|Article Title: Standard Test Method for Ultraviolet Absorption of White Oils|
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1.1. The criterion regulates the test method for ultraviolet absorption of white oils.
1.2. The criterion may be applied to white oil utilization on face-painting, pharmacy and food grade but not applied to that of utilized resolveable into dimethyl sulfoxide and indicating fluorescence or additive with matting property.
1.3. The criterion use international system of unit (SI), The value in mesh unit only for reference.
1.4. The criterion will not intend to put forward its comments on all the safety issues that involve with application, thus before using this criterion, the persons who use this criterion will take their responsibility to implement investigation and establish applicable measures for safety and health care, and check if it is feasible for the defined scope of regulation. For the specificic description of prevention please make reference to Article 7.1~7.2.
2. Quoted Files of Standardization
The provisions stipulated below that quoted by this criterion come into partial provisions of this criterion. Those quoted files with notice of date followed by sheet of modification (not including contents of error correction) or modified version, all of which are no applicable to this criterion, however it is encouragable for each pary who have reached agreement according to this criterion to study on a new version by using these files. Those quoted files with no notice of date, the new version of which will be applicalble to this criterion.
Terms and definations correlative with molecular spectroscopy in ASTM E 131
3. Terms and Definitions
3.1 As to the definitions and symbols correlative with absorption spectum please refer to ASTM E 131. The terms that will be used with special meaning in this method are as follows:
3.1.1 radiant energy
this energy transfer like electromagnetic wave
3.1.2 radiant power P
energy transmission ratio in one beam of radiant energy.
3.2 Specific Terms and Definitions for the criterion are as following:
3.2.1 Absorbance A
Reciprocal of transmittance T, take logarithm with base 10, express in symbols as:
in this equation : T——transmittance (3.2.5)
3.2.2 Absorption coefficient a absorptivity
Absorbance divided by the product of sample optical paths length and concentration, expressed in symbols:
in the equation:
A—— absorptance (3.2.1)
b—— sample optical paths length (3.2.4)
3.2.3 Concentration c
Sample volume in g/L
3.2.4 Sample optical path length b
In the direction of light beam transferring through the surface of sample between beam entry point and outlet point, the distance of which in unit of cm.
3.2.5 Transmittance T
A ratio of radiant power through extract liquid in the absorption pool to that through reference agent. Expressed as:
In the equation:
Pe—radiant power through sample extract liquid
Pc—radiant power through reference agent.
4. Method Brief
To extract sample by using dimethyl sulfoxide, and detect the ultraviolet absorption of the extracted matter within wavelength coverage 260nm~420nm.
5. Significance and Application
5.1 This method can be utilized for proving its feasibility of application of white oil on food, pharmacy and cosmetic products
5.2 There is general requirement on product specification of white oil including food grade, that used as cosmetic, those in special purpose for food and mechanical application and liquid paraffin listed in China Pharmacopoeia ( BookII )
6.1 Spectrophotometer: prepare 1 cm optical length liquid sample absorption pool frame; within wavelength 290 nm or so, adopt rated spectrum band width 1 nm or that narrower, if detected absorption average value turn out to be 0.4 or so, the repetition of the instrument shall be ±1.o%
6.2 Fused silica cells: 2 cells, optical length 1.00cm±0.005cm. Such distance in cm not including the width of absorption cells itself.
6.3 Liquid separate hooper: 125mL, pear shape, with glass plugs, with polytetrafluoroethylene plug cock or other proper plug cock that will not contaminate the applied solvent, ensuring there is no leakage from the liquid separate funnel.
7.1 hexane: analytical reagent, use 1 cm absorption cell, refer to distilled water, when test at above 260 nm wave length, its ultraviolet absorption shall not exceed 0.02 (warning: hexane is extremely easy to combust, and inhaling of it will do harm to human body, and may also sabotage neural cells). The purity of solvents shall meet the following requirements: for any wave length within the scope between 260 nm~420 nm, “reference solution” defined in item 8.3 make distilled water as reference by which its absorptivity curve shall indicate no alien impurity peak, and also absoptivity shall not exceed that of dimethyl sulfoxide refered by distilled water.
Note: if it can not meet requirement, follow the steps for refining: adopt absorption column with 1 m length, 5 cm diameter, fulfill with poral chromatographic silica gel that have been activated (150 ℃，3h)in 0.149 mm~0.074 mm (100meshes~200meshes) up to 3/4 height of absorption column. It can be usually defined 3L~4L hexane product.
7.2 Dimethyl sulfoxide: utilized as spectrum solvents (see note) (warning: combustive, sensitive to skin), clear, water white, content 99.9%, melting point 18.5℃, with 1 cm absorption cell adopted and distilled water as reference, the absorptivity curive shall not exceed 1.0 when at 264 nm, and no alien impurity peak when below 420 nm wave length.
Note: When dimethyl sulfoxide does not meet the requirement mentioned above, it can be purified via infiltration, i.e. through absorption column with activited carbon in granularity 1.68 mm×0.420 (12 meshes×40 meshes), 1.2 m length, 25 mm diameter, with stretching formed narrow openning in 64 diameter at bottom, and there is liquid storage attached on the top of column. Put the glass wool under the absorption column and lay one layer of 13 mm thickness silica gel in granularity 0.707 mm~0.074 mm (25 mesh~200 meshes) or 0.149~0.074mm (100 meshes~200 meshes), then fulfill the absorption column with activated carbon, dump dimethyl sulfoxide into the container at the top of absorption column, go infiltration via activated carbon under atmosphere pressure, collect the purified dimethyl sulfoxide at the bottom of absorption column. For the reason that dimethyl sulfoxide is extremely easy to absorb humidity and reactive chemically with sorts of metal container, thus it shall be stored in glass plug bottles.
7.3 Distilled water: single distilled water and purified water.
8.1 Take 25 mL sample and 25 mL hexane in liquid separate hooper and combine them, add 5.0 mL dimethyl sulfoxide, then strenuously vibrate the mixed for at least 1 minute to fully mixed, stop shaking and leave it still until lower part of solvent appears transparency
Note: If room temperature is low, dimethyl sulfoxide may be easily crystalized resulting in turbidness, so the room temperature shall not be lower than 20 ℃ during test course.
8.2 Dump the lower part of solvent in transparency into another liquid separate funnel, add 2 mL hexane, shake it strenuously, then stop and leaving it still until the lower part of solvent appears transparent, transfer that part into 1 cm absorption cell, labeled as “sample extract liquid”.
8.3 Add 25 mL hexane in liquid separate funnel, then add 5.0 mL dimethyl sulfoxide, strenuously shake the funnel of combined liquid for at least 1 minute, then stop and leave it until the lower part of solvent appears transparent, finally collect that part and pour into another 1 cm absorption cell, labeled as “reference solvent”.
8.4 Within the scope 260 nm~420 nm wave length, refer to “reference solution”, detect the absorptivity of “sample extract liquid”.
Note: if there is difference of temperature between “sample extract liquid” and “reference solution”, it may impact much to detection of absorptivity, therefore it is better even the temperature between them.
8.5 For the samples that contain inhibitor, correction shall be done in accord with Appendix B.
Report ultraviolet absorptivity of white oil under the defined wave length, accuracy to nearest 0.001.
10. Precision and deviation
10.1.1 Repetition: the same operator, use the same instrument, under defined condition, operate normally and correctly on the same sample. Among 20 results continuously operated, one differ from another, from long term observation, there is only one result that exceed 0.014 absorptivity unit.
10.1.2 Reproducibility: various operator at various lab, under defined condition, operate normally and correctly on the same sample, then it turn out two different results. From long term observation, repeat the test for 20 times, only once chance that exceeds 0.044 absorptivity unit.
10.1.3 These precision datas of absorptivity is acquired at a scope of 275 nm~280 nm wave length.
This operation procedure has no deviation, for it only attempt from one test method, so its absorptivity value can be defined.
Correction of Inhibitor Content
B.1. If there is same sufficient inhibitor in some sample and such sample with inhibitor can be used for preparing a kind of concoction, absorptivity correction can be operated on the following steps: the added inhibitor shall have the same concentration as that contained in the sample.
B.2. Weighing at least 50 mg inhibitor, add it in volumetric flask, dilute to scale with sample that contains inhibitor, combine it averagely, If there is need for further dilution, use the white oil containing inhibitor, for acquiring the required concentration of added inhibitor.
B.3. Based on this method, operate the original white oil sample that contains inhibitor, and label as Sample A.
B.4. Based on this method, operate the concoction that contains the known volume of added inhibitor, label as Sample B.
B.5. Absorptivity differential values between Sample B and Sample A at corresponding wave length will be calculated according to the following equation:
In the equation:
Ac—corrected absorptivity at each wave length
B.6. Spot the inflection point at the wave length where there is lower or higher increment on the sample spetrograms.
B.6.1. Draw a datum line tangent to the curve that connect the two points.
B.6.2. Read absorptivity Ad at each wave length along the datum line.
B.7. Compare Ad and Ac at each wave length. If Ac is less than Ad, it indicates that the inhibitor content in the original sample is less than the added volume.
B.8. Within the scope 260 nm~420 nm wave length (including 260 nm and 420 nm), compare the absorptivity of Ac or Ad and reference solvent.