BIOTECH Science Packet Study Guide: Ph Meter & Spectrophotometry

Spectrophotometry Notes



A spectro operates by measuring the transmittance of a sample.



UV Light:

- UV light detects colorless molecules.

- VIS spectrophotometry uses white light to find colorful molecules.



They are used similarly to detect the amount of light that goes through a sample to know
the absorbance of a given sample. You need to know the basics of how to use this machine.



UV spectrum: 100–350 nm (can measure DNA)

VIS spectrum: 350–700 nm to view colored molecules and their maximum absorbance, to
compare to the rest of the colors.



pH:

- pH < 7 has more H⁺ ions (acid)

- A base contains more OH⁻ ions



pH scale ranges from 0–12 showing relative concentrations of H ⁺ and OH ⁻ ions.



OH⁻ concentrations:

10⁻¹⁴, 10⁻¹³, 10⁻¹², 10⁻¹¹, 10⁻¹⁰, 10⁻⁹, 10⁻⁸, 10⁻⁷, 10⁻⁶, 10⁻⁵, 10⁻⁴, 10⁻³, 10⁻²



H⁺ concentrations:

1, 10⁻¹, 10⁻², 10⁻³, 10⁻⁴, 10⁻⁵, 10⁻⁶, 10⁻⁷, 10⁻⁸, 10⁻⁹, 10⁻¹⁰, 10⁻¹¹, 10⁻¹²