Photometric determination of Nitrate in Effluents

Introduction

Excess nitrate in effluents can be problematic because it can lead to contamination of groundwater and subsequent environmental problems. One of these issues is eutrophication—excessive growth of algae and plants—which can adversely affect aquatic ecosystems.¹ As a result, monitoring nitrate levels is critical for environmental reasons. Here we describe nitrate determination in effluents using photometry and Spectroquant^® Nitrate Test Kits.

Experimental Method

The test kit catalog numbers apply for the following methods:

• 1.14542; 1.14773: In concentrated sulfuric acid nitrate ions react with a benzoic acid derivative to form a red nitro compound that is determined photometrically.
• 1.14563; 1.14764; 1.09713: In sulfuric and phosphoric solution nitrate ions react with 2,6-dimethylphenol (DMP) to form 4-nitro-2,6-dimethylphenol that is determined photometrically. The method is analogous to DIN 38405-9.

Reagents, Instruments and Materials

Test Kits

One of the following test kits is necessary for this analysis

• Nitrate Cell Test Method: photometric 0.5 - 18.0 mg/l NO₃-N 2.2 - 79.7 mg/l NO₃^- Spectroquant^® (1.14542)
• Nitrate Cell Test Method: photometric, DMP 0.5 - 25.0 mg/l NO₃-N 2.2 - 110.7 mg/l NO₃^- Spectroquant^® (1.14563*)
• Nitrate Cell Test Method: photometric, DMP 1.0 - 50.0 mg/l NO₃-N 4 - 221 mg/l NO₃^- Spectroquant^® (1.14764*)
• Nitrate Test Method: photometric 0.2 - 20.0 mg/l NO₃-N 0.9 - 88.5 mg/l NO₃^- Spectroquant^® (1.14773)
• Nitrate Test Method: photometric, DMP 0.10 - 25.0 mg/l NO₃-N 0.4 - 110.7 mg/l NO₃^- Spectroquant^® (1.09713*)

*Not compatible with Move 100

Instruments

One of the following instruments is necessary for this analysis

• Spectroquant^® VIS Spectrophotometer Prove 100 (173016)
• Spectroquant^® UV/VIS Spectrophotometer Prove 300 (173017)
• Spectroquant^® UV/VIS Spectrophotometer Prove 600 (173018)
• Spectroquant^® Photometer NOVA 30 (1.09748)
• Spectroquant^® Photometer NOVA 60 (1.09751)
• Spectroquant^® Photometer NOVA 60A (1.09752)
• Spectroquant^® Colorimeter Move 100 (1.73632)

Materials

• Rectangular cells 10 mm (1.14946) and/or
• Rectangular cells 20 mm (1.14947) and/or
• Rectangular cells 50 mm (1.14944)

Sample preparation

Items 1.14542 and 1.14773 tolerate high chloride contents samples (> 1000 mg/l). The tolerance of COD is low for both (1%). Items 1.14563, 1.09713 tolerate high chloride (1000 mg/l) and COD contents (500 mg/l) but no coloration.

Cloudy samples must be filtered before determination.

Analysis

Determine with the above-mentioned test kits.

Calculation

Nitrate content in mg/l NO₃-N = analysis value in mg/l NO₃-N

References

1. Camargo JA, Alonso Á. 2006. Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment. Environment International. 32(6):831-849. https://doi.org/10.1016/j.envint.2006.05.002