II.2.1. Chemical analysis using Inductively Coupled Plasma

The ICP-OES (Inductively Coupled Plasma – Optical Emission Spectroscopy) plasma furnace is specifically designed to detect, and verify, the presence of virtually any contaminant element in a water sample. Additionally ICP furnace can measure the amount of specific trace elements in an aqueous sample to less than 1 ppb. In the technical ICP-OES process, a sample is fed into super hot plasma – heated to near 7760 °C. Atoms in the plasma emit characteristic wavelengths for each element present. The emitted light is then calibrated against scientific standards, providing the indentification and the measurement of contaminants in the aqueous sample.

The equipment for ICP optical emission spectrometry consists of a light source, a spectrometer, a detector and a data processing unit. There are several types of equipment depending on different spectrometers and detectors. The most common type and used in this experiment is shown in Figure 4.[13]

Figure 4: Sequential Type ICP-OES [13].

The actual metal content in all catalysts was analyzed by an inductively coupled plasma (ICP) atomic emission spectrometer (IPC-OES Perkin Elmer Optima 3200RL), allowing moderate to low detection of 0.2-100 ppb.

Example of preparation:

For chemical analysis of ruthenium, the fused samples were prepared as described

below. In a zirconium crucible 0.050 g of dry and homogenized sample was weighted,

five grains of sodium hydroxide and 1.0 g of sodium peroxide were added and the

mixture was fused at 450 °C for 15 minutes, and then left to cool. Cold samples were

dissolved using 25 ml of the mixture of hydrochloric and hydrochloric acid. As the

reaction with the sample was violent and strongly exothermic, this amount of acid was

added in four portions and afterwards each crucible was put into sand bath for a few

minutes. Then the solution was transferred to Teflon vessel. In order to stabilize

zirconium oxide 5 ml of hydrofluoric acid was added and the mixture was left for 1

hour in a sand bath (160 °C). The final stage of the sample preparation was pouring the

solution from the Teflon vessel into a plastic flask and filling up to 250 ml by 1% HCl.

A Perkin Elmer Optima 3200RL spectrometer equipped with cross-flow nebuliser and

Czerny-Turner monocromator was used for the intensity measurements of characteristic

wavelengths. This spectrometer allows easy detection of the emitted radiation when it is

in the range form UV-VIS to near infrared region (180-850 nm). For this range of λ, a

29 monocromator was mounted with gratings having 2400 and 1200 grooves 1/mm

respectively [14].