Dear fellows, I want to make standard curve for H2O2 using different concentrations of H2O2 but the values are same as blank or very near to it when I observed the absorbance at 560 nm. One thing I observed is the solution of H2O2 + water looks transparent. Should I add some chemical like xylenol orange to produce color or my H2O2 activity is very low as its 1 year old.
No! Because your peroxide is old it has converted to water. Get fresh hydrogen peroxide. Be sure you store it in the refridgerator when not in use.
Are you sure you're reading the method correctly? Typically you measure the degradation of a KMnO4 solution by peroxide at 560 nm. Peroxide itself has no absorbance at that wavelength, but the KMnO4 absorbs strongly. The peroxide degrades the permanganate and causes a loss of absorbance to be measured (a negative curve).
You can measure peroxide directly in the low UV, assuming you have just peroxide in water solutions.
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