ISO 6851:2001

Overview

ISO 6851:2001 - Photography - Processing waste - Determination of total amino nitrogen (microdiffusion Kjeldahl method) defines a standardized analytical procedure for measuring total organic nitrogen and ammoniacal nitrogen in photographic processing wastes. The method uses a microdiffusion variant of the Kjeldahl procedure: organic amino nitrogen is converted to ammonium sulfate, ammonia is liberated with alkali, absorbed into boric acid, and quantified by titration with standard sulfuric acid. Measurement ranges are 10–200 mg/L as ammonia (equivalent to 8–160 mg/L as nitrogen).

Key topics and technical requirements

• Method principle: digestion with sulfuric acid/potassium sulfate and mercuric sulfate catalyst, followed by microdiffusion of liberated ammonia and titration of boric acid absorbent.
• Measurable range: 10–200 mg/L (as NH3) or 8–160 mg/L (as N).
• Organic amino nitrogen: can be obtained by subtracting separately determined ammoniacal nitrogen (see ISO 6853) from total Kjeldahl nitrogen.
• Reagents and apparatus: specifies reagent grades and examples (sulfuric acid, potassium sulfate, mercuric sulfate/mercuric oxide catalyst, boric acid, sodium hydroxide, borate absorbent, microdiffusion cells) and references for laboratory glassware (ISO 1042, ISO 648).
• Safety and handling: mandatory laboratory precautions (safety glasses, gloves), explicit hazard codes for caustic/toxic reagents (mercury compounds highlighted), and a specific warning that all pipette operations must use a pipette bulb or plunger.
• Sampling and preparation: refers to established sampling guidance (ISO 5667 series) for representative photographic effluent collection and handling.
• Quality control: use of certified reagent-grade chemicals and standardized volumetric solutions; documentation of reagent preparation and storage.

Applications and users

• Photographic laboratories and print-processing facilities monitoring effluent quality for environmental compliance.
• Environmental and commercial analytical laboratories performing wastewater testing and pollution control analyses specific to photographic effluents.
• Regulatory bodies and consultants evaluating treatment performance or establishing discharge limits for nitrogenous organic content.
• Useful for labs needing a standardized procedure for consistency, comparability, and reporting of total Kjeldahl nitrogen (TKN) in photographic processing wastes.

Related standards

• ISO 6853:2001 - Determination of ammoniacal nitrogen (microdiffusion method) - used together to separate organic amino nitrogen from ammoniacal nitrogen.
• Sampling and reagent/documentation standards referenced in ISO 6851: ISO 5667 series (sampling), ISO 6353 (reagent specifications), ISO 1042 and ISO 648 (laboratory glassware), and ISO 10349-1 (photographic-grade chemicals).

Keywords: ISO 6851:2001, photographic processing waste, total amino nitrogen, Kjeldahl microdiffusion, photographic effluents, total Kjeldahl nitrogen, wastewater testing, ISO 6853.