A newborn develops severe vomiting and symptoms of metabolic acidosis. Urinalysis results are positive for ketones and negative for glucose and other reducing substances. Which of the following screening tests would be positive in this patient? a. Clinitest
b. Ehrilch test
c. DNPH
d. Ferric chloride tube test

DNPH - 2,4-Dinitrophenylhydrazine

Explanation:

This is a chemical compound used for quantitative  identification  of Ketones and Aldehydes in a sample.Since the urine analysis shows positive results for ketone and aldehydes,this is the  test for the this. It is usually marked with  yellow/orange precipitate(ppt) (dinitrophenylhydrazone).The latter is formed as  a results of condensation reaction.

DNPH  is  a solid  compound whose color changes  from  red to orange, when used to test for  the carbonyl groups.Red when pure.

To conduct  the test  1-2drops of the sample is dissolved in 2 ml of ethanol.

This should be added to about 3ml of DNPH,and shake  severely for the solute and solvents to mixed up.

Usually, a precipitate should formed afterwards.However,if this did not appear, 15 minutes intervals should be   observed for the precipitate( yellow or orange ppt) to appear.

The color of the precipitate  depends  nature of the carbon molecule or hydrocarbons in the sample. Thus, if the sample is aromatic that is unsaturated hydrocarbon e.g benzene red ppt appears, However, if straight hydrocarbon molecules (aliphatic) Orange ppt  appears.