Rapid analysis of critical electrolytes and impurities in dialysis solutions

Significance of the topic

Dialysis fluids are medical-grade formulations that directly contact patients and therefore must meet strict safety, compositional and regulatory requirements. Accurate, rapid and reliable analysis of electrolytes, organic acids, sugars and trace impurities in hemodialysis, peritoneal dialysis and blood-anticoagulant solutions is essential for product release, process control and patient safety. Consolidating multiple analytical assays into high-throughput workflows reduces turnaround time, operator burden and cost-per-test while supporting compliance with pharmacopeial and internal quality standards.

Objectives and overview of the application note

This application note describes the analytical requirements for dialysis solutions and presents a consolidated workflow approach using discrete analyzer technology to perform routine wet-chemistry tests. The goal is to demonstrate how a single automated platform can replace several manual or standalone instruments to measure critical parameters such as pH, conductivity, citrate, phosphate, glucose/dextrose, organic acids (acetate, lactate), and other process-relevant ions and impurities, improving throughput and reproducibility in dialysis product testing.

Methodology and analytical approaches

• Regulatory context: Testing begins with verification of water for injection (WFI) according to USP/EP expectations (pH, conductivity, nitrate, total oxidizable nitrogen, total phosphorus).
• Electrolytes and anions: Chloride, sulfate, phosphate and physiologically relevant cations (sodium, potassium, calcium, magnesium, ammonium) are typical targets; ion chromatography (IC) is used for quantitative determination of citrate and phosphate per USP General Chapter <345> and for other anions as needed.
• Organic acids and buffers: Acetic, citric and lactic acids (or their salt forms) are measured because they affect acid–base balance of dialysates and anticoagulant solutions; colorimetric/enzymatic assays or chromatographic methods are used depending on required specificity.
• Carbohydrates and degradation products: Dextrose/glucose content in concentrates and finished solutions is a critical quality attribute. Traditional gravimetric methods have been used for dextrose, while HPLC with UV detection quantifies adenine. Glucose degradation products (GDPs) such as hydroxy methyl furfural, acetaldehyde and formaldehyde are determined by pre-column derivatization followed by HPLC or spectrophotometric methods due to their potential bioincompatibility.
• General parameters: pH, conductivity and alkalinity are measured by electrochemical methods and titration; spectrophotometry is used for a variety of colorimetric and enzymatic assays.
• Multi-technique requirement: Historically, a combination of wet-chemical, titrimetric, ion chromatography and chromatographic (HPLC) techniques has been necessary to cover all critical analytes in dialysis products.

Instrumentation used

• Thermo Scientific Gallery and Gallery Plus discrete analyzers (automated wet-chemistry platform supporting colorimetric/photometric, enzymatic and electrochemical assays).
• Ion chromatography (IC) systems for citrate, phosphate and other anions.
• High-performance liquid chromatography (HPLC) with UV detection for adenine and for assays after derivatization (GDPs).
• Spectrophotometers for standalone colorimetric/UV assays.
• pH and conductivity meters, ion meters and autotitrators for acid/base and conductivity testing.

Main results and discussion

The application note highlights that discrete analyzer technology can centralize many routine dialysis solution analyses that were previously distributed among multiple instruments. Key findings and implications include:

• Simultaneous measurement: Discrete cell technology permits concurrent measurement of diverse analyte classes (ions, organic acids, sugars) from a single sample aliquot, reducing total run time.
• Automation and throughput: Walkaway operation and automated workflows increase sample throughput and reduce operator intervention, improving reproducibility and freeing analyst time for higher value tasks.
• Low reagent consumption: Miniaturized cuvettes and low-volume reagents decrease waste and lower per-test reagent cost.
• Complementary role of chromatographic methods: For analytes requiring high specificity or lower detection limits (e.g., GDPs, adenine), HPLC/IC remain necessary; the discrete analyzer is positioned as a high-throughput front-line QC tool rather than a complete replacement for all chromatographic assays.
• Regulatory alignment: Using IC for citrate and phosphate aligns with USP guidance, while discrete assays cover many routine release tests; an integrated testing strategy supports compliance and efficient lot release.

Benefits and practical applications

• Reduced laboratory footprint: Consolidation of multiple wet-chemistry assays onto a single benchtop instrument simplifies laboratory logistics.
• Cost and labor efficiency: Lower reagent use, fewer instruments to maintain and reduced hands-on time translate into lower cost-per-test and operational savings.
• Faster decision-making: High-throughput analysis accelerates in-process control and batch release timelines important for dialysis product manufacturing.
• Quality assurance: Automated, reproducible procedures reduce operator-dependent variability and support robust QA/QC programs for dialysis fluids and anticoagulant solutions.
• Flexibility: The platform accommodates a wide range of routine assays (pH, conductivity, glucose, organic acids, ions), making it suitable for dialysis concentrates, finished dialysate and associated solutions such as CPDA anticoagulants.

Future trends and applications

• Integration with chromatographic and mass spectrometric methods: Combining high-throughput discrete analysis for routine QC with targeted chromatographic or LC–MS assays for trace impurities will produce comprehensive analytical strategies.
• Real-time and online monitoring: Process analytical technology (PAT) and in-line sensors for continuous monitoring of dialysis fluid composition are likely to expand, reducing reliance on offline batch testing.
• Enhanced detection of GDPs and other trace contaminants: Improved sample preparation, derivatization chemistries and more sensitive detectors will tighten control over bioincompatibility risks.
• Data integration and automation: Laboratory information management systems (LIMS) and digital workflows will further streamline acceptance testing, trending and compliance documentation.
• Miniaturization and green analytics: Continued reduction in reagent volumes and waste, coupled with energy-efficient instrumentation, will support sustainable laboratory practices.

Conclusion

Routine dialysis solution testing spans physicochemical, ionic and organic analytes that historically required multiple laboratory platforms. Discrete analyzer technology provides a practical, high-throughput complement to chromatographic and electrochemical methods for many QC assays, improving throughput, reproducibility and cost-efficiency. For complete control of critical impurities and trace degradation products, chromatographic techniques such as IC and HPLC remain essential; the optimal laboratory workflow combines both approaches to meet regulatory and clinical-safety demands.

Reference

• Thermo Fisher Scientific. Rapid analysis of critical electrolytes and impurities in dialysis solutions. SMART NOTE 73707. SN73707-EN 0720. © 2020 Thermo Fisher Scientific Inc. For Research Use Only. Not for use in diagnostic procedures.