Measuring the reflectance of very small samples using the Agilent Cary 60 Remote Diffuse Reflectance Accessory (DRA)

Importance of the Topic

The accurate measurement of diffuse reflectance from solid samples is critical in industries ranging from printing quality control to forensic document analysis and art conservation. Traditional spectrophotometer sample compartments often cannot accommodate very small specimens, risking compromised data or time-consuming sample preparation. A reliable method for nondestructive, high-precision measurement of sub-millimeter samples supports faster decision-making and enhances analytical confidence.

Objectives and Study Overview

This application note demonstrates how the Agilent Cary 60 UV-Vis spectrophotometer equipped with a Remote Diffuse Reflectance Accessory (DRA) and fiber-optic coupler can accurately collect reflectance spectra from solid ink samples as small as 1 mm. The study evaluates spectral differentiation of colored ink patches printed on paper, assesses noise levels, and examines reproducibility across multiple scans.

Methodology and Instrumentation

Samples were prepared by printing two grids of colored squares (1 mm and 5 mm edge length) onto white paper with an HP C6270 inkjet printer, followed by 30 min of air drying. Measurements were conducted using an Agilent Cary 60 UV-Vis spectrophotometer fitted with the Remote DRA and a fiber-optic coupler. Instrument settings included a wavelength sweep from 360 nm to 800 nm at 2 nm intervals and 1 s averaging time. Baseline correction was performed on unprinted paper, and the DRA’s integrated video camera guided precise sample alignment.

Main Results and Discussion

High-quality reflectance spectra were obtained for all six ink colors at 1 mm dimensions, exhibiting clear spectral separation and minimal noise. The video camera facilitated exact positioning of the 1 mm target area. Reproducibility tests on dark blue squares (1 mm and 5 mm) showed near-perfect overlay of three consecutive scans, underscoring the method’s stability. Close-up inspection of peak regions confirmed excellent spectral consistency.

Benefits and Practical Application

• Enables nondestructive analysis of very small solid samples without special holders.
• Reduces sample preparation time and risk of misalignment.
• Delivers high-precision, low-noise spectra suitable for quality and process control.
• Supports forensic and conservation applications where sample size is limited.

Future Trends and Opportunities

Advances in miniaturized spectroscopic accessories and enhanced imaging may further improve sampling of heterogeneous materials. Integration with chemometric and machine-learning algorithms could automate identification and quantification in complex matrices. Portable or field-deployable versions of remote DRA systems may expand in-situ analysis capabilities for environmental monitoring, cultural heritage studies, and on-site quality assurance.

Conclusion

The Agilent Cary 60 with Remote DRA reliably measures diffuse reflectance from samples as small as 1 mm, providing high-quality, reproducible spectra. The integrated video camera ensures accurate targeting, and the fiber-optic coupling streamlines data acquisition. This approach offers a robust solution for diverse industrial and research applications requiring precise analysis of small solids.

References

1. F. Somma, P. Aloe, G. Schirripa Spagnolo, “Defects in UV-vis-NIR reflectance spectra as method for forgery detections in writing documents,” J. Phys.: Conf. Ser., vol. 249, 012060, 2010.
2. M. Leona, F. Casadio, M. Bacci, M. Picollo, “Identification of the Pre-Columbian Pigment Maya Blue on Works of Art by Noninvasive UV-Vis and Raman Spectroscopic Techniques,” Journal of the American Institute for Conservation, vol. 43, no. 1, pp. 39–54, 2004.