Fast Analysis of Water Samples Comparing Axially-and Radially- Viewed CCD Simultaneous ICP-OES

Importance of the Topic

Rapid and reliable analysis of trace elements in water is critical for environmental monitoring, regulatory compliance and public health protection. Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES) is widely used in water laboratories, but achieving low detection limits and high sample throughput remains a challenge. The introduction of an axially viewed CCD-based simultaneous ICP-OES system offers a significant advancement by combining enhanced sensitivity with fast analysis rates.

Objectives and Overview of the Study

This work compares a newly developed axially viewed CCD simultaneous ICP-OES (Vista AX) with a conventional radially viewed CCD ICP-OES (Vista RL). The study aims to demonstrate improvements in detection limits, sample throughput, precision, stability and overall suitability for routine water testing, with reference to US EPA Contract Required Detection Limits (CRDLs).

Methodology and Instrumentation

An Agilent Vista AX and Vista RL CCD simultaneous ICP-OES, each featuring an echelle polychromator with cross dispersion and a patented VistaChip detector, were employed. The detectors span 167–784 nm continuously with over 70 000 pixels and a readout speed of one million pixels per second. The VistaChip’s signal processing is 80× faster than conventional systems. A glass concentric nebulizer and cyclonic spray chamber, controlled by a mass flow controller, delivered samples to the plasma. Operating conditions included 1.2 kW power, 15 L/min plasma gas, 1.5 L/min auxiliary gas and 0.75 L/min nebulizer flow, with 10 s integration and three replicates per reading. High‐purity reagents and NIST‐matched standards in 1–3.5 % HNO₃ were used.

Main Results and Discussion

• Detection Limits: The axial system achieved detection limits 5–10× lower than the radial system, all below current US EPA CRDLs. The radial configuration met most CRDLs except for As, Tl and Sb.
• Warm-Up Time: Plasma stabilization required approximately 35 minutes from cold start, during which software allowed worksheet setup and autosampler loading.
• Sample Throughput: At 10 s integration, the system analyzed ~220 samples per 8-hour workday (33 samples/hour). Faster modes (1–5 s integration) yielded 38–45 samples/hour.
• Precision and Stability: Short-term precision was typically ≤0.5 % RSD (10 s integration, 30 replicates). Four-hour drift tests showed 0.21–0.98 % RSD using key spectral lines for diagnostic monitoring.
• Water Analysis: Analysis of NIST SRM 1643C and 1643D water samples demonstrated excellent agreement with certified values for major and trace elements, validating accuracy.

Benefits and Practical Applications

The axially viewed CCD ICP-OES system delivers superior sensitivity, enabling compliance with stringent regulatory limits for trace elements. Its high throughput and unattended operation with built-in quality control protocols make it ideal for routine environmental and industrial laboratories. Quick warm-up and minimal maintenance further enhance productivity.

Future Trends and Opportunities

Advances in sample introduction—such as ultrasonic nebulization or vapor generation—could further lower detection limits. Integration with automated workflows, remote monitoring and advanced data analytics will drive deeper insights and efficiency. Emerging applications may include real-time process control, portable field systems and coupling with separation techniques.

Conclusion

The Vista axially viewed CCD simultaneous ICP-OES system markedly improves detection limits, precision and throughput compared to a radially viewed configuration. Its performance meets or exceeds US EPA requirements and delivers reliable, high-speed analysis for water quality laboratories.

References

• Demers D. R. Evaluation of the axially viewed inductively coupled argon plasma source for atomic emission spectroscopy. Appl. Spectrosc. 1979;33:584.
• Faires L. M., Bieniewski T. M., Apel C. T., Niemczyk T. M. Top-down versus side-on viewing of the inductively coupled plasma. Appl. Spectrosc. 1985;39:5.
• Nakamura Y., Takahashi K., Kujirai O., Okochi H., McLeod C. W. Evaluation of axially and radially viewed ICP using an echelle spectrometer with wavelength modulation. J. Anal. At. Spectrom. 1994;9:751.
• Ivaldi J. C., Tyson J. F. Performance evaluation of an axially viewed horizontal ICP for optical emission spectrometry. Spectrochim. Acta Part B. 1995;50:1207.
• Nham T. T. Performance evaluation and applications of an axially viewed ICP-AES. Paper no. 223, 13th Anal. Chem. Conf., Darwin, Australia, 1995.
• Zander A. T., Cooper C. B. III, Chien R. L. Optical detector for echelle spectrometer. US Patent 5,596,407; 1997.
• Barnard T. W., Crockett M. I., Ivaldi J. C., Lundberg P. L., Yates D. A., Levine P. A., Sauer D. J. Solid-state detector for ICP-OES. Anal. Chem. 1993;65:1231.
• US EPA Contract Laboratory Program SOW for Inorganics Analysis Multi-media Multi-concentration. SOW No. 788, 1988.
• US EPA Contract Laboratory Program SOW for Inorganics Analysis and Classical Chemistry Parameters. Draft ILMO 5.0C, 1999.
• Carre M., Poussel E., Mermet J. M. Drift diagnostics in ICP-AES. J. Anal. At. Spectrom. 1992;7:791.