Colorimetric determination of nitrite in clinical, food and environmental samples using microfluidic devices stamped in paper platforms

Abstract

This study reports the use of microfluidic paper-based analytical devices (µPADs) associat e d with colorimetric detection for the determination of nitrite in clinical, food and environment a l samples. µPADs were fabricat ed by simple and fast stamping process in a geomet ry containin g eight circular detection zones and one central zone to sample inlet interconnected by microfluid i c channels . The colorimet ric determination of nitrite was performed through the modified Gries s reaction. Detection zones were spotted with a 0.75 µL aliquot of a solution containing 50 mmol L -1 sulfanilamide, 1.2 mol L -1 hydrochloric acid and 4 mmol L -1 N-(1-napthyl)ethy lenediamin e . The monitoring of the background colorimetric response revealed good stability over 12h for devices stored in the absence of light. After the addition of standard or real samples, the result in g images were captured with a scanner, converted to a color scale and analyzed in the magen t a channel. The analytical sensitivity and the limit of detection achieved after a preconcentrat io n stage were 0.56 (AU/µM ) and 5.6 µM , respectively. The preconcentrat ion provided an enrichment factor of ca. 3.2 times. The concentration levels of nitrite were successful ly determined in saliva, preservative water, ham, sausage and river water samples. The concentrat ion levels attained for each sample using µPADs were compared to the values found by spectrophotomet ry and there was no significative difference from one another at a confiden c e level of 95%.

Determinação de fosfato em refrigerantes utilizando um scanner de mesa e análise automatizada de dados: um exemplo didático para ensino de química

“…Existem vários exemplos relevantes descritos na literatura, tais como para a determinação de nitrito em alimentos, amostras ambientais e amostras clínicas, 4 na determinação do diclofenaco sódico, dipirona sódica e gluconato de cálcio em drogas injetáveis, 5 análise de chás, 6 quantificação de etanol em bebidas, 7 e quantificação de sulfito em bebidas. 8 Além disso, o uso de imagens digitais pode ser uma alternativa para ensaios clínicos, como demonstrado recentemente para creatinina 9 e determinação de glucose, 10 alanina aminotransferase.…”

A paper‐based gas sensor for simultaneous noninstrumental colorimetric detection of nitrite and sulfide in waters

“…A comparison of the analytical performance of the proposed method with previously reported PADs is provided in Supporting Information Table S1. It can be deduced from the table that the proposed paper‐based gas sensor shows improved sensitivity (8‐ to 124‐fold enhancement) when compared with most of PADs and µ‐PADs reported in the literature for nitrite determination [15–19,21,22], and comparable LOD to the one involving electrokinetic stacking 2D‐µPAD, which claimed a 160‐fold enhancement of sensitivity [20]. Besides, the LOD achieved for sulfide determination (0.005 mg/L) is much lower than the lowest concentration level employed in the membraneless gas separation µ‐PAD system (25 mg/L) [23].…”

“…In this sense, relevant contributions have been made on fields such as medical diagnosis, food quality control, and environmental analysis [12]. Particularly, a number of PADs and microfluidic PADs (µ‐PADs) have been reported in the literature for the noninstrumental colorimetric determination of nitrite [15–22] and sulfide [23] with the aim of providing methods amenable to onsite determination at low cost. However, most of the previously reported PADs and µ‐PADs for nitrite determination show reduced sensitivity, thus restricting their applicability to the analysis of samples containing nitrite levels close to or above the parametric value set by the European Union (0.5 mg/L) [24] or the maximum contaminant level set by the US Environmental Protection Agency for nitrite (1 mg/L measured as nitrogen) [25].…”

A Portable, Single-Use, Paper-Based Microbial Fuel Cell Sensor for Rapid, On-Site Water Quality Monitoring

“…Microfluidic paper-based analytical devices (µPADs) have attracted a lot of attention as water quality sensors due to the easy fabrication and cost-effective nature of paper. The most commonly used method for µPAD-based water analysis is the colorimetric detection method [20][21][22]. However, colorimetric techniques can only provide qualitative or semi-quantitative analysis given that a calibration chart and external digital scanners or cameras are provided [23].…”