Faster and better analysis of complex samples in a geochemical laboratory

Significance of the topic

The ability to perform fast, robust and multi-parameter anion analyses in geochemical and environmental laboratories is essential for water quality monitoring, mine-water assessment and geochemical mapping. Laboratories that analyze complex matrices face contradictory demands: measuring very low concentrations of nutrients such as nitrate and phosphate while simultaneously coping with very high concentrations of chloride and sulfate in the same sample batch. Improvements in analytical throughput, method flexibility and automation therefore directly increase laboratory capacity, data quality and the timeliness of environmental decision-making.

Objectives and overview of the study

This case study documents the transition of the Council for Geoscience (CGS) laboratory (Pretoria, South Africa) from a conventional fixed-parameter anion method to a discrete photometric analyzer (Thermo Scientific Gallery Plus). Key objectives were to expand measurable analytes (including Cr(VI), ammonia and cyanide), increase throughput, enable measurement of analytes across very different concentration ranges within a single run, reduce sample rework and strengthen compliance with ISO-17025 accreditation requirements.

Methodology and analytical approach

The Gallery Plus uses discrete photometry: a defined aliquot of sample is dispensed into an individual cuvette, followed by one to three method-specific reagents. After timed incubation the resulting color intensity is measured at an analyte-specific wavelength and converted to concentration using blanks, calibration standards and independent QC materials. The system supports automated dilutions and reanalyses for out-of-range results, barcoded sample and reagent identification, reagent consumption monitoring and LIMS interfacing. A separate module provides conductivity and pH measurement. The laboratory adopted field filtration as a prerequisite because the analyzer requires particle-free, low-color samples.

Instrumentation used

• Thermo Scientific Gallery Plus discrete photometric analyzer (Gallery Plus system).
• Separate conductivity and pH measurement module integrated with the analyzer.
• Ancillary items and software: barcode readers, automated dilution and reanalysis routines, LIMS interface.

Main results and discussion

• Expanded analyte panel: the Gallery Plus enabled routine analyses of F, Cl, NO2, NO3, PO4, SO4 and Cr(VI) and additionally provided capability for ammonia and cyanide determinations.
• Enhanced analytical dynamic range: discrete photometry permitted per-analyte optimization so that low mg/L PO4 measurements and concurrently very high SO4 concentrations (≥2000 mg/L) could be processed in the same analytical run without compromise.
• Throughput improvement: the instrument achieved up to ~350 individual tests per hour versus the prior system that could handle only about 45–50 samples per standard overnight run (without dilutions).
• Calibration and QC: an initial calibration for Cr(VI) over 5.6–149.3 µg/L (duplicates) produced a very high linearity (R² ≈ 0.9992), demonstrating accurate low-level Cr(VI) capability. QC analyses were integrated into routine runs to ensure traceability.
• Operational advantages: automated dilutions, reanalysis, blanking options, minimal waste generation, reagent tracking and LIMS connectivity reduced manual workload and error sources. Barcoded sample/reagent ID enhanced chain-of-custody and traceability.
• Limitations and workflow adaptations: the analyzer requires particulate-free and low-color samples, so field filtration became standard practice to avoid instrument fouling and ensure reliable optical measurements.

Benefits and practical applications

• Environmental monitoring: accurate low-level nutrient (NO3, PO4) and trace contaminant (Cr(VI)) data support drinking-water assessments, river and groundwater monitoring and regulatory compliance testing.
• Mine-water and industrial effluent evaluation: capability to measure both high ionic-strength components (e.g., sulfate, chloride) and low-concentration analytes in the same run streamlines mine-water surveillance programs.
• Geochemical and hydrological mapping: higher throughput and new analytes enable denser sampling campaigns and improved spatial resolution of geochemical surveys.
• Laboratory efficiency and accreditation: automated QC workflows, LIMS integration and ISO-17025 compatible procedures support routine, accredited testing with reduced manual interventions.

Future trends and potential applications

• Method expansion: development and validation of additional photometric assays (e.g., organic-specific parameters or alternative redox species) could further broaden the instruments utility.
• Coupling with upstream sample preparation: integrating automated filtration, solid-phase extraction or on-line dilution systems would address limitations related to particulates and colored samples and permit more direct processing of complex matrices.
• Data integration and automation: enhanced LIMS analytics, remote instrument monitoring and predictive maintenance can further increase uptime and data reliability in high-throughput laboratories.
• Decentralized testing: similar discrete analyzers could be deployed at field laboratories or remote monitoring stations (with appropriate sample pretreatment) to accelerate decision-making in environmental incidents or mining operations.

Conclusion

The deployment of the Thermo Scientific Gallery Plus discrete analyzer at the CGS laboratory demonstrably improved analytical flexibility, sensitivity and throughput for routine geochemical and environmental analyses. Key outcomes include robust low-level detection of nitrate, phosphate and Cr(VI), the ability to handle very different concentration ranges within a single run, and substantial operational efficiencies through automation and LIMS integration. The implementation required only modest workflow changes (notably mandatory field filtration) and positioned the laboratory to expand accredited testing capabilities relevant to environmental monitoring, mining and hydrological mapping.

Reference

Thermo Fisher Scientific. Case study: Faster and better analysis of complex samples in a geochemical laboratory. CGS (Council for Geoscience) implementation report, 2018 (CS71460-EN).