Determination of nickel by photometric titration

Importance of the topic

Photometric titration offers a rapid and precise approach for quantifying trace metals such as nickel in diverse matrices. Reliable determination of nickel is critical in environmental monitoring, industrial quality control and research laboratories to ensure regulatory compliance and product consistency.

Objectives and overview

The study aims to establish a robust method for the determination of nickel(II) via photometric titration using EDTA as titrant and murexide as indicator. Key goals include optimizing the titration parameters, validating performance and demonstrating repeatability for routine analysis.

Methodology and instrumentation

• Technique: Monotonic equivalence point titration (MET) monitored photometrically at 520 nm (Optrode).
• Indicator: Murexide prepared as 0.5 g/L solution.
• Titrant: 0.1 mol/L Na2EDTA•2H2O standardized against Ni2+ standard.
• Buffer: NH3/NH4Cl mixture adjusted to pH 10.
• Instrumentation setup:
  • 907 Titrando with MET U mode and drift criterion of 50 mV/min.
  • 800 Dosino units (2 mL, 5 mL, 10 mL, 50 mL) for precise titrant delivery (0.05 mL increments).
  • 802 Rod Stirrer at speed 8 for uniform mixing.
  • 815 Robotic USB SP for automated handling.
  • Optrode photometer at 520 nm for endpoint detection.
  • Unitrode combined with Pt1000 temperature sensor.

Main results and discussion

Replicate analyses (n=6) of Ni2+ yielded an average concentration of 4.45 g/L with a standard deviation of ±0.003 g/L. The titration curve demonstrated a sharp equivalence point, and the calculated precision and accuracy meet typical quality control specifications. The method equation relates titrant volume to nickel concentration, incorporating titrant normality and molecular weight of Ni.

Benefits and practical applications

• High sensitivity and selectivity for Ni2+ in presence of potential interferents.
• Automated workflow reduces operator variability and increases throughput.
• Minimal sample preparation supports rapid turnaround in QC environments.
• Applicable to environmental waters, industrial process streams and research samples.

Future trends and opportunities

• Integration with flow-through systems for continuous monitoring.
• Miniaturization of photometric sensors for field-deployable titrators.
• Expansion to multi-metal titrations using multiplexed photometric detection.
• Coupling with chemometric tools to improve interference correction.

Conclusion

The presented photometric titration method provides a precise, reproducible and fully automated solution for nickel determination. Its simplicity and reliability make it suitable for routine analytical laboratories requiring stringent quality control.

References

• Application Note T–82: Photometric Determination of Nickel by Optrode (520 nm).