Preservative used for urine in testing for
a. Porphyrins are coloured and fluorescence, while porphyrinogens are colourless.
b. Porphyrins and their derivative, the characteristic spectrum that each exhibits, in both the visible and UV regions eg. sharp absorption curve for a solution of porphyrin 5% HC1 there is sharp absorption band near 400nm is a distinguishing feature of the porphyrin ring and is characteristic of all — porphyrins regardless of the side chains present this band is known soret (SORET) band.
c. Strong red fluorescence, is so characteristic that it is often used to detect small amounts of free porphyrins. The double bonds joining the pyrrole ring of porphyrins, are responsible for this fluorescence.
d. Spectrophotometry is used to test for porphyrins and their precursors.
e. Most common type of porphyria is Porphyria Cutanea tarda.
f. Major characteristic of Porphyria includes intermittent neurological dysfunction and skin sensitivity to sunlight but intermittent acute porphyria shows no skin photosensitivity, unlike the other types.
g. Excess urinary porphobilinogen excretion occurs in variegate porphyria and intermittent acute porphyria. Detection of porphobilinogen in the urine forms the basis for a positive WATSON- SCHWARTZ REACTION in the diagnosis of variegate and intermittent acute porphyria.