tfh 2005 ws chromatographie abhängigkeit der trennleistung eines chromatographischen systems von...
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TFH 2005 WS
Chromatographie
Abhängigkeit der Trennleistung eines chromatographischen Systems von Geschwindigkeit der mobilen Phase
Van Deemter
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Eddy-Diffusion A
Peakform kurz nach der Injektion
Peakform nach Passieren des Säulenbettes
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Diffusion B
Peakform kurz nach der Injektion
Peakform nach Passieren der Säule
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Stoffaustausch C
Veränderung der Peakform durch den Stoffaustausch-Prozess
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Open Tubular Columns
• At a constant pressure• Flow rate is proportional to cross sectional area• Flow rate is inversely proportional to the column length
length
areaflow
For open tubular column this means that we can get Increased linear flow rate and/or a longer columnDecreased Plate height, which means improved better resolution
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Gas Chromatography
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C-Term
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Mass Transport Band Spreading
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Asymmetric Bands
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Comparison of open tubular and packed columns.
• Open tube columns– Higher resolution– Shorter Analysis time– Increased sensitivity– Lower sample capacity
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2D - GC
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Modulators
Thermal modulator
Cryogenic modulator
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Comprehensive GC
• Auch GC x GC oder multidimensional GC.
• 1. Trennung auf „normaler“ Säule.
2. Trennung auf kurzer microbore Säule.
• Gesamtes Effluenz der 1. Säule wird in sehr viele Fraktionen aufgeteilt und auf die 2. Säule gegeben.
• Resultierendes Chromatogramm hat zwei Zeitachsen (die Retentionszeiten der beiden Säulen)
• trapping und Reinjektion durch „Modulator“ bewirken Fraktionsfokussierung.
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Gas Chromatography
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Gas Chromatography
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Gas Chromatography
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Residual Solvents - ICH Topic Q3C
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HPLC - Gas Chromatography
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• She’s a reversed-phase gradient HPLC
This is Ursula
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HPLC
Injector port
guard column
LOAD / INJECT
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• Alltech 450 UV Detector (254nm fixed)
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inector detectorHead Space (80°C) MSD
oven heating rate40°C (6min) 10°C/min90°C (3min) 15°C/min135°C (3min) 15°C/min210°C (3min) 20°C/min250°C (10min)
capillary DB 624length 60 minternal diam. 0.25 mmfilm thickness 1.4µm
GC Conditions
Time needed for one cycle: 55 min
GC HP 6890
SAMPLER HS / OC
Multistage temperature program
HP 5973 - MSD
This is Pat
It is a GC-MS
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Plate THEORY
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HETP = h
In distillation,
Actual plates exist whhere vapour passes through a liquid phaseDuring this mixing, equilibrium between the phases is assumed
The height of a plate can often be directly measured
In a packed column or a capillary the plates can´t be observed – called theoretical plates
Plate theory
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Typical Plate Heights
• GC ~ 0.1 to 1 mm [30 m]
• HPLC ~ 0.01 mm [0,25 m]
• CZE ~ 0.001 mm [0,1 m]
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The Peak
• Ideal chromatographic peaks are Gaussian in peak shape.
• This comes directly from the Craig Model.
• We know certain facts about Gaussian peaks.
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Parameter aus Chromatogramm
Gaussform angenommen
k`= t´R / tR
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Plate theoryPartition coefficient k´
Solute fractions:
mobile phase: 1 / (1+ k´)
stationary phase: k´/ (1+ k´)
ß = rc/2df
1 = 1 / (1+ k´) + k´/ (1+ k´)
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•Alltech’s Heliflex® AT™-1ht GC capillary column is designed for the analysis of samples containing high boiling compounds
and high molecular weight samples. The phase ratio of a column () is equal to the radius of the column divided by twice the film thickness. A higher allows for the elution of high molecular weight samples in a reasonable time; or the elution of medium molecular weight samples at low temperatures. By keeping the temperatures low, the column bleed is also kept to a minimum.
•Phase Ratio: =r/2df•ID df
•0.25 0.25 250•0.32 0.25 320•0.53 1.20 110•0.25 0.10 625•0.32 0.10 800
K = k` x ß
k`= K / ß
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Heat as a separations tool.
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• We could potentially measure the width at half height and knowing it is a Gaussian peak derive the following.
22/1
2
55.5w
tN r
2
2
2
216
rr t
w
tN
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• Resolution = tr / wave = 0.589tr/w1/2 ave
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Factors Affecting Resolution
k`= K / ß
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Oberflächenchemie
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Cross section of a Fused Silica Column Open Tubular
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HTS
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PHASEN
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Choosing the Bonded Phase
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Choosing the Bonded Phase
R = C14 alkyl
R1 = isopropyl shielding
Diisopropyl side groups provide steric protection against low pH
Triple endcapping, shielding
PG = polar amide group
Polar amide group embedded in a long alkyl chain reduces interactiions between basic analytes and silica support