When i used 0.2 mM DPPH, my ascorbic acid readings show no different. Difficult for me to plot the graph.
Firstly make ascorbic acid stock 1 (10mM) : Add 0.0176g Ascorbic Acid Powder to 10ml methanol or ethanol (ethanol is safer as it's a lot less toxic) or water or ethanol. Make stock 2 (5mM): add 500 microliters stock 1 to 500 microliters water or ethanol. Make stock 3 (250uM): Add 50 microliters stock 2 to 950 microliters water or ethanol. Use stock 3 to make standard curve. Standard curve Ascorbic Acid Concentration (uM) microliters stock 3 microliters water 0 0 100 5 2 98 10 4 96 25 10 90 50 20 80 125 50 50 250 100 0 This should give you an excellent standard curve.
I always use 0.06mM DPPH working solution
the typical standard curve of ascorbic acid starts with 1 mg/ml and down with half. so , you need to dilute your crude extrat to half to fall within the ascorbic acid curve.
Thank you for your reply. One more thing, how long can i store my DPPH? Because last time when i did my ascorbic acid standard using 0.5 mM, i can get a nice graph and my absorbance reading is nice. But now when i used the same dpph, i couldn't get the same reading.
I keep the concnetrated stock in the fridge in light proff botle for 2 weeks at most. The working solution wshould be prepared freshly each day.
A very precise answer from Manikandan. Carolynna, it is important to say that a standard as the ascorbic acid (or other) is just used to compare the IC50 of your sample with a value that is commonly referenced. The standard can be vitamin C, trolox, BHT. However, these standards regularly possess a very high antioxidant activity (i.e., very low IC50), so they are just useful as reference values. I invite you to read our paper on antioxidant activity of Annona diversifolia fruits.
Article Chemical composition, color, and antioxidant activity of thr...
This is an interesting topic. Thanks Carolynna for sharing.
I am interested in Dr. A. M. Naim O'Sullivan answer about the ascorbic acid standard curve preparation. I had a few questions here as well.
1) Can I know the range of concentration for the ascorbic acid standards curve which is mentioned above?
2) What is the volume of of DPPH solution used and reaction time before submitted for the UV-Vis for the standard plot.
I hope you all could guide me as well. Thank you very much
- Badges
- Science topic
- Similar topics
- Mathematical Sciences
- Graphs