Manual of basic techniques for a health laboratory - libdoc.who.int

Annex. Reagents and their preparation 367Diacetyl monoxime stock solutionDiacetyl monoxime (also called 2,3-butanedionemonoxime)2 gDistilled waterq.s. 500mlLabel the volumetric flask “DIACETYL MONOXIME STOCK SOLUTION”and write the date. The solution will keep for at least 6 months at 2–8 °C.Colour reagentAcid reagent (No. 6)50mlDiacetyl monoxime reagent50mlMix the acid reagent and stock solution in a 100-ml stoppered flask. Label the flask“COLOUR REAGENT”. The quantities shown above are sufficient for 33 measurements.The reagent must be prepared daily.Urea stock reference solution, 125mmol/lUrea750mgBenzoic acid, 1g/l (0.1%) solution (see No. 30) q.s. 100mlDissolve the urea in about 20ml of the benzoic acid solution in a 100-ml volumetricflask. Make up the volume to 100ml with benzoic acid solution. Label the flask“UREA STOCK REFERENCE SOLUTION 125 MMOL/L” and write the date.Store in a refrigerator. The solution will keep for several months at 2–8 °C.Urea working reference solution, 10mmol/lUrea stock reference solution8 mlBenzoic acid (C 7H 6O 2), 1g/l (0.1%) solution(see No. 30)q.s. 100mlMix the solutions well in a 100-ml volumetric flask. Label the volumetric flask“UREA WORKING REFERENCE SOLUTION 10 MMOL/L” and write the date.Wayson stain (No. 63)Solution A 1:Basic fuchsin2 gAbsolute methanol (CH 3OH)100mlSolution A 2:Methylene blue7 gAbsolute methanol (CH 3OH)100mlCombine the two solutions to give solution A.Solution B (phenol, 50g/l (5%) solution):Phenol (C 6H 5OH)100gDistilled water2000mlAdd solution A to solution B. The staining properties of Wayson stain improve withage. Make the stain in large quantities and dispense it in small amounts in to darkbottles for future use. Label the bottles “WAYSON STAIN” and write the date.Warning: Phenol is corrosive.