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    Fluctuation-enhanced sensing with organically functionalized gold nanoparticle gas sensors targeting biomedical applications. Lentka Łukasz,Kotarski Mateusz,Smulko Janusz,Cindemir Umut,Topalian Zareh,Granqvist Claes G,Calavia Raul,Ionescu Radu Talanta Detection of volatile organic compounds is a useful approach to non-invasive diagnosis of diseases through breath analysis. Our experimental study presents a newly developed prototype gas sensor, based on organically-functionalized gold nanoparticles, and results on formaldehyde detection using fluctuation-enhanced gas sensing. Formaldehyde was easily detected via intense fluctuations of the gas sensor's resistance, while the cross-influence of ethanol vapor (a confounding factor in exhaled breath, related to alcohol consumption) was negligible. 10.1016/j.talanta.2016.06.063
    Determination of Very Low Level of Free Formaldehyde in Liquid Detergents and Cosmetic Products Using Photoluminescence Method. Gholami Ali,Mohsenikia Atefeh,Masoum Saeed Journal of analytical methods in chemistry Formaldehyde is commonly used in detergents and cosmetic products as antibacterial agent and preservative. This substance is unfavorable for human health because it is known to be toxic for humans and causes irritation of eyes and skins. The toxicology studies of this compound indicate risk of detergents and cosmetic formulations with a minimum content of 0.05% free formaldehyde. Therefore, determination of formaldehyde as quality control parameter is very important. In this study, a photoluminescence method was achieved by using 2-methyl acetoacetanilide. Also, the Box-Behnken design was applied for optimization of Hantzsch reaction for formaldehyde derivatization. The investigated factors (variables) were temperature, % v/v ethanol, reaction time, ammonium acetate, and 2-methyl acetoacetanilide concentration. The linear range was obtained from 0.33-20 × 10(-7) M (1-60 μg·kg(-1)) and the limit of detection (LOD) was 0.12 μg·kg(-1). The proposed method was applied for the analysis of Iranian brands of liquid detergents and cosmetic products. The formaldehyde content of these products was found to be in the range of 0.03-3.88%. Some brands of these products had higher concentration than the maximum allowed concentration of 0.2%. High recoveries (96.15%-104.82%) for the spiked dishwashing liquid and hair shampoo indicate the proposed method is proper for the assessment of formaldehyde in detergents and cosmetic products. The proposed methodology has some advantages compared with the previous methods such as being rapid, without the necessity of applying separation, low cost, and the fact that the derivatization reaction is carried out at room temperature without any heating system. 10.1155/2016/1720530
    Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell. Dong Lei,Yu Yajun,Li Chunguang,So Stephen,Tittel Frank K Optics express A ppb-level formaldehyde (H2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variance analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. A side-by-side comparison between two measurement schemes is also discussed in detail. 10.1364/OE.23.019821
    A Robust Static Headspace GC-FID Method to Detect and Quantify Formaldehyde Impurity in Pharmaceutical Excipients. Daoud Agha Dit Daoudy Bashir,Al-Khayat Mohammad Ammar,Karabet Francois,Al-Mardini Mohammad Amer Journal of analytical methods in chemistry Formaldehyde is a highly reactive impurity that can be found in many pharmaceutical excipients. Trace levels of this impurity may affect drug product stability, safety, efficacy, and performance. A static headspace gas chromatographic method was developed and validated to determine formaldehyde in pharmaceutical excipients after an effective derivatization procedure using acidified ethanol. Diethoxymethane, the derivative of formaldehyde, was then directly analyzed by GC-FID. Despite the simplicity of the developed method, however, it is characterized by its specificity, accuracy, and precision. The limits of detection and quantification of formaldehyde in the samples were of 2.44 and 8.12 g/g, respectively. This method is characterized by using simple and economic GC-FID technique instead of MS detection, and it is successfully used to analyze formaldehyde in commonly used pharmaceutical excipients. 10.1155/2018/4526396
    Indirect determination of formaldehyde by square-wave voltammetry based on the electrochemical oxidation of 3,5-diacetyl-1,4-dihydrolutidine using an unmodified glassy-carbon electrode. Pinto Gabriel F,Rocha Diego P,Richter Eduardo M,Muñoz Rodrigo A A,Silva Sidnei G Talanta A novel and indirect voltammetric procedure for the selective determination of formaldehyde is described. It is based on the oxidation of 3,5-diacetyl-1,4-dihydrolutidine (DDL) on an unmodified glassy-carbon electrode (GCE), generated by the selective reaction between formaldehyde and acetylacetone. A single oxidation peak of DDL at +0.8 V was observed, while formaldehyde is not electroactive under this condition, showing that this reaction can be used to indirect and selective detection of formaldehyde. Under the optimized conditions, a linear response between 0.4 and 40.0 mg L and a detection limit of 0.13 mg L were achieved, with a relative standard deviation of 0.7% (n = 10, 10 mg L). Due to the selectivity of this reaction to formaldehyde, this method is free from interference of other aldehydes. The procedure is a promising alternative for rapid formaldehyde determination in a wide range of samples. 10.1016/j.talanta.2019.01.108
    Hollow ZnSnO Cubes with Controllable Shells Enabling Highly Efficient Chemical Sensing Detection of Formaldehyde Vapors. Zhou Tingting,Zhang Tong,Zhang Rui,Lou Zheng,Deng Jianan,Wang Lili ACS applied materials & interfaces In structural hierarchy, inherently hollow nanostructured materials preferentially possessing high surface area demand attention due to their alluring sensing performances. However, the activity of hollow and structural hierarchy nanomaterials generally remains suboptimal due to their hollow space structure and large lateral size, which greatly hamper and limit the availability of inner space active sites. Here, hollow ZnSnO cubes with a controllable interior structure were successfully prepared through a simple and low-cost coprecipitation approach followed with a calcination process. The solid-, single-, double-, and multishelled ZnSnO hollow cubes could be selectively tailored by repeated addition of alkaline solution. The multishelled architecture displayed outstanding sensing properties for formaldehyde vapors due to large specific surface area, less agglomerations, abundant interfaces, thin shells, and high proportion porous structure, which act synergistically to facilitate charge transfer and promote target gas adsorption. 10.1021/acsami.7b03112
    Nanowire-Assembled Hierarchical ZnCoO Microstructure Integrated with a Low-Power Microheater for Highly Sensitive Formaldehyde Detection. Long Hu,Harley-Trochimczyk Anna,Cheng Siyi,Hu Hao,Chi Won Seok,Rao Ameya,Carraro Carlo,Shi Tielin,Tang Zirong,Maboudian Roya ACS applied materials & interfaces Nanowire-assembled 3D hierarchical ZnCoO microstructure is synthesized by a facile hydrothermal route and a subsequent annealing process. In comparison to simple nanowires, the resulting dandelion-like structure yields more open spaces between nanowires, which allow for better gas diffusion and provide more active sites for gas adsorption while maintaining good electrical conductivity. The hierarchical ZnCoO microstructure is integrated on a low-power microheater platform without using binders or conductive additives. The hierarchical structure of the ZnCoO sensing material provides reliable electrical connection across the sensing electrodes. The resulting sensor exhibits an ultralow detection limit of 3 ppb toward formaldehyde with fast response and recovery as well as good selectivity to CO, H, and hydrocarbons such as n-pentane, propane, and CH. The sensor only consumes ∼5.7 mW for continuous operation at 300 °C with good long-term stability. The excellent sensing performance of this hierarchical structure based sensor suggests the advantages of combining such structures with microfabricated heaters for practical low-power sensing applications. 10.1021/acsami.6b11054
    Nonstoichiometric Co-rich ZnCo2O4 Hollow Nanospheres for High Performance Formaldehyde Detection at ppb Levels. Park Hyung Ju,Kim Jinmo,Choi Nak-Jin,Song Hyunjoon,Lee Dae-Sik ACS applied materials & interfaces Since metal oxide semiconductors were investigated as chemiresistors, rapid advances have been reported in this field. However, better performance metrics are still required, such as higher sensitivity and selectivity levels for practical applications. To improve the sensing performance, we discuss an optimal composition of the active sensing material, nonstoichiometric Co-rich ZnCo2O4, prepared by the partial substitution of Co(2+) into Zn(2+) in Co3O4 without altering a hollow sphere morphology. Remarkably, this Co-rich ZnCo2O4 phase achieved detection limits for formaldehyde as low as 13 ppb in experimental measurements and 2 ppb in theory, which were the lowest values ever reported from actual measurements at a working temperature of 225 °C. It was also unprecedented that the selectivity for formaldehyde was greatly enhanced with respect to the selectivity levels against other volatile organic compounds (VOCs). These excellent sensing performances are due to the optimal composition of the Co-rich ZnCo2O4 material with a proper hole concentration and well-organized conductive network. 10.1021/acsami.5b10862
    Miniaturised enzymatic conductometric biosensor with Nafion membrane for the direct determination of formaldehyde in water samples. Nguyen-Boisse Thanh-Thuy,Saulnier Joëlle,Jaffrezic-Renault Nicole,Lagarde Florence Analytical and bioanalytical chemistry A new conductometric enzyme-based biosensor was developed for the determination of formaldehyde (FA) in aqueous solutions. The biosensor was prepared by cross-linking formaldehyde dehydrogenase from Pseudomonas putida with bovine serum albumin in saturated glutaraldehyde vapours (GA) at the surface of interdigitated gold microelectrodes. Nicotinamide adenine dinucleotide cofactor (NAD(+)) was added in solution at each measurement to maintain enzyme activity. Addition of a Nafion layer over the enzyme modified electrode resulted in a significant increase of biosensor signal due to enhanced accumulation of protons generated by enzymatic reaction at the electrode surface. Different parameters affecting enzyme activity or playing a role in ionic transfer through the Nafion membrane were optimised. In optimal conditions (0.045 mg enzyme, 30 min exposure to GA, 0.3 μL of a 1% (v/v) Nafion solution deposit, measurement in 5 mM phosphate buffer pH 7 containing 20 μM NAD(+)), the biosensor signal was linear up to 10 mM FA, and the detection limit was 18 μM. Relative standard deviations calculated from five consecutive replicates of FA solutions were lower than 5% in the 1-10 mM range. The biosensor was successfully applied to the determination of FA in spiked water samples (tap water and Rhone river water), with recoveries in the 95-110% range. 10.1007/s00216-013-7197-2
    Detection of Waterborne and Airborne Formaldehyde: From Amperometric Chemosensing to a Visual Biosensor Based on Alcohol Oxidase. Sigawi Sasi,Smutok Oleh,Demkiv Olha,Gayda Galina,Vus Bohdan,Nitzan Yeshayahu,Gonchar Mykhailo,Nisnevitch Marina Materials (Basel, Switzerland) A laboratory prototype of a microcomputer-based analyzer was developed for quantitative determination of formaldehyde in liquid samples, based on catalytic chemosensing elements. It was shown that selectivity for the target analyte could be increased by modulating the working electrode potential. Analytical parameters of three variants of the amperometric analyzer that differed in the chemical structure/configuration of the working electrode were studied. The constructed analyzer was tested on wastewater solutions that contained formaldehyde. A simple low-cost biosensor was developed for semi-quantitative detection of airborne formaldehyde in concentrations exceeding the threshold level. This biosensor is based on a change in the color of a solution that contains a mixture of alcohol oxidase from the yeast , horseradish peroxidase and a chromogen, following exposure to airborne formaldehyde. The solution is enclosed within a membrane device, which is permeable to formaldehyde vapors. The most efficient and sensitive biosensor for detecting formaldehyde was the one that contained alcohol oxidase with an activity of 1.2 U·mL. The biosensor requires no special instrumentation and enables rapid visual detection of airborne formaldehyde at concentrations, which are hazardous to human health. 10.3390/ma7021055
    Fe-Doped ZnO/Reduced Graphene Oxide Nanocomposite with Synergic Enhanced Gas Sensing Performance for the Effective Detection of Formaldehyde. Guo Weiwei,Zhao Bangyu,Zhou Qilin,He Youzhou,Wang Zhongchang,Radacsi Norbert ACS omega Here, we report the synthesis of Fe-doped ZnO/reduced graphene oxide (rGO) nanocomposites for gas sensing applications via a one-pot hydrothermal process. A wide range of characterization techniques were used to confirm the successful fabrication of the nanocomposite material and to determine the surface area, the structural and morphological properties, the chemical composition, and the purity of the samples, such as Brunauer-Emmett-Teller, X-ray diffraction, Fourier transform infrared, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, and X-ray photoelectron spectroscopy techniques. The gas sensing performance to formaldehyde was studied thoroughly in a temperature-controlled test chamber. Compared to that of the bare ZnO and ZnO/rGO nanocomposites, the as-prepared 5 atom % Fe-doped ZnO/rGO nanocomposites presented significantly enhanced gas sensing performance to formaldehyde at relatively low temperatures. Whereas most formaldehyde sensors operate at 150 °C and can detect as low as 100 ppm concentrations, the presented sensor can detect 5 ppm formaldehyde at 120 °C. Its fast response-recovery time, high stability, and high selectivity make it an ideal sensor; however, it can exhibit degenerative gas sensing performance at elevated relative humidity. The enhanced gas sensing mechanism was explained as the synergic effect of rGO and Fe doping. The results demonstrate that Fe doping and decorating the nanocomposite with rGO are promising approaches for achieving a superior gas sensing performance for the development of ZnO gas sensors for the detection of formaldehyde. 10.1021/acsomega.9b00734
    Highly Sensitive Formaldehyde Detection Using Well-Aligned Zinc Oxide Nanosheets Synthesized by Chemical Bath Deposition Technique. Kim Eun-Bi,Seo Hyung-Kee Materials (Basel, Switzerland) Detection of formaldehyde is very important in terms of life protection, as it can cause serious injury to eyes, skin, mouth and gastrointestinal function if indirectly inhaled. Researchers are therefore putting effort into developing novel and sensitive devices. In this work, we have fabricated an electro-chemical sensor in the form of a field effect transistor (FET) to detect formaldehyde over a wide range (10 nM to 1 mM). For this, ZnO nanosheets (NS) were first synthesized by hydrothermal method with in-situ deposition on cleaned SiO₂/Si (100) substrate. The synthesized materials were characterized for morphology and purity and surface area (31.718 m²/g). The developed device was tested for formaldehyde detection at room temperature that resulted in a linear (96%) and reproducible response with concentration, sensitivity value of 0.27 mA/M/cm² with an error of ±2% and limit of detection (LOD) as 210 nM. 10.3390/ma12020250
    A High-Temperature, High-Throughput Method for Monitoring Residual Formaldehyde in Vaccine Formulations. Stallings Kendra D,Kitchener Rebecca L,Hentz Nathaniel G Journal of laboratory automation Formaldehyde has long been used in the chemical inactivation of viral material during vaccine production. Viral inactivation is required so that the vaccine does not infect the patient. Formaldehyde is diluted during the vaccine manufacturing process, but residual quantities of formaldehyde are still present in some current vaccines. Although formaldehyde is considered safe for use in vaccines by the Food and Drug Administration, excessive exposure to this chemical may lead to cancer or other health-related issues. An assay was developed that is capable of detecting levels of residual formaldehyde in influenza vaccine samples. The assay employs incubation of dosage formulation suspensions with hydralazine hydrochloride under mildly acidic conditions and elevated temperatures, where formaldehyde is derivatized to yield fluorescent s-triazolo-[3,4-a]-phthalazine. The assay has been traditionally run by high-performance liquid chromatography, where runtimes of 15 minutes per sample can be expected. Our laboratory has developed a plate-based version that drastically improved the throughput to a runtime of 96 samples per minute. The assay was characterized and validated with respect to reaction temperature, evaporation, stability, and selectivity to monitor residual formaldehyde in various influenza vaccine samples, including in-process samples. Heat transfer and evaporation will be especially considered in this work. Since the assay is plate based, it is automation friendly. The new assay format has attained detection limits of 0.01 µg/mL residual formaldehyde, which is easily able to detect and quantify formaldehyde at levels used in many current vaccine formulations (<5 µg/0.5-mL dose). 10.1177/2211068213504096
    Micro-Electromechanical Acoustic Resonator Coated with Polyethyleneimine Nanofibers for the Detection of Formaldehyde Vapor. Chen Da,Yang Lei,Yu Wenhua,Wu Maozeng,Wang Wei,Wang Hongfei Micromachines We demonstrate a promising strategy to combine the micro-electromechanical film bulk acoustic resonator and the nanostructured sensitive fibers for the detection of low-concentration formaldehyde vapor. The polyethyleneimine nanofibers were directly deposited on the resonator surface by a simple electrospinning method. The film bulk acoustic resonator working at 4.4 GHz acted as a sensitive mass loading platform and the three-dimensional structure of nanofibers provided a large specific surface area for vapor adsorption and diffusion. The ultra-small mass change induced by the absorption of formaldehyde molecules onto the amine groups in polyethyleneimine was detected by measuring the frequency downshift of the film bulk acoustic resonator. The proposed sensor exhibits a fast, reversible and linear response towards formaldehyde vapor with an excellent selectivity. The gas sensitivity and the detection limit were 1.216 kHz/ppb and 37 ppb, respectively. The study offers a great potential for developing sensitive, fast-response and portable sensors for the detection of indoor air pollutions. 10.3390/mi9020062
    On-line gaseous formaldehyde detection by a microfluidic analytical method based on simultaneous uptake and derivatization in a temperature controlled annular flow. Guglielmino Maud,Bernhardt Pierre,Trocquet Claire,Serra Christophe A,Le Calvé Stéphane Talanta This paper is focused on the improvement of a microfluidic analytical method for the detection of low airborne formaldehyde concentrations, based on only two distinct steps permitting to reduce the response time and to improve the compactness of the device. First, gaseous formaldehyde is trapped into an acetylacetone solution at 65°C through an annular liquid/gas flow and reacts immediately to form 3,5-Diacetyl-1,4-dihydrolutidine which is then quantified by colorimetry using a liquid core waveguide (LCW). To obtain an annular flow, 3 different hydrophilic silica capillaries of 320, 450 and 530µm ID were tested and the corresponding phase diagrams were obtained in the ranges of liquid and gas flows of 5-35µLmin and 5-35mLmin respectively. Finally, the analytical performances were determined using the lowest flow values of 5µLmin and 5NmLmin, ensuring an annular flow and increasing the microdevice autonomy. If the uptake yield of gaseous formaldehyde into the solution was close to 100%, only the 530µm ID capillary permits to obtain a reaction time long enough for a full conversion of formaldehyde into 3,5-Diacetyl-1,4-dihydrolutidine. With a LCW pathlength of 5cm, the microdevice response was perfectly linear in the range 0-154µgm with a detection limit of 1.8µgm. 10.1016/j.talanta.2017.05.038
    Reduced Graphene Oxide-Coated Si Nanowires for Highly Sensitive and Selective Detection of Indoor Formaldehyde. Song Longfei,Luo Linqu,Xi Yan,Song Jianjun,Wang Ying,Yang Liping,Wang Anqi,Chen Yunfa,Han Ning,Wang Fengyun Nanoscale research letters Although significant developments have been made in the low-concentration formaldehyde monitoring in indoor air by using gas sensors, they still suffer from insufficient performance for achieving ppb-level detection. In this work, <100> oriented Si nanowires (SiNWs) with high specific surface area were prepared via metal-assisted chemical etching method (MACE), and then were uniformly coated with graphene oxide (GO) followed by the subsequent reductive process in H/Ar atmosphere at 800 °C to obtain reduced graphene oxide (RGO). The RGO coating (RGO@n-SiNWs) obviously enhances SiNWs sensitivity to low-concentration formaldehyde, benefiting from the increased specific surface area, the sensitization effect of RGO, and the formation of p-n junction between SiNWs and RGO. Specifically, RGO@n-SiNWs exhibits a high response of 6.4 to 10 ppm formaldehyde at 300 °C, which is about 2.6 times higher than that of pristine SiNWs (~ 2.5). Furthermore, the RGO@n-SiNWs show a high response of 2.4 to 0.1 ppm formaldehyde which is the largest permissive concentration in indoor air, a low detection limit of 35 ppb obtained by non-linear fitting, and fast response/recovery times of 30 and 10 s. In the meanwhile, the sensor also shows high selectivity over other typical interfering gases such as ethanol, acetone, ammonia, methanol, xylene, and toluene, and shows a high stability over a measurement period of 6 days. These results enable the highly sensitive, selective, and stable detection of low-concentration formaldehyde to guarantee safety of indoor environment. 10.1186/s11671-019-2921-2
    Manipulating the Defect Structure (V) of InO Nanoparticles for Enhancement of Formaldehyde Detection. Gu Fubo,Li Chunju,Han Dongmei,Wang Zhihua ACS applied materials & interfaces Because defects such as oxygen vacancies (V) can affect the properties of nanomaterials, investigating the defect structure-function relationship are attracting intense attention. However, it remains an enormous challenge to the synthesis of nanomaterials with high sensing performance by manipulating V because understanding the role of surface or bulk V on the sensing properties of metal oxides is still missing. Herein, InO nanoparticles with different contents of surface and bulk V were obtained by hydrogen reduction treatment, and the role of surface or bulk V on the sensing properties of InO was investigated. The X-ray diffraction, ultraviolet-visible spectrophotometer, electron paramagnetic resonance, photoluminescence, Raman, X-ray photoelectron spectroscopy, Hall analysis, and the sensing results indicate that bulk V can decrease the band gap and energy barrier and increase the carrier mobility, hence facilitating the formation of chemisorbed oxygen and enhancing the sensing response. Benefiting from bulk V, InO-H10 exhibits the highest response, good selectivity, and stability for formaldehyde detection. However, surface V does not contribute to the improvement of formaldehyde-sensing performance, and the black InO-H30 with the highest content of surface V exhibits the lowest response. Our work provides a novel strategy for the synthesis of nanomaterials with high sensing performance by manipulating V. 10.1021/acsami.7b16832
    A new formaldehyde sensor from silver nanoclusters modified Tollens' reagent. Chaiendoo Kanokwan,Sooksin Sawarin,Kulchat Sirinan,Promarak Vinich,Tuntulani Thawatchai,Ngeontae Wittaya Food chemistry A selective colorimetric assay for detecting formaldehyde (FA) was proposed based on silver nanoclusters (AgNCs) templated by polymethacrylic acid (PMAA). The chemodosimeter was easily fabricated by the formation of Tollens' reagent in the presence of AgNCs (AgNCs@Tollens). The detection principle was based on the change in the color caused by the change in the particle size from nanoclusters (no LSPR) to nanoparticles (with LSPR) upon the reduction of Tollens' reagent by FA. In the presence of FA, the intensity of a new absorbance band with a maximum at a wavelength of 430 nm corresponding to the LSPR of the AgNPs linearly increased as a function of the FA concentration, exhibiting a color change that could be observed by the naked eye. This method provided a working range of 30-50 µM with lower detection limit (LOD) of 27.99 µM. The proposed method exhibited excellent selectivity towards FA over other aldehyde-containing compounds. 10.1016/j.foodchem.2018.02.030
    An electrochemical impedimetric sensor based on biomimetic electrospun nanofibers for formaldehyde. Dai Hong,Gong Lingshan,Xu Guifang,Li Xiuhua,Zhang Shupei,Lin Yanyu,Zeng Baoshan,Yang Caiping,Chen Guonan The Analyst Herein, simple molecular recognition sites for formaldehyde were designed on electrospun polymer nanofibers. In order to improve the conductivity of the electrospun polymer nanofibers, carbon nanotubes were introduced into the resulting nanofibers. By employing these functionalized nanocomposite fibers to fabricate a biomimetic sensor platform, an obvious change caused by recognition between recognition sites and formaldehyde molecules was monitored through electrochemical impedance spectroscopy (EIS). The experimental conditions were optimized and then a quantitative method for formaldehyde sensing in low concentration was established. The relative results demonstrated that the sensor based on biomimetic recognition nanofibers displays an excellent recognition capacity toward formaldehyde. The linear response range of the sensor was between 1 × 10(-6) mol L(-1) and 1 × 10(-2) mol L(-1), with the detection limit of 8 × 10(-7) mol L(-1). The presented research provided a fast, feasible and sensitive method for formaldehyde with good anti-interference capabilities and good stability, which could meet the practical requirement for formaldehyde assay. 10.1039/c4an02021a
    Separation and analysis of trace volatile formaldehyde in aquatic products by a MoO₃/polypyrrole intercalative sampling adsorbent with thermal desorption gas chromatography and mass spectrometry. Ma Yunjian,Zhao Cheng,Zhan Yisen,Li Jianbin,Zhang Zhuomin,Li Gongke Journal of separation science An in situ embedded synthesis strategy was developed for the preparation of a MoO3 /polypyrrole intercalative sampling adsorbent for the separation and analysis of trace volatile formaldehyde in aquatic products. Structural and morphological characteristics of the MoO3 /polypyrrole intercalative adsorbent were investigated by a series of characterization methods. The MoO3 /polypyrrole sampling adsorbent possessed a higher sampling capacity and selectivity for polar formaldehyde than commonly used commercial adsorbent Tenax TA. Finally, the MoO3 /polypyrrole adsorbent was packed in the thermal desorption tube that was directly coupled to gas chromatography with mass spectrometry for the analysis of trace volatile formaldehyde in aquatic products. Trace volatile formaldehyde from real aquatic products could be selectively sampled and quantified to be 0.43-6.6 mg/kg. The detection limit was achieved as 0.004 μg/L by this method. Good recoveries for spiked aquatic products were achieved in range of 75.0-108% with relative standard deviations of 1.2-9.0%. 10.1002/jssc.201400951
    Determination of Formaldehyde in Water Samples by High-Performance Liquid Chromatography with Methyl Acetoacetate Derivatization. Yoshikawa Kenji,Oshima Yusuke,Inagaki Ayaka,Sakuragawa Akio Bulletin of environmental contamination and toxicology A high-performance liquid chromatography method with methyl acetoacetate derivatization via the Hantzsch reaction was developed for the analysis of formaldehyde (HCHO) in several water samples. Under optimized conditions, HCHO was detected within 4 min and was not affected by excessive derivatization reagents. The calibration curve constructed from the peak height of HCHO was linear, with a correlation coefficient of 0.9998. The relative standard deviation of the peak height from ten replicates was 0.29%. The detection and quantitative limits were 0.96 µg/L and 3.16 µg/L, respectively. A recovery test of HCHO was performed to compare the developed method with the official analysis method (DNPH method). The developed method was used to determine the HCHO levels in several water samples (tap water, river water, and waste water). 10.1007/s00128-018-2461-y
    On-cartridge derivatisation using a calixarene solid-phase extraction sorbent for facile, sensitive and fast determination of formaldehyde in beer. Deng Zhifen,Hu Kai,Zhang Yongming,Zhao Wenjie,Wang Fei,Guo Ling,Zhang Wenfen,He Juan,Huang Yanjie,Zhang Shusheng Food chemistry This work demonstrates the successful application of an on-cartridge derivatisation procedure for facile, fast and sensitive determination of formaldehyde in beer by HPLC-UV. The derivatisation and solid-phase extraction (SPE) were integrated into a novel calixarene SPE sorbent: tetraazacalix[2]arene[2]triazine bonded silica gel. Specifically, 2,4-dinitrophenylhydrazine was adsorbed onto the sorbent in advance, based on the charge-transfer interaction between the macrocyclic molecule and nitrobenzenes. The method was optimised and validated: under the optimal conditions of derivatisation, SPE and HPLC separation, good linearity was obtained in the range of 0.080-3.2μgmL(-1) with a correlation coefficient of 0.9939, the limit of detection was 3.0ngmL(-1) (S/N=3), the limit of quantification was 10ngmL(-1) (S/N=10), and the recovery level using this method was desirable at 75-84%. The developed method was successfully applied to determine formaldehyde content in real beer samples; the results were in the range of 0.11-1.1μgmL(-1). 10.1016/j.foodchem.2016.05.069
    Development of Formaldehyde Biosensor for Determination of Formalin in Fish Samples; Malabar Red Snapper (Lutjanus malabaricus) and Longtail Tuna (Thunnus tonggol). Noor Aini Bohari,Siddiquee Shafiquzzaman,Ampon Kamaruzaman Biosensors Electrochemical biosensors are widely recognized in biosensing devices due to the fact that gives a direct, reliable, and reproducible measurement within a short period. During bio-interaction process and the generation of electrons, it produces electrochemical signals which can be measured using an electrochemical detector. A formaldehyde biosensor was successfully developed by depositing an ionic liquid (IL) (e.g., 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf])), gold nanoparticles (AuNPs), and chitosan (CHIT), onto a glassy carbon electrode (GCE). The developed formaldehyde biosensor was analyzed for sensitivity, reproducibility, storage stability, and detection limits. Methylene blue was used as a redox indicator for increasing the electron transfer in the electrochemical cell. The developed biosensor measured the NADH electron from the NAD⁺ reduction at a potential of 0.4 V. Under optimal conditions, the differential pulse voltammetry (DPV) method detected a wider linear range of formaldehyde concentrations from 0.01 to 10 ppm within 5 s, with a detection limit of 0.1 ppm. The proposed method was successfully detected with the presence of formalin in fish samples, Lutjanus malabaricus and Thunnus Tonggol. The proposed method is a simple, rapid, and highly accurate, compared to the existing technique. 10.3390/bios6030032
    Exploitation of pulsed flows for on-line dispersive liquid-liquid microextraction: Spectrophotometric determination of formaldehyde in milk. Nascimento Carina F,Brasil Marcos A S,Costa Susana P F,Pinto Paula C A G,Saraiva Maria Lúcia M F S,Rocha Fábio R P Talanta Formaldehyde is often added to foods as a preservative, but it is highly toxic to humans, having been identified as a carcinogenic substance. It has also been used for the adulteration of milk in order to diminish the bacteria count and increase the shelf life of the product. Herein, we present a green dispersive liquid-liquid microextraction procedure in a flow-batch system for the determination of formaldehyde in milk. Pulsed flows were exploited for the first time to improve the dispersion of the extractant in the aqueous phase. The Hantzsch reaction was used for the derivatization of formaldehyde and the product was extracted with the ionic liquid (IL) trihexyltetradecylphosphonium chloride with methanol as the disperser. The flow-batch chamber was made of stainless steel with the facility for resistive heating to speed up the derivatization reaction. Spectrophotometric measurements were directly carried out in the organic phase using an optical fiber spectrophotometer. The limit of detection and coefficient of variation were 100 μg L(-1) and 3.1% (n=10), respectively, with a linear response from 0.5 to 5.0 mg L(-1), described by the equation A=0.088+0.116CF (mg L(-1)) in which A is absorbance and CF is formaldehyde concentration in mg L(-1). The estimated recoveries of formaldehyde from spiked milk samples ranged from 91% to 106% and the slopes of the analytical curves obtained with reference solutions in water or milk were in agreement, thus indicating the absence of matrix effects. Accuracy was demonstrated by the agreement of the results with those achieved by the reference fluorimetric procedure at the 95% confidence level. The proposed procedure allows for 10 extractions per hour, with minimized reagent consumption (120 μL of IL and 3.5 μL acetylacetone) and generation of only 6.7 mL waste per determination, which contribute to the eco-friendliness of the procedure. 10.1016/j.talanta.2015.07.076
    Determination of formaldehyde in food and feed by an in-house validated HPLC method. Wahed P,Razzaq Md A,Dharmapuri S,Corrales M Food chemistry Formalin is carcinogenic and is detrimental to public health. The illegal addition of formalin (37% formaldehyde and 14% methanol) to foods to extend their shelf-life is considered to be a common practice in Bangladesh. The lack of accurate methods and the ubiquitous presence of formaldehyde in foods make the detection of illegally added formalin challenging. With the aim of helping regulatory authorities, a sensitive high performance liquid chromatography method was validated for the quantitative determination of formaldehyde in mango, fish and milk. The method was fit-for-purpose and showed good analytical performance in terms of specificity, linearity, precision, recovery and robustness. The expanded uncertainty was <35%. The validated method was applied to screen samples of fruits, vegetables, fresh fish, milk and fish feed collected from different local markets in Dhaka, Bangladesh. Levels of formaldehyde in food samples were compared with published data. The applicability of the method in different food matrices might mean it has potential as a reference standard method. 10.1016/j.foodchem.2016.01.136
    Visual detection of formaldehyde by highly selective fluorophore labeling via gold(III) complex-mediated three-component coupling reaction. Wong Kong-Fan,Deng Jie-Ren,Wei Xiao-Qun,Shao Shi-Ping,Xiang Da-Peng,Wong Man-Kin Organic & biomolecular chemistry A novel method for visual detection of formaldehyde with excellent selectivity via a gold(iii) complex-mediated three-component coupling reaction of resin-linked sterically bulky amines and fluorescent alkynes has been developed. 10.1039/c5ob00966a
    Rapid screening of formaldehyde in food using paper-based titration. Taprab Natchanon,Sameenoi Yupaporn Analytica chimica acta A simple paper-based analytical device (PAD) has been developed to rapidly detect formaldehyde (FA) in food samples. The analysis was based on sulfite assay where FA reacted with excess sulfite to generate sodium hydroxide (NaOH) that was quantified on PAD using acid-base titration. The PAD consisted of a central sample zone connected to ten reaction and detection zones. All detection zones were pre-deposited with polyethylene glycol (PEG) with phenolphthalein (Phph) as an indicator. Reaction zones contained different amounts of the titrant, potassium hydrogen phthalate (KHP). On flowing into reaction zones, the NaOH product reacts with KHP to reach the end point. In the presence of excess NaOH, unneutralized NaOH reached the detection zone and caused Phph color change from colorless to pink. In contrast, when NaOH was less than KHP, the detection zone remained colorless. Concentration of FA can be quantified from the number of pink detection zone(s) which were correlated with a known amount of pre-deposited KHP on the PAD. Total analytical process could be completed within 5 min. Areas of each zone and amounts of reagents added to the corresponding zones of the PAD were optimized to obtain reproducible and accurate results. PAD gave ranges of FA detection of 100-1000 mg L with an interval of 100 mg L and the limit of detection (LOD) was 100 mg L. PADs were stable for up to a month under dark and cold conditions. Analysis of FA in food samples using PAD agreed well with those from the classical sulfite assay. 10.1016/j.aca.2019.03.063
    A biodegradable colorimetric film for rapid low-cost field determination of formaldehyde contamination by digital image colorimetry. Wongniramaikul Worawit,Limsakul Wadcharawadee,Choodum Aree Food chemistry A biodegradable colorimetric film was fabricated on the lid of portable tube for in-tube formaldehyde detection. Based on the entrapment of colorimetric reagents within a thin film of tapioca starch, the yellow reaction product was observed with formaldehyde. Intensity of the blue channel from the digital image of yellow product showed a linear relationship in the range of 0-25 mg L with low detection limit of 0.7 ± 0.1 mg L. Inter-day precision of 0.61-3.10%RSD were obtained with less than 4.2% relative error from control samples. The developed method was applied for various food samples in Phuket and formaldehyde concentration range was non-detectable to 1.413 mg kg. The quantified concentrations of formaldehyde in fish and squid samples provided relative errors of -7.7% and +10.8% compared to spectrophotometry. This low cost sensor (∼0.04 USD/test) with digital image colorimetry was thus an effective alternative for formaldehyde detection in food sample. 10.1016/j.foodchem.2018.01.021
    A Self-Powered Biosensor with a Flake Electrochromic Display for Electrochemical and Colorimetric Formaldehyde Detection. Sun Xiaoxuan,Zhang He,Hao Shuai,Zhai Junfeng,Dong Shaojun ACS sensors The formaldehyde biosensors with the features of cost effectiveness, high specificity, easy operation, and simplicity are urgently desired in routing and field detection of formaldehyde. Here, we report a new design of an enzymatic self-powered biosensor (ESPB) toward formaldehyde detection. The ESPB involves a formaldehyde dehydrogenase/poly-methylene green/buckypaper bioanode as the sensing electrode and a Prussian blue/Au nanoparticles/carbon fiber paper cathode as the electrochromic display. Formaldehyde acts as the fuel to drive the ESPB, relying on that the concentration of formaldehyde can be determined with the ESPB by both directly measuring the variance in short circuit current and observing the color change of the cathode. By measuring the variance in short circuit current, a linear detection range from 0.01 to 0.35 mM and a calculated detection limit of 0.006 mM are obtained, comparable to or better than those reported before. The color change of the cathode can be distinguished easily and exactly via the naked eye after immersing the ESPB in formaldehyde solution for 90 s with the concentration up to 0.35 mM, covering the permissive level of formaldehyde in some standards associated with environmental quality control. Specially, the formaldehyde concentration can be precisely quantified by analyzing the color change of the cathode digitally using the equation of /( + + ). In the following test of real spiked samples of tap water and lake water, the recovery ratios of formaldehyde with the concentrations from 0.010 to 0.045 mM are tested to be between 95 and 100% by both measuring the variance in short circuit current and analyzing the color change of the cathode digitally. In addition, the ESPB exhibits negligible interference from acetaldehyde and ethanol and can be stored at 4 °C for 21 days with a loss of less than 8% in its initial value of short circuit current. Therefore, the ESPB with the capability of working like disposable test paper can be expected as a sensitive, simple, rapid, cost-effective colorimetric method with high selectivity in routing and field formaldehyde detection. 10.1021/acssensors.9b00917
    A simple naphthalene-based fluorescent probe for high selective detection of formaldehyde in toffees and HeLa cells via aza-Cope reaction. Xu Junchao,Zhang Yue,Zeng Lintao,Liu Jinbiao,Kinsella Joseph M,Sheng Ruilong Talanta A simple naphthalene-based fluorescent probe (AENO) for formaldehyde (FA) was successfully synthesized, which exhibited a significant fluorescence turn-on response towards FA in aqueous solution. The probe could quantitatively determine the concentration of FA (0-1.0mM) with excellent selectivity, high sensitivity and low limit of detection (0.57µM). The sensing mechanism was proposed as 2-aza-Cope rearrangement for AENO after reaction with FA, which was confirmed by (1)H NMR, HR-MS, FT-IR, UV-vis and fluorescence spectra. The probe has been employed to determine the FA contents in several commercially available toffee samples with satisfactory performance. Thus, AENO might be used as a promising tool for quantitative detection of FA in food. Furthermore, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing/imaging the FA trace/transportation in cancer cells. 10.1016/j.talanta.2016.08.010
    A New Environmentally-Friendly Colorimetric Probe for Formaldehyde Gas Detection under Real Conditions. Martínez-Aquino Carlos,Costero Ana M,Gil Salvador,Gaviña Pablo Molecules (Basel, Switzerland) A new environmentally-friendly, simple, selective and sensitive probe for detecting formaldehyde, based on naturally-occurring compounds, through either colorimetric or fluorescence changes, is described. The probe is able to detect formaldehyde in both solution and the gas phase with limits of detection of 0.24 mM and 0.7 ppm, respectively. The probe has been tested to study formaldehyde emission in contaminated real atmospheres. The supported probe is easy to use and to dispose, and is safe and suitable as an individual chemodosimeter. 10.3390/molecules23102646
    Enhancing the evanescent field in TiO/Au hybrid thin films creates a highly sensitive room-temperature formaldehyde gas biosensor. Kim Jina,Hong Ung Gi,Choi Youngbo,Hong Surin Colloids and surfaces. B, Biointerfaces Discovery of the relationship between disease and the volatile organic compounds (VOCs) contained in respiratory gas in human bodies has led to the development of analytical methods and detection systems that can be used for diagnosis. Recent studies, however, have encountered problems using these diagnostic tools when operation temperatures are too high and the detection range of the gas concentration falls beyond the limits of diagnosis criteria. In this study, we propose a highly sensitive surface plasmon resonance (SPR) biosensor that is based on an enhanced evanescent wave technique and can be operated at room temperature (RT) for the detection of formaldehyde. The detection system relies on an improved Kretschmann configuration with an enhanced signal transducer algorithm and a novel microfluidic gas channel that can accomplish highly sensitive quantification using ligand-modified TiO/Au hybrid thin film as a RT-operated sensing interface. The detection of formaldehyde was chosen to test this concept, because formaldehyde is a known breast cancer biomarker that exists in human exhalation. When the interface of our sensing system was exposed to formaldehyde, the interaction between the ligand and the analyte produced changes in the SPR profiles of the gold thin film. The linear range of the detection system was 0.2-1.8 ppm with limit of detection at 0.2 ppm. The diagnostic criteria suggest this method could be applied to biological monitoring and diagnostics. 10.1016/j.colsurfb.2019.06.033
    An Aggregation-Induced Emission-Based "Turn-On" Fluorescent Probe for Facile Detection of Gaseous Formaldehyde. Zhao Xujie,Ji Chendong,Ma Le,Wu Zhen,Cheng Wenyu,Yin Meizhen ACS sensors Gaseous formaldehyde (FA), a common indoor pollutant, presents a serious threat to human health. As an efficient tool for FA detection, fluorescent probes exhibit the advantages of low cost, ease of use, facile operation, etc. However, previously developed FA fluorescent probes are mostly based on fluorophores with aggregation-caused quenching features and thus require dispersion in solvent to detect FA. In this study, a fluorescent probe (TPE-FA) based on an aggregation-induced emission (AIE) fluorophore (tetraphenylethylene) has been developed for facile detection of gaseous FA through a fluorescence "turn-on" response. TPE-FA reacts with FA through 2-aza-Cope sigmatropic rearrangement. Based on the AIE features of TPE-FA, we fabricated a portable solid sensor, FA test plate, by directly loading TPE-FA on high performance thin-layer chromatography silica gel plate. The FA test plate achieved sensitive, selective, and quantitative detection of gaseous FA. The detection limit (0.036 mg/m) of the FA test plate is lower than the air quality guideline value of gaseous FA (0.1 mg/m) recommended by WHO. As a solid sensor for gaseous FA, the FA test plate based on AIE molecule is portable, which enables safer and more convenient use and transport compared to solution-based sensors. 10.1021/acssensors.8b00664
    Supramolecular nano-sniffers for ultrasensitive detection of formaldehyde. Akshath Uchangi Satyaprasad,Bhatt Praveena Biosensors & bioelectronics Supramolecular nanoparticle hybrids for biosensing of analytes have been a major focus due to their tunable optical and surface properties. Quantum dots-Gold nanoparticle (QDs-GNP) based FRET probes involving turn on/off principles have gained immense interest due to their specificity and sensitivity. Recent focus is on applying these supramolecular hybrids for enzyme operated biosensors that can specifically turn-on fluorescence induced by co-factor or product formed from enzymatic reaction. The present study focuses on locking and unlocking the interaction between QD-GNP pair leading to differential fluorescent properties. Cationic GNPs efficiently quenched the anionic QD fluorescence by forming nanoparticle hybrid. Quenching interaction between QD-GNP pair was unlocked by NADH leading to QD fluorescence turn-on. This phenomenon was applied for the successful detection of formaldehyde using NAD dependent formaldehyde dehydrogenase. The proposed nano-sniffer could successfully detect formaldehyde from 0.001 to 100000ng/mL (R = 0.9339) by the turn off-turn on principle. It could also detect formaldehyde in fruit juice and wine samples indicating its stability and sensitivity in real samples. The proposed nanoprobe can have wide applications in developing enzyme biosensors in future. 10.1016/j.bios.2017.09.010
    Ultrafast and Efficient Detection of Formaldehyde in Aqueous Solutions Using Chitosan-based Fluorescent Polymers. Li Ping,Zhang Dong,Zhang Yuchong,Lu Wei,Wang Wenqin,Chen Tao ACS sensors Detection of a toxic formaldehyde (HCHO) pollutant in aqueous solutions is of significant importance, because HCHO is widely found in aquatic food because of illicit addition or improper storage. Many small-molecule-based fluorescent probes, which rely on HCHO-specific formaldehyde-amine condensation or the aza-Cope rearrangement reaction, have been developed in terms of facile operation and high selectivity. However, some primary challenging issues are the restricted sensitivity and long equilibrium response time caused by the slow chemical reaction between these small-molecule-based sensors and low-concentration HCHO pollutant in testing samples. Herein, a robust hydrophilic hydrazino-naphthalimide-functionalized chitosan (HN-Chitosan)-based polymeric probe is reported, which takes advantage of specific chemical reaction between HCHO and grafted hydrazino-naphthalimide groups to trigger a "turn-on" fluorescence response. Superior to its small-molecule analogs, HN-Chitosan is based on random coil polymer chains of biopolymeric chitosan, which is thus capable of employing the cooperative binding effect of multiple hydrazino-naphthalimide recognition sites and adjacent hydroxyl groups to "enrich" the low-concentration HCHO pollutant around the polymer chains via weak supramolecular interactions. Therefore, the HCHO-specific chemical reaction with grafted hydrazino-naphthalimide groups is significantly accelerated, resulting in the unprecedented ultrafast equilibrium fluorescence response (less than 1 min) and high sensitivity. Encouraged by its satisfying sensitivity, selectivity, fast response, and wide linear detection range, we successfully expand its application to real-world food and water analysis. In view of the modular design principle of our polymeric probe, the proposed strategy could be generally applicable to construct powerful polymeric probes for ultrafast detection of other important pollutants. 10.1021/acssensors.8b00835