Determination of ultra-trace formaldehyde in air using ammonium sulfate as derivatization reagent and capillary electrophoresis coupled with on-line electrochemiluminescence detection

Selective determination of formaldehyde by high-performance liquid chromatography with porous graphitic carbon column using N,N'-bis(9-anthrylmethyl)propane-1,3-diamine as derivatizing reagent

Aromatic compounds containing two secondary amino groups were designed and prepared as new derivatizing reagents for aldehydes. One of them, N,N'-bis(9-anthrylmethyl)propane-1,3-diamine (APD), could achieve selective determination of formaldehyde (FA) on a porous graphitic carbon (PGC) column using xylenes, chlorobenzene, and 1-chloronaphthalene as mobile phases by high-performance liquid chromatography (HPLC). The APD-FA derivative was eluted from the PGC column, while the other APD-aldehyde derivatives remained on the column during the HPLC measurements. This specific elution was not observed using mobile phases such as acetonitrile, 1,4-dioxane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, chloroform, benzene, toluene, benzyl alcohol, 2-ethyl-1-hexanol, and pyridine. The APD-FA derivative had a six-membered ring of two tertiary amines identified using ¹H NMR spectroscopy. When the π-π interaction of the solvent molecule of the mobile phase with PGC overcame that between the APD-FA derivative and PGC, the APD-FA derivative could be eluted from the column. The best resolution between the peak of the APD-FA derivative and that of free APD was observed when using o-xylene. The optimum derivatization and the HPLC conditions for selective HPLC determination of FA were to conduct the derivatization of FA by heating in an aqueous phase with APD in o-xylene at 100 °C. In this method, FA could be derivatized with APD at a mildly neutral pH of 6.7, unlike the low pH required for the derivatization of aldehydes with 2,4-dinitrophenylhydrazine (DNPH), which is commonly used for the derivatization of aldehydes. The detection and quantification limits of FA were 0.8 and 3.5 ng mL^-1 in this HPLC method with fluorescent detection, respectively. This selective HPLC method could be applied to the determination of FA in various water samples. It was found that only APD among the derivatizing reagents containing two secondary diamines was useful for the selective determination of FA.

Analytical derivatizations in environmental analysis

Analytical derivatization is a technique that alters the structure of an analyte and produces a product more suitable for analysis. While this process can be time-consuming and add reagents to the procedure, it can also facilitate the isolation of the analyte(s), enhance analytes' stability, improve separation and sensitivity, and reduce matrix interferences. Since derivatization is a functional group analysis, it improves selectivity by separating reactive from neutral compounds during sample preparation. This technique introduces detector-orientated tags into analytes that lack suitable physicochemical properties for detection at low concentrations. Notably, many regulatory bodies, especially those in the environmental field, require these characteristics in analytical methods. This review focuses on note-worthy analytical derivatization methods employed in environmental analyses with functional groups, phenol, carboxylic acid, aldehyde, ketone, and thiol in aqueous, soil, and atmospheric sample matrices. Both advantages and disadvantages of analytical derivatization techniques are discussed. In addition, we discuss the future directions of analytical derivatization methods in environmental analysis and the potential challenges.

Electrochemiluminescence of Ru(bpy)32+/thioacetamide and its application for the sensitive determination of hepatotoxic thioacetamide

Thioacetamide (TAA) is a well-known hepatotoxic substance, so it is important to determine its presence and content in food and environmental samples. Herein, we report a highly sensitive determination method for TAA based on the electrochemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)32+) for the first time by using TAA as a new coreactant for Ru(bpy)32+ ECL via an anodic route. The developed Ru(bpy)32+-TAA ECL system allows the determination of TAA with a good dynamic linear range and low limit of detection (LOD) of 0.1 μM to 1000 μM and 0.035 μM (3σ/m), respectively. In addition, the established ECL system can be applied to detect TAA in fruit juice and waste water samples with outstanding recoveries.

A high-response formaldehyde sensor based on fibrous Ag-ZnO/In2O3 with multi-level heterojunctions

Timely detection of formaldehyde is pivotal because formaldehyde is slowly released from the indoor decorative materials, jeopardizing our healthy. Herein, a high-response formaldehyde gas sensor based on Ag-ZnO/In₂O₃ nanofibers was successfully fabricated. Compared with all the control samples, the hybrid exhibits superior sensitivity (0.65 ppm^-1), excellent selectivity (≥ 12.5) and durable stability (the deviation value ≤ 3%). Particularly, an ultra-high response value of about 186 towards 100 ppm of formaldehyde at 260 °C was achieved, heading the list of outstanding candidates. Additionally, the limit of detection is as low as 9 ppb. The enhanced gas sensing properties can be mainly attributed to multi-level heterojunctions (n-n heterojunction and Ohmic junction) and the "spill-over" effect of Ag, ultimately increasing the adsorption of gas molecules on the surface of sensing material. This work verifies that proper design of multi-level heterojunctions significantly upgrade the sensing performance.

Simultaneous enrichment and analysis of tobacco alkaloids by microextraction coupled with mass spectrometry using a poly (N-isopropyl-acrylamide-co-divinyl-benzene-co-N, N'-methylene diacrylamide) monolithic column

Herein, we realized the simultaneous online detection of six tobacco alkaloids (TAs) by in-tube solid-phase microextraction (In-tube SPME) coupled with mass spectrometry by a rapid, sensitive, and matrix effect-free method requiring no chromatographic separation and only minimal sample pre-treatment. A poly (N-isopropylacrylamide-co-divinylbenzene-co-N, N'-methylenediacrylamide) [Poly (NIPAAm-co-DVB-co-MBAA)] monolithic column was designed according to the chemical structures of selected TAs and used as an extraction medium engaging in hydrophobic, π-π, and hydrogen bonding interactions with analytes, allowing them to be effectively extracted. A number of important parameters were systematically optimized to achieve maximal extraction efficiency. The ion intensity of the TAs signals obtained by in-tube SPME-MS were higher than the direct MS mode by about 400 folds with the signal-to-noise ratio improved by 2-7 folds. The detection limits of the six TAs were determined as 1.99-4.06 ng g^-1, with good linearity with correlation coefficients exceeding 0.99 obtained under optimal extraction conditions. Besides, TA recoveries in cigarette tobacco spiked at three concentration levels were in the range of 76.4-100.2%, and the corresponding RSDs (n = 5) were obtained as 4.32-7.16%. The extraction performance of the poly (NIPAAm-co-DVB-co-MBAA) monolithic column was well reproducible, with intra- or inter-day precision RSDs determined not to exceed 7.38%. Finally, no marked matrix effects were observed when the developed method was applied to the analysis of both high-abundance and trace-level TAs in practical samples, and the above technique was therefore concluded to be well suited for the detection of TAs in cigarette tobacco or other products.

Nanometer-Thick Newton Black Film for Selective Formaldehyde Gas Detection

A fluorescence spectroscopic assay using Newton black film (NBF) for sensitive and selective detection of gaseous formaldehyde at room temperature is reported. The method relies on the Hantzsch reaction of formaldehyde with ammonium citrate and acetylacetone, plus a combination of the large surface area-to-volume ratio (5 × 10⁸ m^-1) and efficient uptake of gas by the nanometer-thick aqueous core of NBF. The assay has a limit of detection (LOD) of 4 ppb, a linear signal-to-concentration correlation up to 300 ppb of HCHO gas in the air, and a nonlinear monotonic increasing correlation in the range of 300 ppb to 1.2 ppm. It is unaffected by relevant analytes such as acetaldehyde, benzaldehyde, acetone, and propionaldehyde. We also demonstrate the sensing of formaldehyde outgassing from a plywood sample using this method and the results agree with the factory specifications.

Applications of capillary electrophoresis with chemiluminescence detection in clinical, environmental and food analysis. A review

This paper reviews the latest developments and analytical applications of chemiluminescence detection coupled to capillary electrophoresis (CE-CL). Different sections considering the most common CL systems have been included, such as the tris(2,2'-bipyridine)ruthenium(II) system, the luminol and acridinium derivative reactions, the peroxyoxalate CL or direct oxidations. Improvements in instrumental designs, new strategies for improving both resolution and sensitivity, and applications in different fields such as clinical, pharmaceutical, environmental and food analysis have been included. This review covers the literature from 2010 to 2015.

The preparation of high-quality water-soluble silicon quantum dots and their application in the detection of formaldehyde

This paper reports the synthesis of water-soluble fluorescence silicon quantum dots (Si QDs) through a hydrothermal route with urea propyl triethoxysilane (UPTES) as the source of silicon and sodium citrate as the deoxidizer.

A three-dimensional silver nanoparticles decorated plasmonic paper strip for SERS detection of low-abundance molecules

The fabrication of SERS substrates, which can offer the advantages of strong Raman signal enhancement with good reproducibility and low cost, is still a challenge for practical applications. In this work, a simple three-dimensional (3D) paper-based SERS substrate, which contains plasmonic silver-nanoparticles (AgNPs), has been developed by the silver mirror reaction. This paper strip was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), etc. Pretreatment of the paper as well as the reaction time, temperature, and reagent concentrations for the silver mirror reaction were varied for further studies. With the optimized experimental parameters, the AgNPs synthesized and distributed in-situ on the paper strip could give more favorable SERS performance. The limit of detection (LOD) as low as 10(-11)M for Rhodamine 6G (R6G) and 10(-9)M for p-aminothiophenol (p-ATP) plus wide linear range for the log-log plot of Raman intensity versus analyte concentration were achieved. The detection of R6G in rain water was also carried out successfully. The merits of this protocol include low cost, easy operation, high sensitivity and acceptable stability, which make it ideal for the detection of environmental samples in trace amounts.

Investigation on formaldehyde release from preservatives in cosmetics

OBJECTIVE

To understand formaldehyde residue in cosmetics, an investigation on formaldehyde release from eight preservatives (methenamine - MA, paraformaldehyde - PF, poly(p-toluenesulfonamide-co-formaldehyde) -PTSAF, quaternium-15 - QU, imidazolidinyl urea - IU, diazolidinyl urea - DU, dimethyloldimethyl hydantoin - DMDM and bronopol - BP) under various conditions was performed.

METHODS

The concentration of released formaldehyde was determined by high-performance liquid chromatography with photodiode array detection after derivatization with 2,4-dinitrophenylhydrazine.

RESULTS

The amounts of formaldehyde release were in the order of PF > DU > DMDM ≈ QU ≈ IU > MA > BP > PTSAF. The releasing amounts of formaldehyde were the highest in the presence of aqueous matrices for the releasers except QU and IU, and the releasing effect was also relative to pH. More formaldehyde was released with longer storage time and higher temperature. Furthermore, all preservatives in cosmetic matrices released fewer amounts of formaldehyde than in pure aqueous or organic matrices, and the formaldehyde-releasing amounts were also cosmetic specific.

CONCLUSION

Formaldehyde release was dependent on the matrix, pH, time and mainly temperature, and the releasing effect was also cosmetic specific.

Determination of gibberellins in soybean using tertiary amine labeling and capillary electrophoresis coupled with electrochemiluminescence detection

A novel sensitive method based on tertiary amine labeling for the analysis of gibberellins (GAs) by capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection was proposed. GA3 was tagged with 2-(2-aminoethyl)-1-methylpyrrolidine (AEMP) using N, N'-dicyclohexylcarbodiimide (DCC) and 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine (HOOBt) as coupling agents in acetonitrile to produce GA3-AEMP-derivative. The GA3-AEMP-derivative was injected into CE by electrokinetic injection and detected by Ru(bpy)3(2+)-based ECL. The parameters affecting derivatization, detection and separation such as concentration of reactants, detection potential, pH and concentration of separation buffer, were investigated in detail. Under optimum conditions, the linear concentration range for GA3 was from 2.0×10(-7) to 1.28×10(-4)M with a correlation coefficient of 0.9997. The detection limit was 8×10(-8)M (S/N=3). The relative standard deviations of migration time, peak intensity and peak area for nine continuous injections of 2.0×10(-5)M GA3-AEMP-derivative were 1.0%, 2.1% and 4.2%, respectively. The developed approach was successfully applied to the determination of total GAs in the stem, leaf and seed of soybean (Glycine max [L.] Merr.) with recoveries in the range from 89.6% to 99.3%.

Formaldehyde gas sensors: a review

Many methods based on spectrophotometric, fluorometric, piezoresistive, amperometric or conductive measurements have been proposed for detecting the concentration of formaldehyde in air. However, conventional formaldehyde measurement systems are bulky and expensive and require the services of highly-trained operators. Accordingly, the emergence of sophisticated technologies in recent years has prompted the development of many microscale gaseous formaldehyde detection systems. Besides their compact size, such devices have many other advantages over their macroscale counterparts, including a real-time response, a more straightforward operation, lower power consumption, and the potential for low-cost batch production. This paper commences by providing a high level overview of the formaldehyde gas sensing field and then describes some of the more significant real-time sensors presented in the literature over the past 10 years or so.