Analytical Chemistry II ChEm 321 India Gray

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

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

Instrument Components Source Analytical Input Signal Output (Stimulus) Information Transducer Processor Transducer 1. 2. 3. 4. 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)

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

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

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

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

Infrared (ir) spectroscopy

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.

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

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

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 2-1000 MM

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

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

Mass “Spectrometry” Sample Inlet System Ion Source Mass Analyzer electron multiplier Inlet System Ion Source Mass Analyzer Detector (m/z) 10-5-10-8 torr Signal Processor Vacuum System Batch Direct Probe Gas Chromatograph Liquid Chromatograph Turbo pump Diffusion pump Readout M. Crowther 5/8/2018