Nowadays it is very important to analyze as many samples as possible in the shortest amount of time. In the laboratory of the Institute of Food Science at the University of Debrecen, a lot of plant and food samples are studied. For these tests Thermo iCAP 6300 inductively coupled plasma optical emission spectrometer (ICP-OES) is being applied. In most samples there are some elements present only at very low concentrations, while others can be found in a larger scale. The settings of the instrument apply to each element, but can be changed as well. Therefore, our intention was to determine the optimal measurement settings for all elements with the lowest detection limits, by examining the variable parameters.

We have studied the following variable parameters: the RF power, the velocity of the peristaltic pump, the flow rate of the nebuliser- and auxiliary gases. These factors are not independent of each other as they have a complex effect on the plasma performance and thus on the detection limit.

During the measurements, an orange/white 0.64 mm inner diameter tube was used. For optimization, a 10 mg/dm3 multielement solution was used diluted from a 1000 mg/dm3 Merck stock solution. This standard solution contains Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr and Zn elements. To determine the background (blank), high purity deionized water was used (MilliQ). During our investigations two parameters were adjusted to the values as they were used in the previous, usual routine measurements. The intensity was measured by changing the third parameter. During the measurements 20 sec integration time by axial view and 10 sec integration time by radial view were used, in duplicate. The results show that the optimal settings for all elements are 75 revolutions/min (rpm) speed of the peristaltic pump, 0.75 dm3/min nebuliser gas flow rate and 1 dm3/min auxiliary gas flow rate. The RF power resulted as an optimum 950 W for the macroelements and 1350 W for other elements.

Summarizing the results of measurements we have found the optimal parameters to determine the composition of different plant and food samples with lower detection limits.

Keywords: optimization, ICP-OES, inductively coupled plasma, spectrometry