Chromatographie liquide haute performance: instrumentation

An HPLC instrument consists of six major components: a mobile phase reservoir for storing solvents, a pump to deliver the mobile phase, an injector to introduce the sample, an analytical column where separation occurs, a detector to identify separated components, and a data system to generate chromatograms. These components work together to separate liquid samples under high pressure.

Modern HPLC instruments use reciprocating piston pumps that create a pulsed mobile phase flow. A pulse damper smooths out these pulses to ensure consistent solvent delivery. The pump draws HPLC-grade solvents from the mobile phase reservoir and delivers them at high pressure into the analytical column, maintaining precise flow rates throughout the separation process.

Gradient elution gradually changes the composition of the mobile phase during analysis, enhancing separation of complex mixtures based on their polarity. Gradient controllers maintain consistent solvent flow rates during this process. This technique allows better resolution of compounds with varying chemical properties compared to using a single, constant mobile phase composition.

The sample is introduced using either a manual loop injector or an autoinjector before the mobile phase reaches the column. These injection systems introduce the analyte mixture into the mobile phase stream. Automated systems allow for consistent, reproducible sample introduction, while manual injection provides flexibility for variable sample volumes.

The analytical column, packed with a stationary phase and maintained at constant temperature by a column oven, is where analyte components separate based on their interactions with both the mobile and stationary phases. Guard columns and scavenger columns may protect the main column from contamination. The separated components then travel to the detector for identification.

The detector identifies separated analyte components and generates characteristic signals. A computer-aided program translates these signals into a chromatogram, which displays the separation results. The eluent carrying the separated components either goes into waste or is collected at a fractional collector for further analysis.

HPLC-grade solvents maintain high purity required for accurate analysis. Dissolved gases must be removed using a degasser, such as a vacuum pumping system or sparging with helium, to prevent bubble formation that could disrupt flow and detection. Proper solvent preparation ensures consistent mobile phase delivery and reliable chromatographic results.