Determination of iodoform in drinking water by PAL SPME Arrow and GC/MS

Importance of the Topic

Routine chlorination of drinking water generates disinfection by-products (DBPs), including iodinated trihalomethanes such as iodoform. Iodoform has a very low odor and taste threshold (0.02–5 µg/L), making sensitive detection critical for water quality management and regulatory compliance.

Objectives and Study Overview

This study aimed to establish a fast, solvent-free, and highly sensitive method for quantifying iodoform in tap water using PAL SPME Arrow extraction coupled to gas chromatography–mass spectrometry (GC/MS). Both immersion and headspace extraction modes were evaluated, comparing two sorption phases and conventional SPME fibers.

Methodology and Instrumentation

Water samples were prepared by spiking tap water with iodoform standards (10–1000 ng/L). Two PAL SPME Arrow sorbents were tested: polydimethylsiloxane (PDMS) and divinylbenzene (DVB). Immersion extraction was performed at 25 °C for 60 min with agitation; headspace extraction at 70 °C for 60 min in salted samples. Desorption was carried out at 200 °C for 2 min.

Used Instrumentation

• SPME System: PAL SPME Arrow Tool with PDMS (20 mm×100 µm) or DVB (20 mm×120 µm) sorbents; PAL SPME Tool with DVB fiber (10 mm×65 µm)
• GC: Varian 3400 with 30 m×0.25 mm BGB-5 column (0.25 µm film)
• Carrier Gas: Hydrogen at 2.0 psi
• MS: Varian Saturn Ion Trap; mass range 100–300 m/z

Main Results and Discussion

• Sorption Phase Selection: DVB exhibited ~3-fold higher signal than PDMS for iodoform.
• Arrow vs. Fiber: PAL SPME Arrow provided 8× higher recovery in immersion and 26× in headspace mode compared to conventional DVB fibers.
• Detection Limits: Immersion LOD of 15 ng/L (S/N > 3) and headspace LOD of 2 ng/L (S/N > 3).
• Precision and Linearity: Relative standard deviation of 3.8% at 50 ng/L (n = 5); linear calibration from 10 to 1000 ng/L (HS) and 50 to 1000 ng/L (immersion).
• Thermal Stability: Iodoform showed minimal decomposition up to 220 °C; 200 °C desorption optimized for complete analyte release.

Benefits and Practical Applications

The method is rapid, solvent-free, and highly sensitive, enabling reliable monitoring of iodoform well below sensory thresholds. The mechanical robustness of the SPME Arrow design ensures consistent performance for routine QA/QC and compliance testing in water supply laboratories.

Future Trends and Applications

Further developments may include simultaneous extraction of multiple DBP classes (e.g., haloacetic acids), miniaturized and automated SPME-GC/MS workflows for on-site analysis, and integration of chemometric or AI-driven data interpretation to enhance throughput and decision support in water quality management.

Conclusion

The PAL SPME Arrow method coupled with GC/MS provides a robust, sensitive, and reproducible approach for quantifying iodoform in drinking water, surpassing conventional SPME fibers and meeting regulatory and sensory threshold requirements.

References

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2. Cancho B., Fabrellas C., Diaz A., Ventura F., Galceran T., “Determination of the Odor Threshold Concentrations Of Iodinated Trihalomethanes in Drinking Water,” J. Agric. Food Chem., 2001, 49, 1881–1884.
3. Allard S., Charrois J.W.A., Joll C.A., Heitz A., “Simultaneous analysis of 10 trihalomethanes at nanogram per liter levels in water using solid-phase microextraction and gas chromatography mass-spectrometry,” J. Chromatogr. A, 2012, 1238, 15–21.
4. Liu X., Wei X., Zheng W., Jiang S., Templeton M.R., He G., Qu W., “An Optimized Analytical Method for the Simultaneous Detection of Iodoform, Iodoacetic Acid, and Other Trihalomethanes and Haloacetic Acids in Drinking Water,” PLoS ONE, 2013, 8(4):e60858, doi:10.1371/journal.pone.0060858.