Quantitation of Nucleic Acids – Trace Measurement Using TrayCell and Nano Stick –

Importance of the Topic

The ability to accurately quantify nucleic acids at sub-microliter volumes is critical in life science research, where sample availability is often limited. UV-VIS spectrophotometry continues to serve as a reliable approach for determining nucleic acid purity and concentration. Developing microvolume measurement techniques enhances sample economy and expedites analytical workflows.

Objectives and Study Overview

This example demonstrates trace-level quantitation of lambda-DNA using the Shimadzu UV-1900 UV-VIS spectrophotometer equipped with two microvolume cells (TrayCell and Nano Stick). The study evaluates linearity, precision, and accuracy for both cells and highlights the instrument’s integrated Biomethod Mode for biomolecule quantitation.

Methodology and Experimental Design

1. Sample Preparation: Five lambda-DNA standards (27.5–440 ng/µL) and an unknown sample isolated by ethanol precipitation.
2. UV-1900 Settings:
   
   • Calibration wavelength: 260 nm (primary), 320 nm (baseline)
   • Spectral scan range: 220–330 nm
   • Scan speed: Low
   • Data interval: 1.0 nm
3. TrayCell Measurements:
   
   • Optical path: 1.0 mm
   • Sample volume: 4 µL
4. Nano Stick Measurements:
   
   • Optical path: 0.5 mm
   • Sample volume: 3 µL

Used Instrumentation

• Shimadzu UV-1900 UV-VIS spectrophotometer
• Hellma Analytics TrayCell microvolume cell (1.0 mm path)
• SINCO Nano Stick microvolume cell (0.5 mm path)

Main Results and Discussion

• TrayCell:
  
  • Calibration slope: 0.0021 (concentration vs absorbance)
  • Correlation coefficient (R²): 0.9999
  • Unknown sample: 373 ng/µL (3× diluted), 1020 ng/µL (undiluted)
  • Repeatability (440 ng/µL): CV = 0.41 %
• Nano Stick:
  
  • Calibration slope: 0.0010 (concentration vs absorbance)
  • Correlation coefficient (R²): 0.9999
  • Unknown sample: 365 ng/µL (3× diluted), 1066 ng/µL (undiluted)
  • Repeatability (440 ng/µL): CV = 0.47 %
• Biomethod Mode: Provides six predefined protocols (Nucleic Acid, Lowry, BCA, Bradford, Biuret, UV) with automatic calculations of purity ratios and concentrations, plus an on-screen results capture.

Benefits and Practical Applications

Microvolume spectrophotometry with TrayCell and Nano Stick offers:

• Accurate DNA quantitation from 3–4 µL samples
• High linearity and precision suitable for routine QC
• Quick purity assessment via absorbance ratios
• Streamlined workflows through Biomethod Mode integration

Future Trends and Applications

• Integration with microfluidic platforms for automated sample handling
• Single-cell and low-input DNA/RNA analysis
• Development of portable, field-deployable spectrophotometers
• Expansion of biomethod libraries for broader analyte quantitation

Conclusion

The Shimadzu UV-1900 combined with TrayCell or Nano Stick enables robust and precise quantitation of nucleic acids from minimal sample volumes. Excellent linearity, low coefficients of variation, and versatile Biomethod protocols make this solution well suited for research, QA/QC, and other applications requiring trace-level measurements.