Overview
ISO 11083:1994 specifies a spectrometric method for determining chromium(VI) in water using 1,5-diphenylcarbazide. This internationally recognized standard focuses on accurate measurement of dissolved hexavalent chromium concentrations within the range of 0.05 mg/L to 3 mg/L. The method can be extended to higher concentrations through sample dilution. Chromium(VI) is an important contaminant due to its toxicity and environmental impact, making precise water quality testing essential.
The method involves the formation of a red-violet chromium-1,5-diphenylcarbazone complex that is measured spectrometrically at wavelengths between 540 nm and 550 nm. Sample pretreatment steps stabilize chromium valency states and address interferences from other substances to ensure reliable results.
Key Topics
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Scope and Application
Applicable for dissolved chromium(VI) in surface waters, effluents, and industrial wastewater, with adaptable concentration ranges.
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Principle
Chromium(VI) reacts with 1,5-diphenylcarbazide to form a colored complex, measured photometrically.
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Reagents and Solutions
Use analytical-grade reagents such as sodium hydroxide, phosphoric acid solutions, aluminium sulfate, sulfite solution, and 1,5-diphenylcarbazide in acetone.
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Sample Collection and Pretreatment
Samples are collected in glass bottles, buffered, and adjusted for pH. Pretreatment steps remove or neutralize oxidizing/reducing agents that could affect chromium valency.
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Interferences
The method addresses interference from metals like lead, barium, silver, molybdenum, mercury, vanadium, and iron by employing selective precipitation and filtration. Special care is taken with samples containing oxidizing or reducing substances to prevent chromium valency changes.
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Apparatus
Requires a photometer or spectrometer with 10-50 mm path length cells, membrane filtration devices, pH meters, and gas flow controls for air purging.
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Calibration and Measurement
Calibration curves are created using chromium(VI) standards, with absorbance measured after 5-15 minutes of complex formation. Blank and sample measurements are taken concurrently to correct for turbidity and background absorption.
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Calculation and Reporting
Chromium(VI) concentration is calculated considering absorbance differences, dilution factors, and calibration sensitivity. Results are reported with appropriate precision based on concentration levels.
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Precision and Accuracy
Interlaboratory tests confirm method repeatability, reproducibility, and recovery rates aligning with quality requirements for reliable chromium(VI) determination.
Applications
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Water Quality Monitoring
Enables environmental agencies and water treatment facilities to monitor chromium(VI) levels in natural and wastewaters, ensuring compliance with environmental standards and public health safety.
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Industrial Effluent Analysis
Used by chemical and galvanic industries to measure chromium discharge before release, supporting pollution control and regulatory compliance.
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Research and Laboratory Testing
Provides a standardized, reproducible method for laboratories conducting chemical water analyses related to environmental assessments or remediation projects.
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Wastewater Treatment Optimization
Helps in evaluating treatment efficacy for chromium removal by tracking chromium(VI) concentrations at various stages in treatment processes.
Related Standards
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ISO/TC 147 – Water Quality series
ISO 11083:1994 is part of the broader Water Quality standards developed by ISO Technical Committee 147, which covers physical, chemical, and biochemical testing methods.
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ISO 6639 – Water quality – Determination of chromium (total) in water
Complementary to chromium(VI) assessment, this standard specifies methods for total chromium analysis, aiding comprehensive chromium monitoring.
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ISO 5667 series – Water quality – Sampling
Provides guidelines on sampling techniques critical to maintaining sample integrity for methods like ISO 11083.
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EPA Methods for Chromium Analysis
Environmental Protection Agency (EPA) methods such as EPA 218.7 also detail hexavalent chromium determination for regulatory applications, serving as practical references alongside ISO standards.
Keywords: ISO 11083, chromium(VI) determination, water quality testing, spectrometric method, 1,5-diphenylcarbazide, hexavalent chromium analysis, environmental water analysis, wastewater monitoring, chemical water testing.
Open preview (PDF)Water quality — Determination of chromium(VI) — Spectrometric method using 1,5-diphenylcarbazide
