Analysis of Geosmin and 2-Methylisoborneol Utilizing the Stratum PTC and Aquatek 70

Význam tématu

Detecting geosmin and 2-methylisoborneol (MIB) at ultra-trace levels is critical for ensuring drinking water quality. These compounds impart earthy and musty off-odors at concentrations as low as single parts per trillion, making their reliable quantification vital for water utilities, regulatory compliance, and consumer acceptance.

Cíle a přehled studie / článku

The primary objective of this application note was to develop and validate a purge-and-trap (P&T) gas chromatography/mass spectrometry (GC/MS) method capable of detecting geosmin and MIB at the 1 ppt threshold. Key goals included optimizing purge efficiency, achieving high sensitivity through selective ion monitoring (SIM), and demonstrating method linearity, precision, and accuracy across a relevant concentration range.

Použitá metodika

The method employed a 25 mL water sample fortified with 10 % (w/v) salt to enhance headspace partitioning. Samples were processed on a Stratum PTC autosampler coupled with cryofocusing, followed by injection into an Agilent 7890A GC and detection with an Agilent 5975C inert XL MS in SIM mode. Key steps:

• Sample purge: 12 min at 0 °C with 45 mL/min helium flow.
• Cryofocusing: trap cooling to –100 °C to concentrate analytes.
• Thermal desorption: rapid heating to 225 °C, transfer into GC column.
• GC oven program: initial hold at 40 °C, ramp to 240 °C.
• MS detection: monitoring target ions (95, 107, 108, 112, 125, 126 m/z) with 100 ms dwell time.

Použitá instrumentace

• Stratum PTC purge-and-trap system with Aquatek 70 autosampler and cryofocusing module.
• Gas chromatograph: Agilent 7890A with J&W Scientific DB-VRX column (30 m × 0.25 mm × 1.4 µm).
• Mass spectrometer: Agilent 5975C inert XL operating in SIM mode.
• Carrier gas: helium at ~1.0 mL/min; splitless inlet at 220 °C.

Hlavní výsledky a diskuse

Calibration was linear (R²=1.000) over 1–100 ppt for both analytes, with relative standard deviations below 7 % at 10 ppt. Method detection limits (MDL) were 0.114 ppt for geosmin and 0.236 ppt for MIB, well below the target 1 ppt. Accuracy in spike-recovery studies ranged from 104 % to 107 %. The optimized salt concentration and sample volume significantly enhanced purge efficiency for these low-volatility compounds.

Přínosy a praktické využití metody

By achieving sub-ppt detection limits with robust precision and accuracy, this P&T-GC/MS approach supports routine monitoring of off-odor compounds in drinking water. Laboratories can implement this workflow for regulatory compliance, process control in water treatment plants, and forensic investigations of taste and odor complaints.

Budoucí trendy a možnosti využití

Future developments may involve coupling the purge-and-trap system with high-resolution mass spectrometry for enhanced selectivity, automation of sample preparation to increase throughput, and integration with data analytics platforms for real-time monitoring of water distribution networks.

Závěr

The optimized P&T-GC/MS method combining Stratum PTC with cryofocusing delivers reliable, ultra-trace detection of geosmin and MIB. With excellent linearity, sensitivity, and reproducibility, it meets the stringent requirements of modern drinking water analysis.