Rapid quantification of humic components in concentrated humate fertilizer solutions by FTIR spectroscopy
- 118 Downloads
The use of humic substances is under thorough discussion of state-of-the-art agricultural science. They are marketed mostly as concentrated aqueous solutions of potassium or sodium humates, which are produced by alkali extraction of raw organic matter such as lignite, leonardite, or peat. Due to the presence of clay minerals in the raw materials, humate solutions are characterized with a substantial content of silicates. At the same time, rapid quantification techniques for selective determination of humic components and silicates in humate solutions are missing. The aim of this work was to develop an IR spectroscopic technique for rapid quantification of humic substances (HSs) and silicates in concentrated humate solutions with the minimum sample preparation, which could be used for quality control of humic fertilizers.
Materials and methods
Sodium humate from Sigma-Aldrich and two potassium humate fertilizers available on the market were used for the experiments. For FTIR measurements, thin-layer open-cell (DialPath) transmission and attenuated total reflectance (ATR) accessories were used. The secondary focus of this work was the use of a compact portable IR spectrometer, which can be used in the field. Total carbon analyzer and ICP-AES for determination of silicon and aluminum contents were used.
Results and discussion
FTIR spectra were registered for both dry samples and aqueous solutions of the humates. The most intense bands in IR spectra of HS were characterized with linear concentration dependences in the range of concentrations of 2–200 g L−1 of HS. The most sensitive band was shown to be 1560 cm−1. It corresponded to carboxyl groups (COO−) of humates (limits of detection [recalculated to carbon] for transmission and ATR modes are 3 and 1 g L−1, respectively). The band at 1015 cm−1 was attributed to silicate. It did not overlap with the bands of organic constituents and could be used for silicate quantification. The proposed technique can identify different trademarks of the fertilizers by the amount of both HS and silicate.
Rapid determination of humate and silicate components comprising three samples of humic fertilizers was proposed without isolation of the analytes from solution.
KeywordsATR Humate aqueous solutions Humic substances Infrared spectroscopy Silicates
This work was supported by the Russian Science Foundation (project 16-14-00167).
- Allard B, Borén H, Grimvall A (1991) Humic substances in the aquatic and terrestrial environment: proceedings of an international symposium, Linköping, Sweden, August 21–23, 1989. Springer-VerlagGoogle Scholar
- Billingham K (2015) Humic products: potential or presumption for agriculture. Department of Primary Industries, New South WalesGoogle Scholar
- Elsohaby I, Burns JB, Riley CB, Shaw RA, McClure JT (2017) Application of laboratory and portable attenuated total reflectance infrared spectroscopic approaches for rapid quantification of alpaca serum immunoglobulin G. PLoS One 12:e0179644. https://doi.org/10.1371/journal.pone.0179644 CrossRefGoogle Scholar
- Gerstl Z (1989) Toxic organic chemicals in porous media. Ecological studies. Springer-Verlag, BerlinGoogle Scholar
- Hemati A, Alikhani H, Bagheri Marandi G (2012) Extractants and extraction time effects on physicochemical properties of humic acid. Extractants and extraction time effects on physicochemical properties of humic acid. Int J Agric Res Rev 2:975–984Google Scholar
- Lynch BM, Smith-Palmer T (1992) Interpretation of FTIR spectral features in the 1000-1200 cm−1 region in humic acids - contributions from particulate silica in different sampling media. Can J Appl Spectrosc 37:126–131Google Scholar
- Mahoney KJ, McCreary C, Depuydt D, Gillard CL (2017) Fulvic and humic acid fertilizers are ineffective in dry bean. Can J Plant Sci 97:202–205Google Scholar
- Malcolm RL (1976) Method and importance of obtaining humic and fulvic acids of high purity. J Res U S Geol Surv 4:37–40Google Scholar
- Orlov DS (1995) Humic substances of soils and general theory of humification. A A Balkema Publishers, RotterdamGoogle Scholar
- Pinheiro JP, Monteiro ASC, Janot N, Groenenberg BJ, Rosa AH (2017) Trace metal thermodynamic speciation with humic substances: the NICA-Donnan model. Quim Nova 40:1191–1203Google Scholar
- Ramer G, Lendl B (2013) Attenuated total reflection fourier transform infrared spectroscopy. John Wiley & Sons, Ltd, Online. https://doi.org/10.1002/9780470027318.a9287
- Senesi N, Miano TM (1994) Humic substances in the global environment and implications on human health: proceedings of the 6th International Meeting of the International Humic Substances Society, Monopoli (Bari), Italy, September 20–25, 1992. ElsevierGoogle Scholar
- Sparks DL (2003) Environmental soil chemistry (second edition). Academic Press, BurlingtonGoogle Scholar
- Stevenson FJ (1994) Humus chemistry: genesis, composition, reactions. Wiley. https://doi.org/10.1111/j.1574-6968.1994.tb07310.x
- Tan KH (2014) Humic matter in soil and the environment: principles and controversies, second edition. CRC Press, Boca RatonGoogle Scholar
- Tanaka T, Nagao S, Ogawa H (2002a) Attenuated total reflection fourier transform infrared (ATR-FTIR) spectroscopy of functional groups of humic acid dissolving in aqueous solution. Analytical Sciences/Supplements 17:i1081–i1084. https://doi.org/10.14891/analscisp.17icas.0.i1081.0
- Veryho N, Ponikowska I, Latour T (2016) Humus acids - physico-chemical properties, the mechanism of action and applications in balneotherapy. Acta Balneol 58:45–49Google Scholar
- Violante A, Bollag JM, Gianfreda L, Huang PM (2002) Dynamics, mobility and transformation of pollutants and nutrients. Elsevier Science, AmsterdamGoogle Scholar