Protein Procedure HELP! PLEASE!

[DODOCON1]

Hello, I want to attempt this science project for my high school science fair but am having a little trouble figuring out the Procedure. Here is the link to the whole project:

http://scssi.scetv.org/mims/schools/blh ... charl1.htm
Procedure Page:
http://scssi.scetv.org/mims/schools/blh ... charl4.htm

It reads: "A protein, albumin, was placed into four test tubes for each of the seven pH levels being used. Then the buffer solution for each pH level was placed into their respective tubes. After a period of ten minutes, Ninhydrin Isopropanol was placed into one of the tubes for each pH. This was repeated every ten minutes. After being centrifuged, the solutions were observed for color change and the absorbance was recorded using a A protein, albumin, was placed into four test tubes for each of the seven pH levels being used. Then the buffer solution for each pH level was placed into their respective tubes. After a period of ten minutes, Ninhydrin Isopropanol was placed into one of the tubes for each pH. This was repeated every ten minutes. After being centrifuged, the solutions were observed for color change and the absorbance was recorded using a spectrophotometer at 580nm.

I have a couple questions:
Does this mean that Albumin was placed into a total of 28 test tubes?

What does the author of the project mean by the buffer solution for each PH Level? What is a buffer solution?

What does the author of the project mean by "after being centrifuged."

I do not get how the PH level was measured in this experiment (Go to the data/results page.) Does the spectrophotometer measure PH Lever?

Please anyone who can answer these questions and offer any sort is input is greatly appreciated!!