Overview
ISO 10136-2:1993 specifies flame spectrometric methods for the determination of sodium oxide (Na2O) and potassium oxide (K2O) in aqueous extract solutions produced from any kind of glass or glassware. The standard covers sample preparation, use of flame emission (FES), flame atomic absorption (FAAS) and filter flame spectrometry, calibration with reference solutions, and expression of results as micrograms of oxide per millilitre (or related to surface area for extracted glass pieces). The method is intended for hydrolytic resistance and durability testing where alkali release (Na, K) must be quantified.
Key topics and technical requirements
- Principle: spray the extract solution into the flame of an emission or absorption spectrometer (or into a filter flame spectrometer).
- Measurement lines: sodium - 589.0 nm; potassium - 766.5 nm (for FES and FAAS). Filter FES uses appropriate filters for these lines.
- Spectrochemical buffer: a cesium chloride (CsCl) buffer is specified where necessary to reduce interferences; very low-concentration borosilicate extracts may not require buffer.
- Sample preparation: acidification/filtration for turbid samples, pre-treatment of borosilicate storage bottles, dilution or modification of extract to a sample measuring solution, and addition of buffer (typically 5% of flask volume).
- Calibration: prepare stock and standard solutions (Na from NaCl; K from KCl) and construct calibration graphs from a set of reference solutions covering the instrument’s optimum working range.
- Typical working ranges (instrument-dependent): FES/FAAS commonly used for low µg/ml concentrations; filter FES for higher ranges (see instrument guidance in the standard).
- Reagents and apparatus: analytical-grade reagents, hydrochloriс acid for pre-treatment, ashless filter papers, FAAS/FES or filter FES spectrometer, Class A volumetric glassware and pipettes.
Applications and who uses it
- Quality control and compliance testing in:
- Glass and glassware manufacturing (laboratory and pharmaceutical glassware, cookware, packaging)
- Research on chemical durability and hydrolytic resistance of glass formulations
- Independent test laboratories and materials characterization labs performing extract solution analysis
- Regulatory and standards bodies comparing alkali release against specifications or pharmacopoeial limits
- Advantages: provides specific quantification of Na and K (expressed as oxides) rather than total alkalinity from titration, enabling more detailed assessment of glass durability and performance.
Related standards
- Other parts of the ISO 10136 series (methods for CaO/MgO, Al2O3, SiO2, B2O3, Fe2O3 determination)
- Standards referenced for glassware, reagents and water quality such as ISO 3585 (borosilicate glass), ISO 3696 (water for analytical laboratory use), and glass hydrolytic-resistance test standards (e.g., ISO test methods for extract preparation).
Keywords: ISO 10136-2, glass analysis, extract solutions, sodium oxide, potassium oxide, flame spectrometric methods, FES, FAAS, filter flame spectrometer, cesium chloride buffer, hydrolytic resistance.
