Disposable Microchamber with a Microfluidic Paper-Based Lid for Generation and Membrane Separation of SO₂ Gas Employing an In Situ Electrochemical Gas Sensor for Quantifying Sulfite in Wine

Abstract

This work presents a fully disposable microchamber for gas generation of a sample solution. The microchamber consists of a cylindrical well-reactor and a paper-based microfluidic lid (μFluidic lid), which also serves as the reagent loading and dispensing unit. The base of the reactor consists of a hydrophobic membrane covering an in-house graphene electrochemical gas sensor. Fabrication of the gas sensor and the three-layer μFluidic lid is described. The μFluidic lid is designed to provide a steady addition of the acid reagent into the sample solution instead of liquid drops from a disposable syringe. There are three steps in the procedure: (i) acidification of the sample in the reactor to generate SO2 gas by the slow dispensing of the acid reagent from the μFluidic lid, (ii) diffusion of the liberated SO2 gas through the hydrophobic membrane at the base of the reactor, and (iii) in situ detection of SO2 by cathodic reduction at the graphene electrode. The device was demonstrated for quantitation of the sulfite preservative in wine without heating or stirring. The selectivity of the analysis is ensured by the combination of the gas-diffusion membrane and the selectivity of the electrochemical sensor. The linear working range is 2–60 mg L–1 SO2, with a limit of detection (3SD of intercept/slope) of 1.5 mg L–1 SO2. This in situ method has the shortest analysis time (8 min per sample) among all voltammetric methods that detect SO2(g) via membrane gas diffusion.

Achieving broad availability of SARS-CoV-2 detections via smartphone-based analysis

“…For instance, some electrochemical sensors can detect non-nucleic acids such as antigens and antibodies while detecting nucleic acids [ 139 ]; Some electrochemical analyses can recognize unamplified SARS-CoV-2 RNAs so fast and sensitive that 4 copies of the virus in 80 μL saliva can be detected within 1 min [ 149 ]; Some reported electrochemical probes even have higher sensitivity than the PCR test [ 150 ], but most of these approaches require further validation with clinical samples. Although these methods have been considered low-cost strategies, the frequently used signal output instrument (Sensi-smart) in combination with a smartphone is relatively expensive (about 15,000 US dollars or more) [ [151] , [152] , [153] ]. On the other hand, some USB-disk electrochemical workstations have recently been developed and achieved lower-cost analysis [ 154 ].…”

Toward nanofluidics‐based mass spectrometry for exploring the unknown complex and heterogeneous subcellular worlds

“…The noteworthy properties of microfluidic paper-based devices have already been summarized. 12,[68][69][70] Paper can be used for paperspray ionization, which offers a simple and direct sampling approach in ambient ionization mass spectrometry for the simple analysis of chemical and biological species in a sample solution. For instance, Basuri et al developed a new ambient ionization technique, microdroplet impact-induced spray ionization mass spectrometry, which allowed to construct a sequential ionization method (Figure 3B).…”

Organic Semiconductor Nanosheets for Sulfite Detecting Based on Activation of Sulfite and a Synergetic Chemiluminescence Resonance Energy Transfer Process in a Mild System of Fe2+-SO32–

“…Sulfur dioxide (SO 2 ) as one kind of air pollution exists in the form of two derivatives of sulfite (SO 3 2– ) and bisulfite (HSO 3 – ) in an aqueous solution. , Excess sulfite not only causes extreme environmental pollution like acid rain but also negatively affects human health, particularly for those who suffer from asthma. − Therefore, the direct and accurate detection of sulfite is of great significance for environmental monitoring and disease diagnosis. Activation of sulfite (SO 3 2– ) to produce more active free radicals plays an important role in sulfite detection and wastewater treatment. − Chemiluminescence (CL) is a spectral analysis method based on the light radiation phenomenon in the absence of an external light source. − Specifically, as in situ spectral analysis method, a CL signal is used to monitor intermediate substances by capturing the light signal emitted during the reaction with short detecting time resolution (from μs to ms). , It is well known that CL emissions can be generated by chemical activation of sulfite with oxidants like MnO 4 – , Ce 4+ , I 2 , Mn 3+ , et al The CL reaction mechanism of sulfite oxidation occurs from autodecomposition of S 2 O 6 2– generated by SO 3 ̇ – as follows: , M n + + S O 3 2 − → H S O 3 • + M ( n − 1 )+ 2 S O 3 •− → S 2 O 6 2 …”