Thermometric analysis of aluminum by back- titration
Applications | 2020 | MetrohmInstrumentation
Accurate determination of aluminum is essential in industries dealing with clays, zeolites and alumino silicate materials where traditional fluoride titration methods fail due to silica interference. A robust, rapid and interference resistant analytical approach is needed for quality control and research applications.
The study adapts a thermometric complexometric back titration method for aluminum quantification in challenging matrices. The goal is to employ a thermometric indicator to achieve a clear endpoint and reduce analysis time while maintaining precision.
Samples of aluminum sulfate and potassium alum are dissolved in the presence of excess EDTA and ammonia. The mixture is boiled for five minutes to promote complex formation, then cooled. An aliquot is buffered, spiked with hydrogen peroxide and titrated automatically. Excess EDTA is back titrated with copper II solution while monitoring temperature changes with the Thermoprobe. The rapid decomposition of hydrogen peroxide upon free copper II appearance yields a sharp exothermic signal marking the endpoint.
The method delivers highly reproducible results with relative standard deviations below 0.3 percent. In eight replicates of aluminum sulfate the mean aluminum content was 7.87 percent with 0.25 percent RSD. Ten replicates of potassium alum yielded a mean of 5.11 percent aluminum with 0.20 percent RSD. Typical analysis time is under three minutes and the thermometric curve shows a distinct temperature rise at endpoint.
Emerging directions include extending thermometric back titration to other metal ions in complex matrices, integrating with flow injection and microfluidic platforms for high throughput screening, and field deployable systems for on site monitoring. Coupling with separation techniques and remote data analysis tools can further enhance applicability in environmental and industrial settings.
The thermometric back titration method offers a rapid, robust and precise alternative for aluminum determination in samples containing silicates. Its high enthalpy response, automation capability and short runtime make it suitable for laboratory quality control and research applications.
Metrohm AG AN H 127 Thermometric analysis of aluminum by back titration Application Note
Titration
IndustriesEnvironmental
ManufacturerMetrohm
Summary
Importance of the Topic
Accurate determination of aluminum is essential in industries dealing with clays, zeolites and alumino silicate materials where traditional fluoride titration methods fail due to silica interference. A robust, rapid and interference resistant analytical approach is needed for quality control and research applications.
Objectives and Study Overview
The study adapts a thermometric complexometric back titration method for aluminum quantification in challenging matrices. The goal is to employ a thermometric indicator to achieve a clear endpoint and reduce analysis time while maintaining precision.
Used Instrumentation
- 859 Titrotherm with Thermoprobe and tiamo light software
- 800 Dosino dosing drive
- Dosing Unit 10 mL for automated reagent delivery
- 10 mL buret, magnetic stirrer and titration vessel
Methodology and Instrumentation
Samples of aluminum sulfate and potassium alum are dissolved in the presence of excess EDTA and ammonia. The mixture is boiled for five minutes to promote complex formation, then cooled. An aliquot is buffered, spiked with hydrogen peroxide and titrated automatically. Excess EDTA is back titrated with copper II solution while monitoring temperature changes with the Thermoprobe. The rapid decomposition of hydrogen peroxide upon free copper II appearance yields a sharp exothermic signal marking the endpoint.
Main Results and Discussion
The method delivers highly reproducible results with relative standard deviations below 0.3 percent. In eight replicates of aluminum sulfate the mean aluminum content was 7.87 percent with 0.25 percent RSD. Ten replicates of potassium alum yielded a mean of 5.11 percent aluminum with 0.20 percent RSD. Typical analysis time is under three minutes and the thermometric curve shows a distinct temperature rise at endpoint.
Benefits and Practical Applications
- Fast analysis with results in two to three minutes
- High precision and low relative standard deviations
- Minimal maintenance and no electrode drift
- Effective in the presence of silicate interferences
- Automated operation reduces operator variability
Future Trends and Opportunities
Emerging directions include extending thermometric back titration to other metal ions in complex matrices, integrating with flow injection and microfluidic platforms for high throughput screening, and field deployable systems for on site monitoring. Coupling with separation techniques and remote data analysis tools can further enhance applicability in environmental and industrial settings.
Conclusion
The thermometric back titration method offers a rapid, robust and precise alternative for aluminum determination in samples containing silicates. Its high enthalpy response, automation capability and short runtime make it suitable for laboratory quality control and research applications.
Reference
Metrohm AG AN H 127 Thermometric analysis of aluminum by back titration Application Note
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