Abstract
A fast and easy electrochemical method for nitrate determination in leafy vegetables was developed. It is a much cheaper method compared to the HPLC method or chemiluminescence detection, the most sensitive method in determination of nitrate, which requires expensive instrumentation. A nitrate ion selective electrode was employed and the electric potentials were measured before and after a series of standard nitrate solutions added to the vegetable sample solution without any pre-treatment.
Highlights
It is well known that some green leafy vegetables such as spinach and lettuce contain high levels of nitrate (NO3-) [1,2,3], while nitrite (NO2-) content in many types of fresh vegetables is much lower than nitrate [3,4,5]
A series of electric potentials were measured after a series of standard nitrate solutions were added to a romaine lettuce sample solution
SigmaPlot 13.0, 38.25 μM nitrate was found to be the initial nitrate concentration present in the sample (X0), E0 is 400.4 mV, and the slope (S) was 62.83 mV which was pretty close to 59.16 mV, the theoretical value at 25 °C
Summary
It is well known that some green leafy vegetables such as spinach and lettuce contain high levels of nitrate (NO3-) [1,2,3], while nitrite (NO2-) content in many types of fresh vegetables is much lower than nitrate [3,4,5]. An UVVis spectroscopic method, either based on deconvolution of UV spectra of a number of references to reconstitute the UV spectrum of an unknown sample to determine nitrate concentration or based on the quantitative reaction of nitrate with 2-sec-butylphenol to form a yellow complex in alkaline medium which has maximum absorbance at 418 nm has been used [22,23] These methods either need special pretreatment, such as converting nitrate to nitrite determine nitrite content, or reacting with special reagents to generate a colored compound, or need special and expensive instrumentations such as chemiluminescence detection and HPLC. We determined nitrate content in fresh spinach, fresh romaine lettuce, fresh iceberg lettuce, fresh celery, and canned spinach obtained from a local supermarket
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