GC-MS Analysis of Diethylene Glycol and Ethylene Glycol in Toothpaste Using Thermo Scientific TraceGOLD GC Column with SafeGuard

Significance of the Topic

Adulteration of consumer products such as toothpaste with toxic compounds like diethylene glycol (DEG) poses serious health risks. Robust analytical methods are essential to detect trace levels of DEG and ethylene glycol (EG) in complex matrices. Gas chromatography–mass spectrometry (GC-MS) provides both sensitivity and specificity, enabling regulatory compliance and ensuring product safety.

Study Objectives and Overview

This study evaluates the semi-quantitative analysis of DEG and EG in toothpaste at levels down to 0.5 mg/g, following an FDA-recommended GC-MS protocol. Two column configurations were compared:

• TraceGOLD TG-WaxMS GC column with integrated 5 m SafeGuard.
• TraceGOLD TG-WaxMS GC column coupled to a 5 m guard column via a press-fit.

The goal was to assess method performance, signal-to-noise, and retention time consistency for both formats.

Methodology

Sample preparation followed the FDA guideline:

• Weigh 1 g of toothpaste into a centrifuge tube and add 5 mL water; mix.
• Suppress foam by adding two 2.5 mL aliquots of acetonitrile; mix and centrifuge.
• Transfer 500 µL supernatant to an autosampler vial; spike with 50 µL of internal standard (1,3-propane diol, 5 mg/mL).
• Prepare un-spiked, low (0.1 mg/mL) and high (0.5 mg/mL) DEG/EG standards in 1:1 acetonitrile/water similarly.

Chromatographic separation used a 30 m × 0.25 mm × 0.25 µm TG-WaxMS column under a temperature gradient from 100 °C to 250 °C. Helium was carrier gas at 1.0 mL/min constant flow; split ratio 20:1; injection volume 1 µL.

Used Instrumentation

The analysis employed:

• Thermo Scientific TRACE GC Ultra gas chromatograph.
• TraceGOLD TG-WaxMS column (30 m × 0.25 mm, 0.25 µm) with 5 m SafeGuard or 5 m Guard via press-fit.
• TriPlus autosampler with 10 µL fixed needle syringe.
• ISQ single quadrupole mass spectrometer with electron ionisation (29–400 amu scan, 0.25 s scan time).

Main Results and Discussion

• Both column formats detected EG and DEG at 0.5 mg/g with good linearity.
• Retention times on SafeGuard vs press-fit: EG at 6.37 min vs 6.07 min; DEG at 10.00 min vs 9.66 min.
• Signal-to-noise for glycerol increased from 25 RMS (press-fit) to 47 RMS (SafeGuard), indicating reduced dead volume and leak sources.

Benefits and Practical Applications

The method supports semi-quantitative screening of toxic glycols in toothpaste for quality control and regulatory monitoring. Integrated guard technology simplifies column maintenance, enhances data quality, and reduces downtime.

Future Trends and Opportunities

Improvements may include automated sample handling for higher throughput, miniaturized GC-MS systems for field testing, advanced data processing with machine learning for rapid flagging of adulteration, and expansion to other cosmetic and pharmaceutical matrices.

Conclusions

Both TraceGOLD TG-WaxMS configurations meet FDA requirements for detecting DEG and EG in toothpaste. The integrated SafeGuard column provides superior signal-to-noise performance and operational robustness, making it a preferred choice for routine screening.

References

[1] FDA method, Gas Chromatography-GC-MS Screening Procedure for the Presence of Diethylene Glycol and Ethylene Glycol in Toothpaste, ucm113209.htm