Butylated Hydroxy Anisole (BHA)

A. DETERMINATION OF PURITY
A-0 GENERAL
Two methods, that is, infrared and colorimetric methods, have been specified. Either method could be used.

A-1 INFRARED METHOD
A-1.1 Procedure
Weigh 1000 g of butylated hydroxy anisole into a 10 ml volumetric flask, dissolve it in carbon disulphide, dilute to the mark with this solvent and mix thoroughly. Fill a 0.15 mm liquid cell with the solution, insert in an infrared spectrometer and measure the spectrum from 10.5 to 12.5 m using the 1.3 cm rock salt plate in the reference beam, 2x slits and normal scanning speed. Draw a background line on the spectrogram from 11.0 to 12.0 m . Determine the net absorption of the sample at 11.42 m by subtracting the background absorption at this Wave length from the total absorption of the sample. Refer the net absorption value at a previously prepared standard reference curve to obtain the apparent butylated hydroxy anisole assay.

A-1.1.1 Preparation of Standard Reference Curve
Weigh 0.900, 0.950 and 1.000 g of 3-tertiary butyl- hydroxy anisole reference standard into three 10-ml volumetric flasks. Dissolve the samples in carbon disulphide, dilute to the mark with this solvent and mix thoroughly. Measure the spectra of these three samples using the same conditions described under A-1.1, obtain the net absorption of the three samples at 11.42 m and 'plot these values against the percentage of butylated hydroxy anisole. The 0.900, 0.950 and 1.000 g samples represent 90, 95 and 100 percent butylated hydroxy anisole, respectively.

A-1.1.2 Isomer Ratio Test
Melt the sample in a water-bath and stir thoroughly. Weigh 1.000 g of the molten sample into a 10-ml volumetric flask. Dilute to the mark with carbon disulphide and shake until the sample is completely dissolved. Measure the infrared spectrum of the solution from 10 to 12 m using a 0.4-mm cell with a 1.3-cm rock salt plate in the reference beam. From the percentage transmittance readings at 10.75 and 10.95 m, calculate the optical density values. Divide the optical density at 10.75 m by that at 10.95 m to obtain the optical density ratio. (Exact position of these absorption bands may vary, depending upon the instrument. If a recording instrument is used. The position of minimum transmission on the chart should be taken with a non-recording instrument the exact length and slit setting should be determined.) Using the optical density ratio value, determine the percentage of 3-tertiary butyl- hydroxy anisole in the sample by means of a calibration curve.

A-1.1.2.1 Preparation of calibration curve
Weigh (a) I000 mg of 3-tertiarybutylhydroyanisole;
(b) 900 mg of 3-tertiarybutylhydroyanisole and 100 mg of 2-tertiarybut1hydroxyanisole;
(c) 800 mg of 3-tertiarybutylhydroxyanisole and 200 mg of 2-tertiarybutylhydroxyanisole to an accuracy of ±1 mg into three 10-ml volumetric flasks, dilute to the mark with carbon disulphide and shake until the sample is completely dissolved. Measure the infrared spectra for each of these three mixtures following the same procedure used for the sample. Plot the calculated optical density ratios obtained against the corresponding concentrations of 3-tertiarybutyl- hydroxy anisole.

A-1.2 Calculation
Calculate the true butylated hydroxy anisole assay using the following equation:
BHA, percent by mass = Apparent butylated hydroxy anisole assay (A-1.1 and A.1.11) + 0.16 [100- percent of 3- tertiarybutylhydroxy- anisole (A-1.1.2 and A-1.1.2.1)]

A-2 COLORIMETRIC METHOD
A-2.1 Regents
A-2.1.1 Ethanol - 80 percent
A-2.1.2 Borax -2.0 percent, aqueous
A-2.1.3 2, 6-dichloroquinonechlorimide – 0.01 percent
A-2.2 Procedure
Prepare a solution of pure butylated hydroxy anisole in 80 percent ethanol containing 5.0 mg per millilitre. Place suitable aliquots (1 to 12 mI) of the butylated hydroxy anisole solution into small glass - stoppered bottles to give a range of 5-60 mg per aliquot. Add enough 80 percent ethanol to each bottle to give a total of 12 ml. Then add 2 ml of aqueous borax and 2 mI of 2,6-dichloroquinonechlorimide. Age the samples and the blank for 15 minutes. Using the blank as a reference standard, determine the optical density at 610 nm on a colorimeter or spectophotometer. Plot tile standard curve on regular coordinate paper using optical density versus concentration of butylated hydroxy anisole per aliquot. The points should fall on or near a straight line.
Proceed as above using a sample solution in 80 percent ethanol. From the optical density find out the purity of butylated hydroxy anisole using the standard curve.

B. DETERMINATION OF MELTING POINT
B-1 APPARATUS
B-1.1 Oven or Oil-Bath
Maintained at about 75°C.
B-1.2 Sample Tube
25 mm x 150 mm test-tube closed with a cork stopper having two holes - one at the centre to take thermometer and one at the side to take an agitator.

B-1.3 Agitator
With a paddle formed by bending a piece of stainless steel wire to form a loop surrounding the thermometer.

B-1.4 Thermometer
B-1.5 Air Bath Tube
B-l.6 Water-Bath
Maintained between 55°C and 60°C

B-2 PROCEDURE
Melt a representative sample by means of an oven or oil bath at about 75°C. Take a sample tube fill it to a depth of about 90 mm. Insert the stopper carrying the thermometer and stirrer, adjusting the thermometer so that the thermometer immersion mark is at the surface. The tip of the bulb should be about 1 cm from the bottom of the tube. Place the sample tube in an air- bath tube, and then place the air-bath tube in water-bath maintained between 55° and 60°C. Gently stir the molten sample at the rate of about 20 strokes per minute. Record temperature readings at 30 second intervals to 0.1 oC. The temperature of the sample will fall gradually at first, rise slightly and become nearly constant for 3 to 5 minutes. If the lowest descending temperature is more than 1.0°C below the average temperature of the plateau, the determination should be repeated using a slightly warmer water-bath. The temperature at which the thermometer reading is constant for 5 consecutive readings is taken as the melting point.

C. DETERMINATION OF SULPHATED ASH
C-1 REAGENT
C-1.1 Concentrated Sulphuric Acid
C-2 PROCEDURE
Weigh accurately about 2g of the material in a tared crucible. Ignite, gently at first, until the material is thoroughly charred, cool, moisten the residue with 1 mI of sulphuric acid and ignite gently till the carbon is completely consumed. Cool the crucible in a desiccator and weigh.

NOTE: Carry out the ignition in a place protected from air currents and use as low a temperature as possible to effect the combustion of carbon.

C-3 CALCULATI0N
Sulphated ash, percent by mass =

(M1 / M2) x 100, where
M1 = mass in g, of the residue; and
M2= mass in g, of the material taken for the test

D. DETERMINATION OF IRON
D-1 REAGENT
D-1.1 Bromine Solution
Prepare a saturated solution of bromine by agitating 2 to 3 mi of bromine with 100 mI of cold water in a glass- stoppered bottle, the stopper of which should be lubricated with petroleum. Store in a cool place and protect from light.

D-1.2 Hydrochloric Acid
D-1.3 Ammonium Persulphate
D-1.4 Ammonium Thiocyanate Solution
Dissolve 8 G of ammonium Thiocyanate (NH4CNS), in sufficient water to make 100 mI.

D-1.5 Standard Iron Solution
5 mg iron per mI.

D-2 PROCEDURE
To one gram of the sample add 2 ml of hydrochloric acid and evaporate to dryness on a steam-bath. Dissolve the residue in 2 mI of hydrochloric acid and 20 mI of water, add a few drops of bromine solution, and boil the solution to remove the bromine. Cool, dilute with water to 25 m1, then add 59 mg of ammonium persulphate and 5 ml of ammonium thiocyanate solution. Any red or pink colour shall not exceed that produced in a control containing 1.0 ml of standard iron solution ( 5 mg. Fe ).

E. DETERMINATION OF PHENOLIC IMPURITIES
E-1 PROCEDURE
Phenolic Impurities are determined by the method using silica gel G plates.
Solution 1- Dissolve 0.25 g of BHA in 10 ml of ether
Solution 2- Dilute 1 ml of Solution 1 to 10 ml with ether and then dilute 1 mI of this solution to 20 mI with ether. Use the final dilution as Solution 2
Spot 2 ml each of Solution 1 and Solution 2 on separate TLC plates and properly identify them. Place them in developing chamber containing chloroform as solvent and allow the solvent to ascend to a point of 15 cm above the sample spots. Develop the chromatograms by spraying a mixture containing 100 mI of 10.5 percent ferric ferro cyanide solution and 25 ml of 5 percent ferric chloride solution. Any blue violet spots appearing on chromatogram I (other than the major spot and the spot at Rf 0.35) are not more intense than the major spot appearing on chromatogram 2.

F. DETERMINATION OF SPECIFIC ABSORPTION
F-1 PROCEDURE
Prepare 1 percent solution of butylated hydroxy anisole in ethanol and find out its specific absorption in a suitable spectrophotometer using 1 cm cell at wavelengths 290 nm and 228 nm. For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2:1960 'Rules for rounding off numerical values (revised)'. The number of significant places -retained in the rounded off value should be the same as that of the specified value in this standard.