Independent guide to ÄKTA™ systems

Fluidic path

In a basic ÄKTA™ pure configuration, buffer flows from the inlet valve → system pumps → pressure monitor → mixer → injection valve → column valve → column → back through the column valve → UV monitor → conductivity monitor → outlet valve → fraction collector or waste. Optional modules, such as a pH valve or extra column and inlet valves, add positions to this path, and other ÄKTA™ models differ. Check the flow-path diagram for your own system; knowing the order helps you trace where air, pressure and contamination enter.

Pumps

ÄKTA™ pure has two system pumps, each with a pair of pump heads delivering low-pulsation flow to the mixer. Flow and pressure ranges are model-specific: the data file lists up to 25 mL/min at 20 MPa for ÄKTA™ pure 25 and up to 150 mL/min at 5 MPa for ÄKTA™ pure 150. The system pressure monitor can reduce flow automatically to avoid a defined pressure limit. Air in a pump head causes erratic flow; follow the system manual for priming, purging and seal maintenance.

UV monitor

Depending on configuration, the monitor is fixed at 280 nm, fixed at 260 and 280 nm, or variable wavelength. On ÄKTA™ pure a 2 mm flow cell is supplied as standard, with shorter or longer cells available for higher or lower concentrations. Deposits in the flow cell can raise the baseline or add noise; clean it with the solutions and procedure given in the system manual.

At 280 nm, protein absorbance comes mainly from tryptophan and tyrosine, with a small contribution from cystine (disulfide bonds); free cysteine contributes little. Concentration can be estimated with the Beer–Lambert law (A = ε·c·l) and an extinction coefficient measured or predicted from sequence. Sequence predictions are less reliable for proteins without tryptophan, and scattering from aggregates or other absorbing species biases the result.

Conductivity monitor

Measures solution conductivity, which depends on ion type, concentration and temperature; it is not a direct ionic-strength reading. It is the usual way to confirm gradient delivery during IEX and HIC runs. A flat conductivity trace during a programmed salt gradient points to a delivery problem, for example the wrong inlet or buffer, an inlet or valve fault, or air in a pump.

Column valve

Connects the flow path to one or more column positions and, on some valves, provides bypass and reverse flow. Equilibrate a column in place before a run, and avoid drawing air into the packed bed.

Fraction collector

Fractions can be collected at fixed volumes or by peak detection based on UV level or slope. Fraction size and trigger settings depend on the column, peak volume and downstream use. The detector-to-collector delay volume must be accounted for so that fractions match the peaks in the chromatogram.

Sources and scope

Cytiva™, ÄKTA™ pure data file (official, accessed 2026-09-25) supports the configuration, flow path, pump, UV flow-cell and pressure-monitor statements for ÄKTA™ pure only. Pace et al. (1995), Protein Science 4:2411 (peer-reviewed; a full-text copy was read 2026-09-25) supports the 280 nm chromophore statements. Consult the manual for your exact system and configuration for limits and maintenance procedures.