ISO 10136-6:1993

Overview

ISO 10136-6:1993 specifies an internationally recognized method for the determination of boron(III) oxide (B2O3) in extract solutions from glass and glassware using molecular absorption spectrometry. This part of the ISO 10136 series focuses on the precise quantification of boron content released during hydrolytic resistance tests of various glass products, particularly borosilicate laboratory and pharmaceutical glassware, neutral glass, tableware, and kitchenware.

The method's core principle is the complexation of boron in the test extract solution with azomethine H, forming a colored complex whose optical density is measured at 415 nm via molecular absorption spectrometry. Using 20 mm optical cells ensures accurate and repeatable absorbance readings, which are correlated to B2O3 concentrations.

Key Topics

• Scope and Applicability
  The standard applies to extract solutions obtained from any glass or glassware, covering laboratory glassware, pharmaceutical packaging, drinking bottles, tableware, and cooking utensils. It addresses boron concentrations too low for classical titration or flame atomic absorption methods, necessitating molecular absorption spectrometry techniques.

• Analytical Principle
  Boron is reacted with azomethine H to create a distinct colored complex. The absorbance of this complex at 415 nm is proportional to the boron content, measured as boron(III) oxide (B2O3). The method includes acidification and buffering steps to dissolve interfering hydroxides and carbonates ensuring reliable readings.

• Reagents and Preparation
  The reagent system includes azomethine H, ascorbic acid, buffer solutions, and a revealing solution with EDTA and citric acid. Solutions must be prepared with analytically pure reagents and high-purity water in accordance with ISO 3696 standards.

• Calibration and Measurement
  Calibration curves are established using boron oxide standard solutions ranging from 0 to 50 µg of B2O3. The optical density of samples and blanks is measured against these references, allowing calculation of boron oxide concentration in the sample solution.

• Instrumentation
  The method requires a molecular absorption spectrometer capable of measuring optical density at 415 nm, along with 20 mm pathlength optical cells. Laboratory glassware complying with ISO standards ensures consistent sample handling and test accuracy.

Applications

ISO 10136-6:1993 is essential for laboratories and manufacturers focused on:

• Quality control of laboratory and pharmaceutical glassware
  Ensuring compliance with hydrolytic resistance standards and safety for chemical and biological applications.

• Testing of borosilicate glass and related materials
  Quantifying the leaching of boron oxide which can affect product performance, durability, and regulatory compliance.

• Analysis of kitchenware and tableware
  Monitoring boron release into food-contact materials to maintain health and safety standards.

• Research and development
  Studying the chemical stability and surface characteristics of new glass formulations under hydrolytic conditions.

Related Standards

ISO 10136-6:1993 is part of a comprehensive series on glass and glassware extract solution analysis. Complementary parts include:

• ISO 10136-1: Determination of silicon dioxide (SiO2) by molecular absorption spectrometry.
• ISO 10136-2: Determination of sodium and potassium oxides by flame emission or absorption spectrometry.
• ISO 10136-3: Determination of calcium and magnesium oxides by atomic absorption spectroscopy.
• ISO 10136-4: Determination of alumina (Al2O3) by molecular absorption spectrometry.
• ISO 10136-5: Determination of ferric oxide (Fe2O3) by molecular and atomic absorption spectrometry.

Additional relevant ISO references for related test equipment and methodologies include ISO 4802 (hydrolytic resistance testing), ISO 3585 (borosilicate glass properties), and ISO 3696 (water for laboratory use).

Keywords: ISO 10136-6, boron(III) oxide determination, molecular absorption spectrometry, borosilicate glass testing, hydrolytic resistance, glassware analysis, azomethine H complexation, B2O3 measurement, glass extract analysis, laboratory glassware quality control.