Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

Moderators: honeev, Leonid, amiradm, BioTeam

Post Reply
Posts: 1
Joined: Sun Sep 28, 2008 1:44 am


Post by cmeikle20 » Sun Sep 28, 2008 1:51 am

I need help with a problem.

If you add 3mL of water to 1mL of NADH, mix and get an absorbance of 0.2, what is the original concentration of the NADH solution?

User avatar
Inland Taipan
Inland Taipan
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Post by MrMistery » Sun Sep 28, 2008 5:26 am

i think you need to look at a calibration curve...
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

Posts: 672
Joined: Fri Mar 30, 2007 4:23 am


Post by blcr11 » Sun Sep 28, 2008 12:33 pm

You can't really answer the question unless you've been given the wavelength at which the absorbance was measured--or use a calibration curve like MrMistrey said, and even then they probably should at least tell you the wavelength. You need to use Beer's Law and the molar absorbtivity (molar extinction they called it in the Elder Days) at the wavelength used to calculate the concentration of NADH in the cuvet. The coefficient is wavelength-dependent; the value changes dramatically sometimes over very small ranges of wavelengths. Then you know you made a 1:3 dilution of NADH:water so you can multiply the concentration of NADH in the cuvet by 4 to find the concentration in the original solution.

Post Reply

Who is online

Users browsing this forum: No registered users and 17 guests