We prepared two solutions, which were Sodium phosphate monobasic and Sodium phosphate Dibasic.
We used 250 ml of 0.1M Sodium phosphate Monobasic, which equal 2.9995g, we added it to the 250ml beaker and added 50.0ml of water to dissolve it. On the same time, we prepared 250ml of 0.1 Sodium phosphate Dibasic, which equal to 3.549g; we added 50.0ml of water to be dissolved. We made these two solutions in order to get their PH. We started with PH 6.0 buffer from Sodium phosphate monobasic solution, we added 50ml of Sodium phosphate Dibasic to 250ml beaker, placed PH probe, then added solution Sodium phosphate monobasic until PH was between (5.9-6.1), and we called it solution
C.
We did the 7.0 buffer by adding 50ml of Sodium phosphate Dibasic solution to 250 beaker, we placed PH probe, then added Sodium phosphate monobasic until PH was
(6.9-7.1) to make solution D. Lastly, we added 50ml of Sodium phosphate monobasic to 250 ml beaker, placed the PH probe, and added Sodium phosphate Dibasic until the PH was (7.9-8.1), and we called it solution E.
PH meter was calibrated and standardized with 3 different solutions which were
PH 3,PH7, and PH10. In experiment 3.2, we labeled 4 test tubes #1,#2,#3,#4,then we placed 1 ml of PNP 0.1 solution in each of the 4 test tubes. We added 3ml of solution C to test tube #1,added 3ml of solution D to test tube #2.also, 3ml of solution E to test tube #3.we added 3ml of PH a buffer to test tube #4, that by using #5 and #10 from experiment 3-1.
In experiment 3-3, we diluted standard PNP with PH 10 buffer making the final volume 4ml. We made 5 standards: 10 µM, 20 µM, 30 µM, 50 µM, 75 µM PNP. Then, we measured absorbance of each sample at wavelength determined in experiment 3-2. We first diluted 1 ml of the unknown with 3rd of buffer. Second, we measured absorbance at wavelength 460nm, which determined from experiment 3-2.