Sulphamethoxazole/Sulfamethoxazole

CAS number: 723-46-6

Molecular formula: C10H11N3O3S

molecular weight: 253.27

Chemical structure:

Sr No.TestSpecificationResult
1AppearanceA white or almost white crystalline powderWhite crystalline powder
2SolubilityAs per BP 2016Complies
3Identification
a) Melting point1690C –   1720C1710C
b) IRThe infrared absorption spectrum of samplePositive
is concordant with the   spectrum of
Sulfamethoxazole CRS
c) TLCAs per BP 2016Complies
d) Chemical testShould give the positive reaction of primary aromatic aminesComplies
4Appearance of solution
a) Clarity of solutionNot more than 3.0 NTU1.1 NTU
b) Colour of solutionNot more intensely coloured than referenceComplies
solution Y5,BY5 or GY5
5AcidityNot more than 0.30 ml of 0.1 M sodium hydroxide solution0.17 ml
6Related substances by HPLC
Impurity A (Acetyl SMX)Not more than 0.100 %Below Disregard Limit
Impurity B (Sulfanilyl SMX )Not more than 0.100 %0.04%
Impurity C (Isoxamine)Not more than 0.100 %Below Disregard Limit
Impurity D (Sulfanilic acid)Not more than 0.100 %Below Disregard Limit
Impurity E (Sulfanilamide)Not more than 0.100 %Below Disregard Limit
Impurity F ( Isomeric SMX)Not more than 0.100 %Below Disregard Limit
Any other impurity
Unknown Impurity – INot more than 0.100 %Below Disregard Limit
Unknown Impurity - IINot more than 0.100 %Below Disregard Limit
Total impurityNot more than 0.300 %0.07%
7Heavy metalsMaximum 20 ppmLess than 20 ppm
8Loss on DryingMaximum 0.50 % w/w0.30 % w/w
9Sulphated ashMaximum 0.10 % w/w0.04 % w/w
10AssayNot less than 99.0 % and not more than100.2 % w/w
101.0 % calculated with   reference to the
dried substance
11Additional test
a) Sieve test------------99.8 % < 90 microns
b) Bulk density-------------
c) Related substances by TLCNot more than 0.5 % eachLess than 0.5 %