Analysis of the Contrast Dye Iohexol in Human Urine/Serum using PaperSpray Technology

Significance of the Topic

PaperSpray technology significantly reduces analysis time and sample preparation complexity for measuring iohexol, a contrast agent widely used to evaluate kidney function through glomerular filtration rate assessment.

Objectives and Study Overview

The study aimed to replace traditional multi-step LC/MS workflows with a rapid, automated PaperSpray approach for quantifying iohexol in human urine and serum matrices using a simplified spike-and-spot protocol.

Methodology

• Sample preparation: direct spiking of iohexol into urine (1–1500 µg/mL) and serum (5–1500 µg/mL) followed by application on disposable paper strips.
• Internal standard: ioversol dissolved in methanol; one-step vortex and centrifugation for serum samples.
• Spray solvent: 95% acetonitrile, 5% water, 0.1% formic acid.
• Acquisition: five replicate analyses per concentration level, 1 minute per run.

Instrumentation

• VeriSpray™ PaperSpray ion source with automated plate loader accommodating up to 240 samples.
• Thermo Scientific™ TSQ Altis™ triple quadrupole mass spectrometer.
• Xcalibur™ software for sequence control and TraceFinder™ for quantitative data processing.

Results and Discussion

The method achieved limits of quantitation of 1 µg/mL in urine and 5 µg/mL in serum, with calibration curves linear (R² ≥ 0.98) over 1–1500 µg/mL (urine) and 5–1500 µg/mL (serum). Precision was ≤10% RSD in urine and ≤15% in serum; accuracy was within ±20% at all levels. Quality control samples at low, medium, and high concentrations met acceptance criteria for both matrices.

Benefits and Practical Applications

• Fast turnaround (<2 min) for iohexol quantification in clinical laboratories.
• Minimal sample preparation reduces labor, solvent use, and contamination risk.
• Streamlined workflow supports high-throughput GFR assessments.

Future Trends and Possibilities

• Integration with laboratory automation and data management systems for real-time clinical decision support.
• Extension of PaperSpray methods to additional biomarkers and therapeutic drug monitoring.
• Advances in mass spectrometer sensitivity and miniaturization enabling potential point-of-care applications.

Conclusion

The automated VeriSpray PaperSpray method provides a rapid, reliable, and user-friendly alternative to conventional LC/MS workflows for iohexol analysis in urine and serum, enhancing clinical evaluation of kidney function.

References

1. Ion V, Legoff C, Cavalier E, et al. Determination of iohexol by capillary blood microsampling and UHPLC-MS/MS. Journal of Pharmaceutical Analysis. 2019 Aug;9(4):259-265.
2. Vicente FB, Vespa G, Miller A, Haymond S. Quantification of iohexol in serum by high-performance liquid chromatography-tandem mass spectrometry. Methods in Molecular Biology. 2016;1383:185-193.
3. Thomas A, Larry C. Ultraperformance liquid chromatography-tandem mass spectrometry assay for iohexol in human serum. Clinical Chemistry. 2009;55(7):1196-1202.