Linear Peristaltic Pump

FIGURE 25.5 Continuous flow pattern for a representative, (a) syringe, (b) cassette, and (c) linear peristaltic pump at 10 mL/h. 

Linear peristaltic pumps transport fluid through a flexible duct using traveling contraction waves. In a typical linear peristaltic pump, discrete translational elements rhythmically compress a straight section of flexible tube, moving fluid volumes. In contrast to rotary peristaltic pumps, linear peristaltic pumps usually do not use rollers or sliding contact elements. Because a moving boundary displaces fluid and induces the flow, linear peristaltic pumps are an example of positive-displacement pumps. 

Peristaltic Pumps, Fig. 2 A typical macroscale linear peristaltic pump design. A set of translating actuators cyclically compresses a flexible tube. The number of actuators may vary. Features of macroscale rotating... 

Linear peristaltic pumps transport fluid through a flexible duct using traveling contraction waves. In a typical linear... 

Side-outlet gradient maker for linear gradients (e.g., Hoefer SG50 for standard gels and Hoefer SGI5 for mini-format gels Amersham Pharmacia Biotech) Peristaltic pump capable of delivering 1 to 6 ml/min... 

ICP-MS is a multielement technique that is suitable for trace analysis it offers a long linear range and low background for most elements. ICP-MS is a technique where the ions produced in inductively coupled plasma are separated in a mass analyzer and detected. The sample solution is fed into a nebulizer by a peristaltic pump. The nebulizer converts the liquid sample into a fine aerosol that is transported into the plasma by an Ar gas flow. In the plasma the sample is evaporated, dissociated, atomized, and ionized to varying extents. The positive ions and molecular ions produced are extracted into the mass analyzer. Detailed descriptions of the ICP-MS technique can be found in a number of textbooks.13,14... 

The FIA system consisted of TMI modules (Tecniques Mesura Instrumentacio), a five-channel peristaltic pump, an eight-channel injection valve, an eight-channel distributed valve, and a colorimeter connected to an interface and to an IBM-PC microcomputer. A specific application software, Qcontroll , was used for data acquisition, with a continuous historical trend, and a scheduled control program for sequential analysis. In a previous scheme as in Fig. 1, free enzymes were used and the whole system was calibrated for a linear range of 0.05-1.0 g of ethanol/ L of standard ethanol solutions, and the product of the reaction was passed through the colorimeter. 

The solution was pumped through the system at a flow rate of 1 ml/min with a peristaltic pump. The sample (0.1-1 ml) was introduced with a three-way valve or a chromatographic sample loop valve. The height of the resulting temperature peak was used as a measure of the substrate concentration and was found to be linear with substrate concentration over a wide range. Typically it was 0.01 -100 mM, if not limited by the amount of enzyme or deficiency in any of the reactants. 

All the materials used for the sample collection were made of either Linear Polyethylene (LPE, 1 litre bottles, storage container) or teflon tubing, with the exception of a short length of silicone tubing (C-flex) in the head of the peristaltic pump. The materials were carefully cleaned according to procedures commonly used for trace metal analyses in seawater [23] ... 

A steady concentration of the reactant is not observed when the confluent reagent stream is not properly added. Pronounced differences in matrix composition (e.g., colour and suspended matter), flow rates and viscosity of the carrier and confluent streams may result in a pulsed addition of the confluent stream. The effect is random, but if the fluid-propelling device is a peristaltic pump, it is characterised by a typical frequency, dictated by the rotation speed of the peristaltic pump. A pulsating flow is then established, leading to undulations in the recorded peak. The effect is reduced if the involved streams converge with similar mean linear velocities. As the effect is characterised by a constant frequency, the modulated signal (ripple) is easily filtered out. 

Constant flow, also called linear flow (Fig. 3.4a). This is the most widely used in flow injection and segmented flow analysis, ideally presenting no temporal variations in flow rate. If there is a slight sinusoidal variation, especially with peristaltic pumps (see 6.1.1), a pulsating flow is established. 

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