Detection Of Formaldehyde In Air Research Articles

Formaldehyde gas sensors based on a quartz crystal microbalance modified with aniline-doped polyvinyl acetate nanofibers.

Real-time detection of formaldehyde in the atmosphere remains challenging. The available gaseous formaldehyde sensing methods offer limited sensitivity, selectivity, and robustness. We modified a quartz crystal microbalance (QCM) system for selective detection of formaldehyde in air. The QCM surface was functionalized with polyvinyl acetate (PVAc) nanofibers and doped with 2, 4, and 6 wt% aniline to improve the selectivity and sensitivity of the sensor. The chemical content and morphological structure of PVAc nanofibers doped with aniline were confirmed by Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The results showed that the modified QCM sensor had a sensitivity of 0.056 Hz ppm-1 with a response and recovery times of 200 s and 90 s, respectively. It gave limits of detection (LOD) and limit of quantification (LOQ) of 28 ppm and 96 ppm, respectively. Moreover, the modified QCM was selective towards formaldehyde compared to the other gases. The current workplace exposure limit (WEL) for formaldehyde is 2 ppm, with a time-weighted average over eight hours. Future work will focus on improving the reported QCM sensor to meet the required LOD for formaldehyde detection in the environment and industrial sites.

Formaldehyde biosensing in air using fluorescent bacterial bioreporter cells

ABSTRACT Formaldehyde is a genotoxic volatile organic pollutant and one of the causative agents of sick building syndrome. Despite of its hazardous carcinogenic effects, it has been still used in daily life products and household materials. Hence, determination of formaldehyde both in ambient air and drinking water sources is crucial to prevent its adverse health effects. Whole-cell biosensors have emerged as bio-sentinels for environmental monitoring to assess pollution in air, water and soil. Herein whole-cell bacterial bioreporter was developed based on a DNA damage response gene promoter and green fluorescent reporter protein, and the cells were entrapped in calcium-alginate hydrogel beads for sensitive detection of formaldehyde in air. Immobilisation enables portability, on-site detection ability and integration into mobile devices. Alginate bead-immobilised bioreporter could successfully detect formaldehyde in gas phase at concentration minimum of 8.1 ppm. This detection limit is useful for monitoring cumulative doses of bioavailable gaseous formaldehyde and taking precaution to avoid acute toxicity of formaldehyde. The developed bioreporter system is simple, low-cost, performable at room temperature and free of sample pre-treatment. The findings of this study will facilitate future research for the creation of portable and user-friendly devices for on-site and real-time environmental formaldehyde gas detection.

Universal Nanoplatform for Formaldehyde Detection Based on the Oxidase-Mimicking Activity of MnO2 Nanosheets and the In Situ Catalysis-Produced Fluorescence Species.

Formaldehyde (HCHO) pollution is a scientific problem of general concern and has aroused wide attention. In this work, a fluorometric method for sensitive detection of formaldehyde was developed based on the oxidase-mimicking activity of MnO2 nanosheets in the presence of o-phenylenediamine (OPD). The MnO2 nanosheets were prepared by the bottom-up approach using manganese salt as the precursor, followed by the exfoliation with bovine serum albumin. The as-prepared MnO2 nanosheets displayed excellent oxidase-mimicking activity, and can be used as the nanoplatform for sensing in fluorometric analysis. OPD was used as a typical substrate because MnO2 nanosheets can catalyze the oxidation of OPD to generate yellow 2,3-diaminophenazine (DAP), which can emit bright yellow fluorescence at the wavelength of 560 nm. While in the presence of formaldehyde, the fluorescence was greatly quenched because formaldehyde can react with OPD to form Schiff bases that decreased the oxidation reaction of OPD to DAP. The main mechanism and the selectivity of the platform were studied. As a result, formaldehyde can be sensitively detected in a wide linear range of 0.8-100 μM with the detection limit as low as 6.2 × 10-8 M. The platform can be used for the detection of formaldehyde in air, beer, and various food samples with good performance. This work not only expands the application of MnO2 nanosheets in fluorescence sensing, but also provides a sensitive and selective method for the detection of formaldehyde in various samples via a new mechanism.

Optical detection of formaldehyde in air in the 3.6 µm range.

The optical detector of formaldehyde designed for sensing cancer biomarkers in air exhaled from human lungs with possible application in free atmosphere is described. The measurements were performed at wavelengths ranging from 3595.77-3596.20 nm. It was stated that at the pressure of 0.01 atm this absorption band exhibits the best immunity to typical interferents that might occur at high concentration in human breath. Multipass absorption spectroscopy was also applied. The method of optical fringes quenching by wavelength modulation and signal averaging over the interferences period was presented. The application of such approaches enabled the detection limit of about single ppb to be achieved.

A novel single-fluorophore-based ratiometric fluorescent probe for detection of formaldehyde in air

A single-fluorophore-based ratiometric fluorescent probe based on anthracene carboximide was developed for detection of formaldehyde. In the presence of formaldehyde, the fluorescence emission would change from red to yellow-green, and the probe showed excellent sensitivity, selectivity and anti-interference. Furthermore, the response mechanism was illustrated to be that change in fluorescent signal is resulted from variation of substituent group on the 6th position of anthracene ring. A test paper was developed by loading probe onto filter paper strip. With this test paper, the detection of gaseous formaldehyde could be carried out conveniently, visually and quickly. 2009 Elsevier Ltd. All rights reserved.

An aldimine condensation reaction based fluorescence enhancement probe for detection of gaseous formaldehyde

Formaldehyde, a volatile organic compound that is ubiquitous in gas pollutants, has an indelible hazard to the health system of humans. Development of simple and convenient ways for the visual detection of formaldehyde in air is still of importance and challenging. In this paper, we report a new type of fluorescence enhancement probe (FAP), which directly exhibited fluorescence enhancement response to formaldehyde with high sensitivity and selectivity. The FAP was synthesized through the substitution reaction between hydrazine and NBD (7-nitrobenzo-2-oxa-1, 3-diazolyl) chloride, that the hydrazine group acted as both fluorescence quencher based on the photo-induced electron transfer (PET) pathway and reaction triggering factor for selectively recognizing formaldehyde. When the FAP was incubated with a formaldehyde-containing circumstance, Schiff base compound was produced by means of the aldimine condensation reaction which inhibited the PET pathway from hydrazine group to NBD, and thus turned on the fluorescence of the FAP significantly. It is worth mentioning that the FAP showed more remarkable response to formaldehyde under acid conditions. Under the optimal experimental conditions, the FAP responded linearly toward formaldehyde in a wide range of 0.015–0.8 mg•L−1, while the fluorescence enhancement was close to 30 times. This FAP was successfully used to detect gaseous formaldehyde in indoor air.

Design of a Portable Formaldehyde Meter

This paper describes the design of a portable formaldehyde detector instrumentation which is based on the C8051F021 microcontroller. Using the Dart sensors for detection of formaldehyde and AD8571 precision operational amplifier for signal amplification, this meter will achieve real-time detection of formaldehyde in the air. The instrument's low power consumption, intelligent and portable features are suitable for the rapid detection of formaldehyde in indoor air.

Direct detection of formaldehyde in air by a novel NAD +- and glutathione-independent formaldehyde dehydrogenase-based biosensor

An amperometric enzyme-based sensor-system for the direct detection of formaldehyde in air is under investigation. The biosensor is based on a native bacterial NAD +- and glutathione-independent formaldehyde dehydrogenase as biorecognition element. The enzyme was isolated from Hyphomicrobium zavarzinii strain ZV 580, grown on methylamine hydrochloride in a fed-batch process. The sensor depends on the enzymatic conversion of the analyte to formic acid. Released electrons are detected in an amperometric measurement at 0.2 V vs. Ag/AgCl reference electrode by means of a redox-mediator. To optimize the sensing device, Ca 2+ and pyrroloquinoline quinone (PQQ) were added to the buffer solution as reconstitutional substances. At this stage, the sensor shows linear response in the tested ppm-range with a sensitivity of 0.39 μA/ppm. The signal is highly reproducible with respect to sensitivity and base line signal. Reproducibility of sensitivity is more than 90% within the same bacterial batch and even when enzyme of different bacterial batches is used.

Potentiometric detection of formaldehyde in air by an aldehyde dehydrogenase FET

This paper reports on a system for sampling atmospheric formaldehyde by dissolution in an aqueous solution followed by the monitoring of the aldehyde using an ion-sensitive field-effect transistor (ISFET) in conjunction with an enzyme specific for this pollutant. Formaldehyde dehydrogenase from Pseudomonas putida was chosen on the basis of its characteristics to be coupled to the ISFET transducer. This enzyme, using oxidized nicotinamide adenine dinucleoside (NAD) as cofactor, catalyses the oxidation of a molecule of formaldehyde with the parallel production of two protons, which are sensed by the ISFET. The working conditions were chosen to obtain a linear response of the sensor up to 200 μM formaldehyde. On the basis of the enrichment obtained by the sampling system, the detection limit of 10 μM formaldehyde in aqueous solution, achieved by the ISFET biosensor, corresponds to an atmospheric concentration of the formaldehyde in the ppb range.