With ICP emission spectrometry, many spectral lines are emitted for each element. The fact that spectral lines for samples containing several elements can overlap is well known as spectral interference. For this reason, it is necessary to use a spectrometer with a resolution over a certain level. Even then, spectral interference might be possible. This article describes a way to measure water samples using inductively coupled plasma-optical emission spectroscopy using a simultaneous instrument with a CCD detector and a software package that incorporates the knowledge of experienced analysts as a database, simplifying the selection and confirmation of wavelengths, to allow high precision and interference-free analytical results.

It is estimated that more than 100,000 chemical substances are contaminating our drinking water every day. As water is the basis for a healthy life, strict control as well as a sophisticated and reliable water purification and supply is a crucial condition for health and the prevention of epidemics all over the world.

A wealth of analytical methods exists for the quality control of drinking water and wastewater. The method and type of instrumentation employed is dictated by the composition and formulation of the samples to be measured. Spectroscopy is the preferred method if quick and simple information about the sample material is required, both qualitatively and quantitatively. The optimum spectroscopic method is determined by the sample characteristics.

Atomic spectroscopy applying atomic absorption spectrometers and inductively coupled plasma–optical emission spectrometry (ICP-OES) instruments is used widely for the accurate determination of major, minor, and trace elements in aqueous solutions. Experimental data have been generated using international reference material as well as real life samples from various locations. Performance of different system configurations has been evaluated, and optimized methods have been prepared for achieving the highest sensitivity and lowest detection limits.

Multielement analysis of aqueous solutions in compliance with international drinking water regulations is one of the main application areas of ICP-OES.

Experimental

The system used in this study (ICPE-9000, Shimadzu Europa GmbH, Germany) is suitable for axial and radial plasma observation. Its high-performance echelle optics with special "Schmidt mirror" enable the effective use of the entire 1024 × 1024 pixel CCD detector area. In this way, a resolution of higher than 0.005 nm is attained over the entire wavelength range of 167–800 nm. The detector, which has an antiblooming function, reliably acquires signal intensities, even at long exposure times. All samples can therefore be determined accurately within one single analysis sequence, including samples with very different element concentrations. The "reprocessing" function of the software (ICPEsolution, Shimadzu) enables the determination of additional elements or changing the concentration range for alternate wavelengths without the need for new measurements.

The vacuum optics combined with mini torch technology considerably reduce argon gas consumption. The torch used here reduces the argon gas consumption by half that of conventional torches without loss in sensitivity. In addition, time-consuming rinsing of the optics with ultrapure gas is no longer necessary. The system is ready for operation and stable within the shortest possible time. Equipped with the optional autosampler, the system can be fully automated for high sample throughput operation. The system status is monitored continuously and can be retrieved at any time, whenever needed.

Table I: ICPE-9000 system parameters for water analysis

Method development and data analysis software: The software described earlier offers users additional support with two integrated assistant functions. The "Development Assistant" creates complex calibrations, from the selection of optimal wavelengths up to the composition of standard concentrations. In combination with the "Monitor Function" for qualitative analysis, this assistant points to possible interference problems or incorrect wavelength selection before the actual calibration takes place, and displays solutions for method modification or error correction. The "Diagnosis Assistant" evaluates data already measured, and compares this with information from various databases. Data evaluation and recalculation have never been more straightforward, as the complete emission spectrum of a sample is continuously available.