Abstract
In this work, the design of a microfluidic paper-based analytical device (μPAD) for the quantification of nitrate in urine samples was described. Nitrate monitoring is highly relevant due to its association to some diseases and health conditions. The nitrate determination was achieved by combining the selectivity of the nitrate reductase enzymatic reaction with the colorimetric detection of nitrite by the well-known Griess reagent. For the optimization of the nitrate determination μPAD, several variables associated with the design and construction of the device were studied. Furthermore, the interference of the urine matrix was evaluated, and stability studies were performed, under different conditions. The developed μPAD enabled us to obtain a limit of detection of 0.04 mM, a limit of quantification of 0.14 mM and a dynamic concentration range of 0.14–1.0 mM. The designed μPAD proved to be stable for 24 h when stored at room temperature in air or vacuum atmosphere, and 60 days when stored in vacuum at −20 °C. The accuracy of the nitrate μPAD measurements was confirmed by analyzing four certified samples (prepared in synthetic urine) and performing recovery studies using urine samples.
Highlights
Nitrite and nitrate are both nitrogen anions found in the human body either due to an endogenous process or through ingestion of water and food, such as vegetables and processed meats [1]
As mentioned above, the color reaction chosen for the developed μPAD was the Griess reaction for nitrite determination, so the color reaction layer was adapted from a previously reported work by Ferreira et al [2]
Because the incubation at 30 ◦C would impair the μPAD field application and, considering the target concentrations were below 2 mM, a choice was made to carry out the determination at room temperature
Summary
Nitrite and nitrate are both nitrogen anions found in the human body either due to an endogenous process or through ingestion of water and food, such as vegetables and processed meats [1] These anions have been often associated with cancer, especially nitrite, either from direct ingestion or the nitrate reduction by bacteria in the digestive system [2,3]. When nitrite reaches the acidic environment of the stomach, and is combined with amine or amide, it may form toxic and carcinogenic compounds such as nitrosamines and nitrosamides [2] Nitrite acts both as a substrate for the respiration of tumor cells and a signal molecule for their growth. Monitoring nitrate levels becomes essential for the prevention of diseases such as infections and cancer
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
