Automated Sample Preparation in Quality Control of Eye-Drop Formulation

Significance of the Topic

The determination of active pharmaceutical ingredients in eye-drop formulations is critical for patient safety and therapeutic efficacy. Dexamethasone and chloramphenicol combinations are widely used to treat ocular inflammation and prevent infection. Automating sample preparation enhances throughput, minimizes human error, ensures reproducibility, and aligns with modern laboratory quality control requirements.

Objectives and Study Overview

This study aimed to implement and evaluate a fully automated workflow for preparing calibration standards and diluting viscous eye-drop samples using the Agilent 7696A Sample Prep WorkBench with WeighStation. Key goals included assessing linearity, repeatability, accuracy, and cross-contamination in a typical quality control setting.

Used Instrumentation

• Agilent 7696A Sample Prep WorkBench with integrated WeighStation
• Two Agilent 7693A Automated Liquid Samplers (500 µL and 50 µL syringes)
• Agilent 1290 Infinity HPLC System with UV detection at 254 nm
• Poroshell 120 column (2.1 × 100 mm, 2.7 µm particle size)

Methodology and Instrumentation

The automated method comprised two sequences: preparation of a four-level calibration series and dilution of eye-drop samples. In both sequences, the WorkBench tared empty vials, paused for manual addition of solid standards or viscous sample, then automatically weighed and performed serial dilutions. Calibration stocks were diluted tenfold, then mixed to achieve target concentrations of dexamethasone (16–64 µg/mL) and chloramphenicol (80–320 µg/mL). Sample vials received a single drop of formulation, exact mass determination, and 1 mL mobile phase for dilution. Chromatographic separation used a gradient from 20% to 50% acetonitrile in 0.3% phosphoric acid (pH 3) over 5 min at 0.5 mL/min, injection volume 1 µL, detection at 254 nm.

Main Results and Discussion

The automated calibration series demonstrated excellent linearity (R² > 0.999 for both analytes). Six replicate preparations of the lowest standard yielded RSDs of 1.5% (chloramphenicol) and 2.7% (dexamethasone). Three distinct eye-drop formulations (dexamethasone-only, chloramphenicol-only, combination) were accurately quantified, with recoveries between 90% and 105% and no detectable cross-contamination. Repeatability of sample prep showed RSD < 1% for corrected concentration values.

Benefits and Practical Applications

• Significant reduction in solvent consumption and waste generation
• Elimination of volumetric glassware and manual pipetting variability
• Precise handling of viscous formulations through weight-based dilution
• Improved traceability of sample masses via integrated weighing station
• Enhanced laboratory efficiency and data consistency for routine QC

Future Trends and Possibilities

Advancements may include integration with laboratory information management systems (LIMS) for full digital traceability, expansion to multi-analyte and complex matrix workflows, miniaturized or microfluidic sample handling modules, and application of machine learning for dynamic method optimization and predictive maintenance.

Conclusion

The Agilent 7696A Sample Prep WorkBench with WeighStation successfully automated the preparation of calibration standards and dilution of viscous eye-drop samples, delivering high linearity, repeatability, and accuracy while reducing waste and manual error. This approach demonstrates a robust solution for modern pharmaceutical quality control laboratories.

References

Agilent Technologies. Automated Sample Preparation in Quality Control of Eye-Drop Formulation. Application Note 5991-3591EN, February 6, 2014.