Overview
ISO 19929:2017 specifies a standardized MALDI-TOF-MS method for determining the average molecular mass and mixture ratio of poly(ethylene glycol) (PEG) and its derivatives. The method covers PEG and derivatives with molecular masses from 500 g·mol−1 to 20 000 g·mol−1 and calculates composition using a calibration curve where peak area ratio is plotted against mass ratio. The standard can also be applied to other polymers having a monomeric unit similar to PEG.
Key Topics and Requirements
- Scope and applicability: Quantitative MALDI-TOF-MS analysis of PEG and related polymers (500–20 000 g·mol−1); applicable to mixtures of different end groups.
- Principle: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) with calibration of time-of-flight to molecular mass.
- Sample preparation: Guidance on preparation of polymer standards, polymer/matrix/salt solutions, and deposition on the MALDI target.
- Recommended reagents:
- Matrices: α-cyano-4-hydroxycinnamic acid (CHCA) and dithranol.
- Salts: lithium, sodium, potassium salts (e.g., iodides, trifluoroacetates).
- Solvents: methanol and tetrahydrofuran (THF).
- Calibration:
- Mass-axis calibration using synthetic or biopolymer standards (see Annex A).
- Intensity-axis calibration through standard polymer mixtures; calibration curve constructed from peak area ratio vs mass ratio.
- Data processing and results:
- Calculation of molecular mass distribution (MMD), number-average molecular mass (Mn), peak areas, and mass ratios.
- Software-supported integration of isotopic peaks or use of the most abundant isotopic peak where necessary.
- Quality and reporting: Requirements for precision, instrument settings, calibration records, and test reports.
Applications and Users
ISO 19929 is intended for practical use in:
- Polymer manufacturing quality control (PEG products and PEGylated materials)
- Analytical and research laboratories conducting polymer characterization
- Pharmaceutical and biotech labs analyzing PEG-based excipients or PEGylated drugs
- Instrument manufacturers and service labs validating MALDI-TOF-MS methods
- Interlaboratory studies and standardization projects to ensure reproducible quantitative MALDI data
Typical applications include composition analysis of polymer mixtures, monitoring polymer synthesis and end-group differentiation, and quantitative comparison of polymer batches.
Related Standards
- ISO 10927:2011 - Determination of molecular mass and molecular mass distribution by MALDI-TOF-MS
- ISO 472 - Plastics - Vocabulary
Keywords: ISO 19929, MALDI-TOF-MS, poly(ethylene glycol), PEG, molecular mass, mixture ratio, calibration curve, polymer analysis.