CN107167536A - A kind of method that high performance liquid chromatography determines transformer oil furfural content - Google Patents
A kind of method that high performance liquid chromatography determines transformer oil furfural content Download PDFInfo
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- CN107167536A CN107167536A CN201710422809.7A CN201710422809A CN107167536A CN 107167536 A CN107167536 A CN 107167536A CN 201710422809 A CN201710422809 A CN 201710422809A CN 107167536 A CN107167536 A CN 107167536A
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Abstract
The invention discloses a kind of method that high performance liquid chromatography determines transformer oil furfural content, comprise the following steps：（1）Transformer oil is pre-processed：Transformer oil to be measured is aoxidized using oxidizing method；After oxidation, extracted by extractant of ethanol, obtain extract one；Use ethanol to be extracted for extractant in untreated transformer oil to be measured, obtain extract two；（2）The yield that transformer oil is oxidized to furancarboxylic acid is determined：With step（1）Under the middle oxidizing method of identical and oxidizing condition, the reaction yield that furfural in transformer oil is oxidized to furancarboxylic acid is determined；（3）Using high effective liquid chromatography for measuring：Wherein, liquid phase chromatogram condition is：The chromatographic column used is phenylpropyl bonded silica gel chromatographic column, and mobile phase is sodium citrate saline solution and methanol, wherein, the pH of sodium citrate saline solution is 4 ~ 5；（4）The calculating of furfural content.The present invention can realize furfural Accurate Determining in transformer oil product.
Description
Technical field
The invention belongs to transformer technology field, and in particular to a kind of high performance liquid chromatography determines transformer oil furfural content
Method.
Background technology
Transformer oil, refers to be used in the oil-filled electric equipments such as transformer, the class for playing insulation, cooling and arc extinguishing is exhausted
Edge oil product.In oil-filled electric equipment, due to constitute solid insulation fibrous material aging cause cellulose decomposition and
Several compounds, such as furfural and furan derivatives are produced, furan derivatives are largely attracted on paper, and fraction is dissolved in oil
In.The presence of these materials can as operational outfit solid insulating and aging degrees diagnosis basis, can also be used as to dissolving
The supplement of gas analysis.
The content method of furfural is mainly in detection transformer oil at present：Using furfural in methanol extraction oil, then use
High-efficient liquid phase color spectrometry, but there are following problems with the method：Although furfural has preferably selectivity in transformer oil,
Can be extracted into from transformer oil in methanol, but extraction yield is only 70% or so, it is impossible to by the furfural in transformer oil compared with
Completely extract, so as to cause the furfural Detection accuracy in transformer oil relatively low.
The content of the invention
In view of the shortcomings of the prior art, transformer oil furfural is determined it is an object of the invention to provide a kind of high performance liquid chromatography
The new method of content, this method can more accurately measure the content of furfural in transformer oil.
In order to achieve the above object, the technical solution adopted by the present invention is as follows：
A kind of method that high performance liquid chromatography determines transformer oil furfural content, comprises the following steps：
(1) transformer oil is pre-processed：
Transformer oil to be measured is aoxidized using oxidizing method；After oxidation, extracted by extractant of ethanol,
Obtain extract one；
Use ethanol to be extracted for extractant in untreated transformer oil to be measured, obtain extract two；
(2) transformer oil is oxidized to the yield measure of furancarboxylic acid：
It is oxidized to under the oxidizing method of identical and oxidizing condition in step (1), determining furfural in transformer oil
The reaction yield of furancarboxylic acid；
(3) high effective liquid chromatography for measuring is used：
1) the furancarboxylic acid content in extract one is determined；
2) the furancarboxylic acid content in extract two is determined；
Wherein, liquid phase chromatogram condition is：The chromatographic column used is citric acid for phenylpropyl bonded silica gel chromatographic column, mobile phase
Sodium-salt aqueous solution and acetonitrile, wherein, the pH of sodium citrate saline solution is 4~5；
(4) calculating of furfural content：
1) furfural in the transformer oil determined is oxidized to the reaction yield of furancarboxylic acid and is designated as a；
2) the furancarboxylic acid content in the extract two determined is designated as n1；
3) the furancarboxylic acid content in the extract one determined is n2；
4) calculating of furfural content：Furfural content=(n2-n1) M2/aM1；
Wherein, the theoretical growing amount of yield a=purpose products (reality) growing amount/purpose product, M1 is mole of furancarboxylic acid
Quality, M2 is the molal weight of furfural.
Compared with prior art, technical scheme has the beneficial effect that：
(1) present invention establishes the new method that furfural content in transformer oil is quantitatively detected using high performance liquid chromatography,
Furfural Accurate Determining in oil product can be achieved, it is ensured that the stable fortune property of transformer safety, quantitative detection transformation can be increased using the technology
The means of furfural content method, improve detection sensitivity in device oil.
The present invention can be achieved to the effective detection of furfural content in transformer oil, more accurately, directly, reliably evaluate and set
Standby operation conditions, periodic detection using unit will have directive significance to high voltage electric equipment, it is ensured that equipment safety is stable
Operation.The technical method is easy to implement once setting up, is substantially shorter manpower and time cost, with great society and economy
Benefit.
(2) present invention is had found first, and in the transformer oil containing finite concentration scope furfural, transformer oil is used into oxygen
Agent method is aoxidized, and its furancarboxylic acid reaction yield is certain, and the present invention uses oxidizing method, and its yield is higher, accessory substance
It is less.
(3) although furfural has preferably selectivity in transformer oil, it can be extracted into from transformer oil in methanol,
But extraction yield is only 70% or so, it is impossible to which the furfural in transformer oil is more completely extracted, and the polarity of furancarboxylic acid ratio
The polarity of furfural is big, and extraction efficiency is higher, and then the accuracy of measure furancarboxylic acid is more larger than furfural, so that determining the standard of furfural
True property is larger.
(4) present invention according to the characteristics of transformer oil after transformer oil and oxidation gropes to a set of that detection is tied
More accurate, the sensitive high-efficient liquid phase chromatogram condition parameter of fruit.
Brief description of the drawings
The Figure of description for constituting the part of the present invention is used for providing a further understanding of the present invention, and of the invention shows
Meaning property embodiment and its illustrate be used for explain the present invention, do not constitute inappropriate limitation of the present invention.
Fig. 1 is methanol：Sodium citrate saline solution=30：70 HPLC spectrograms.
Fig. 2 is methanol：Sodium citrate saline solution=40：60 HPLC spectrograms.
Fig. 3 is the HPLC spectrograms of minimum detectable level.
Fig. 4 is the HPLC spectrograms in embodiment 4.
Embodiment
It is noted that described further below is all exemplary, it is intended to provide further instruction to the present invention.Unless another
Indicate, all technologies used herein and scientific terminology are with usual with general technical staff of the technical field of the invention
The identical meanings of understanding.
It should be noted that term used herein above is merely to describe embodiment, and be not intended to restricted root
According to the illustrative embodiments of the present invention.As used herein, unless the context clearly indicates otherwise, otherwise singulative
It is also intended to include plural form, additionally, it should be understood that, when in this manual using term "comprising" and/or " bag
Include " when, it indicates existing characteristics, step, operation and/or combinations thereof.
As background technology is introduced, deposited in the prior art using the furfural in high performance liquid chromatography measure transformer oil
In certain deficiency, in order to solve technical problem as above, the present invention proposes a kind of high performance liquid chromatography and determines transformer oil
The new method of furfural content, comprises the following steps：
(1) transformer oil is pre-processed：
Transformer oil to be measured is aoxidized using oxidizing method；After oxidation, extracted by extractant of ethanol,
Obtain extract one；
Use ethanol to be extracted for extractant in untreated transformer oil to be measured, obtain extract two；
(2) transformer oil is oxidized to the yield measure of furancarboxylic acid：
It is oxidized to under the oxidizing method of identical and oxidizing condition in step (1), determining furfural in transformer oil
The reaction yield of furancarboxylic acid；
(3) high effective liquid chromatography for measuring is used：
1) the furancarboxylic acid content in extract one is determined；
2) the furancarboxylic acid content in extract two is determined；
Wherein, liquid phase chromatogram condition is：The chromatographic column used is citric acid for phenylpropyl bonded silica gel chromatographic column, mobile phase
Sodium-salt aqueous solution and methanol, wherein, the pH of sodium citrate saline solution is 4~5；
(4) calculating of furfural content：
1) furfural in the transformer oil determined is oxidized to the reaction yield of furancarboxylic acid and is designated as a；
2) the furancarboxylic acid content in the extract two determined is designated as n1；
3) the furancarboxylic acid content in the extract one determined is n2；
4) calculating of furfural content：Furfural content=(n2-n1) M2/aM1；
Wherein, M1 is the molal weight of furancarboxylic acid, and M2 is the molal weight of furfural.
The following is making to be expanded on further to each step：
In step (1), the furfural of certain content is contained in transformer oil, after oxidation, furfural furancarboxylic acid is converted into, due to chaff
The polarity of acid is larger, and after suitable extractant, extraction yield is larger, so that the detection of furfural is converted into the detection of furancarboxylic acid,
Testing result is more accurate.
It is preferred that, the specific method of oxidizing method oxidation transformer oil includes：Transformer oil is used into potassium permanganate
Or 2~4h of hypochlorite oxidation, then be acidified with hydrochloric acid.
It is further preferred that the oxidizing temperature of potassium permanganate is 50~70 DEG C.
It is preferred that, the addition of oxidant is：The volume ratio of liquor potassic permanganate and transformer oil is：0.5~1：10,
The concentration of the solution of potassium permanganate is 70~80-% (w/w), and the volume ratio of sodium hypochlorite and transformer oil is 1~2：10.
The present invention is using ethanol as extractant, and the efficiency for extracting furancarboxylic acid is higher, while the furfural of extraction is less efficient.
It is preferred that, the volume ratio of reaction solution and ethanol after oxidation is 10：2~3.During extraction, sample is shaken in machinery
It is dynamic to vibrate at least 3min thereon, sample is stood, until ethanol and oil phase are kept completely separate.
It is preferred that, the pH value of extractant is 6~7.It is further preferred that the pH value of extractant is 6.5.
, should when detecting the furancarboxylic acid that furfural is changed into often to contain a small amount of furancarboxylic acid in the transformer oil to be measured of processing
This part furancarboxylic acid is excluded.
In step (2), when furfural is oxidized into furancarboxylic acid using method for oxidation, reaction yield tends not to be 100%,
That is, even if by furfural complete oxidation, being also not necessarily completely converted into furancarboxylic acid, other accessory substances may be produced.
So needing to determine the reaction yield that furfural is oxidized to furancarboxylic acid, when determining reaction yield, by blank transformer oil
A certain amount of furfural is dissolved, mixes, is aoxidized using the oxidizing condition in step (1), after oxidation, the content of furancarboxylic acid is determined,
So as to which furfural is oxidized to the reaction yield of furancarboxylic acid in calculating transformer oil.The present invention has found first, is containing finite concentration scope
In the transformer oil of furfural, transformer oil is aoxidized using oxidant method, its furancarboxylic acid reaction yield is certain, and this is also accurate
Determine the basis of furfural.
In step (3)：
It is preferred that, mobile phase is：Sodium citrate saline solution：The volume ratio of methanol is (60~80)：(20~40).Enter one
Walk preferably, mobile phase is：Sodium citrate saline solution：The volume ratio of methanol is 60：40.
It is preferred that, sodium citrate saline solution is the sodium dihydrogen citrate aqueous solution, the disodium citrate aqueous solution or citric acid three
Sodium water solution.It is further preferred that the sodium citrate saline solution is the sodium dihydrogen citrate aqueous solution.
It is preferred that, the concentration of the sodium citrate saline solution is 0.03~0.2mol/L.It is further preferred that the lemon
The concentration of the lemon acid sodium-salt aqueous solution is 0.05mol/L.
It is preferred that, the pH of the sodium citrate saline solution is 4.5.
It is preferred that, the Detection wavelength of the furancarboxylic acid is 222nm.
It is preferred that, flow velocity：0.5~1ml/min；Column temperature：35~38 DEG C；Sample size：5μL.It is further preferred that flow velocity：
0.8ml/min；Column temperature：35℃.
In order that technical scheme can clearly be understood by obtaining those skilled in the art, below with reference to tool
The embodiment of body describes technical scheme in detail.
Embodiment 1 chromatographic condition is probed into
1st, the selection of mobile phase
(1) phenylpropyl bonded silica gel chromatographic column (5 μm, 4.6 × 150mm of Φ) is chosen；
Sample：Using the ethanol solution of the furancarboxylic acid after oxidation, aoxidized using potassium permanganate, refer to embodiment 2.
Following mobile phase is selected when probing into, below as just typical case：
Methanol：Volume ratio=30 of water：70, chromatographic behavior：There is no chromatographic peak conditions of streaking, but post effect is poor；
Acetonitrile：Volume ratio=30 of water：70, chromatographic behavior：Chromatographic peak trails；
Methanol：Volume ratio=30 of 0.05mol/L aqueous sodium acetate solutions：70, chromatographic behavior：There is bifurcated in chromatographic peak；
Methanol：Volume ratio=30 of 0.05mol/L sodium citrate salts (sodium dihydrogen citrate, pH4.5) aqueous solution：70, chromatogram
Behavior：Chromatographic peak profile and post effect are preferable, but retention time is longer；
Methanol：Volume ratio=40 of 0.05mol/L sodium citrate salts (sodium dihydrogen citrate, pH4.5) aqueous solution：60, chromatogram
Behavior：Chromatographic peak profile and post effect are preferable, and retention time is moderate；
Methanol：The 0.05mol/L sodium ascorbyl phosphate aqueous solution (NaH2PO4, pH4.5) volume ratio=30：70, chromatographic behavior：
Post effect is poor；
(2) phenylpropyl bonded silica gel chromatographic column (5 μm, 4.6 × 150mm of Φ) is chosen, mobile phase is methanol：0.05mol/L
Sodium citrate salt (sodium dihydrogen citrate, pH4.5) aqueous solution.
Work as methanol：Volume ratio=20 of 0.05mol/L sodium citrate salts (sodium dihydrogen citrate, pH4.5) aqueous solution：When 80,
Retention time is 16.3min, and post effect is 3156；
Work as methanol：Volume ratio=30 of 0.05mol/L sodium citrate salts (sodium dihydrogen citrate, pH4.5) aqueous solution：When 70,
Retention time is 9.2min, and post effect is 3145；HPLC spectrograms are shown in Fig. 1.
Work as methanol：Volume ratio=40 of 0.05mol/L sodium citrate salts (sodium dihydrogen citrate, pH4.5) aqueous solution：When 60,
Retention time is 6.4min, and post effect is 3238；HPLC spectrograms are shown in Fig. 2.
In summary study, understand by analysis, the mobile phase of prioritizing selection is methanol and 0.05mol/L sodium citrate salts
The aqueous solution.Methanol：0.05mol/L sodium citrates saline solution=(60~80)：(20~40) can be used as preferably mobile phase.
Consider, optimal is combined as methanol：0.05mol/L sodium citrates saline solution=40：60.
2nd, the selection of chromatographic column and the selection of sodium citrate saline solution：
Choose octadecylsilane chemically bonded silica chromatographic column, octyl silane group silica gel chromatographic column and phenylpropyl bonded silica
Glue chromatographic column, is 5 μm, 4.6 × 150mm of Φ.
Mobile phase：Methanol：Volume ratio=40 of sodium citrate salt (sodium dihydrogen citrate, pH4.5) aqueous solution：60；
Flow velocity：0.8ml/min；
Column temperature：35℃；
Sample：Using the ethanol solution of the 0.02mg/L furancarboxylic acids after oxidation, aoxidized using potassium permanganate, refer to reality
Apply example 2；
Sample size：5μL；
Detection wavelength：222nm.
Retention time (RT) under the different reverse-phase chromatographic columns of table 1 and sodium citrate salt concentration of aqueous solution
As shown in Table 1, when sodium citrate saline solution is relatively low, chromatographic peak is unstable；Use octadecylsilane bonded silica
During glue chromatographic column, analysis time is longer, elutes more difficult；It is shorter using the octyl silane group silica gel chromatogram column analysis time；
During using phenylpropyl bonded silica gel chromatographic column, furancarboxylic acid belongs to aromatic compound, and its pi-electron meets 4N+2 rules, is 6 electrons
System, but phenyl post has special reservation to the material with phenyl ring, and key is sent because that can be formed.Although phenyl column polarity compares octadecyl
Silane group silica gel chromatographic column is big, but phenyl post has special reservation to the material with armaticity, therefore can form pi bond, from
And make it that retention time is moderate.It is applicable in 0.03~0.2mol/L sodium citrate saline solution, but salinity is too high,
Chromatographic column and analytical instrument can be damaged, so optimal selection is sodium citrate saline solution 0.05mol/L.
3rd, the selection of the pH value of sodium citrate saline solution
Chromatographic column：Phenylpropyl bonded silica gel chromatographic column (5 μm, 4.6 × 150mm of Φ)
Mobile phase：Methanol：0.05mol/L sodium citrate salts ((sodium dihydrogen citrate) aqueous solution=40：60；PH is adopted when adjusting
It is adjusted with sodium hydroxide or citric acid.
Flow velocity：0.8ml/min；
Column temperature：35℃；
Sample：Using the ethanol solution of the 0.02mg/L furancarboxylic acids after oxidation, aoxidized using potassium permanganate, refer to reality
Apply example 2；
Sample size：5μL；
Detection wavelength：222nm.
Retention time (RT) under the sodium citrate saline solution difference pH of table 2
| pH | 3 | 4 | 4.5 | 5 | 6 | 7 |
| Retention time (min) | 3.1 | 6.2 | 6.4 | 6.3 | 6.8 | 7.2 |
| Post is imitated | 3158 | 3214 | 3258 | 3192 | 2537 | 1539 |
As shown in Table 2, when the pH of sodium citrate saline solution is 3, retention time is too short, is unfavorable for chromatography；PH is 7
When, post effect is low, and peak shape is bad, and retention time is longer.To sum up, prioritizing selection pH is 4~5, and post effect and peak shape are preferable, retention time
It is moderate, suitable for chromatography.
4th, the selection of Detection wavelength
Test limit under the different Detection wavelengths of table 3
| Detection wavelength | 222nm | 242nm | 252nm |
| Minimum detectable level | 5.2μg/L | 8μg/L | 12μg/L |
As shown in Table 3, at 222nm, furancarboxylic acid has larger absorption, and peak area response is larger, and the sensitivity of detection is non-
Chang Gao, therefore using 222nm as the Detection wavelength of furancarboxylic acid.
The different detection parameter of screening and optimizing of the present invention, reaches the separation detection effect excellent to furancarboxylic acid in transformer oil
Really.To sum up, the detection method of furancarboxylic acid of the present invention, comprises the following steps：On the high performance liquid chromatograph with UV-detector,
The chromatographic column used is for phenylpropyl bonded silica gel chromatographic column, mobile phase：Sodium citrate saline solution：The volume ratio of methanol is
60：40, the concentration of the sodium citrate saline solution is 0.05mol/L, and pH is 4.5, and Detection wavelength is 222nm.
The preparation of solution to be measured：Precision measures extract one or extract two, is placed in volumetric flask, is used as solution to be measured.
The preparation of standard liquid：Precision weighs furancarboxylic acid standard items in beaker, plus is placed in after ethanol dissolving in volumetric flask, dilute
Release the furancarboxylic acid storing solution that 1mg/L is prepared to graduation mark.And the concentration needed for testing is diluted to this storing solution, it is molten as standard
Liquid.
Sample introduction, measures the furancarboxylic acid peak area on spectrogram respectively respectively.Using the conventional computational methods (ratio of both peak areas
Value) it is that can obtain, the furancarboxylic acid content in solution to be measured.
Embodiment 2
The selection of method for oxidation：
Before it is determined that being best suitable for the method for oxidation of the present invention, the present invention passes through the research of a variety of method for oxidation and groped.
Wherein, verification experimental verification, Kang Nichanuofa can also produce other substantial amounts of accessory substances while furancarboxylic acid is prepared, and which increase chromatogram
The difficulty of separation；The oxidation efficiency of catalyst oxidizing process is relatively low, it is impossible to furfural is more completely oxidized into furancarboxylic acid, and this is unfavorable for
The detection of furancarboxylic acid.And use oxidizing method, the present invention find first, containing finite concentration scope furfural (5.2 μ g/L~
Between 5mg/L) transformer oil in, by transformer oil using oxidant method aoxidize, its furancarboxylic acid reaction yield is certain, and this
Invention uses oxidizing method, and its yield is higher, and accessory substance is less.
Illustrated by taking preferred oxidizing method as an example：
0.010g, 0.020g, 0.030g furfural are dissolved in 10ml blank transformer oil respectively, fully mixed；Then
The abundant reflux oxidation 3h of potassium permanganate is slowly added dropwise, oxidizing temperature is 50 DEG C, the volume ratio of liquor potassic permanganate and transformer oil
Example is 0.5：10, the concentration of the solution of potassium permanganate is 70% (w/w), then is acidified with hydrochloric acid, you can all aoxidize furfural.Through
Detection is crossed, 0.0113g, 0.227g and 0.034g furancarboxylic acid is obtained, calculated yield is 98%.And do not had using this method
The presence of furfural is detected, illustrates that the furfural in transformer oil has completely reacted.
Wherein, theoretical growing amount × 100% of yield (%)=purpose product (reality) growing amount/purpose product.
Embodiment 3
(1) selection of extractant species：
Choose methanol, ethanol, water, methanol：The volume ratio of water is 1：1st, the volume ratio of second alcohol and water is 1：1 this 5 kinds for extraction
Take agent.
Experimental method：
0.010g furancarboxylic acid and 0.010g furfurals are dissolved in 10ml blank transformer oil, fully mixed；Then on choosing
State 5 kinds of extractants to be extracted, the pH of extractant is 6.5, extractant：The volume ratio of blank transformer oil is 10：3, extraction
When, sample is vibrated into 5min on mechanical vibrator, sample is stood, until extraction phase and oil phase are kept completely separate.
Experimental result is shown in Table, and can be obtained by table 4, different extractants, and furancarboxylic acid is different with the extraction efficiency of furfural.Wherein, adopt
When with ethanol being extractant, the extraction efficiency highest of furancarboxylic acid, while the extraction efficiency of furfural is minimum.
The extraction yield of the different extractants of table 4
(2) selection of Solvent quantity
0.010g furancarboxylic acid is dissolved in 10mL blank transformer oil, fully mixed, analogue transformer oil is obtained；Then
It is respectively 10 according to volume ratio with ethanol by analogue transformer oil：1、10：2、10：3、10：4 adding proportion is extracted, will
Extractant pH is adjusted to as 6.5.During extraction, sample is vibrated into 5min on mechanical vibrator, sample is stood, until extraction phase
It is kept completely separate with oil phase.
Experimental result is shown in Table, and can be obtained by table 5, the extractant of Different adding amount, and the extraction efficiency of furancarboxylic acid is different.Wherein, when
Analogue transformer oil：The volume ratio of ethanol is 10：When 2~3, the extraction efficiency of furancarboxylic acid is higher, with the increasing of ethanol addition
Plus, extraction efficiency has declined on the contrary.
The extraction yield of the Different adding amount extractant of table 5
The detection of furfural in the transformer oil to be measured of embodiment 4
Simulate the preparation of transformer oil to be measured：Weigh 0.0487mg furfurals and 0.00255mg furancarboxylic acids are dissolved in 10# blank transformations
In device oil, fully mix, be settled to 25mL, obtain the 10# transformer oil to be measured that concentration is 2.465mg/L.Entered using this oil sample
Row analysis detection.
A kind of method that high performance liquid chromatography determines transformer oil furfural content, comprises the following steps：
(1) transformer oil is pre-processed：
It is slowly added dropwise using 70% (w/w) potassium permanganate into 10# transformer oil to be measured, abundant reflux oxidation 3h, oxygen
It is 50 DEG C to change temperature, and the volume ratio of liquor potassic permanganate and transformer oil is 0.5：10, then be acidified with hydrochloric acid, you can by furfural
All oxidations.After oxidation, add ethanol and extracted, wherein, the volume ratio of reaction solution and ethanol after oxidation is 10：3, extraction
The pH for taking agent is 6.5, obtains extract one.
Untreated transformer oil to be measured is extracted using above-mentioned same method, extract two is obtained；
(2) transformer oil is oxidized to the yield measure of furancarboxylic acid：
0.010g, 0.020g, 0.030g furfural are dissolved in 10ml blank 10# transformer oil respectively, fully mixed；So
After be slowly added dropwise the abundant reflux oxidation 3h of potassium permanganate, oxidizing temperature is 50 DEG C, the volume of liquor potassic permanganate and transformer oil
Ratio is 0.5：10, the concentration of the solution of potassium permanganate is 70% (w/w), then is acidified with hydrochloric acid, you can all aoxidize furfural.
Calculated yield is 97%.
(3) high effective liquid chromatography for measuring is used：
Chromatographic condition is as follows：
Chromatographic column：GP-Phenyl phenyl chromatographic columns sepax, 5 μm, 4.6 × 150mm of Φ, Sai Fen scientific ＆ technical corporation of the U.S.；
Mobile phase：Methanol：Volume ratio=40 of sodium citrate salt (sodium dihydrogen citrate, pH4.5) aqueous solution：60；
Flow velocity：0.8ml/min；
Column temperature：35℃；
Sample size：5μL；
Detection wavelength：222nm.
The HPLC in the content of the furancarboxylic acid in extract one and extract two, extract one is determined using above chromatographic condition
Spectrogram is shown in Fig. 4.
And the content of the furancarboxylic acid in determination step (2), so that calculated yield.
(4) calculating of furfural content：
1) furfural in the transformer oil determined is oxidized to the reaction yield of furancarboxylic acid and is designated as a, a=0.97；
2) the furancarboxylic acid content in the extract two determined is designated as n1, n1=2.3mg/L；
3) the furancarboxylic acid content in the extract one determined is n2, n2=0.1mg/L；
4) calculating of furfural content：Furfural content=(n2-n1) M2/aM1=1.944mg/L；
Wherein, M1 is the molal weight of furancarboxylic acid, and M2 is the molal weight of furfural.
Test above in triplicate.
For checking test result accurately and reliably, the present invention is directly detected using efficient liquid-phase chromatography method of the prior art
Furfural in transformer oil to be measured, detection method is specific as follows：
(1) extract：10# transformer oil to be measured is extracted using methanol, the volume ratio of transformer oil and methanol is
10:1, extraction time is 2min, obtains extract；
(2) high-efficient liquid phase chromatogram condition：
Chromatographic column：Octadecylsilane chemically bonded silica chromatographic column, 5 μm, 4.6 × 150mm of Φ.
Mobile phase：Eluted using 85% (v/v) methanol aqueous solution；
Flow velocity：0.8ml/min；
Column temperature：40℃；
Sample size：5μL；
Detection wavelength：280nm.
The content of furfural in extract is determined using above method, furfural content is 1.835mg/L after testing, content is less than
The testing result of the present invention, it is seen then that in extraction, directly extract the less efficient of furfural, so as to cause the furfural content of detection
It is relatively low.
Experimental example：
The present invention has also probed into method precision, the degree of accuracy and the recovery of standard addition of the high performance liquid chromatography detection furancarboxylic acid,
By taking the method for the high performance liquid chromatography detection furancarboxylic acid in embodiment 4 as an example.Using replica test, recovery of standard addition experiment investigation
The repeatability and accuracy of this method.
(1) repeatability is investigated：
Experiment：Compound concentration be 0.01mg/L furancarboxylic acid transformer oil, sample detection 6 times, the precision of computational methods and
The degree of accuracy, as a result such as table 6, calculates its relative standard deviation RSD=1.63%, illustrates that its repeatability is good.
The method precision of table 6 and degree of accuracy experimental result
(2) recovery of standard addition is investigated
Various concentrations furancarboxylic acid oil standard liquid is configured, is determined according to the method described above, its recovery of standard addition is calculated for 95%-
105%.
Both the above verification experimental verification using this high-performance liquid chromatography method furancarboxylic acid content the method degree of accuracy it is higher,
It is reproducible.
The preferred embodiments of the present invention are the foregoing is only, are not intended to limit the invention, for the skill of this area
For art personnel, the present invention can have various modifications and variations.Within the spirit and principles of the invention, that is made any repaiies
Change, equivalent substitution, improvement etc., should be included in the scope of the protection.
Claims (15)
1. a kind of method that high performance liquid chromatography determines transformer oil furfural content, it is characterized in that, comprise the following steps：
（1）Transformer oil is pre-processed：
Transformer oil to be measured is aoxidized using oxidizing method；After oxidation, extracted, obtained by extractant of ethanol
Extract one；
Use ethanol to be extracted for extractant in untreated transformer oil to be measured, obtain extract two；
（2）The yield that transformer oil is oxidized to furancarboxylic acid is determined：
With step（1）Under the middle oxidizing method of identical and oxidizing condition, determine furfural in transformer oil and be oxidized to furancarboxylic acid
Reaction yield；
（3）Using high effective liquid chromatography for measuring：
1）Determine the furancarboxylic acid content in extract one；
2）Determine the furancarboxylic acid content in extract two；
Wherein, liquid phase chromatogram condition is：The chromatographic column used is sodium citrate salt for phenylpropyl bonded silica gel chromatographic column, mobile phase
The aqueous solution and methanol, wherein, the pH of sodium citrate saline solution is 4 ~ 5；
（4）The calculating of furfural content：
1）The reaction yield that furfural in the transformer oil of measure is oxidized to furancarboxylic acid is designated as a；
2）Furancarboxylic acid content in the extract two of measure is designated as n1；
3）Furancarboxylic acid content in the extract one of measure is n2；
4）The calculating of furfural content：Furfural content=（n2-n1）M2/aM1；
Wherein, M1 is the molal weight of furancarboxylic acid, and M2 is the molal weight of furfural.
2. the method as described in claim 1, it is characterized in that：Step（1）In, oxidizing method aoxidizes the specific of transformer oil
Method includes：Transformer oil is used into 2 ~ 4h of potassium permanganate or hypochlorite oxidation, then is acidified with hydrochloric acid.
3. method as claimed in claim 2, it is characterized in that：The oxidizing temperature of potassium permanganate is 50 ~ 70 DEG C.
4. method as claimed in claim 2, it is characterized in that：The addition of oxidant is：Liquor potassic permanganate and transformer oil
Volume ratio be：0.5~1：10, the concentration of the solution of potassium permanganate is 70 ~ 80-%（w/w）, sodium hypochlorite and transformer oil
Volume ratio is 1 ~ 2：10.
5. the method as described in claim 1, it is characterized in that：Step（1）In, the volume ratio of reaction solution and ethanol after oxidation
For 10：2~3.
6. the method as described in claim 1, it is characterized in that：Step（2）In, when determining reaction yield, by blank transformer oil
Middle a certain amount of furfural of dissolving, is mixed, using step（1）In oxidizing condition aoxidized, after oxidation, determine furancarboxylic acid and contain
Amount, so that furfural is oxidized to the reaction yield of furancarboxylic acid in calculating transformer oil.
7. the method as described in claim 1, it is characterized in that：Step（3）In, mobile phase is：Sodium citrate saline solution：Methanol
Volume ratio be（60~80）：（20~40）.
8. method as claimed in claim 7, it is characterized in that：Mobile phase is：Sodium citrate saline solution：The volume ratio of acetonitrile is
60：40.
9. the method as described in claim 1, it is characterized in that：Step（3）In, sodium citrate saline solution is sodium dihydrogen citrate water
Solution, the disodium citrate aqueous solution or trisodium citrate aqueous solution.
10. method as claimed in claim 9, it is characterized in that：The sodium citrate saline solution is the sodium dihydrogen citrate aqueous solution.
11. the method as described in claim 1, it is characterized in that：Step（3）In, the concentration of the sodium citrate saline solution is
0.03~0.2 mol/L。
12. method as claimed in claim 11, it is characterized in that：The concentration of the sodium citrate saline solution is 0.05 mol/
L。
13. the method as described in claim 1, it is characterized in that：Step（3）In, the pH of the sodium citrate saline solution is
4.5。
14. the method as described in claim 1, it is characterized in that：Step（3）In, the Detection wavelength of the furancarboxylic acid is 222nm.
15. the method as described in claim 1, it is characterized in that：Step（3）In, flow velocity：0.5~1 ml/min；Column temperature：35~38
℃；Sample size：5μL.
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