Benefits of a Unique Multichannel Sipper Flow-Cell Pump for UV-Vis Measurements

Significance of the Topic

The routine analysis of liquid samples by UV-Vis spectrophotometry is widely used in pharmaceutical quality control, environmental monitoring and research laboratories. Sample handling and manual cuvette filling often limit throughput and introduce variability. Automating sample delivery increases efficiency without compromising analytical precision or accuracy.

Objectives and Study Overview

This study compared traditional manual cuvette measurements with an automated multichannel flow-cell pump accessory (Cary Sipper) for quantifying vitamin C (L-ascorbic acid) in effervescent tablets. Key goals were to evaluate calibration linearity, measurement precision, accuracy against label claim and overall time savings.

Methodology and Instrumentation

Ultraviolet-visible absorbance measurements were performed on an Agilent Cary 3500 Multicell UV-Vis spectrophotometer, configured with and without the Cary Sipper accessory.

• Standards: Eight L-ascorbic acid solutions (0–70 mg/L) in 0.1 M HCl (pH 1.5) covering 0–4 Abs absorbance range.
• Samples: Twenty individual effervescent tablets (labelled 1000 mg vitamin C) crushed and prepared to yield 0–70 mg/L solutions.
• Instrument parameters: Wavelength 200–350 nm, bandwidth 1 nm, scan interval 1 nm, integration 0.1 s.
• Sipper settings: Pump speed 80 rpm; fill, hold, rinse times optimized for single and three-channel flow cells.

Main Results and Discussion

The calibration curves with and without the Sipper showed excellent linearity (R2 ≥ 0.9997). Precision across six replicates of each sample yielded %RSD of 0.19%, well below typical pharmacopeial limits (2%). Quantitation results deviated from the 1000 mg label claim by an average of 1.8% (Sipper) and 1.9% (manual), within ±10% USP acceptance. Time-study comparisons for 30 measurements demonstrated:

• Single cuvette manual: 21 min 30 s
• Three cuvettes manually filled and read simultaneously: 16 min 26 s (24% time reduction)
• Single flow cell Sipper: 19 min 32 s (9% reduction)
• Three flow cells Sipper: 7 min 30 s (65% reduction)

Benefits and Practical Applications

The Cary Sipper accessory integrated with UV-Vis software delivers:

• Substantial throughput gains and workflow efficiency.
• Consistent rinse and sample delivery reducing cross-contamination risk.
• Maintenance of high photometric precision and accuracy.
• Labor savings and reduced operator fatigue in routine analyses.

Future Trends and Opportunities

Expanding multichannel sample handling and further automating spectroscopic workflows will support high-throughput QA/QC and research needs. Integration with laboratory information management systems and coupling with microfluidic or online reaction monitoring can enhance real-time process control. Advanced spectral scanning and chemometric methods will further leverage automated sample delivery for complex mixture analysis.

Conclusion

The Cary Sipper multichannel flow-cell pump significantly accelerates routine UV-Vis analysis while maintaining or improving precision and accuracy compared to manual cuvette methods. Its integration into spectral software ensures reproducible operation and method standardization. This accessory is well suited for laboratories seeking to optimize throughput without sacrificing data quality.

References

1. Dietary Supplements Compendium, 2019, United States Pharmacopeia, US Government Printing Office, Washington, DC, 2019