Concentration Analysis of Ultra-microvolume Samples by UV-Vis Spectroscopy

Significance of the Topic

Modern pharmaceutical and biotechnology research demands fast, accurate quantification of nucleic acids and proteins in minimal sample volumes. UV-Vis spectroscopy with ultra-microvolume cells preserves valuable samples, streamlines workflows, and reduces error-prone dilutions.

Aims and Study Overview

This study introduces a method for nondestructive analysis of microvolume samples using the Agilent Cary 60 UV-Vis spectrophotometer equipped with TrayCell 2.0. It evaluates precision, linearity, and dynamic range across varying concentrations of BSA protein and herring sperm DNA.

Methodology and Instrumentation

• Instrumentation: Double-beam Cary 60 UV-Vis with xenon flash lamp, room-light immunity.
• TrayCell 2.0 Ultra-Microvolume Cell: interchangeable pathlength caps (0.1, 0.2, 1.0, 2.0 mm).
• Samples: BSA and herring sperm DNA prepared in PBS, serial dilutions for 1–400 mg/mL (protein) and 5–1500 ng/µL (DNA).
• Software: Agilent Cary WinUV v5.1.3 for Scan and Concentration modules.
• Cleaning: simple wiping of sample window and cap mirror without removing cell holder.

Main Results and Discussion

• Reproducibility: Ten consecutive scans of 20 ng/µL DNA (0.04 Abs) demonstrated high repeatability with 1 mm cap.
• Linearity: DNA analysis showed linear response from 5 to 1500 ng/µL up to 2.4 Abs. BSA protein linear across 1–400 mg/mL by selecting appropriate cap—1.0 mm (up to 40 mg/mL), 0.2 mm (up to 200 mg/mL), 0.1 mm (up to 400 mg/mL).
• Dynamic Range Expansion: Swapping caps extends quantification range, eliminating the need for time-consuming dilutions.

Benefits and Practical Applications

• Non-destructive microvolume measurements conserve scarce samples.
• Reduced sample handling and elimination of dilutions minimize errors.
• High sensitivity and room-light immunity enhance data quality.
• Environmentally sustainable design certified by My Green Lab ACT Label.

Future Trends and Applications

• Integration with automated cell changers and temperature control for high-throughput assays.
• Adaptation to kinetic studies and real-time monitoring in microfluidic platforms.
• Further miniaturization and coupling with complementary detection methods (e.g., fluorescence).
• Expansion to broader wavelength ranges for diverse analyte characterization.

Conclusion

The Agilent Cary 60 UV-Vis with TrayCell 2.0 offers a robust platform for accurate, reproducible quantification of nucleic acids and proteins in ultra-microvolumes. Its versatility, ease of cleaning, and extended dynamic range enhance laboratory efficiency and sample preservation.

References

• Weragoda G., Alwan W., Zieschang F. Concentration Analysis of Ultra-microvolume Samples by UV-Vis Spectroscopy; Agilent Technologies Application Note, December 2022.