Tenuous link but an interesting application of a peristaltic pump in a Cambridge University process to determine ages and origins of geological samples
In the world of earth sciences, ultra-pure concentrated acids are needed to separate out elements such as strontium, rubidium, lead, and rare earth elements from rocks, prior to the measurement of isotopic ratios for determination of age and origin.
These acids generally are purified on site prior to use to remove trace metal and other impurities and stored in FEP Teflon bottles.
Whilst the preparation of pure concentrated acids is a fairly common laboratory application, the Department of Earth Sciences at Cambridge University has been among the first to use the new Sci-Q 323 peristaltic pump from Watson-Marlow Bredel, in order to improve safety and efficiency in a process to purify both concentrated nitric and hydrochloric acids.
In the application, the pump delivers acid to a quartz sub-boiling still operating with a constant overflow, requiring a steady measured delivery of acid over an eight hour period.
Previously this had been achieved with a simple drip feed from a reservoir, but the operation required close supervision and the regular opening of the fume cupboard to top up the reservoir, with an attendant risk of spillage.
Now acid is pumped directly from bulk containers stored within the fume cupboard, requiring far less input from laboratory staff and improving safety.
Hazel Chapman, a research associate at the Department of Earth Sciences first thought of using a peristaltic pump to feed the still after she saw one being used in an inductively coupled plasma application.
She spoke to the department's workshop technicians, who were already familiar with the Watson-Marlow Bredel Sci-Q range of pumps for science, and they in turn contacted the company to arrange for a suitable pump to be supplied.
The pump chosen for the application was the Sci-Q 323 supplied with three 313D pumpheads to give up to three pumping channels for three stills. Using Marprene tubing with 1.6mm bore and 1.6mm wall thickness the system generally runs at just 4rpm to give a flow rate of around 150ml per hour.
Dr Chapman said of the pump: "We've been very happy with the way that the new pump works.
So far it has proved to be both accurate and reliable, and it is also simple to operate - the large LCD display is very clear and the well spaced out keys are easy to use, even with gloves on." Mike Sullivan, UK marketing manager at Watson-Marlow Bredel commented: "With a choice of five drive types and five pump heads, the Sci-Q 323 range gives users the ability to choose the precise solution to meet their needs without over-specifying and paying for unwanted features.
In this application the choice of the 323S model gives fine speed control (in 1rpm intervals) without the added cost of some of the sophisticated functionality found on other 323 models.
In every respect the Sci-Q 323 has been designed specifically for scientific and laboratory applications, bringing powerful performance to the benchtop."
