GC-MS Screening of Polymer Extractables & Leachables: Sample Prep, Chromatography & Mass Spectra

In pharmaceutical packaging, medical devices, and food-contact plastics, polymer additives (antioxidants, plasticisers, slip agents, residual monomers) can migrate out of the material. Extractables and Leachables (E&L) analysis identifies and quantifies these compounds to prevent toxicological hazards. Gas Chromatography-Mass Spectrometry (GC-MS) is the gold standard for volatile and semi-volatile migrants. In India, leading contract research organisations (CROs) and analytical labs (e.g., SGS India, TUV SUD, and HLL Lifecare) run E&L screening programs to certify medical bags, IV tubes, and syringes for international markets.

• Distinguish "extractables" from "leachables" in medical polymer qualification.
• Set up sample preparation extraction protocols (Soxhlet, pressurized liquid extraction, head-space).
• Describe the components of a GC-MS system (injector, capillary column, electron ionization source, quadrupole analyzer).
• Interpret mass spectra using fragmentation patterns and NIST library database searches.
• Reference E&L regulation standards including ISO 10993-18 and USP <1663>.

3.1 Extractables vs. Leachables

• Extractables: Compounds that can be extracted from a polymer under exaggerated solvents and temperature conditions. They represent the worst-case potential migrants.
• Leachables: Compounds that migrate from the polymer into the actual drug product or food under normal storage and use conditions. Leachables are typically a subset of extractables.

3.2 Sample Preparation and Extraction Methods

To analyze additives, they must be extracted into a solvent phase without dissolving the polymer backbone:

• Soxhlet Extraction: Continuous refluxing of hot solvent (hexane, isopropyl alcohol) over the shredded polymer.
• Sonication: Ultrasonic agitation to accelerate diffusion.
• Headspace GC-MS: Heated sample vial releases volatile organic compounds (VOCs) directly into the gas phase for syringe sampling, bypassing solvent injection.

3.3 GC-MS System Physics

1. Chromatography separation: The extract is vaporised at the injector ($250^\circ$C) and carried by Helium gas through a fused silica capillary column coated with a stationary phase (e.g., 5% phenyl methylpolysiloxane). Compounds separate based on boiling point and partition coefficient.
2. Ionization: Separated analytes enter the MS source, hit by a 70 eV electron beam (Electron Ionization, EI), fragmenting molecules into positive ions.
3. Mass Analysis: Quadrupole mass filters separate fragment ions based on mass-to-charge ratio ($m/z$). A detector counts the ions to generate a fragmentation spectrum.

Problem: A medical grade PVC tubing sample is extracted with hexane. GC-MS screening shows a major peak at retention time 18.2 minutes. The mass spectrum of this peak displays prominent fragment ions at $m/z = 149$, $m/z = 167$, and $m/z = 279$, with a molecular ion peak ($M^{+\bullet}$) at $m/z = 390$. Identify the compound and explain the fragmentation mechanism.

Solution:

1. Analyze the mass spectra fragmentation pattern:

• Molecular weight $MW = 390$ g/mol.
• The fragment ion at $m/z = 149$ is the highly stable phthalic anhydride/protonated phthalate ion ($[\text{C}_8\text{H}_5\text{O}_3]^+$), which is the classic mass spectrometry fingerprint for phthalate plasticisers.
• The fragment at $m/z = 279$ corresponds to the loss of one 2-ethylhexanol alkyl chain ($[M - \text{C}_8\text{H}_{17}]^+$).
• The compound is identified as Di(2-ethylhexyl) phthalate (DEHP), also known as dioctyl phthalate (DOP), which has $MW = 390.56$ g/mol.

Interpretation: The tubing contains DEHP, a widely used but highly regulated plasticiser in medical PVC. Since DEHP is known to be endocrine-disruptive, its presence must be flagged. The leachables risk under normal saline contact must be evaluated to ensure patient exposure remains below the tolerable daily intake (TDI) limits of ISO 10993-17.

HLL Lifecare Limited (Thiruvananthapuram) manufactures blood bags, catheters, and contraceptive devices. Their quality control labs run GC-MS testing to comply with European MDR and US FDA guidelines. They monitor E&L profiles to verify that plasticisers like DEHP do not leach into stored blood above safe concentrations.

Indian analytical laboratories qualify plastic food containers by running migration tests conforming to Bureau of Indian Standards code IS 9845.

• Leachables: Compounds migrating into drug products under real-world usage conditions.
• Quadrupole: Mass analyser using oscillating RF and DC electric fields to filter ions by $m/z$.
• $m/z = 149$: The signature fragment ion indicating phthalate plasticisers in electron ionization mass spectrometry.
• Soxhlet: Glass extraction apparatus providing continuous solvent washing of solid samples.
• Zeta Potential: (Irrelevant to chromatography, colloidal parameter).

1. ISO 10993-18 — Biological evaluation of medical devices — Part 18: Chemical characterization of medical device materials within a risk management process
2. USP <1663> — Assessment of Extractables Associated with Pharmaceutical Packaging/Delivery Systems (United States Pharmacopeia)
3. USP <1664> — Assessment of Drug Product Leachables
4. IS 9845 — Bureau of Indian Standards (BIS) methods of analysis for determination of overall migration of plastic materials in contact with foodstuffs

1. Explain why Electron Ionization (EI) at 70 eV is termed a "hard" ionization technique and contrast it with Chemical Ionization (CI) for molecular weight determination.
2. Detail the extraction solvents and temperature profile recommended in USP <1663> for executing a worst-case extractables study on a cyclic olefin copolymer (COC) syringe plunger.
3. Draw a schematic diagram of a gas chromatograph coupled to a single quadrupole mass spectrometer, labelling all critical fluidics and vacuum boundaries.

Q1. Which class of compounds is characterized by a dominant fragment ion at $m/z = 149$ in EI-MS?

• C) Phthalate plasticisers

Q2. Under ISO 10993-18, "Extractables" represent:

• B) The compounds that can be released under worst-case solvent and temperature conditions

Q3. Headspace GC-MS is preferred over solvent extraction when analyzing:

• A) Volatile organic compounds and residual monomers

Q4. The carrier gas commonly used in gas chromatography is:

• C) Helium

Q5. Which Indian standard governs overall migration testing methods for plastics in contact with food?

• B) IS 9845