Evaluation of the Mark-VI Spray Chamber for Flame Atomic Absorption Spectrometry

Significance of the Topic

The design of the spray chamber is a critical factor in flame atomic absorption spectrometry. It governs the uniform mixing of sample aerosol with fuel gas, minimizes carbon deposits and burner blockages, reduces signal noise and interferences, and accelerates drainage to maintain analytical throughput and reliability.

Objectives and Study Overview

This work evaluates the performance of the Agilent Mark-VI spray chamber under various conditions. Key aspects include aerosol drainage, carbon build-up, resistance to burner blockage with high-solids samples, suppression of volatilization interferences, characteristic concentration, detection limits, and long-term signal stability.

Methodology and Instrumentation

Experiments were conducted on a SpectrAA-40 flame AAS system using standard lamp currents, slit widths, and wavelengths. The Mark-VI chamber was compared to a conventional design. Nebulizer settings, burner position and gas flows were optimized for sensitivity or high-solids operation. Cleaning procedures included ultrasonic detergent and chromic acid baths.

Instrumentation

• SpectrAA-40 atomic absorption spectrometer
• Agilent Mark-VI spray chamber with polypropylene body
• High-efficiency pneumatic nebulizer (Pt-Ir capillary, Ta venturi)
• Ceramic nebulizer face-plate and adjustable glass impact bead
• Dual-head mixing paddle for enhanced mixing and droplet removal
• Agilent Mark-5A/Mark-5 nitrous-oxide/acetylene and air-acetylene burners

Results and Discussion

Drainage Performance

The Mark-VI chamber’s steeply sloped floor, recessed wide-bore drainage tube and ceramic face-plate yield rapid solution clearing. A 1 000 mg/L Cu standard returned to baseline within 5 s after aspiration, eliminating drainage-related signal spikes observed for over 100 s in conventional chambers.

Carbon Build-Up

Efficient tangential acetylene injection and paddle-induced mixing maintain uniform flame stoichiometry, reducing local fuel-rich zones. The Mark-VI chamber endures rich nitrous-oxide/acetylene flames longer than conventional designs before carbon fouling.

Burner Blockage with High-Solids Samples

In simulations of steel pyro-sulfate fusate, 5 % NaCl solutions and sugar-rich soft drinks, the Mark-VI chamber showed markedly slower signal decay and delayed blockage. For example, aluminium in steel simulant degraded <10 % over 12 min versus 50 % for a conventional chamber, and soft-drink aluminium absorbance dropped 50 % after 340 s instead of 230 s.

Interference Studies

Adjustable bead and paddle reduced droplet size, lowering volatilization interferences. Aluminium interference on Mg fell from 32 % suppression in a conventional chamber to 13 % in the Mark-VI. Sodium sulfate enhancement of Mo absorbance was negligible with the Mark-VI design.

Characteristic Concentrations and Detection Limits

Characteristic concentrations for Cu, Pb and Al were comparable between systems (e.g. Al ~0.73 mg/L). Detection limits (2σ) were competitive or improved, such as Cu at 0.003 mg/L (Mark-VI) vs. 0.004 mg/L (conventional).

Signal Noise and Stability

A uniform fine‐droplet aerosol reduced flicker noise and drift. Aluminium signal noise decreased noticeably compared to conventional chambers. A 10 µg/mL Cr solution in 5 % sugar remained within ±0.5 % of baseline over 28 min.

Benefits and Practical Applications

• Enhanced performance with difficult matrices (high salts, sugars, refractory oxides)
• Reduced maintenance from slower carbon and solids deposition
• Adjustable aerosol concentration for sensitivity or robustness
• Competitive detection limits and stable long-term operation

Future Trends and Potential Applications

Advances may include integration of microfabricated spray chambers, automated aerosol optimization, real-time diagnostics, greener materials, and coupling with hyphenated techniques (e.g. GC-AAS, LC-AAS). Smart interlocks and remote monitoring will further improve safety and uptime.

Conclusion

The Agilent Mark-VI spray chamber delivers rapid drainage, minimized carbon build-up, superior resistance to burner blockage, reduced interferences, and stable, low‐noise signals without sacrificing sensitivity. Its adaptable design supports a broad range of challenging samples in flame AAS.

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