14 Causes of Metals Analysis Failure

Importance of the Topic

Accurate and efficient determination of metal concentrations by ICP-OES is a cornerstone of quality control in food, water, pharmaceutical, and environmental laboratories. Frequent sample remeasurement introduces delays, increases operational costs, and risks damaging a laboratory’s reputation by delaying results to clients. Identifying and preventing the common causes of remeasurement is essential for improving laboratory productivity and ensuring regulatory compliance.

Objectives and Overview of the Study

This analysis reviews the principal factors leading to reruns of ICP-OES samples and quantifies their impact on laboratory efficiency. Drawing on survey data, real‐world case examples, and instrument performance metrics, it highlights both instrument‐ and sample‐related failures. The goal is to offer actionable strategies to minimize reruns and optimize laboratory workflows.

Methodology and Instrumentation

The study combines an online poll of over 200 ICP‐OES users, a case narrative from a practising analyst, and performance data from routine quality checks. Key instrumentation includes:

• ICP-OES with axial and radial plasma viewing
• Autosampler with peristaltic pump tubes
• Glass concentric nebulizer and spray chamber assembly
• Argon gas supply and humidifier
• Auxiliary techniques for cross‐checking, such as ICP-MS and GC

Automated instrument performance tests were used to detect sensitivity, drift, and precision issues before daily runs.

Key Findings and Discussion

Survey respondents reported remeasuring an average of 15% of their ICP-OES samples, translating to roughly 82 hours (two workweeks) of annual rework for a mid‐size lab. The causes fall into two categories:

• Instrument-related causes (e.g., nebulizer blockages, torch injector deposits, dirty optics, pump tubing issues, carry‐over, suboptimal method settings).
• Sample-related causes (e.g., spectral interferences, calibration errors, contamination of blanks and standards, incorrect sample preparation, high matrix effects, overrange concentrations).

Common instrument failures often manifest as signal drift, poor sensitivity, or sudden loss of signal. Routine torch and nebulizer cleaning, daily performance checks, and proper pump tubing maintenance can eliminate many of these issues. Sample-related errors, such as inter-element effects, calibration mix‐ups, and contamination, require robust standard operating procedures, use of certified reference materials, and matrix matching.

Benefits and Practical Applications

Implementing the recommended preventive measures can:

• Reduce sample reruns by up to 80%, freeing analyst time for higher‐value tasks.
• Lower consumable and labor costs associated with redundant analyses.
• Improve turnaround times and strengthen client trust in reported results.
• Decrease operator stress and staff turnover by minimizing unexpected overtime.

Future Trends and Opportunities

Emerging developments promise further reductions in reruns and enhanced data quality:

• Real‐time diagnostics and predictive maintenance powered by instrument connectivity and AI.
• Advanced spectral deconvolution and automated inter-element correction in ICP software.
• Intelligent autosampler sequencing that adapts rinse times based on sample composition.
• Integration of laboratory information management systems (LIMS) for automated QC tracking and digital SOP compliance.
• Alternative plasma sources and miniaturized optics for improved robustness against contamination.

Conclusion

Minimizing sample remeasurement in ICP-OES hinges on a disciplined combination of preventative maintenance, method validation, and rigorous quality control procedures. By addressing both instrument‐ and sample‐related failure modes, laboratories can enhance throughput, reduce costs, and deliver reliable data that support critical decision‐making.