Title: Chem. 231
1Chem. 231 2/4 Lecture
2Announcements I
- Homework Set 1 is due 2/6
- New Set will be available 2/6 (hopefully) which
will be due 2 weeks later - Quiz 1 on 2/11 on homework and topics covered in
class (setting up files, data transfer and
processing, and simple extraction covered today) - Website Update
- Writing guidelines
- List of Books and Journals
- Example Quiz (from 2007)
- Im Working on Procedures for Set 2 Labs
3Announcements II
- Todays Topics
- Simple Extractions (emphasis on equipment,
procedures and tests and on ones we can do) - Solids into liquids
- Gases into liquids
- Gases into solids
- Solids from liquids or gases (filtration)
- Liquids into liquids
- Solvent removal
4Announcements III
- Lab Today
- Set 1 Labs are ready (but work was not planned in
syllabus) - Should plan on making a multi-component standard
for qualitative analysis - Todays work should be focused on learning to use
instruments
5Simple Extractions
- Purposes (repeat from Chem 230)
- Isolate compound of interest (only very simple
samples) - Trap and Concentrate Analyte(s)
- Remove interferences
- Split sample into classes
6Simple Extractions
- Solid into Liquid
- Best to choose solvent with good solubility for
analytes (e.g. similar Kow and functional groups
as solvent) - Sample prep (finely ground powder will lead to
better extraction) - Agitation (shakers, ultrasound bath)
- Soxhlet Extractors
Soxhlet Extractor show example
to condensor
Extraction Thimble
round bottom flask with solvent
1) Round bottom flask is heated, solvent
evaporates
2) Solvent condenses and fills extraction thimble
3) Once reaching loop, solvent siphons out and
back to round bottom flask
7Simple ExtractionsGases to Liquids
- May be used for trapping carbonyls in
derivatization lab - Equipment (repeat from Chem 230)
- Bubblers, mist chambers, denuders
- Best Conditions (larger KH constants)
- lower temperatures
- solvent polarity (although less volatile solvents
needed) - pH (if trapping acids or bases)
8Simple ExtractionsGases to Solids
heating wire
trapping flow
- Traditional method to trap gases (e.g. volatile
hydrocarbons) using cartridge - Can be combined with purging to transfer volatile
compounds from water to solid - Desorption flow direction is usually reversed
- Most commonly used with thermal
desorption/injection into GC - Best Conditions
- Keep cartridge cool during trapping
- Can choose trapping material for selectivity or
efficiency
desorbing flow
9Simple ExtractionsGases to Solids - SPME
- SPME is used most with GC analysis
- More on procedure later since can also be used
for liquid samples and with liquid removal - Will use in extraction lab (headspace for
standards and samples) - Advantages
- simple (no solvent for gases)
- efficient
- Disadvantages
- not exhaustive
- harder to make quantitative (must maintain
similar conditions)
10Simple ExtractionsFiltration/Centrifugation
- Purpose
- to trap precipitated analytes/solutes (solids
from liquids) - to trap aerosol particles (from gases)
- to remove solids (needed before HPLC/GC analysis)
- Centrifugation (only for liquids)
- Best if isolating solids
- Filtration
- Large quantities (use side arm flasks)
- Small quantities (use syringe filters)
11Simple ExtractionsLiquid Liquid Extraction
- Equipment (show examples)
- traditional separatory funnel (show example)
- smaller scale conical vials (cone shape needed
to remove most of one phase) syringes - Separation Basis polarity partitioning
(remember likes dissolves likes rule) - Liquid Phases
- Two phases must be immiscible (form two distinct
layers) - Most common with water organic
- Also possible with polar non polar organic
(methanol hexane), but few organic solvent sets
are immiscible - Lower layer is denser (water in hexane water but
chloroform in water chloroform)
12Simple ExtractionsLiquid Liquid Extraction
- Practical Aspects
- solvent choices
- common to remove compounds from water to go to
organic solvent (faster evaporation, better for
GC injection) - organic solvent (non-polar solvent for least
polar analytes, moderately polar for somewhat
polar analytes) - emulsions make some liquid liquid extractions
problematic - selectivity also is important (e.g. use of
toluene to selectively retain aromatics over
alkanes) - modifiers
- can modify water by adjusting pH (ionized
compounds stay in water) - salts can also be added to help in transferring
organics to organic phase
13Simple ExtractionsSolvent Reduction/Removal
- Purposes
- Switch solvents (e.g. methanol to CDCl3 for NMR)
- Concentrate sample
- Remove volatiles
- Nitrogen drying
- used with volatile solvents/volatile solutes
- often for solvent reduction (not complete
removal) - Rotory Evaporators
- Typically used with solvents more volatile than
water - Has both pressure and temperature controls
(usually manual) - Bumping can occur
to vacuum bleed (control), traps and vacuum pump
condensor
rotation
round bottom flask
water bath
14Simple Extractions Solvent Reduction/Removal
- Freeze Drying
- More commonly used with water
- Better for many biological samples (susceptible
to thermal decomposition) - Procedure
- Sample is frozen
- Sample in container is connected to a vacuum
(with low T water trap between sample and vacuum) - Low pressure causes water to stay in ice form
- Difficult with small samples (can melt before
connection is complete)
15Some Questions
- A chemist is interested in extracting furanyl
compounds from charred wood. Chunks of charred
wood are placed in methanol and shaken for 30
minutes. Repeated extractions show the
efficiency is not great. List two ways to
improve extraction. - Small quantities of particulates are expected in
mL samples to be analyzed by HPLC. Suggest a way
to remove them. - Describe how a chromatogram produced by
Chemstation (Agilent 1100 system) can be
transferred to an Excel file. In this method,
will how it was integrated be retained?
16Simple ExtractionGas to Solid SPME Procedure
- Will be used in SPME lab
- The needle pierces the septum to a sample (sample
can be gas, liquid, or headspace) - The sheath is removed allowing trapping of
analytes on fiber - Stirring helps the transfer
- The sheath goes back and the needle is withdrawn
- The needle pierces the septum to a GC, the sheath
is withdrawn and the analyte is desorbed by the
heated GC injector
Fiber
For lab work, it is critical to have the sheath
on when piercing septum
GC Inlet