¿How many types of pumps are there in HPLC?
High-performance liquid chromatography is an important separation technique in analytical chemistry. The ultimate aim of HPLC analysis is to separate, identify, and quantify analytes in a mixture of sample solutions. A liquid chromatography instrument includes a solvent reservoir, pump, column, injector, and detector.
As the name indicates it needs to generate pressure. Unlike other chromatography techniques, High-performance liquid chromatography is needed to generate pressure by pumps. Without a suitable pump, it is not possible to perform HPLC analysis. The pump of HPLC generates pressure on the mobile phase to pass through the column. As the particle size of the HPLC column is very small, the surface area is high and even separation is efficient. However the very high pressure is necessary to flow the mobile phase, therefore HPLC requires pumps capable of generating high pressure. In general, 500 to 4500 psi are the acceptable pressure in the HPLC system.
The HPLC pump has the following stringent requirements:
- Generate enough pressure through the HPLC column.
- It has continuous and reproducible flow without fluctuations in the HPLC system.
- Aptness for a broad range of HPLC solvents used.
- The pump should be capable of taking solvent from one or more reservoirs with pulse-free output at different flow rates.
- Generate uniform pressure without fluctuations.
- It can simple to apply and operable for the long term.
Based on these necessities of pumps, there are three types of HPLC pumps are available.
1. Syringe pumps
2. Reciprocating pumps
3. Pneumatic pumps
Syringe type HPLC pump:
It is a simple method used in the early years. This pump works by generating a pulse-less delivery. This type of pump consists of a big syringe that is motorized by an electronic motor used to drive a steady flow rate. This is suitable for isocratic elution but inconvenient for the gradient elution since it cannot change the mobile phase composition and its capacity.
Reciprocating pump (piston pump):
It is a widely used pump since its precise flow rate produces high pressure. It has a small motor-driven piston which pushed the mobile phase due to the forward and backward action of the piston present. The reciprocating pump can work as an isocratic and gradient mode.
As the name indicates the gas is used to suppress the mobile phase present in a collapsible solvent container. This type of pump provides pulse-free flow and has a simple operation. But because of disadvantages such as the low capacity of solvents, the pump rate varies with viscosity and low-pressure generation.
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