Chapter 4 - HPLC/UHPLC instrumentation and trends Flashcards
Some HPLC systems need to be biocompatible because of
the use of high-salt mobile phases that is corrosive to stainless steel.
PEEK stands for
polyetheretherketone
Multisolvent pumping systems are classified on how
solvent blending is achieved.
The typical dwell volume of a low-pressure mixing HPLC system is
~ 1 mL
Dwell time is important in _______ analysis.
gradient
Dwell volumes of binary systems range from
0.1 to 0.4 mL.
Dwell volumes of quaternary systems range from
0.4 to 0.8 mL
Primary performance criteria for autosamplers is
sampling precision and carryover.
Precision level of most autosamplers
<0.2% RSD for peak area
Carryover of most autosamplers
<0.05%
Minimum injection volume of HPLC
∼ 5 μL
Minimum injection volume for UHPLC
∼ 1 μL
An HPLC detector measures the
concentration of eluting analytes.
Absorbance equation
Absorbance (A) = molar absorptivity (𝜀) × path length (b) × concentration (c)
Absorbance is equal to _____ if 90% of the light is absorbed, and equal to _____ if 99% of incident light is absorbed.
1.0; 2.0
A UV/Vis detector consists of
a deuterium lamp, monochromator, and a small flow cell
The limit of detection in a PDA is
3x the noise.
In a UV/Vis detector, sensitivity is specified by
baseline noise (peak-to-peak or root mean square noise).
Typical UV/Vis wavelength range
190-600 nm
A typical UV/Vis with a deuterium lamp has low sensitivity above ______ nm
400
In UV/Vis, when a single wavelength is detected, between _______ nm usually passes through the flow cell.
5-8
Benchmark detector noise level
±1 x 10-5 AU/cm
Typical lifetime of a deuterium lamp
∼2000 hours
Preferred detector for HPLC method development.
PDA (photodiode array detector)
Most PDAs have a spectral resolution of about
1 nm.
Temperatures higher than 60∘C are often used to allow
higher flow rates without exceeding system pressure limits by reducing solvent viscosity.
