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

Significance of the Topic

Accurate measurement of the reflectance of very small solid samples is essential for diverse industrial and scientific applications. Being able to analyze areas down to one millimeter enhances quality control, forensic examinations, and non-destructive analysis in art and material science.

Objectives and Study Overview

This application note evaluates the performance of the Agilent Cary 60 UV-Vis spectrophotometer equipped with the Remote Diffuse Reflectance Accessory (DRA) for measuring reflectance spectra from colored ink patches on paper as small as 1 mm.

Methodology and Instrumentation

Two grids of square patches in six colors and two sizes (1 mm and 5 mm) were printed on white paper using an inkjet printer and left to air dry. A baseline correction was performed on an unprinted area.

Instrumentation used for measurements included

• Agilent Cary 60 UV-Vis spectrophotometer
• Cary 60 Remote DRA with integrated video camera
• Fiber optic coupler
• Cary WinUV software

Spectra were acquired from 800 to 360 nm in 2 nm steps with a one second averaging time and baseline correction enabled. The video camera ensured precise alignment of each colored patch within the DRA sampling port.

Main Results and Discussion

The integrated video camera allowed straightforward positioning of 1 mm patches. Reflectance spectra of six colors showed distinct profiles with low noise. Triplicate scans of dark blue patches at both 1 mm and 5 mm sizes demonstrated excellent reproducibility, with overlaid spectra matching closely. Close-up views around the main absorption peaks confirmed minimal variability between repeated scans.

Benefits and Practical Applications

The Remote DRA accessory enables non-contact reflectance measurement on samples as small as 1 mm, delivering rapid, high-quality, and reproducible data. This capability supports quality control in commercial printing and paint manufacturing, process monitoring in automotive coatings, forensic document authentication, and non-destructive art conservation.

Future Trends and Applications

Future developments may integrate automated sample positioning for high throughput analysis, couple reflectance measurements with imaging for spatial mapping, and miniaturize accessories for sub-millimeter sampling. These advances could broaden applications in microanalysis, biomedical diagnostics, and advanced materials research.

Conclusion

The Agilent Cary 60 combined with the Remote DRA provides reliable reflectance measurements from solid samples down to 1 mm. The system delivers low-noise spectra, clear differentiation between colors, and outstanding reproducibility. The integrated video camera greatly simplifies sample alignment, making the setup ideal for a wide range of research and industrial uses.

References

1. Somma F Aloe P Schirripa Spagnolo G Defects in UV vis NIR reflectance spectra as method for forgery detection in writing documents J Phys Conf Ser 2010 249 012060
2. Leona M Casadio F Bacci M Picollo M Identification of the Pre Columbian Pigment Maya Blue on Works of Art by Noninvasive UV Vis and Raman Spectroscopic Techniques J Amer Inst Conserv 2004 43 1 39 54