title: Stable reagents and a suitable routine procedure for the cystinuria test.
abstract: A simplification of the borohydride-cyanonitrosylferrate (nitroprusside) test for cystine in urine is described. The borohydride reagent is stabilised by cooling and by using pure components. Octanol-1 is used to reduce foaming. The cyanonitrosylferrate reagent is stabilised by sulphite and by storage at -80 degrees C. Compared with previous methods, it is possible to use higher (more than 4 times) dilutions of urine. An aqueous cystine solution may be used as a standard for visual evaluation; for the previous methods there is no well defined material for standardisation. The described procedure is intended for visual evaluation; the method is also suitable for quantitation by photometry.
mesh_terms: D001894:Borohydrides; D003555:Cystinuria / Q000652:urine*; D006801:Humans; D006851:Hydrochloric Acid; D008722:Methods; D009599:Nitroprusside
chemical_list: D001894:Borohydrides; D009599:Nitroprusside; D006851:Hydrochloric Acid