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Home , Ammonium oxalate, Murexide

J Clin Pathol: first published as 10.1136/jcp.29.11.1038 on 1 November 1976. Downloaded from

1038 Technical method

Technical method Simplified qualitative chemical the phosphate test: first add two drops of a 10%° hydroxide solution, one drop of 20 % analysis for urinary calculi nitric acid, and then two to three drops of the ammonium-molybdate reagent. Heating the J. KLEEBERG mixture will produce the characteristic yellow Research Department, Rothschild- UniversityHospital, colour ofammonium-molybdate-phosphate. Haifa, Israel The 'three glass slide' technique to be described here SLIDE II TEST FOR is meant for qualitative stone analysis only and Two to three milligrams of stone powderismixedwith applies especially to small calculi. double the amount of resorcinol powder and 2 drops of concentrated sulphuric acid, and the mixture is Material and methods heated. The appearance of a deep blue (not green!) colour is proof of oxalate (Dorronsorro and Bi-distilled water; acetic acid 10%; hydrochloric Fernandez, cited by Higgins (1954)). If oxalate is acid 10%; nitric acid 20%; sulphuric acid conc; found, must also be present. (Resorcinol and ammonium hydroxide solution 10%; sodium sulphuric acid produce coloured compounds with hydroxide solution 10 %; resorcinol powder; satura- dicarbonic acids (Feigl, 1956).) ted aqueous solution of ammonium-molybdate. Magneson reagent: 1 mg of nitro-phenyl-azo- SLIDE III TESTS FOR , CARBONATE, resorcinol is dissolved in 100 ml of 2-N-sodium MAGNESIUM AND CALCIUM hydroxide. (a) 2-3 mg of stone powder is moistened with 2 dropscopyright. of 10% hydrochloric acid, gently warmed, and SLIDE I TESTS FOR AMMONIUM URATE, URIC examined for bubbles with a magnifying glass: ACID, CYSTINE, XANTHINE, AND PHOSPHATE evidence ofcarbonate. OXALATE (b) The material is washed into a small bowl with 5-6 Stone powder (2-3 mg) is moistened on an ordinary drops of a warm 10% sodium hydroxide solution and glass slide with two to three drops of 20% nitric acid covered with a watchglass to which a moistened and is slowly heated over a small flame to dryness indicator paper adheres. Evaporating ammonia will and then for a further 5-10 seconds but without be indicated by a colour change of the paperstrip or charring. The following results may be noticed: by a fog of if a glass rod http://jcp.bmj.com/ (a) formation of a conspicuous reddish-brown moistened with concentrated fuming hydrochloric froth indicating ammonium urate; acid is held over the bowl. (Warning: ammonia in (b) formation ofa flat purplish-brown layer, evidence the air of the laboratory may give a false picture.) of uric acid. (Energetic oxidation of uric acid by (c) The fluid and the remaining powder are transfer- heat and nitric acid decomposes the intermediate red into a test tube and boiled with 1 2-1-5 ml (25 split-product alloxanthin sufficiently for the drops) of 10% hydrochloric acid over a small flame

evaporating ammonia to produce at least partly for one minute, then alkalinized with 10% ammo- on October 1, 2021 by guest. Protected the characteristic purple coloured , the nium hydroxide (in excess). Whether a turbidity or ammonium salt of purpuric acid); precipate has formed or not, 2-3 ml distilled water (c) total combustion, except for a small charred are added and the mixture is divided into two test sticky part, often accompanied by a disagreeable tubes. One part is tested for magnesium by the smell-evidence of cystine; addition of 2 ml ofa 10% sodium hydroxide solution (d) a greyish-white layer, indicating oxalate, phos- and 2 drops of the magneson reagent. A change of phate or both; the violet colour to blue indicates magnesium. (e) a whitish-green layer, evidence of xanthine. (d) The other half of the material is acidified with Addition of potassium hydroxide produces a 2-0-2-5 ml (40-50 drops) of 10% acetic acid; a dis- brilliant red colour; appearing turbidity indicates phosphate; a persistent (f) whatever the outcome of the procedure with heat turbidity is evidence of oxalate. The latter is proof of andnitricacid,theresidueon the slide is still fit for calcium, too. If acidification has produced dissolu- tion of turbidity or if the fluid has remained clear Received for publication 10 May 1976 from the beginning, the addition of a few drops of a J Clin Pathol: first published as 10.1136/jcp.29.11.1038 on 1 November 1976. Downloaded from

Technical method 1039

5 % solution would produce If the examiner always uses the same amount of turbidity if calcium is present, but the precipitation chemicals and stone powder and always uses the of calcium oxalate may take up to two hours. same technique, that is, heating-time, etc, the method allows a semiquantitative estimate of a stone's Comment composition. Here the grade of the various test- sensitivities may serve as a guide also: the magneson Over the last five years this technique has proved and the molybdate-phosphate tests are very sensitive, reliable in our laboratory and has been controlled by but the murexide reaction is less sensitive and the other well-known analytical methods. If only 5-6 mg resorcinol-oxalate test still less so. of calculus material are analysed, small quantities of Pure calcium carbonate stones hardly ever occur in unevenly distributed stone components may escape human urine (Herring, 1962). Carbonate concretions the examiner. Therefore, if the size of the calculus are formed as complex-salts with apatite. Therefore, permits, specimens from the centre, a layer, and the the presence of carbonate includes the presence of shell should be tested separately. calcium and of phosphate. The outcome of the first slide analysis may be If the presence of cystine remains uncertain interpreted in even greater detail: if, with or without according to the first slide-test, the following simple a positive murexide test, a part of the stone powder reaction is recommended (Kleeberg, 1972). Not less remainsasawhitish-grey layer and ifthis layer has not than 5 mg of stone powder are boiled with 1 ml of shown the molybdate-phosphate reaction, then the 5% sodium hydroxide solution until a lemon-yellow only practical conclusion must be that the material is colour appears (approx 1 minute). Acidifying with calcium oxalate. Such a conclusion without further 10% hydrochloric acid destroys the colour and the analytical tests seems to me permissible when, by smell of hydrogen sulphide or blackening of lead- unfortunate circumstances, not more than 2 or 3 mg acetate paper confirms the presence of cystine. of urinary 'sand' are available. Xanthine stones are It is advisable to wear protective glasses because a so rare that they need not be taken into account in glass slide may splinter when heated. routine laboratory technique. So far, even the widely copyright. applied therapy with xanthine-oxidase inhibitors References during the past few years has not yet changed this situation. Dorronsorro, B. and Fernandez, 0. (Cited by Higgins, C. C. Heating of the stone powder on the first slide with (1954)). In Urology, edited by M. F. Campbell, Vol. I, p. 767. Saunders: Philadelphia. nitric acid should be continued for some 5-10 Feigl, F. (1956). Spot Tests in Organic Analysis [Vol. II of seconds after dryness has been achieved, but charring 'Spot Tests'], 5th ed., p. 243. Elsevier, Amsterdam. must be avoided. If this does occur despite careful Herring, L. C. (1962). Observations on the analysis of ten and slow heating, this part of the material may thousand urinary calculi. J. Urol. 88, 545-562. have J. Kleeberg, (1972). Farbteste ftir den qualitativen Nachweis http://jcp.bmj.com/ been cystine or protein (blood), both rare occur- von Cystin und Harns5ure in Harnsteinen. Urologe [A]., rences. 11, 321-323. on October 1, 2021 by guest. Protected