The method test methods were carried out in the analysis of Sodium Sulphate. Sodium sulphate assay by Ion Exchange Method and Gravimetric Method.
REFERENCE
EP 97 - European Pharmacopoeia.
Health & Safety Data Sheets for
Reagents & Chemicals used in the analysis.
Health & Safety Data Sheets for samples being analyzed.
PRINCIPLES
Sulphate is indicated by forming the insoluble barium salt and this is confirmed by adding dilute iodine which is not decolourised showing the absence of sulphites & dithionates. The mixture is then decolourised by adding Tin (II) chloride solution. On boiling, no coloured precipitate is produced distinct from selenates and tungstates.
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CHEMICALS & REAGENTS
1.0 Water - De-ionised or distilled.
2. 0.25 M Barium Chloride - 6.0 g of BaCl2 2H2O (Analytical reagent) dissolved in 100 ml of Water.
3. 2 M Hydrochloric Acid - HCl 7.3g (Analytical reagent) made up to 100 ml Water.
4. 0.05M Iodine solution (I2) -
Dissolve 2 grams of Potassium Iodide (Analytical Reagent) in the minimum amount of
water add 1.3 g Iodine (Analytical Reagent) and dilute to 100 ml with
water.
5. Tin (II) chloride solution -
Dissolve 33 g of Tin (II) Chloride (Analytical Reagent) in 10 ml hydrochloric
acid 36% w/w dilute to 100 ml with water. To keep the solution add a piece of
granulated tin (Analytical Reagent) and store it in the dark.
6. Hydrochloric acid 36% w/w
(Analytical Reagent)
EQUIPMENT
1. Boiling tube 50 ml
2. Bunsen Burner
INTERFERENCE - No interference
SAMPLING - No special requirements
Procedure Sulphates Test
1. To 40 to 50 mg of the substance
being examined dissolved in 5 ml of water or to 5 ml of the prescribed solution
add 1 ml of 2 M hydrochloric acid and 1 ml of 0.25 M barium chloride. A white
precipitate is produced.
2. Add 0.1 ml of iodine solution
to the suspension obtained during reaction A; the suspension remains yellow (distinction
from sulphites and dithionites) but is de-colourised by adding, dropwise,
tin(II) chloride solution (distinction from iodates). Boil the mixture; no
coloured precipitate is produced (distinction from selenates and tungstates).
A11 CALCULATION OF RESULTS - n/a
ACCURACY
A qualitative test will show sulphates
as a present.
REPORT
1. Report sulphate as positive or negative. Quote the name of the analyst, test method and any recommendations. Ensure the sample is identified.
Sodium Sulphate Assay by Ion Exchange Method
B1 SECTION B. Titration with Sodium
hydroxide EP method Scope - suitable for sodium sulphate analysis
REFERENCE
EP 97 - European Pharmacopoeia
Health & Safety Data Sheets for
Reagents & Chemicals used in the analysis
Health & Safety Data Sheets for samples being analysed
PRINCIPLE
A solution containing a known
amount of the sample is passed through an Ion Exchange column which removes the
sodium ion replacing it with a hydrogen ion. The resulting solution is
titrated with a volumetric solution of IM Sodium Hydroxide. The hydrogen ion
concentration is then calculated as the equivalent Sodium Sulphate content.
REFERENCE STANDARD
1 M Sodium Hydroxide with a
certificate guaranteeing the strength.
CHEMICALS & REAGENTS
- Water - De-ionized or distilled
- 0.1 M Sodium Hydroxide (Volumetric Solution)
- 1 M Sodium Hydroxide (Volumetric Solution)
- Methyl Orange Solution - 0.1% w/v solution in 20% ethanol
Sensitivity: Not more than 0.1 ml is
sufficient to change the colour to red
EQUIPMENT
- 200mm x 20 mm column packed with strongly acidic ion-exchange resin at a flow rate of about 4 ml per minute.
- 500 ml conical flask.
- 50 ml Burette - Calibrated.
- Balance weighing to the nearest 0.1 mg.
INTERFERENCE
If a significant amount of other
anions and cations are present the calculation will not give the correct
percentage of Sodium Sulphate.
SAMPLING
Precautions: The Health and Safety
Datasheets for the samples being collected or analyzed.
B9.1 Powders need to be sampled with
care and it is best to take the sample from several points and pass them through
a quartering device to ensure the sample is representative of the whole. Ensure
that the sample is sealed so it does not pick up moisture.
PROCEDURE
Precautions: Read Health & Safety
Data Sheets for all Chemicals & Reagents before commencing the analysis.
Weigh accurately 1.2 - 1.4 g in 50 ml
of water and pass through a column (200 mm x 20 mm) packed with strongly acidic
ion-exchange resin at a flow rate of about 4 ml per minute. Elute with water
(about 300 ml) until 50 ml requires not more than 0.05 ml of 0.1 M sodium
hydroxide VS for neutralisation. Titrate the elute with 1M sodium hydroxide VS
using methyl orange solution as an indicator. Each ml of 1 M sodium hydroxide S is
equivalent to 0.0710 g of Na2SO4.
CALCULATION OF RESULTS
% Na2SO4 = 0.0710 x V x100 % (Where W
= Weight taken & V = Volume of 1 N Sodium Hydroxide)/W
ACCURACY
A uniform sample, result should
give a precision of ±0.5%.
REPORTS
The results shall be reported to
the nearest 0.1% as a percentage of Sodium Sulphate (Anhydrous) Identify the
sample and state whether the result
meets the specification. The report shall quote the test method the
analyst, any recommended action and date of analysis.
Sodium sulphate Assay by Gravimetric Method
An assay using the
Gravimetric Method used in Weinheim for denture products.
SCOPE
Generally applicable for sulphates -
takes longer than the volumetric method but is more accurate
REFERENCE
The method used for denture cleanser raw
materials in Weinheim
DEFINITIONS AND PRINCIPLE
After the reaction with barium chloride,
the barium sulfate obtained is determined by gravimetric analysis.
REFERENCE STANDARD
A Sodium Sulphate (Anhydrous
dried) with an assay certificate may be used to check this method if required.
CHEMICALS & REAGENTS
Concentrated hydrochloric acid
36%w/w (Analytical reagent)
20% barium chloride solution (Use
barium chloride analytical reagent)
De-ionised water or distilled
water
EQUIPMENT
- A3 filter crucible.
- Suction bottle.
- Water-jet vacuum pump.
- Drying oven 105 ± 2°C.
- Muffle furnace 500 ± 10°C.
- Folded filter.
- Balance reading to 0.01 g.
- 300-ml beakers.
- 100-ml graduated cylinder.
INTERFERENCE
The method is reasonably robust for
pure chemicals but the mixture continuing Ethylene Diamine Tetra Acetic acid will
interfere and dissolve the barium sulphate. Salts other than Sodium as the
cation will not give an accurate result as the calculation cannot take this
into account. Tung states that Selenate’s impurities also interfere.
Procedure
Precautions: Read the Health & Safety
Data Sheets for Chemicals & Reagents used in this analysis and also read the
Instruction Manuals for all equipment used in the analysis.
Weigh 3±0.3 g of a representative
sample of the test substance, accurate to 0.01 g, into a 300-ml beaker and dissolve
in 100 ml of water. After the evolution of gas has stopped, carefully
(evolution of gas) add 10 ml of concentrated hydrochloric acid. Filter the
solution through a folded filter until clear and flush the filter with 10 ml of
water. Heat the collected filtrate to boiling with stirring, and slowly add 50
ml of 20% barium chloride solution. Heat for an additional 5 min and cool the
sample overnight.
Filter the resulting precipitate by
suction through a pre-tempered (2 h, 500 °C) and weighed filter crucible (m1)
and wash the precipitate with 50 ml of hot water. Then dry the crucible to
constant weight, first in the drying oven (30 min, 105 °C) and then in the
muffle furnace (500 °C), and re-weigh (m2).
CALCULATION OF RESULTS
Let:
SO4 = sulfate content as %
m2 = weight of the full crucible in g
m1 = weight of the empty crucible in g
F = analytic factor, 0.4116
E = weighed-in quantity in g
Then:
(m2 - m1) x 100 x F (m2 - m1) x 100 x
0.6075
SO4 = ------------------ % ; % Na2SO4 =
-------------- %
E E
ACCURACY
The method gives good precision and on the final weight of 1.000 g of Barium Sulphate, a precision of 0.005 g shall be
achievable. The true result will be lower than this due to the solubility of
Sodium Sulphate. The calculation will not be correct if there is contamination
from metal ions such Ca or K, Dithionates and Sulphites will give inaccuracy.
REPORTS
Report the Sodium Sulphate as
Anhydrous Sodium Sulphate to the nearest 0.1% and quote the method as 24176C
and the name of the analyst. Ensure the sample is correctly identified and state
whether it is within specification. Also, give any recommended action
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