Introduction to Microscale Laboratory

1
Introduction to Microscale Laboratory
2
Required Reading Before Class

• Exercise 1, Options A B
• Exercise 2
• Techniques 1-3, 5, 6, 7.2-7.4 (4th ed.)
• Techniques 1, 2, 3.1-3.4 (3rd ed.)

3
Measuring Volume Weight

• Automatic Pipets (or Micropipets)
• Can be adjusted for any volume within its defined
  range
• Accuracy of delivery up to four digits
• Not for use with corrosive liquids
• Dispensing Pumps
• Good for use when larger amounts (gt0.1mL) of
  liquids are being dispensed

4
Measuring Volume Weight

• Syringes
• Useful when anhydrous conditions must be
  maintained
• Other instruments
• Provide rough estimates for measuring volume
• Graduated Cylinders
• Beakers
• Conical Vials
• Flasks

5
Heating Cooling Methods

• Aluminum Block
• Handles most heating applications in the
  microscale laboratory
• Smaller holes will hold conical reaction vials
• Block may be cooled rapidly in cold water
• Calibration of Hot Plate
• Measure the temperature of several dial settings
  using an aluminum block and thermometer

6
Heating Cooling Methods

• Heating/ Mixing Organic Solutions
• As a general rule, set the temperature of an
  aluminum block 20oC higher than the desired
  temperature of your reaction mixture
• To stir solutions, use a magnetic spin vane (for
  conical vials) or a magnetic stir bar (for
  round-bottom flasks)
• Inert, teflon boiling stones should be added when
  boiling a mixture w/o stirring.

7
Heating Cooling Methods

• Hot Water Bath
• Suitable alternative for temperatures below 80oC
• Uniform heating occurs with a hot water bath, as
  opposed to sand baths aluminum blocks, where
  gradients are likely to exist.
• Temperature of a reaction mixture will be closer
  to the temperature of a water bath than using
  other heating devices

8
Heating Cooling Methods

• Cold Baths
• Ice bathsgood for cooling to 0oC
• Add solid NaCl to cool in the range
• of 0 to 10oC
• Dry ice/ isopropyl alcohol bathscool
• to 78.5oC
• Liquid nitrogen bathscool to extremely low
  temperatures (-198.5oC)

9
Heating Under Reflux

• Microscale Reflux Apparatus
• Allows you to heat mixtures for a long time
  without having to watch it constantly
• Condensers
• Used to prevent loss of product via evaporation
  (2 types)
• Water-Cooled Condenserwater flows through
  condenser _at_ bottom out the top
• Air-Cooled Condenserjust a long tube attached on
  top

10
Heating Under Reflux

• You must use a condenser when
• Vigorous boiling is desired
• Chemicals being used are volatile
• During condensations, a reflux ring is formed.
  This indicates the height at which condensation
  has reached, preferrably no higher than halfway
  up the walls of the condenser.
• Be sure to adjust the conditions so that the
  reflux ring doesnt exceed this height to avoid
  loss of product!

11
Procedural Notes

• Option A (Automatic Pipet)
• The pipets digits are read from top to bottom
• You must multiply the number in the window by a
  factor of 10 to get the volume in microliters
• (1mL 10-3mL)
• Important Do not set the pipet to dispense
  outside of its calibrated range!
• Dont forget to put a disposable tip on the end
  of the pipet discard of it appropriately after
  use

12
Procedural Notes

• Exercise 2 (Pipet Calibration)
• Follow the instructions on calibrating a single
  pasteur pipet, and then if you desire, you can
  make more by lining up the pipets side-by-side
  and marking the clean pipet in the same spot that
  your calibrated pipet has been marked. You may
  store these in your lab drawers for later use.
• Exercise 2 (Extraction)
• Precision is important with this exerciseyou
  should try this procedure several times to get
  accustomed to it.