DialPath Sampling Accessory

Importance of the Topic

Transmission FTIR analysis of liquid samples and thin films is essential for routine quality control and research in chemical, pharmaceutical, food and industrial sectors. Traditional transmission cells often require complex assembly, suffer from variable pathlengths, sample loss, air bubble interference and lengthy cleaning. The DialPath accessory simplifies fixed-pathlength transmission measurements by combining ATR-style ease of use with precise quantitative performance.

Study Objectives and Overview

This technical overview presents the design and capabilities of the Agilent DialPath sampling accessory for FTIR systems. Key goals are to demonstrate how a rotating dial with preset pathlengths enables reliable transmission spectra of liquids and polymer films without conventional flow or demountable cells. The document also surveys real-world applications and compares performance with ATR and cell-based methods.

Methodology and Instrumentation

The DialPath accessory employs three factory preset pathlengths (30, 50, 100 or 50, 100, 200 micrometres) with repeatability of ±0.25 micrometres. Custom pathlengths up to 1000 micrometres can also be configured. ZnSe windows deliver high energy throughput over the 5100 to 600 cm-1 spectral range. Sample introduction involves placing a small drop or positioning a film on the window, rotating the dial to the desired pathlength and acquiring spectra on Agilent Cary 630, 4500 or 5500 FTIR instruments. A light-path cleanliness check validates the cell before each measurement.

Main Results and Discussion

Reproducible fixed pathlengths allow analysis of peaks of varying intensity on the same sample without dilution. The accessory handles viscous and volatile liquids, avoiding sample loss or evaporation during analysis. Polymer films are measured directly without mounting, and different regions of nonhomogeneous films can be probed by repositioning. Comparative studies demonstrate that DialPath data matches or exceeds the quality of spectra obtained with ATR and traditional transmission cells, while reducing sample preparation time and solvent use.

Benefits and Practical Applications

• Rapid, reproducible transmission measurements without cell assembly or alignment
• Minimal sample volume and simplified cleaning, even for sticky or volatile fluids
• Versatile analysis of multiple peak intensities in a single run
• Direct film measurement for polymer and coating samples
• Portability and at-site screening capabilities

Future Trends and Opportunities

Future developments may include expanded custom pathlength ranges, integration with automated sampling systems, coupling with chemometric and hyphenated techniques, and broader application to complex biological or environmental matrices. Advances in detector sensitivity and software algorithms will further enhance quantitative accuracy and ease of use.

Conclusion

The Agilent DialPath accessory offers a user-friendly, robust solution for fixed pathlength transmission FTIR measurements of liquids and films. Its reproducible performance, minimal sample handling and compatibility with multiple Agilent FTIR platforms make it a valuable tool for both qualitative and quantitative analysis across diverse fields.

References

• Agilent Application Note Measurement of liquid samples using the Cary 630 FTIR spectrometer with DialPath accessory
• Agilent Application Note Measurement of volatile liquids
• Agilent Application Note At-site screening of adulterant levels in bovine milk
• Agilent Application Note Monitoring biodiesel FAME content in diesel
• Agilent Application Note Determination of phenolic antioxidants DBPC and DBP in electrical insulating oil
• Agilent Application Note Quantification of simethicone in pharmaceutical samples