LAB 2- Instrumentation

Question 1

micropipettes

Answer 1

• used for measuring extremely small volumes (in μl range)
• always select smallest pipette size that will handle the required volume (for greater accuracy)
• push plunger all the way to make sure all excess liquid has been extreted
• DO NOT lay pipettes on side or fluid may leak into barrel
• use plastic knob at top to adjust volume
• with very small volumes, expel liquid as drop against inside wall of tube

Question 2

microlitre(μl)

Answer 2

1 ml = 1000μl

Question 3

types of micropipettes used

Answer 3

-each distuinguished by max volume it is intended to measure
P20: dispenses 2-20μl
P200: dispenses 20-200μl
P1000: dispenses 100-1000μl

Question 4

how to read volume on microipipette

Answer 4

P1000: upper digit in red represents 1000s place, then 100s place, then 10s place
P200: read like regular
P20: upper digit represents 10s place, next down 1s place, red digit at bottom represents decimal

Question 5

spectrometer

Answer 5

instrument used to measure absorbance of light by substances in solution
-can be set to measure T or A

Question 6

transmittance

Answer 6

ratio of transmitted light to incident light, expressed as percentage

Question 7

how does a spectrometer work?

Answer 7

Within the spectrophotometer, white light derived from an internal light source is separated into light of different wavelengths (and hence different colours) by passing the white light through a prism. The spectrophotometer can be programmed or set to select a particular colour
of this separated light (a specific wavelength of light energy) to illuminate a cuvette (or spec-appropriate test tube) that is best for the solution of interest. When light of the selected wavelength is passed through a cuvette (or test tube) containing a sample of your solution of interest, some of this incident light will be absorbed by the dissolved solute while the rest of the light will be
transmitted through it. The more diffused solute present in your solution (i.e. the higher the concentration of dissolved solute), the greater the absorbance of the selected wavelength will be. Light that is transmitted through the sample cuvette (or tube) is detected by a detector and converted to an electrical signal. The strength of this signal can be measured and displayed on a meter.

Question 8

use of a blank

Answer 8

blank containing solvent (water, buffer, etc.)and absent of molecules of interest are used to zero out the spectrometer

Question 9

solution prepartion equation

Answer 9

C1V1=C2V2
C1: initial concentration (100%)
V1:how much stock solution you need too add (and distilled water)
C2: concentration you need to make
V2: volume you need to end up with
eg. In preparing our solutions, we want to keep the total volume constant at 5 ml. For your first calculation,
your initial ‘concentration’ is 100%, or C1= 100. C2 is the concentration you need to make (i.e.
90%) and your final volume will be 5ml. So you need to solve for V1.
100(x)=90(5)

Question 10

serial dilution

Answer 10

involves the process of taking a sample and diluting it through a series of standard volumes of sterile diluent

Question 11

dilution factor (DF) (ratio)

Answer 11

DF=Vi/Vf