HD 415 S1:1981
(Main)Detection and determination of specified anti-oxidant additives in insulating oils
Detection and determination of specified anti-oxidant additives in insulating oils
Gives the detection methods for the anti-oxidant additives in hydrocarbon insulating oils as well as determination methods of these additives.
Nachweis und Bestimmung spezieller Antioxidantien in Isolierölen
Détection et dosage d'additifs antioxydants spécifiques présents dans les huiles isolantes
Donne les méthodes de détection des additifs antioxydants présents dans les huiles à base d'hydrocarbures ainsi que les méthodes de dosages de ces additifs.
Detection and determination of specified anti-oxidant additives in insulating oils (IEC 60666:1979)
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Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-1999
Detection and determination of specified anti-oxidant additives in insulating oils
(IEC 60666:1979)
Detection and determination of specified anti-oxidant additives in insulating oils
Nachweis und Bestimmung spezieller Antioxidantien in Isolierölen
Détection et dosage d'additifs antioxydants spécifiques présents dans les huiles
isolantes
Ta slovenski standard je istoveten z: HD 415 S1:1981
ICS:
29.040.10 Izolacijska olja Insulating oils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME CEI
INTERNATIONALE IEC
INTERNATIONAL
Première édition
STANDARD
First edition
1979-01
Détection et dossage d'additifs antioxydants
spécifiques présents dans les huiles isolantes
Detection and determination of specified
anti-oxidant additives in insulating oils
© IEC 1979 Droits de reproduction réservés — Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
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utilisée
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Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http: //www.iec.ch
CODE PRIX
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PRICE CODE
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Pour prix, voir catalogue en vigueur
•
For price, see current catalogue
– 3 –
CONTENTS
Page
FOREWORD 5
PREFACE 5
Clause
1. Scope 7
SECTION I — METHODS FOR THE DETECTION OF ANTI-OXIDANT ADDITIVES
2. Detection of 2.6-di-tert-butyl-paracresol (DBPC) by thin layer chromatography
2.1 Summary of the method
2.2 Reagents 7
2.3 Equipment
2.4 Procedure
Detection of n-phenyl-a-naphtylamine (PAN) and n-phenyl-(3-naphtylamine (PBN) by thin
3.
layer chromatography 9
3.1 Summary of the method 9
3.2 Reagents 9
3.3 Equipment 9
3.4 Procedure
11 4. Detection of anthranilic acid in new insulating oils by thin layer chromatography
4.1 Summary of the method
4.2 Reagents
4.3 Equipment
4.4 Procedure
SECTION II — METHODS FOR THE DETERMINATION OF ANTI-OXIDANT ADDITIVES
5. Determination of 2.6-di-tert-butyl-paracresol
5.1 Quantitative determination by infra-red spectrophotometry
5.2 Semi-quantitative determination by thin layer chromatography
6. Determination of n-phenyl-13-naphtylamine by spectrophotometry
6.1 Summary of the method
6.2 Reagents
23 6.3 Equipment
6.4 Procedure
6.5 Calculation
6.6 Lower limit of detection
FIGURE 24
– 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
DETECTION AND DETERMINATION OF SPECIFIED ANTI-OXIDANT
ADDITIVES IN INSULATING OILS
FOREWORD
I) The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on which all the
National Committees having a special interest therein are represented, express, as nearly as possible, an international
consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use and they are accepted by the National Committees in that
2)
sense.
In order to promote international unification, the IEC expresses the wish that all National Committees should adopt the
3)
text of the IEC recommendation for their national rules in so far as national conditions will permit. Any divergence
between the IEC recommendation and the corresponding national rules should, as far as possible, be clearly indicated in the
latter.
PREFACE
This standard has been prepared by Sub-Committee 10A: Hydrocarbon Insulating Oils, of IEC
Technical Committee No. 10: Liquid and Gaseous Dielectrics.
Drafts were discussed at the meetings held in Baden-Baden in 1975 and in Moscow in 1977. As a
result of this latter meeting, a draft, Document 10A(Central Office)39, was submitted to the National
Committees for approval under the Six Months' Rule in August 1978.
The National Committees of the following countries voted explicitly in favour of publication:
Netherlands
Australia
Poland
Austria
Belgium Romania
South Africa (Republic of)
Bulgaria
Spain
Czechoslovakia
Sweden
Denmark
Switzerland
Egypt
Turkey
France
Union of Soviet
Germany
Socialist Republics
Hungary
United Kingdom
Israel
United States of America
Italy
Other IEC publications quoted in this standard:
Publications Nos. 474: Test Method for Oxidation Stability of Inhibited Mineral Insulating Oils.
590: Determination of the Aromatic Hydrocarbon Content of New Mineral Insulating Oils.
- 7 -
DETECTION AND DETERMINATION OF SPECIFIED ANTI-OXIDANT
ADDITIVES IN INSULATING OILS
Scope
1.
The methods described are to be used for the detection and determination of specified anti-
oxidant additives in new hydrocarbon insulating oils. The detection methods are to be applied to
assess whether or not a hydrocarbon insulating oil contains an anti-oxidant additive as specified
by the supplier.
The determination methods are used for the quantitative determination of anti-oxidant addi-
tives previously detected by the appropriate detection method.
Note. - In certain cases, the. methods described may also be used for oils in service.
SECTION I - METHODS FOR THE DETECTION OF ANTI-OXIDANT ADDITIVES
2. Detection of 2.6-di-tert -butyl-paracresol (DBPC) by thin layer chromatography
2.1 Summary of the method
The anti-oxidant additive is extracted from the oil with a suitable solvent. The solvent from
the extract is evaporated and the residue analyzed by thin layer chromatography with the aid of
a specific reagent.
2.2 Reagents
- Methanol, analytical grade.
- n-heptane, analytical grade.
Phosphomolybdic acid: solution of 5 g phosphomolybdic acid in 100 ml isopropanol.
-
Ammonia solution, analytical grade (density at 20 °C: 0.91 g/cm3).
-
Di-isopropyl ether, analytical grade.
-
2.3 Equipment
Usual thin layer chromatography (TLC) equipment.
-
- Silica-gel coated plates.
- Microsyringe.
2.4 Procedure
Extract 50 ml of the insulating oil three times with 20 ml portions of methanol.
-
Combine the extracts and evaporate the methanol to a final volume of about 5 ml taking care
-
to avoid overheating. It is best to carry out the evaporation under a nitrogen stream.
– 9 –
Apply 20 µl of the concentrated extract on a TLC plate and develop the plate in a lined tank
with a mixture of 99.5% n-heptane plus 0.5% di-isopropyl ether until the solvent front has
travelled 10 cm up.
– Remove the plate from the tank and dry.
After air-drying, spray the plate with the phosphomolybdic reagent.
–
at ambient temperature (the colour will appear more quickly if the plate is heated to
– Dry
approximately 90 °C for a few minutes) and expose the chromatographic plate to ammonia
vapours.
The DBPC appears as a blue spot on a white background.
– Limit of detection: about 0.005% by mass on the oil as such. To aid in identifying the
developed colour, repeat the above using a standard solution, 0.2% by mass of DBPC in an
insulating base oil.
3. Detection of n-phenyl- a-naphtylamine (PAN) and n-phenyl- (3-naphtylamine (PBN) by thin layer
chromatography
3.1 Summary of the method
The oil sample is dissolved in a suitable solvent and analyzed by thin layer chromatography
with the aid of a suitable chromogenic agent.
3.2 Reagents
– Dichloromethane, analytical grade.
–
Mixture of 97 % of iso-octane (2.2.4 trimethyl pentane) and 3% of ethyl acetate, analytical
grade.
Diazotized p-nitroaniline. The reagent is prepared immediately before use by adding solution
No. 1 to an equal volume of cold solution No. 2.
Solution No. 1: dissolve 1.44 g sodium nitrite in 250 ml water (stock solution).
Solution No. 2: dissolve 2.8 g p-nitroaniline in 32 ml warm concentrated hydrochloric acid
and make up with water to 250 ml (stock solution). Store in brown glass
bottle.
– 1% dichlorobenzoquinone-4-chlorimine (DCLQ) ethanolic solution.
3.3 Equipment
– Usual TLC equipment.
– Silica-gel coated plates.
– Hair dryer.
– Microsyringe.
3.4 Procedure
– Dilute 5 ml of insulating oil with 5 ml of dichloromethane and apply 20 µl of this solution to
the TLC plate.
– The plate is developed in a lined tank with the mixture of iso-octane and ethyl acetate (97/3
vol.). When the solvent front has travelled 10 cm up, the plate is removed and air dried.
– 11 –
Spray the freshly prepared diazotized reagent on the plate. If PAN is present in the sample,
an orange spot appears at an approximate RF of 0.20-0.25. If PBN is present in the sample, a
violet spot appears at an approximate RF of 0.15-0.18.
The sensitivity of the detection may be improved by gently heating the plate with a hair dryer.
– Alternatively 1% DCLQ solution can be used as the chromogenic reagent in place of the
diazotized p-nitroaniline spray. PAN appears as a yellow-brown spot and PBN as a dark
mauve spot. Gentle heating favours the appearance of the coloured spots.
– For semi-quantitative determinations and to aid in identifying the developed colours, the
spots obtained may be compared with those obtained using standard solutions of PAN and
PBN in insulating base oil.
– Limit of detection: about 0.005% by mass.
4. Detection of anthranilic acid in new insulating oils by thin layer chromatography
4.1 Summary of the method
A drop of oil–dichloromethane solution is applied to a TLC plate and the base oil as well as
any phenolic or amino oxidation inhibitors are removed to the top of the plate, using toluene as
the solvent system. Anthranilic acid is retained at the starting point and is then eluted with a
highly polar solvent system and detected with a specific chromogenic reagent.
4.2 Reagents
– Toluene, analytical grade.
– Mixture of 90% ethylacetate-10% ethanol (anhydrous), analytical grade.
– 1% dichlorobenzoquinone-4-chlorimine (DCLQ) ethanolic solution, analytical grade.
– Dichloromethane, analytical grade.
4.3 Equipment
– Usual TLC equipment.
Silica-gel coated plates.
–
– Microsyringe.
4.4 Procedure
– Dilute 5 ml of oil with 5 ml of dichloromethane. Apply 20 µl of this solution into a TLC plate.
– Develop the plate in a lined tank with toluene until the solvent front has travelled 15 cm
approximately.
Remove the plate from the tank and allow it to dry.
– Make a second run in a lined tank to a solvent front height of 10 cm with the 90/10 ethylace-
tate-ethanol mixture.
Air dry the plate and then spray it with the 1% DCLQ ethanolic solution.
Anthranilic acid appears after a few minutes as a mauve spot at an approximate RF of 0.20-
0.25.
Limit of detection about 0.003% by mass.
–
To aid in the identification of the developed colour, this may be compared with that obtained
from a solution of anthranilic acid in insulating base oil.
– 13 –
SECTION II – METHODS FOR THE DETERMINATION
OF ANTI-OXIDANT ADDITIVES
- -
5. Determination of 2.6-di-tert butyl paracresol
5.1 Quantitative determination by infra-red spectrophotometry
5.1.1 Summary of the method
This method determines the amount of di-tert-butyl-paracresol (DBPC) in new mineral oils
by measurement of the infra-red absorption at the (O-H) stretching frequency of hindered
phenols. The method gives a quantitative determination of the additional hindered phenols
present in the sample oil compared with the base oil. If the original base oil is not available for
comparison, the total phenols present can be determined, but the overall precision of the
determination may be comparatively reduced. The detection limit will increase accordingly.
This method is applicable for DBPC concentrations in the range 0.02%-0.90% by mass.
The method is not specific for DBPC. A negative detection (below 0.05%) ensures the
absence of DBPC, but a positive detection does not indicate the presence or absence of DBPC.
The absorbance of the (O-H) stretching frequency at 3 650 cm- is measured in 1.5 mm path-
length cells, and the DBPC content obtained from a standard calibration graph prepared by
adding weighed quantities of DBPC to the original base oil.
5.1.2 Reagents
Carbon tetrachloride, analytical grade.
–
– 2.6-di-tert-butyl-paracresol, analytical grade.
Notes 1. – All reagents used in infra-red spectroscopy must be stored in brown bottles and away from light.
2. – Carbon tetrachloride is widely used in infra-red spectroscopy; however, when due to legal or safety regula-
tions its use is forbidden, any other solvent may be used provided that it dissolves completely the oil and that
it does not absorb in the infra-red band used.
5.1.3 Equipment
– Double-beam infra-red spectrophotometer having a resolution of better than 5 cm- 1 at
and covering the range 4 000 cm- 1 to 3 000 cm-1.
3 500 cm- 1
– A matched pair of 1.5 mm path-length liquid cells with sodium chloride windows.
5.1.4 Sample condition
Samples should be shielded from heat and direct sunlight at all times, and should be dried by
filtering through a dried Whatman No. 1 filter paper before use.
– 15 –
5.1.5 Calibration
Standard calibration solutions are prepared by dissolving weighed amounts of DBPC in
weighed amounts of the dried base oil (see note of Sub-clause 5.1.7).
At least five calibration solutions should be prepared covering the range 0.02% to 0.50%
DBPC by mass.
Intermediate standards can be prepared if necessary when the approximate concentration of
DBPC in the sample is known.
The absorbance at 3 650 cm- 1 of the calibration solutions is measured by the method
(A3650)
detailed in Sub-clause 5.1.7, and a calibration curve prepared by plotting against % DBPC
A3650
content. The calibration should produce a straight line passing through the origin, according to
the Beer-Lambert law of absorption:
A = loglf " KCD
where:
A = absorbance
/o = intensity of incident radiation
I = intensity of transmitted radiation
K = extinction coefficient (constant
...
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