Derivatives of 1-naphthyl ethylenediamine dihydrochloride for standardization of direct-bilirubin assays done with the Technicon "SMAC".
The Jendrassik--Groff assay for direct bilirubin was adapted for analysis rates of 150/h on the Technicon "SMAC" continuous-flow analyzer. This requires development of a standard that is compatible with the other 19 channels on this analyzer. N-1-Naphthyl ethylenediamine dihydrochloride has been used for standardization of direct bilirubin assays, but we found it to be unsuitable because values for potassium are falsely elevated when potassium is determined with a valinomycin ion-selective electrode. This interference can be eliminated by alkylating the aliphatic amine group in the standard. The resulting compounds undergo the coupling reaction in the same way as the original compound and function equally well as standards for the direct bilirubin reaction. The only limitation of these analogs is their decreased solubility at physiological pH in some cases. Thus only certain alkyl groups are suitable.
Determination of direct-reacting bilirubin on the SMA 12-60.
1. An improved method for the determination of direct-reacting bilirubin on the Technicon SMA 12/60 AutoAnalyzer is presented. 2. The addition of a blank channel to the direct-reacting bilirubin manifold improves the accuracy and precision of the determination. 3. The use of N-1-naphthyl ethylenediamine dihydrochloride as a secondary standard for direct-reacting bilirubin is suggested. 4. The effect of N-1-naphthyl ethylenediamine dihydrochloride on eighteen determinations available as standard methods on the Technicon SMA 12/60 AutoAnalyzer is presented.
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more