The method covers sulphate analysis for impurities for raw materials.
It is not intended to be used for Sulphate assays where there is a high
Sulphate content. The following table details the tests that are covered:Â
 {tocify} $title={Table of Contents}
SCOPE
Suitable for soluble materials from 10 ppm up to 1200 p.p.m
of sulphate (SO4) Test is
described in the EP 97
REFERENCE
2.1 EP 97 European Pharmacopoeia 1997
2.2 Health & Safety Data for Chemical Reagents used in
this test method.
2.3 Health & Safety Sheets for samples analysed by this
method
3. DEFINITIONS
4. PRINCIPLE OFÂ Sulphate content
The acidic solution is treated with barium chloride solution
under standard conditions to produce opalescence (Barium Sulphate) white colour
which is matched for its intensity of colour against a standard. Samples equal
or less than the standard pass. The colour is compared using a matching pair of
Nessler tubes under good even lighting.
5. REFERENCE STANDARD
Potassium Sulphate - Analytical Reagent is used as the
reference
10 ppm ethanolic sulphate solution: Dilute 1.0 ml of a
0.181% w/v solution of potassium sulphate in 30% ethanol to 100 ml with 30%
ethanol.
6. REAGENTS & CHEMICALS FOR SULPHATE CONTENTÂ
6.1 Water - De-ionised or distilled water. - Used boiled and
cooled water when preparing and diluting sample test solutions and standards
(Carbon Dioxide free)
6.2 Ethanol 30% (Dilute from 96%)
6.3 Barium Chloride Solution 25% w/v
6.4 Acetic Acid (5M) C2H4O2 (60x5) 300 g / litre
6.5 Hydrochloric Acid 36% w/v Analytical Reagent
6.6 2 M Hydrochloric Acid.
7 EQUIPMENT
7.1 Balance weighing to nearest 0.1 mg.
7.2 1 pair of matching Nessler tubes
7.3 Nessler holder with black background
7.4 Glass stirring rod.
7.5 Stopwatch
or clock
7.6 1ml glass ml pipette
7.7 2 ml graduated pipette
7.8 15 ml pipette
7.9 25 ml measuring cylinder
7.10 pH indicating papers.
7.11 100 ml volumetric flask.
8. INTERFERENCE
It is important to adjust the test solution and sample so
the pH is correct. The stirring and addition of the barium chloride need to be
done in the same way so the opalescence occurs under the same conditions.
Samples with EDTA salts cannot be compared as they will dissolve Barium Sulphate.
9. SAMPLING PROCEDURE
Precautions: Read Health & Safety Data sheets for raw
materials before sampling.
When sampling powders care is required to ensure the sample represents
the whole. It may be necessary to select several samples and pass them through
a quartering device to ensure the final sample is representative of the whole.
If the test uses a sample below 1 g it is advisable to prepare a 10% solution and
use an appropriate volume to give the right weight.
Ethanol Formula, Molar Mass, Uses and PropertiesÂ
10. PROCEDURE OF SULPHATE CONTENT
Precautions: Read Health & Safety Data Sheets on
Chemical
Reagents before carrying out this analysis.
10.1 Dissolve x* gm of sample in 6 ml of water.
For strong alkalies adjust to pH 5 - 8 with about 7.5 ml of concentrated
hydrochloric acid then dilute to 15 ml with water. (measuring cylinder) -
transfer to Nessler tube. For alkali salts add acid dropwise until pH is in
range. Select weight required to give the ppm (maximum)
25 = 6 g
50Â = 3 g
100 = 1.5 g
150 =Â 1.0
g
1200 = 0.5 g plus dilution Dilution 55 ml water + 6.2
ml 2M hydrochloric acid. Take 15 ml for a test.
10.2 Prepare the following solutions simultaneously in
matched Nessler cylinders:
Test Reference
25% w/v Barium chloride solution 1.0 ml 1.0 ml
10 ppm Ethanolic sulphate solution 1.5 ml Shake the contents
of each cylinder, stand for 1 minute then add:
Prepared test solution 15.0 ml -
10 ppm Sulphate solution - 15.0 ml
Acetic acid (5M) 0.5 ml 0.5 ml
Mix the contents of each cylinder
and allow to stand for 5 minutes.
Compare the solutions by viewing them against a black background.
The sample complies with the test
if any opalescence produced in the sample solution is not more intense than
that produced in the reference solution.
11 CALCULATION OF RESULTS - Not
applicable
12 ACCURACIES
This is a limited test so the
precision may vary up to 10%
13 REPORTS
The test report shall state the result as equal to, less than or greater than the test limit. If it is greater than the limit it fails the test otherwise it passes. Quote the test method 24027 and the limit of sulphate in ppm (maximum), the name of the analyst, the date of testing and the identification of the sample. Also, state any recommended attention.
The Test for Nickel in Dimethylglyoxime (Diacetyl Dioxide)
