Determination of Nickel by Dimethylglyoxime Titration

Importance of the Topic

Nickel quantification is essential in environmental monitoring, quality control of materials and pharmaceutical applications. Accurate and selective methods are needed to distinguish nickel from potential interferences such as cobalt.

Objectives and Overview

This study outlines an exothermic thermometric titration method using sodium dimethylglyoximate for precise determination of Ni(II). The approach targets samples without cobalt and suppresses other metal interferences.

Methodology and Instrumentation

The method relies on the reaction between Ni(II) and dimethylglyoximate in buffered ammonia, producing an exothermic endpoint detected by a temperature sensor. Key reagents include:

• 0.5 mol/L disodium dimethylglyoximate titrant, standardized against metallic nickel
• Ammonia/ammonium chloride buffer (NH3/NH4Cl)
• Optional potassium sodium tartrate to complex Fe(III), Al(III) or Cr(IV)

Procedural steps involve pipetting an aliquot containing ~50–70 mg Ni(II) into a titration vessel, adding buffer, then titrating at 2 mL/min to a single exothermic endpoint. Data are recorded at 20 Hz and smoothed with a factor of 50.

Used Instrumentation

• Thermometric titrator with temperature sensor (thermistor)
• Spinring-equipped titration beaker
• Standard laboratory volumetric flasks and pipettes

Main Results and Discussion

Ten replicate analyses of a NiSO4 solution yielded a mean Ni concentration of 22.29 ± 0.02 g/L, demonstrating high precision. The calculated percentage of nickel matched expected values, confirming method accuracy. The second derivative curve effectively pinpoints the exothermic endpoint.

Benefits and Practical Applications

• High selectivity for nickel in complex matrices
• Rapid endpoint detection without visual indicators
• Robustness against common interferences when using tartrate
• Applicability in QA/QC, environmental and industrial sample analysis

Future Trends and Possibilities

Advancements may include integration with automated flow systems, enhanced thermometric sensors for increased sensitivity, and coupling with data analytics for real-time monitoring in industrial processes. Miniaturization could enable on-site field analysis.

Conclusion

The thermometric titration with dimethylglyoxime offers a reliable, precise and interference-resistant technique for nickel determination. Its simplicity and reproducibility make it suitable for diverse analytical settings.

References

• Thermo Scientific Application Note No. H-023: Determination of Nickel by Dimethylglyoxime Titration