Nitrogen Profile in Fertilizer by IR Absorption Spectroscopy

• By: Mitra S.K ADMIN
• April 06 2022
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ABSTRACT:

Determination of Nitrate Nitrogen, Urea –Nitrogen and Ammoniacal Nitrogen in fertilizer samples by IR spectroscopy. The main forms of Nitrogen in fertilizer are Ammoniacal Nitrogen, Urea Nitrogen and Nitrate Nitrogen. In this study, FTIR –ATR spectra of Nitrate, Urea and Ammoniacal Nitrogen standard solution with low to high concentration were prepared by using Potassium Bromide (KBr). The result showed that the wavenumber of Nitrate –Nitrogen (at a region 824 cm^-1) Urea- Nitrogen (at a region1674 cm^-1 for C=O bond, 1590 cm^-1 for N-H bond, 1459 cm^-1 for C=N bond). Ammoniacal Nitrogen (at a region 1362 cm^-1) in different fertilizer samples.

KEYWORDS: Fertilizer, Nitrate-Nitrogen, Urea-Nitrogen, Ammoniacal-Nitrogen, Fourier Transform Infrared Spectroscopy, Attenuated Total Reflectance, Potassium –Bromide.

INTRODUCTION:

Effect of nitrogen fertilizer on plant growth:

Nitrogen is an essential element for plant growth and development. It is a major component of amino acid, the building blocks of protein. Without proteins, plants wither and die. Nitrogen is a part of the chlorophyll molecule which is involved in creating food for plant through photosynthesis. Lack of nitrogen shows chlorosis (yellowish colour) of the plants. Due to environmental pollution, high nitrate concentration accumulates in the edible parts of leafy vegetables, particularly if excess nitrogen fertilizer has been applied. Consuming these crops can harm human health, these developing a suitable strategy for the agriculture application of nitrogen fertilizer is important. Although inorganic nitrogen compounds (i.e. NH₄⁺, NO₃^-, NO₂^-) account for less than 5% of the total nitrogen in the soil, they are the main form of the element absorbed by the most plants. Urea is a source of nitrogen, an essential nutrient crucial for crop growth and development. Urea is the most important nitrogenous fertilizer because of its high Nitrogen Content. Inorganic and organic fertilizer are applied to maintain the nutrient condition of different cropping system.

• Methods and materials:

2.1 Classical method for estimation of Urea - Nitrogen:

Kjeldahl Method: The kjeldahl method consists in a procedure of catalytically supported mineralization of organic material in a boiling mixture of sulphuric acid and sulphate salt at digestion temperature at 420 ° C. During the process the organically bonded nitrogen is converted into ammonium sulphate. Alkalizing the digested solution liberates ammonia which is quantitatively steam distilled and determined by titration.

Materials: The test reagents were Sulphuric acid, Copper sulphate, Potassium sulphate, Boric acid, Sodium hydroxide.

Time required: Minimum 3-4 hrs.

Structure:

2.2 Classical method for estimation of Nitrate - Nitrogen:

Cadmium Reduction Method: The nitrate is reduced to Nitrite in presence of cadmium granules. The nitrite produced is determined by diazotizing with sulphanilamide and coupling with N-(1-napthyl) ethlenediamine to form a highly coloured azo dye which is measured colorimetrically at 543nm.

Materials: The test reagents were Sulphanilamide, NEDA, EDTA, Cd granules, Copper Sulphate.

Time required: Minimum 3-4 hrs.

Structure:

2.3 Classical method for estimation of Ammoniacal - Nitrogen:

Phenate Method: An intensely blue coloured compound, indophenol by the reaction of ammonia, hypochlorite and phenol catalysed by sodium nitroprusside at a wavelength of 640 nm.

Materials: The test reagents were Ammonia, Phenol, Sodium Nitroprusside, Sodium hypochlorite

Time required: Minimum 3-4 hrs.

Structure:

3.0   Limitation of classical method:

• Relatively long analysis time.
• Requires hazardous chemicals.
• Requires high Costing.

Proposed method (FTIR method)

4.0   ADVANTAGE OF THE PROPOSED METHOD:

• Cost effective.
• Can be completed in very short time.
• Does not require any sample preparation.
• Very selective.
• Require only one chemical (KBr).
• Time saving.

5.0  FTIR instrument

Fourier Transformed Infrared Spectroscopy (Thermo Scientific; Model no: Nicolet iS10), Equipped with an Attenuated Total Reflectance (ATR), and Transmittance having OMNIC       software was used for analysis and data processing.

Attenuated Total Reflectance (ATR):

Transmittance:

5.1 Principle of FTIR:

Fourier-transform infrared spectroscopy (FTIR) is a technique used to obtain an infrared spectrum of absorption and reflectance of a solid or liquid.

An FTIR spectrometer simultaneously collects high-spectral-resolution data over a wide spectral range. In this study, –CONH₂ bond, -NO₃ bond and N-H bond present in fertilizer were evaluated by IR spectrometry.

Wavenumber selected for urea(-CONH₂):

-CONH₂ for Urea at a region 1674 cm^-1 for C=O, 1590 cm^-1 for N-H, 1459 cm^-1 for C=N (showing stretching frequency of the bond) were evaluated and quantified.

Wavenumber selected for nitrate(-NO₃): 

-N –H for Ammoniacal Nitrogen at a region 1362 cm^-1 (showing stretching frequency of the bond) was evaluated and quantified.

Wavenumber selected for ammoniacal nitrogen (N-H):

- NO₃^- for Nitrate–Nitrogen at 824 cm^-1 was evaluated and quantified. (Bending frequency of the bond).

5.2 BRIFE DESCRIPTION OF FTIR METHOD:

PREPARATION OF STANDARD CURVE:

The Urea, Potassium Nitrate and Ammonium chloride standard (Analytical Grade with 99.5%    purity) were used for preparation of standard curve by FTIR. The standards were dried at 105 deg C for 1 hr. for removal of inherent moisture.

UREA STANDARD:

The Urea Standard as such 50%, 30 % and 10% diluted with KBr and made homogeneous by mixing thoroughly with mortar and pestle.

Potassium nitrate:

The Potassium Nitrate Standard as such 40%, 20 % and 10% diluted with KBr and made homogeneous by mixing thoroughly with mortar and pestle.

Ammonium chloride:

The Ammonium Chloride Standard as such 20%, 10 % and 5% diluted with KBr and made homogeneous by mixing thoroughly with mortar and pestle.

5.3 Preparation of standard curve:

Separate standard curve was prepared for quantifying Urea-Nitrogen, Nitrate-Nitrogen and Ammoniacal Nitrogen content of fertilizer samples.

ESTIMATION OF UREA NITROGEN CONTENT OF FRETILIZER SAMPLEs:

ESTIMATION OF nitrate- NITROGEN CONTENT OF FRETILIZER SAMPLES:

ESTIMATION OF ammoniacal- NITROGEN CONTENT OF FRETILIZER SAMPLES

CONCLUTION :

• The Urea Nitrogen, Nitrate Nitrogen and Ammoniacal Nitrogen content of fertilizer samples analyzed by the proposed FTIR spectrometry are giving comparative results with that of classical methods.
• The proposed method was found to be very fast, accurate and cost effective in compare to classical methods.
• The proposed method is also very safe method for analysis. It does not require the use of any hazardous chemicals and heating instrument.
• Thus, it may be proposed that for the stated fertilizer samples the proposed FTIR can be employed for regular analysis, so that a large number of samples can be analyzed per day. (Approx. 20-30 samples).

Contributed by : Atrayee Saha & Tapashri Bagch