrum of described stearic acid standard items for ordinate determination coordinate points, linear fit is carried out to described coordinate points, set up the typical curve by coordinate axis zero point, and obtain the typical curve equation of formula (1), wherein A is regression coefficient;
m＝AY(1)
Obtain the melting heat flow graph spectrum of testing sample under the same conditions; By the quality m of described testing sample
1with the peak height Y of 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 for described stearic acid melting peak is 68-72 DEG C, and end temp is 75-85 DEG C;
Wherein also comprise and the typical curve equation m=AY of formula (1) is corrected to obtain stearic corrected purity in testing sample
step, be specially: use vapor-phase chromatography purity stearic in testing sample is characterized, obtain stearic purity ψ in testing sample; Utilize stearic purity in described testing sample
calculate relative deviation C with the stearic purity ψ of vapor-phase chromatography gained, described regression coefficient A and the value of the relative deviation C obtained are substituted in following formula (3), must regression coefficient A ' be corrected;
A’＝A(1+C)(3)
Correction regression coefficient A ' is adopted to obtain stearic corrected purity in described testing sample by following formula (4)
Or obtaining the method correcting regression coefficient A ' is: obtain stearic purity in multiple testing sample respectively
and use vapor-phase chromatography to obtain stearic purity ψ in each testing sample respectively; Utilize the purity obtained by formula (2)
calculate the mean relative deviation C ' of described multiple testing sample with the ψ using vapor-phase chromatography to obtain, and itself and described regression coefficient A are substituted in formula (3), must regression coefficient A ' be corrected.
2. the method for detection purity of stearic acid according to claim 1, is characterized in that: when utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, initial temperature is lower than 50 DEG C, and end temp is higher than 90 DEG C.
3. the method for detection purity of stearic acid according to claim 1, is characterized in that: when utilizing stearic acid standard items or testing sample to obtain melting heat flow graph spectrum, scan with the heating rate of 2-20 DEG C/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 |
| 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 |
| CN105784762A (en) * | 2016-04-29 | 2016-07-20 | 山东大学 | Quick purity testing and analyzing method for low-melting-point materials |
| 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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