Phenylpyruvic acid reacts with trivalent iron ions to produce a blue color, interfering with the color development and causing a false-negative reaction of the phosphate is removed by turning it into magnesium ammonium phosphate, this experiment is from the Mudanjiang Medical College, the undergraduate 5-year clinical laboratory guidance

Operation method

Phenylketonuria qualitative screening test

Principle

Phenylpyruvic acid reacts with trivalent iron ions to produce a blue color, which interferes with the color development leading to a false-negative reaction where the phosphate is turned into magnesium ammonium phosphate and removed.

Materials and Instruments

Ferric chloride solution Phosphate precipitant Ehydrochloric acid

Move

I. Experimental reagents:

1, ferric chloride solution, weigh FeCl6?6H2O 10g, dissolve and dilute to 100 ml with distilled water.

2, phosphate precipitant: take magnesium chloride (MgCl2?6H2O) 2.3 grams, magnesium oxide 1.4 grams and concentrated chlorine 2 ml. Add distilled water to dissolve and add to 100 ml.

3, according to hydrochloric acid

Second, the experimental method:

l, take 4 ml of urine, add 1 ml of phosphate precipitant. Mixed and filtered.

2, to the filtrate with 2-3 drops of concentrated hydrochloric acid, so that it is acidified and then add 2-3 drops of ferric chloride solution.

3, the blue-green color appears to remain 2-4 minutes does not recede when positive.

Caveat

l, show the blue-green reaction immediately recedes for the urine black branch or p-hydroxyphenylpyruvic acid, this time should be used as a negative reaction of phenylpropionic acid.

2、Bilirubin can be positive.

3， urinary phenylpropanone handle acid at room temperature is easy to decompose, especially alkaline urine is more, so it must be tested immediately with a fresh specimen. Otherwise, a little sulfuric acid or muscimol should be added to preservative and then put in the refrigerator so that can be stored for several days.

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