1. Analytical Chemistry II ChEm 321
India Gray

2. Summary Components of Instrumentation Signals and Noise
UV-VIS Spectroscopy
Fluorescence
IR Spectroscopy
NMR
Gas and Liquid Chromatography
Mass Spectrometry

3. Components of Instrumentation
Source (stimulus)
Analytical Information
Input Transducer
Signal Processor
Output Transducer

4. Instrument Components
Source Analytical Input Signal Output
(Stimulus) Information Transducer Processor Transducer

5. Signals and noise
Signal has regularity; a pattern that is reproducible
Noise is random; variations in measurements
Chemical – Variations in temperature and pressure that effect chemical equilibria and signal response
Instrumental
Thermal – since e- are always in “motion” it causes occasional charge or voltage fluctuations
Shot – fluctuations in charge due to uneven flow of e-
Environmental – components that conduct currents act as antennas and pick up electrical signals
Flicker – not well known; depends on frequency
Reduce by hardware (shielding/filtering) and software (smoothing/digital filtering)

6. UV-Vis Spectroscopy
Measures molar absorptivity vs. wavelength by reading electronic transitions (e- excitations)
Has high selectivity and good accuracy
Ease and convenience of data
Use for organic and inorganic species

7. Agilent 8453 UV-Vis Multichannel Spectrometer grating placed
AFTER the sample
all λs detected at once

8. fluorescence X-ray For elements greater than 5 (Boron) Precise
Measures remission of x-rays from excited atoms
Solids and non-volatile liquids

9. Infrared (ir) spectroscopy
Gives identity of organic and inorganic and functional groups
Symmetry of molecular groups in solid state
Measures excitation of molecular vibrations by light absorption
For solids

10. Infrared (ir) spectroscopy

11. Nuclear magnetic resonance (Nmr)
Measures reorientation of magnetic nuclei in magnetic field
Helps determine structure, identity of organic compounds, molecular conformations and configurations
Can use liquid and soluble solids
Determines chemical type and # of atoms
Look at 1H, 19F, 13C, 31P, etc.

12. Superconducting Magnet
Superconducting – sustains current without resistance (or electrical heating) when cold (4K)
MUST BE HOMOGENOUS:
Spin sample
Shim coils
Lock (field-frequency)

13. Types of Chromatography- Based on Phase
Mobile Phase
Stationary Phase
gas supercritical fluid liquid
column planar
GLC GSC
TLC PC
LSC BPC IEC SEC

14. Gas Chromatography Analysis of volatile organics
Has efficient separation technique
Partitions vapor phase and substrate
Mobile phase:
gas
Stationary phase:
liquid or solid
Analyte:
must be volatile MM

15. Liquid chromatography
Analysis of volatile and ionic materials
Partitions liquid and substrate
Time consuming
Multi-component analysis

16. Mass spectrometry
Determines structure and identity of organic compounds
Analysis of trace volatile in non-volatiles
Measures ionization of molecules and cracking of molecule into fragment ions

17. Mass “Spectrometry” Sample Inlet System Ion Source Mass Analyzer
electron multiplier
Inlet
System
Ion
Source
Mass
Analyzer
Detector
(m/z)
torr
Signal
Processor
Vacuum
System
Batch
Direct Probe
Gas Chromatograph
Liquid Chromatograph
Turbo pump
Diffusion pump
Readout
M. Crowther
5/8/2018