Peristaltic Pump Tubing

If the instrument uses a peristaltic pump, the sample is pumped at about 1 mL/min into the nebulizer. The constant motion and pressure of the pump rollers on the pump tubing, which is typically made from a polymer-based material, ensure a continuous flow of liquid to the nebulizer. However, over time, this constant pressure of the rollers on the pump tubing has the tendency to stretch it, which changes its internal diameter, and therefore, the amount of sample being delivered to the nebulizer. The impact could be a change in the analyte intensity, and therefore, a degradation in short-term stability. 

Therefore, the condition of the pump tubing should be examined every few days, particularly if your laboratory has a high sample workload or if extremely corrosive solutions are being analyzed. The peristaltic pump tubing is probably one of the most neglected areas, so it is absolutely essential that it be a part of your routine maintenance schedule. Here are some suggested tips to reduce pump tubing-based problems  

Ensure tubing is placed correctly in channel of the peristaltic pump. Periodically check flow of sample delivery, and throw away tubing if in doubt Replace tubing if there is any sign of wear do not wait until it breaks. 

With high sample workload, change tubing every day or every other day. Release pressnre on pump tubing when instrument is not in use. 

Pump tubing is a consumable itan— keep a large supply of it on hand. 

Replace tubing if there is any sign of wear do not wait until it breaks. 

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The analysis speed is determined (a) by the ICP or AA system flush-out characteristics and (b) by the mixing and sample-transfer rates of the dilutor. TTie latter can readily be adjusted by increasing the flow-rate of the peristaltic pump tubes. The steady diluted stream can easily be adjusted in order that only a few seconds is required to flush out the previous sample and to set up a steady stable flow. Although peristaltic pumps are... 

Table 5.1. Shoulder colour code for peristaltic pump tubing.

A peristaltic pump, tubes to collect the elution, UV cuvettes, spectrophotometer. 

Assemble the peristaltic pump tubes, injector, reactor, and detector as described in the instrument operation manual or by your instructor. There will be three peristaltic pump tubes, one for the carrier (0.89 mm i.d., orange-orange color-coded stops), one for the reagent (0.89 mm i.d., orange-orange), and one for the sample (0.89 mm i.d., orange-orange). 

Polyurethanes are another class of TPEs. They are a large family of chemical compounds that can consist of ether-based, ester-based, polycarbonate-based or polypropylene-based varieties. A number of copolymers are also included , polyurethanes are combinations of macroglycols and diisocyanates that have been polymerized into tough and elastic materials. TPE polyurethanes have been used for peristaltic pump tubing, parenteral solution tubing and catheters. The tables list the majority of those that are commercially available. Among others are those either of limited supply, available for proprietary use only or that have been successful, but recently discontinued such as ... 

A growing number of uses for TPEs in food-processing equipment include beverage-dispenser pumps and food-container seals. In tbe medical-use area, uses include peristaltic pump tubing, syringe stoppers, catheters, and hospital tubing and sheeting. 

The robustness of SIA. In fact, the liquids only come into contact with the walls of the glass syringes and Teflon tubing, as no peristaltic pump tubes are used. 

Aging of the peristaltic pump tubes may modify the sample dilution. Some of the analytical channels tend to form precipitates on the cuvette walls, thus changing the spectrophotometer response, especially after a period of analysing high compound concentrations. Temperature effects may alter the equilibrium state of the formation of the spectrophotometri-cally detected compound, and, finally, the stability of some of the reagents is limited. 

ICP source. All the components, including the peristaltic pump tubing (a typical lifetime of 1-2 weeks, based on a normal eight-hour working day, is expected), the spray chamber (sample chamber type changes sensitivity ... 

FIGURE 16.1 A commercially available digital thermoelectric flow meter to diagnose problems associated with peristaltic pump tubing and nebulizer blockages. (Courtesy of Glass Expansion, Inc.)... 

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