Determination of Boron by Graphite Furnace AAS: Comparison of Different Modifiers

Significance of the topic

Boron determination in water matrices is crucial for environmental monitoring and public health due to its biochemical effects and occurrence in natural and industrial effluents. Graphite furnace atomic absorption spectrometry (GFAAS) offers high sensitivity, but boron’s tendency to form refractory carbides complicates accurate analysis. Effective chemical modifiers can address sensitivity loss, memory effects and tube wear, optimizing the method for routine analysis.

Study Objectives and Overview

This study compared various chemical modifiers for boron GFAAS to identify the optimal reagent combination that maximizes sensitivity, minimizes memory effects and extends graphite tube lifespan. The performance of modifiers such as magnesium, calcium, nickel, palladium, lanthanum and zirconium-based approaches was assessed, and the best method was validated on environmental water samples (river water, drinking water and sewage).

Methodology

An Agilent SpectrAA-250 Plus equipped with a GTA-97 graphite furnace and PSD-97 dispenser was used. Samples were injected with 20 µL of modifier solution prior to each run. A hollow cathode boron lamp at 249.8 nm with deuterium background correction was employed. The temperature program covered drying, pyrolysis and atomization at 2800 °C. Pyrolytic coated graphite tubes were used. Working boron standards and modifier solutions were prepared in Type I water with nitric acid as needed. Analytical peaks were quantified by absorbance area and height.

Used Instrumentation

• Agilent SpectrAA-250 Plus Atomic Absorption Spectrometer
• GTA-97 Graphite Tube Atomizer
• PSD-97 Programmable Sample Dispenser
• Hollow cathode boron lamp (20 mA)
• Deuterium lamp for background correction

Results and Discussion

Nickel and palladium increased boron vaporization efficiency compared to alkaline earth elements. Lanthanum enhanced signals but caused severe furnace corrosion. Zirconium pretreatment prevented boron–carbon interactions. A mixed modifier of zirconium nitrate and nickel nitrate delivered the best performance with a characteristic mass of 200 pg, negligible memory effect and tube lifetime extended to about 200 atomization cycles. The optimized method eliminated multiple cleaning cycles and pre-treatment requirements while providing reproducible results.

Practical Applications and Benefits

• High sensitivity and precision (RSD ≤ 1.9 % at 0.9 mg/L, ≤ 1.2 % at 2.0 mg/L)
• Low detection (0.06 mg/L) and quantification limits (0.18 mg/L)
• No memory effect and no need for standard additions
• Extended graphite tube lifespan and reduced analysis time
• Suitable for river, drinking and sewage water analysis

Future Trends and Potential Applications

Ongoing developments may explore alternative modifier chemistries, integration with automated sample preparation and coupling with hyphenated techniques for multi-element analysis. Miniaturized and portable GFAAS systems could benefit from robust modifiers to enable on-site boron monitoring in diverse matrices.

Conclusion

The combination of zirconium nitrate and nickel nitrate as chemical modifiers in GFAAS significantly improves boron determination by enhancing sensitivity, eliminating memory effects, shortening analysis times and prolonging graphite tube life. The method is validated for environmental water analysis without the need for pre-treatment or standard additions.

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