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Lecture 17:Chromatographic Detectors
CU- Boulder CHEM 5181
Mass Spectrometry & Chromatography
Prof. Jose-Luis JimenezFall 2002
Part I:General Detector
Properties
Important Detector Properties
• Signal-to-Noise Ratio– Sensitivity– Baseline noise
• Selectivity• Others
– Baseline drift– Response time– Dynamic range– Linear range
Detection Sensitivity
From Snyder
Detection Noise
From Snyder
Example of Signal-to-Noise Ratio (SNR)
From McNair
Relative Precision vs. Concentration
From Snyder
Detector Noise vs. Detector Drift
From McNair
Detection Selectivity
From Snyder
Definition of Detector Response Time
From McNair
Effect of Detector Time Constant
From McNair
Detector Dynamic Range
From McNair
Detector Linearity
From McNair
Part II:GC Detectors
Most Common Detectors
• Flame Ionization Detector (FID)– C atom counter
• Thermal Conductivity Detector (TCD)• Electron-Capture Detector (ECD)• MS• Up to 60 other types of detectors used
Flame Ionization Detector
From Rubinson
FID Response
From McNair
FID Implementations I
From Skoog
FID Implementations II
From McNair
Effect of H2 Flow Rate on FID Response
From McNair
Effect of Air Flow Rate on FID Response
From McNair
Need for Other Detectors than FID
From McNair
Thermal Conductivity Detector
From Rubinson2
Thermal Conductivity Detector (TCD)
From Schwedt
Thermal Conductivities of Carriers & Analytes
From McNair
Electron-Capture Detector (ECD)
From McNair
ECD Detector
From Rubinson2
Relative ECD Responses
From McNair
Properties of GC Detectors
From McNair
Concentration vs. Mass Flow Rate Detectors
From McNair
Nitrogen-Phosphorus Detector
From Rubinson2
Photoionization Detector
From Rubinson2
Infrared Detection
From Skoog
Atomic Emission Detector
From Skoog
Concentration Ranges for GC Detectors
From McNair
GC Detectors Comparison I
From McNair
GC Detectors Comparison II
From Rubinson
GC Detectors Comparison III
From Settle
GC Detectors Comparison IV
From Grant
Part III:HPLC Detectors
HPLC Detectors
• Most common: UV absorption• Alternative detectors when:
– Analytes don’t have UV absorption– Analyte concentrations are too low for UV abs.– Sample interferences are important– Structural information is required
UV Detectors
From Skoog & Snyder
Choosing a UV Wavelength
UV Diode Array Detection
From Snyder
UV Diode Array Detection
Micro-Capillary Absorption Detection
From Rubinson
Dual-Beam HPLC Detector
From Rubinson
UV Absorptivity of Common Organic Functional Groups
From Snyder
UV Absorption Spectra at Low UV Wavelengths
From Snyder
How to Increase SNR in UV Detection
From Snyder
Universal HPLC Detectors
• Used when – you want a response for all solutes on the
mobile phase• UV can have 100 to 1000 fold differences in
sensitivity between molecules– Analytes do not absorb UV
Refractive Index Detector
Evaporative Light Scattering Detector
From Snyder
Universal HPLC Detectors
From Snyder
Fluorescence Detector
From Snyder
Arrangement of LC Fluorescent Detector
From Rubinson
Other HPLC
Detectors
From Snyder
Light Scattering Detector
From Rubinson
Amperometric Detector
Viscometric Detector
From Rubinson
Post-Column Chemical Reaction Detection
From Schwedt
HPLC Detectors Comparison I
From Skoog
HPLC Detectors Comparison II
From Rubinson
HPLC Detectors Comparison III
From Cunico
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