Overview
ISO 6333:1986 outlines a standardized spectrometric method for determining manganese levels in water using the formaldoxime reaction. This internationally recognized procedure applies to surface water and drinking water, allowing accurate measurement of manganese concentrations ranging from 0.01 mg/l to 5 mg/l. For samples with manganese above 5 mg/l, dilution is recommended before analysis. The method provides reliable and reproducible results, essential for monitoring water quality and ensuring compliance with environmental and health standards.
Key Topics
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Scope and Application
- Applicable to manganese determination in both surface and drinking waters
- Suitable concentration range: 0.01 mg/l to 5 mg/l
- Higher concentrations require sample dilution for accuracy
- Not intended for heavily polluted industrial wastewater
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Analytical Principle
- Formation of a red-orange manganese-formaldoxime complex
- Measurement of absorbance at approximately 450 nm using spectrometry
- Linear calibration curve enables quantification based on absorbance intensity
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Reagents and Preparation
- Use of potassium or sodium peroxodisulfate as oxidizing agents
- Formaldoxime reagent preparation for complex formation
- EDTA solution to reduce interference from iron and other metals
- Proper acidification of samples to stabilize manganese and prevent adsorption
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Sample Handling and Pretreatment
- Acidifying water samples to pH near 1 to dissolve suspended manganese forms
- Pre-oxidation via autoclaving or boiling to convert manganese into reactive forms
- Usage of analytical-grade reagents and deionized or distilled water for accuracy
- Ensuring clean glassware through acid washing to avoid contamination
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Measurement and Calibration
- Calibration curves created using standardized manganese solutions at known concentrations
- Different cuvette path lengths for low (100 mm) and high (10 mm) concentration ranges
- Regular calibration to maintain method reproducibility and accuracy
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Interferences and Mitigation
- Iron(II) ions form competing complexes with formaldoxime, affecting measurement
- Addition of EDTA and specific reagent mixtures (hydroxylammonium chloride with ammonia) to mask interference
- Monitoring for cobalt, calcium, magnesium, and phosphate ions influencing accuracy
- Centrifugation to remove turbidity after complex formation, if necessary
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Safety Precautions
- Handling of hazardous chemicals like formaldehyde and hydroxylamine derivatives under fume hoods
- Use of personal protective equipment: gloves, goggles, and face protection
- Proper disposal and storage of reagents to minimize exposure risks
Applications
Related Standards
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ISO/TC 147 – Water Quality
- The technical committee responsible for the development and maintenance of water-related analytical methods including manganese determination.
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Other ISO methods for trace metal analysis in water such as ISO 8288 for iron and ISO 6334 for copper, complementing the manganese determination method to provide a comprehensive water quality profile.
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National and regional standards for water quality assessment, often referencing ISO 6333 to ensure uniformity and accuracy in manganese testing.
Keywords: ISO 6333, manganese determination, water quality standard, formaldoxime spectrometric method, surface water analysis, drinking water analysis, spectrophotometry manganese, water contaminant testing, manganese concentration measurement, analytical chemistry water standards.
