Simulation of Capillary Electrophoresis for CAFO Waste Analysis
Authors: Struk Daniel , Heist Christopher A. , Hesketh Peter J. 
Published: September 2023

CAFO (Concentrated animal feed operations) wastewater is a promising source for fertilizer to apply to soils in agriculture. However the overapplication of nutrients is just as much of a problem as underapplication [1,2]. The waste material requires analysis of the ionic composition prior to enrichment as a fertilizer. Current methods for ion concentration analysis including Ion Chromatography, Flow Injection Analysis, and High Pressure Liquid Chromatography, which are laboratory instruments. Although some development of portable instruments has been undertaken by NASA/JPL and other groups [3], these techniques are not yet suitable for low cost portable analysis systems. Capillary Electrophoresis methods have been applied to analysis of lake water [4], biological samples [5], food [6], agricultural products [7] providing a rapid analysis at lower cost than laboratory tests. In this study simulated capillary electrophoresis for the separation of several essential plant nutrients in their anionic forms: sulfate, nitrate, chloride, and phosphate was undertaken. The relative concentrations for these anions were chosen to be similar to those found in [8.9] with a 1:100 dilution. The conditions for the separation are listed in Table 1.

Several buffer solutions were simulated including borate, sodium phosphate, and the combination of lactic acid and histidine. Separations using borate and sodium phosphate caused the four anions to elute in less than one minute in most cases, which could lead to their misidentification as they are eluting too rapidly. Separations using lactic acid and histidine were slower, but consequently had more time between each peak allowing for an easier detection. The total separation time can be tailored through the concentration of the two buffer components while still allowing greater time between elutions.

References

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[2] Rashid, Ghazunfar, et al. "Influence of Nitrogen Fertilizer on Nitrate Contents of Plants: A Prospective Aspect of Nitrate Poisoning in Dairy Animals." Pakistan Journal of Zoology 51.1 (2019).

[3] R. D. Kidd,et al., “Ion Chromatography-on-a-Chip for Water Quality Analysis,” 45th International Conference on Environmental Systems ICES, 12-16 July 2015, Bellevue, Washington, paper # 2015-141.

[4] C. B. Freitas, R. C. Moreira, M. G. de Oliveira Travares, W. K. T. Coltro, “ Monitoring of nitrite, nitrate, chloride and sulfate in environmental samples using electrophoresis microchips coupled with contactless conductivity detection,” Talanta, Vol. 147, pp. 335-341 (2016).

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[6] N. Oztekin, M. S. Nutku, F. B. Erim, “Simultaneous determination of nitrite and nitrate in meat products and vegetables by capillary electrophoresis,” Food Chemistry, Vol. 76, pp. 103-106 (2002).

[7] M. Timm, B. M. Jorgensen, “Simultaneous determination of ammonia, dimethylamine, trimethylamine, and trimethylamine-N-oxide in fish extracts by capillary electrophoresis with indirect UV-detection,” Food Chemistry, Vol. 76, pp. 509-518 (2002).

[8] Chastain, John P., et al. "Swine manure production and nutrient content." South Carolina confined animal manure managers certification program. Clemson University, SC (1999): 1-17.

[9] Bradford, Scott A., et al. "Reuse of concentrated animal feeding operation wastewater on agricultural lands." Journal of Environmental Quality 37.S5 (2008): S-97.

Figure 1