Loop Injector for HPLC
The operating pressure of an HPLC is sufficiently high that we cannot inject the sample into the mobile phase by inserting a syringe through a septum (as we can do in gas […]
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HPLC Pumps
A typical HPLC includes between 1–4 reservoirs for mobile phase solvents. The mobile phase solvents are pulled from their reservoirs by the action of one or more pumps. Shown here is a close-up […]
Gradient Elution Separation of Flavonoid Mixture
The illustration below shows the gradient elution separation of a mixture of flavonoids. Mobile phase A is an aqueous solution of 0.1% formic acid and mobile phase B is 0.1% formic acid […]
Using a Solvent Triangle to Optimize an HPLC Separation
One strategy for finding the best mobile phase for an HPLC separation is to use the solvent triangle, which allows us to explore a broad range of mobile phases with just seven […]
HPLC Column
The most common type of HPLC column is a stainless steel tube with an internal diameter between 2.1 mm and 4.6 mm and a length between 30 mm and 300 mm. The […]
HPLC Instrumentation
The photo below shows an example of a typical HPLC instrument with insets showing close-up views of the pumps that move the mobile phase through the system, and the plumbing used to inject […]
Finding the Area for Overlapping Chromatographic Peaks
In a GC analysis the area under the peak is proportional to the amount of analyte injected onto the column. The peak’s area is determined by integration, which usually is handled by […]
GC-MS
The figure below provides a block diagram of a typical gas chromatography-mass spectrometer (GC–MS) instrument. As illustrated here, a three component mixture enters the GC. When component A elutes from the column, it enters […]
Electron Capture Detector
Shown here is a schematic diagram of electron capture detector (ECD) for gas chromatography. The detector consists of a β-emitter, such as 63Ni. The emitted electrons ionize the mobile phase, which is […]
Flame Ionization Detector
The schematic diagram below shows a flame ionization detector for gas chromatography. The eluent from the column mixes with H2 and is burned in the presence of excess air. Combustion of organic […]
Thermal Conductivity Detector
One of the earliest gas chromatography detectors takes advantage of the mobile phase’s thermal conductivity. As the mobile phase exits the column it passes over a tungsten-rhenium wire filament (see figure below). […]
GC Injectors
Shown here is a schematic diagram of a heated GC injector port for use with packed columns. The needle from the syringe pierces a rubber septum and enters into the top of […]