ALS Environmental is pleased to announce that following revalidation, our reporting limit for method WAS022, Total and Kjeldahl Nitrogen, will be lowered to 0.2mg/l.

The ALS Environmental method for the determination of nitrogen, utilises Skalar automated segmented flow instrumentation and is accredited to the MCERTS standard for trade effluents, treated and untreated sewage samples.

Under appropriate conditions, nitrite reacts with sulphanilamide and N-(1-Naphthyl) ethylenediamine dihydrochloride to form a pink coloured complex (the Griess reaction). The intensity of the pink coloration is directly proportional to the concentration of nitrite present and can be measured at a wavelength of 540nm. Quantification is made by comparison with standard solutions of known concentration.

The segmented flow instrument operates two chemistry channels; on the first, the use of a mild reducing agent, hydrazinium sulphate, converts any nitrate to nitrite prior to the formation of the colour. Consequently, this channel measures the sum of the nitrate and nitrite present; this is referred to as total oxidised nitrogen (TON). On the second channel, a powerful UV catalysed alkaline oxidation is undertaken to convert nitrogen compounds to nitrate. These nitrates are then reduced to nitrite prior to colour formation via the Griess reaction; this channel will consequently measure total nitrogen. Kjeldahl nitrogen (TKN) is calculated by subtracting the TON result from the total nitrogen result, with total organic nitrogen calculated by subtracting the ammonia result (determined separately) from the Kjeldahl nitrogen result.

Inorganic Chemistry Operations Manager at ALS Environmental, Christopher Law, comments:

“The reduction in our total nitrogen reporting limit further demonstrates ALS Environmental’s commitment to providing the highest quality service within the environmental analysis sector and comes on the back of several recent reporting limit reductions within the Inorganics department.”

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If you have any queries about this, or any other analytical offering, please contact us or call 02476 421213.