Since German scientists Robert Bunsen (*1811 – †1899) and Gustav Kirchhoff (*1824 – †1887) have discovered, that the color of a flame changed once an element was introduced, atomic spectroscopy has developed into one of the most successful analytical methods, which is applied every day worldwide and routinely. Among the different methods in atomic spectroscopy both multielement methods ICP-MS and ICP-OES have been extremely successful for the analysis of liquids. Both are based on the same inductively coupled plasma source, either used as an emission or an ion source for mass spectrometry. For transport of the liquid sample peristaltic pumps are well established to overcome any change in the composition leading to changes in viscosity thus reducing matrix effects. The working principle is based on compression and relaxation of a trapped liquid volume in an elastic tubing, which is fixed in the pumping head and pressed against a curved pressure plate. By rotation of the roller head the entrapped volume is transported continuously into direction of the nebulizer. The liquid sample is only in contact with metal-free material of the tubing and can be transported over longer distances to the ICP spectrometer. The transported volume is variable and can be affected by the number of rolls in the head, the rotation velocity and the inner diameter of the tubing. The material for the elastic tubing can be selected depending on the chemical properties of the analyte solution. However, sometimes signal pulsations are observed with very sensitive devices, so that they need to be reduced by manually optimizing the pressure of the pressure plate. Such an optimization is not required any more for a new generation of pumps. It is based on the “easy click” principle, where the pressure of the plate is adjusted already by a spring, so that no manual optimization is needed any more, and the analysis sequence can be started immediately.
In an investigation of the Bundesanstalt für Materialforschung und -prüfung (BAM) in Berlin, Germany, Spetec has tested two different peristaltic pumps and the „Easy Click“ pump operated on a simultaneously measuring ICP-OES instrument, to see whether or not any difference of the analytical figures of merit can be observed (the whole report is available on request). This investigation had demonstrated that all analytical figures of merit including limits of detection (LOD) and signal stability of in total ten elements (Al, Bi, Co, Cr, Cu, Fe, Mg, Mn, Ni, Se) from a standard solution do not differ significantly for all tested pumps. The resulting LODs measured are in the lower µg/L range and standard deviations of less than 1 % for eight and less than 2 % for the remaining two elements have been achieved.
As a final result Spetec can say that the „Easy Click“-pump can compete with the two reference pumps concerning the analytical figures of merit but excels with easy and fast changing of tubing without any further adjustment.
