The method test methods were carried out in the analysis of Sodium Sulphate. Sodium sulphate assay by Ion Exchange Method and Gravimetric Method
Identify of Sodium Sulphate
REFERENCE
A1 EP 97 - European Pharmacopoeia
A2 Health & Safety Data Sheets for
Reagents & Chemicals used in the analysis
A3 Health & Safety Data Sheets for samples being analyzed
PRINCIPLES
A4.1 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
A6.1 Water - De-ionised or distilled
A6.2 0.25 M Barium Chloride - 6.0 g of
BaCl2 2H2O (Analytical reagent) dissolved in 100 ml of Water
A6.3 2 M Hydrochloric Acid - HCl 7.3g
(Analytical reagent) made up to 100 ml Water.
A6.4 0.05M Iodine solution (I2) -
Dissolve 2 grams Potassium Iodide (Analytical Reagent) in the minimum amount of
water and add 1.3 g Iodine (Analytical Reagent) and dilute to 100 ml with
water.
A6.5 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.
A6.6 Hydrochloric acid 36% w/w
(Analytical Reagent)
EQUIPMENT
A7.1 Boiling tube 50 ml
A7.2 Bunsen Burner
A8 INTERFERENCE - No interference
A9 SAMPLING - No special requirements
Procedure Sulphates test
A10.1 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.
A10.2. 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
A12 ACCURACY
A qualitative test will show sulphates
as a present.
A13 REPORT
A13.1 Report as sulphate as positive
or negative. Quote name of analyst, test method 24176A and any
recommendations. Ensure 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
B2 REFERENCE
B1 EP 97 - European Pharmacopoeia
B2 Health & Safety Data Sheets for
Reagents & Chemicals used in the analysis
B3 Health & Safety Data Sheets for samples being analysed
PRINCIPLE
B4.1 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.
B5. REFERENCE STANDARD
B5.1 1 M Sodium Hydroxide with a
certificate guaranteeing the strength.
B6. CHEMICALS & REAGENTS
B6.1 Water - De-ionized or distilled
B6.2 0.1 M Sodium Hydroxide
(Volumetric Solution)
B6.3 1 M Sodium Hydroxide (Volumetric
Solution)
B6.6 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
B7. EQUIPMENT
B7.1 200mm x 20 mm column packed with
strongly acidic ion-exchange resin at a flow rate of about 4 ml per minute.
B7.2 500 ml conical flask.
B7.3 50 ml Burette - Calibrated
B7.4 Balance weighing to nearest 0.1
mg
B8. INTERFERENCE
B8.1 If a significant amount of other
anions and cations are present the calculation will not give the correct
percentage of Sodium Sulphate.
B9. 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.
B10 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.
B11. CALCULATION OF RESULTS
% Na2SO4 = 0.0710 x V x100 % (Where W
= Weight taken & V = Volume of 1 N Sodium Hydroxide)/W
B12. ACCURACY
A uniform sample, result should
give a precision of ±0.5%.
B13. REPORTS
B13.1 The results shall be reported to
the nearest 0.1% as percentage Sodium Sulphate (Anhydrous) Identify the
sample and state whether the result
meets the specification. The report shall quote the test method 24176B, the
analyst, any recommended action and date of analysis.
sodium Sulphate Assay by Gravimetric Method
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 ANDÂ Â PRINCIPLE
After 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 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 cools 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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