Photometric Determination of Nitrate in Manure

Abstract

This protocol describes the photometric determination of nitrate in manure using Spectroquant^® test kits and a spectrophotometer. Following the sample preparation, including centrifugation and filtration, the nitrate measurement is performed using specific test kits, ensuring precise results. 

Section Overview:

• Introduction
• Reagents, Instruments and Materials
• Experimental Procedure
• Analysis
• Calculation
• References

Spectroquant^® spectrophotometers - Prove 100 plus, Prove 300 plus, & Prove 600 plus

Introduction

Nitrates are nitrogen-based salts with the anion NO₃^-, and an important class of primary nitrogen source for a plant’s growth. They are converted to proteins, the building blocks of life, in the plants as soon as they are absorbed by the root system¹. While soil is a provider of nitrates for plants, research suggests that composts used for plant growth are also a rich source of nitrates. Nitrification, the process of nitrates synthesis from ammonia by oxidation occurs during composting². However, when the concentration of nitrates is excessive in compost, it gets leached into soil and groundwater, thereby spiking the nitrate to toxic levels in them. This process is called nitrate-leaching³. It is therefore important to analyze the precise levels of nitrates in compost.

This application note details the photometric determination of nitrate in manure.

Reagents, Instruments and Materials

Nitrate Test Kits & Nitrate test Reagents

For the measurement, one of the following Spectroquant^® test kits is necessary:

• Spectroquant^® Nitrate Cell Test (1.14542)
• Spectroquant^® Nitrate Cell Test (1.14563)*
• Spectroquant^® Nitrate Cell Test (1.14764)*
• Spectroquant^® Nitrate Test (1.14773)
• Spectroquant^® Nitrate Test (1.09713)*

*not compatible with Move 100

Instrument(s) & Devices

For the measurement, one of the following Spectroquant^® photometers is necessary:

• Spectroquant^® VIS Spectrophotometer Prove 100 Plus (1.73026)
• Spectroquant^® UV/VIS Spectrophotometer Prove 300 Plus (1.73027)
• Spectroquant^® UV/VIS Spectrophotometer Prove 600 Plus (1.73028)
• Spectroquant^® Colorimeter Move 100 (1.73632)

Also, legacy systems

• Spectroquant^® Spectrophotometer Prove 100/300/600
• Spectroquant^® Photometer NOVA 30/60/60A

Software for Data transfer

• Optional Spectroquant^® Prove Connect to LIMS software package (Y.11086) to transfer your data into an existing LIMS system.

Instrument Accessories

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

Other Reagents and Accessories

• Water for analysis (1.16754)
• Membrane filter with 0.45 µm pore diameter

Experimental Procedure

Sample Preparation

• In a 250 mL standard volumetric flask place 25 mL of the sample, fill up to volume with water for analysis, and mix well. 
• For 15 minutes separate the mixture at 5000 turns per minute in the centrifuge, decant the supernatant solution, and additionally filter it through a membrane filter.

Analysis

Determine with one of the above-mentioned test kits.

Calculation

Nitrate content in mg/kg NO₃^-= analysis value in mg/L NO₃^- x 10

See more applications for photometry at Protocols and Application Notes

References

1. Beware of nitrates. Extension. 2015 Jun 18. [Internet].[cited 08 Aug 2024]. Available from: https://extension.colostate.edu/disaster-web-sites/beware-of-nitrates/

2. Cáceres R, Malińska K, Marfà O. 2018. Nitrification within composting: A review. Waste Management. 72119-137. https://doi.org/10.1016/j.wasman.2017.10.049

3. Maynard AA. 1993. Nitrate Leaching from Compost-Amended Soils. Compost Science & Utilization. 1(2):65-72. https://doi.org/10.1080/1065657x.1993.10757875