{"id":31017,"date":"2025-11-12T17:11:24","date_gmt":"2025-11-12T10:11:24","guid":{"rendered":"https:\/\/nhathuocngocanh.com\/bp\/?p=31017"},"modified":"2025-11-18T16:57:02","modified_gmt":"2025-11-18T09:57:02","slug":"thiamazole","status":"publish","type":"post","link":"https:\/\/nhathuocngocanh.com\/bp\/thiamazole\/","title":{"rendered":"Thiamazole"},"content":{"rendered":"

(Ph. Eur. monograph 1706)<\/p>\n

C_{4<\/sub>H_{6<\/sub>N_{2<\/sub>S 114.2 60-56-0<\/p>\n}}}

Action and use<\/strong><\/p>\n

Thionamide antithyroid.<\/p>\n

DEFINITION<\/h2>\n
1-Methyl-1,3-dihydro-2H-imidazole-2-thione.<\/p>\n
Content<\/strong><\/p>\n
98.0 per cent to 101.0 per cent (dried substance).<\/p>\n
CHARACTERS<\/h2>\n
Appearance<\/h3>\n
White or pale brown, crystalline powder.<\/p>\n
Solubility<\/h3>\n
Freely soluble in water, freely soluble in methylene chloride, freely soluble or soluble in ethanol (96 per cent).<\/p>\n
IDENTIFICATION<\/h2>\n
First identification: A, C.<\/p>\n
Second identification: A, B, D.<\/p>\n
A. Melting point (2.2.14): 143 \u00b0C to 146 \u00b0C.<\/p>\n
B. Dissolve 25 mg in 10 mL of a 0.28 per cent V\/V solution of sulfuric acid R and dilute to 50.0 mL with the same solution. Dilute 1.0 mL of this solution to 100.0 mL with a 0.28 per cent V\/V solution of sulfuric acid R. Examined between 200 nm and 300 nm (2.2.25), the solution shows 2 absorption maxima, at 211 nm and 251 nm. The ratio of the absorbance measured at the absorption maximum at 251 nm to that measured at the absorption maximum at 211 nm is 2.5 to 2.7.<\/p>\n
C. Infrared absorption spectrophotometry (2.2.24).<\/p>\n
Preparation<\/em> Discs.<\/p>\n
Comparison<\/em> thiamazole CRS.<\/p>\n
D. Thin-layer chromatography (2.2.27).<\/p>\n
Test solution<\/em> Dissolve 5.0 mg of the substance to be examined in methanol R and dilute to 5.0 mL with the same solvent.<\/p>\n
Reference solution (a)<\/em> Dissolve 5.0 mg of thiamazole CRS in methanol R and dilute to 5.0 mL with the same solvent.<\/p>\n
Reference solution (b)<\/em> Dissolve 5.0 mg of 2-methylimidazole R in methanol R and dilute to 5.0 mL with the same solvent. Dilute 1.0 mL of this solution to 2.0 mL with the test solution.<\/p>\n
Plate<\/em> TLC silica gel F_{254<\/sub> plate R.<\/p>\n}
Mobile phase<\/em> concentrated ammonia R1, 2-propanol R, toluene R (1:24:75 V\/V\/V).<\/p>\n
Application<\/em> 10 \u03bcL.<\/p>\n
Development<\/em> Over 2\/3 of the plate.<\/p>\n
Drying<\/em> In air.<\/p>\n
Detection<\/em> Examine in ultraviolet light at 254 nm.<\/p>\n
System suitability<\/em> Reference solution (b):<\/p>\n
\u2014 expose the plate to iodine vapour for 30 min; the chromatogram shows 2 clearly separated spots.<\/p>\n
Results<\/em> The principal spot in the chromatogram obtained with the test solution is similar in position and size to the principal spot in the chromatogram obtained with reference solution (a).<\/p>\n
TESTS<\/h2>\n
Solution S<\/h3>\n
Dissolve 2.0 g in water R and dilute to 20.0 mL with the same solvent.<\/p>\n
Appearance of solution<\/h3>\n
Solution S is clear (2.2.1) and not more intensely coloured than reference solution B6 (2.2.2, Method II).<\/p>\n
Related substances<\/h3>\n
Gas chromatography (2.2.28).<\/p>\n
Test solution<\/em> Dissolve 0.100 g of the substance to be examined in chloroform R and dilute to 10.0 mL with the same solvent.<\/p>\n
Reference solution (a)<\/em> Dilute 1.0 mL of the test solution to 100.0 mL with chloroform R. Dilute 1.0 mL of this solution to 10.0 mL with chloroform R.<\/p>\n
Reference solution (b)<\/em> Dissolve 5.0 mg of thiamazole impurity A CRS, 5.0 mg of 1-methylimidazole R1 and 5.0 mg of thiamazole impurity C CRS in chloroform R and dilute to 50.0 mL with the same solvent. Dilute 1.0 mL of this solution to 10.0 mL with chloroform R.<\/p>\n
Column:<\/p>\n
\u2014 material: fused silica,<\/p>\n
\u2014 size: l = 30.0 m, \u00d8 = 0.25 mm,<\/p>\n
\u2014 stationary phase: base-deactivated phenyl(5)methyl(95)polysiloxane R (film thickness 0.5 \u03bcm).<\/p>\n
Carrier gas<\/em> helium for chromatography R.<\/p>\n
Flow rate<\/em> 1.5 mL\/min.<\/p>\n
Split ratio<\/em> 3:20.<\/p>\n
Temperature:<\/p>\n\n\n\n\n\n\n
<\/td>\n Time (min)<\/strong><\/td>\n Temperature\u00a0(\u00b0C)<\/strong><\/td>\n<\/tr>\n
Column<\/td>\n 0 – 2<\/p>\n
2 – 7<\/p>\n
7 -22<\/td>\n
100<\/p>\n
100 \u2192 250<\/p>\n
250<\/td>\n<\/tr>\n
Injection port<\/td>\n <\/td>\n 150<\/td>\n<\/tr>\n
Detector<\/td>\n <\/td>\n 250<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Detection<\/em> Flame ionisation.<\/p>\n
Injection<\/em> 1 \u03bcL.<\/p>\n
Relative retention<\/em> With reference to thiamazole (retention time = about 6.5 min): impurity A = about 0.3; impurity B = about 0.4; impurity C = about 0.7.<\/p>\n
System suitability<\/em> Reference solution (b):<\/p>\n
\u2014 resolution: minimum 1.5 between the peaks due to impurity A and impurity B.<\/p>\n
Limits:<\/p>\n
\u2014 impurities A, B, C: for each impurity, not more than the area of the corresponding peak in the chromatogram obtained with reference solution (b) (0.1 per cent),<\/p>\n
\u2014 any other impurity: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (a) (0.1 per cent),<\/p>\n
\u2014 total: not more than 5 times the area of the principal peak in the chromatogram obtained with reference solution (a) (0.5 per cent),<\/p>\n
\u2014 disregard limit: 0.2 times the area of the principal peak in the chromatogram obtained with reference solution (a) (0.02 per cent).<\/p>\n
Loss on drying (2.2.32)<\/h3>\n
Maximum 0.5 per cent, determined on 1.000 g by drying in an oven at 105 \u00b0C for 2 h.<\/p>\n
Sulfated ash (2.4.14)<\/h3>\n
Maximum 0.1 per cent, determined on 1.0 g.<\/p>\n
ASSAY<\/h2>\n
Dissolve 0.250 g in 75 mL of water R. Add 15.0 mL of 0.1 M sodium hydroxide, mix and add with stirring, about 30 mL of 0.1 M silver nitrate. Continue the titration with 0.1 M sodium hydroxide, determining the end point potentiometrically (2.2.20).<\/p>\n
1 mL of 0.1 M sodium hydroxide is equivalent to 11.42 mg of C_{4<\/sub>H_{6<\/sub>N_{2<\/sub>S.<\/p>\n}}}
IMPURITIES<\/h2>\n
Specified impurities A, B, C.<\/p>\n
$\"Thiamazole\"$ <\/p>\n
A. 2,2-dimethoxy-N-methylethanamine,<\/p>\n
$\"Thiamazole\"$ <\/p>\n
B. 1-methyl-1H-imidazole,<\/p>\n
$\"Thiamazole\"$ <\/p>\n
C. 1-methyl-2-(methylsulfanyl)-1H-imidazole.<\/p>\n","protected":false},"excerpt":{"rendered":"
(Ph. Eur. monograph 1706) C4H6N2S 114.2 60-56-0 Action and use Thionamide antithyroid. DEFINITION 1-Methyl-1,3-dihydro-2H-imidazole-2-thione. Content 98.0 per cent to 101.0 per cent (dried substance). CHARACTERS Appearance White or pale brown, crystalline powder. Solubility Freely soluble in water, freely soluble in methylene chloride, freely soluble or soluble in ethanol (96 per cent). IDENTIFICATION First identification: A,…<\/p>\n","protected":false},"author":5,"featured_media":31084,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[174],"tags":[],"class_list":["post-31017","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicinal-substances"],"acf":[],"_links":{"self":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/comments?post=31017"}],"version-history":[{"count":3,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017\/revisions"}],"predecessor-version":[{"id":32274,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017\/revisions\/32274"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media\/31084"}],"wp:attachment":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media?parent=31017"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/categories?post=31017"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/tags?post=31017"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

<\/td>\n	Time (min)<\/strong><\/td>\n	Temperature\u00a0(\u00b0C)<\/strong><\/td>\n<\/tr>\n
Column<\/td>\n	0 – 2<\/p>\n 2 – 7<\/p>\n 7 -22<\/td>\n	100<\/p>\n 100 \u2192 250<\/p>\n 250<\/td>\n<\/tr>\n
Injection port<\/td>\n	<\/td>\n	150<\/td>\n<\/tr>\n
Detector<\/td>\n	<\/td>\n	250<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Detection<\/em> Flame ionisation.<\/p>\n Injection<\/em> 1 \u03bcL.<\/p>\n Relative retention<\/em> With reference to thiamazole (retention time = about 6.5 min): impurity A = about 0.3; impurity B = about 0.4; impurity C = about 0.7.<\/p>\n System suitability<\/em> Reference solution (b):<\/p>\n \u2014 resolution: minimum 1.5 between the peaks due to impurity A and impurity B.<\/p>\n Limits:<\/p>\n \u2014 impurities A, B, C: for each impurity, not more than the area of the corresponding peak in the chromatogram obtained with reference solution (b) (0.1 per cent),<\/p>\n \u2014 any other impurity: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (a) (0.1 per cent),<\/p>\n \u2014 total: not more than 5 times the area of the principal peak in the chromatogram obtained with reference solution (a) (0.5 per cent),<\/p>\n \u2014 disregard limit: 0.2 times the area of the principal peak in the chromatogram obtained with reference solution (a) (0.02 per cent).<\/p>\n Loss on drying (2.2.32)<\/h3>\n Maximum 0.5 per cent, determined on 1.000 g by drying in an oven at 105 \u00b0C for 2 h.<\/p>\n Sulfated ash (2.4.14)<\/h3>\n Maximum 0.1 per cent, determined on 1.0 g.<\/p>\n ASSAY<\/h2>\n Dissolve 0.250 g in 75 mL of water R. Add 15.0 mL of 0.1 M sodium hydroxide, mix and add with stirring, about 30 mL of 0.1 M silver nitrate. Continue the titration with 0.1 M sodium hydroxide, determining the end point potentiometrically (2.2.20).<\/p>\n 1 mL of 0.1 M sodium hydroxide is equivalent to 11.42 mg of C_{4<\/sub>H_{6<\/sub>N_{2<\/sub>S.<\/p>\n}}} IMPURITIES<\/h2>\n Specified impurities A, B, C.<\/p>\n $\"Thiamazole\"$ <\/p>\n A. 2,2-dimethoxy-N-methylethanamine,<\/p>\n $\"Thiamazole\"$ <\/p>\n B. 1-methyl-1H-imidazole,<\/p>\n $\"Thiamazole\"$ <\/p>\n C. 1-methyl-2-(methylsulfanyl)-1H-imidazole.<\/p>\n","protected":false},"excerpt":{"rendered":" (Ph. Eur. monograph 1706) C4H6N2S 114.2 60-56-0 Action and use Thionamide antithyroid. DEFINITION 1-Methyl-1,3-dihydro-2H-imidazole-2-thione. Content 98.0 per cent to 101.0 per cent (dried substance). CHARACTERS Appearance White or pale brown, crystalline powder. Solubility Freely soluble in water, freely soluble in methylene chloride, freely soluble or soluble in ethanol (96 per cent). IDENTIFICATION First identification: A,…<\/p>\n","protected":false},"author":5,"featured_media":31084,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[174],"tags":[],"class_list":["post-31017","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicinal-substances"],"acf":[],"_links":{"self":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/comments?post=31017"}],"version-history":[{"count":3,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017\/revisions"}],"predecessor-version":[{"id":32274,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/31017\/revisions\/32274"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media\/31084"}],"wp:attachment":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media?parent=31017"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/categories?post=31017"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/tags?post=31017"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

Appearance<\/h3>\nWhite or pale brown, crystalline powder.<\/p>\n

Solubility<\/h3>\nFreely soluble in water, freely soluble in methylene chloride, freely soluble or soluble in ethanol (96 per cent).<\/p>\n

Solution S<\/h3>\nDissolve 2.0 g in water R and dilute to 20.0 mL with the same solvent.<\/p>\n

Appearance of solution<\/h3>\nSolution S is clear (2.2.1) and not more intensely coloured than reference solution B6 (2.2.2, Method II).<\/p>\n

Sulfated ash (2.4.14)<\/h3>\nMaximum 0.1 per cent, determined on 1.0 g.<\/p>\n

Appearance<\/h3>\n
White or pale brown, crystalline powder.<\/p>\n

Solubility<\/h3>\n
Freely soluble in water, freely soluble in methylene chloride, freely soluble or soluble in ethanol (96 per cent).<\/p>\n

Solution S<\/h3>\n
Dissolve 2.0 g in water R and dilute to 20.0 mL with the same solvent.<\/p>\n

Appearance of solution<\/h3>\n
Solution S is clear (2.2.1) and not more intensely coloured than reference solution B6 (2.2.2, Method II).<\/p>\n

Sulfated ash (2.4.14)<\/h3>\n
Maximum 0.1 per cent, determined on 1.0 g.<\/p>\n