Determination Of Formaldehyde In Air Research Articles

Responsive photonic hydrogel for colorimetric detection of formaldehyde

Formaldehyde (FA) can damage DNA, cause liver and kidney dysfunction, and ultimately lead to malignant tumors. Therefore, it is essential to develop a method that can conveniently detect FA with high detection sensitivity. Here, a responsive photonic hydrogel was prepared by embedding three-dimensional photonic crystal (PC) into amino-functionalized hydrogel to construct a colorimetric sensing film for FA. The amino groups on the polymer chains of the photonic hydrogel reacts with FA to increase the crosslinking density of the hydrogel, resulting in its volume shrinkage and a decrease in microsphere spacing of the PC. That causes the reflectance spectra blue-shift of more than 160 nm and color change from red to cyan for the optimized photonic hydrogel, achieving the sensitive, selective and colorimetric detection of FA. The constructed photonic hydrogel shows good accuracy and reliability for practical determination of FA in air and aquatic products, providing a new strategy for designing other target analytes responsive photonic hydrogels.

Comparison of Methods for the Determination of Formaldehyde in Air

ABSTRACTDifferent methods have been used for the determination of the amount of formaldehyde present in the air. The Hantzsch method uses derivatization with acetyl acetone, and the fluorescence signal of the resulting chromophore is highly selective for formaldehyde. The 2,4-dinitrophenylhydrazine procedure allows measuring of carbonyl compounds in combination with high-performance liquid chromatography. In contrast, the 3-methyl-2-benzothiazolonehydrazone method delivers the sum of aliphatic aldehydes, although it is reported to be selective for formaldehyde. To compare the performance of these methods, 13 samples of wooden furniture were measured. Further characterization was performed with a formaldehyde source and one oriented-strand board. As expected, the results of the 2,4-dinitrophenylhydrazine and Hantzsch methods provided excellent correlation. However, the formaldehyde concentrations obtained from the 3-methyl-2-benzothiazolonehydrazone method showed almost no correlation with the 2,4-dinitrophenylhydrazine and Hantzsch values. The results demonstrated that there was significant error in calculation with the use of the 3-methyl-2-benzothiazolonehydrazone method for determining the presence of a specific aliphatic aldehyde in a mixture of volatile organic compounds in the air. In addition, emission tests of an artificial formaldehyde source revealed excessively high concentrations of formaldehyde with the 3-methyl-2-benzothiazolonehydrazone method. Therefore, it was found that the 3-methyl-2-benzothiazolonehydrazone method was not suitable for the determination of the presence of formaldehyde in the air due to interferences of other organic compounds and systematic analytical artifacts.

A Sensitive Formaldehyde Sensor Based on Cataluminescence Coupled with Thermal Desorption

A sensitive cataluminescence-based detecting technology using nanosized Mo4V6Ti10O47 as a probe was proposed for determination of formaldehyde in air. Trace formaldehyde was firstly absorbed on active carbon at room temperature to concentrate, then desorbed at 75°C to determine. The method showed high selectivity to formaldehyde at wavelength of 575nm, satisfying activity at temperature of 260°C and good stability at carrier flow rate of 145 ml/min. The linear range of CTL intensity versus concentration of formaldehyde was 0.04~78 mg/m3, and the detection limit (3σ) was 0.02 mg/m3. The recovery of artificial sample was 96.8%-103.4% by this method. There was no response to CO, CO2, SO2, NH3, methanol, ethanol, benzene, toluene and xylenes.

Determination of formaldehyde in air in selected hospital-histopathology laboratories in Cagayan de Oro, Philippines

The study focused on the occupational exposure of gaseous formaldehyde (HCHO) in selected hospital-histopathology laboratories in Cagayan de Oro. This was carried to estimate the potential levels of HCHO during gross-cutting period using absorbent medium between two time intervals. Modified passive sample set-ups of 2,4-dinitrophenylhydrazine (DNPH) and DNPH-coated silica were used for air sample collection between 1 h and 3 h intervals and were analyzed spectrometrically. Infrared (IR) analysis for DNPH-coated silica sample showed relevant peaks of the known IR spectra of formaldehyde hydrazone: 1,600–1,636 cm −1 (C N); 1,000–1,350 cm −1 (C N); 2,945–2,900 cm −1 (aliphatic stretch); 3,218–3,080 cm −1 (NH N); and 880–900 cm −1 (meta disubstituted aromatic). Generally, gaseous HCHO concentrations in three histopathology laboratories during its gross-cutting period exceeded the recommended exposure ceiling limits of American Conference of Industrial Hygienists (ACGIH) and United States Department of Labor-Occupational Safety and Health Administration (USDOL-OSHA) (0.3–0.75 ppm). Absorbing efficiency of DNPH set-up was statistically different from that of DNPH-coated silica set-up. Increased concentration was observed for the 3 h interval using DNPH-coated (0.93 ± 0.32 ppm (Hospital A), 0.80 ± 0.59 ppm (Hospital B), and 1.03 ± 0.36 ppm (Hospital C)). Thus, the installation of exhausts ventilation system was seen necessary to minimize occupational exposure.

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

The reaction between formaldehyde and ammonium ion to produce hexamethylenetetramine is well known. The reaction conditions are very easily controlled in situ and the experiment operation is very simple. However, such derivatization reaction for trace formaldehyde determination using capillary electrophoresis (CE) electrochemiluminescence (ECL) has not been reported before. In this study, the application of ammoniun sulfate as derivatization reagent to in-situ determination of formaldehyde in air was reported. Based on ECL enhancement of tris(2,2′-bipyridyl)ruthenium(II) with hexamethylenetetramine, a novel approach for the determination of ultra-trace formaldehyde in air using CE coupled with on-line ECL of tris(2,2′-bipyridyl)ruthenium(II) has been developed. The parameters affecting separation and detection such as detection potential, concentration and pH of phosphate buffer, and electrokinetic voltage, were investigated. Under the optimal conditions, the linear concentration range of formaldehyde in air was from 0.48μg/m3 to 96mg/m3 (linear range covering 5 orders of magnitude). The limit of detection (3σ) was 0.15μg/m3. The relative standard deviations of peak height and migration time for six consecutive injection of 1ng/mL formaldehyde derivative were 0.9% and 0.8%, respectively. The recoveries of formaldehyde in air were between 99.3% and 101%.

A novel and sensitive formaldehyde gas sensor utilizing thermal desorption coupled with cataluminescence

Abstract A highly sensitive gas sensor based on thermal desorption coupled with cataluminescence (TD/CTL) using TiO 2 -Y 2 O 3 (mass ratio 1:3) as a probe was firstly proposed for the determination of formaldehyde in air. Quantitative analysis was performed at an optimal adsorbent of active carbon, thermal desorption temperature of 140 °C, catalytic temperature of 195 °C, a wavelength of 490 nm and a flow rate of 280 mL/min. The linear range of CTL intensity versus concentration of formaldehyde was 0.026–1.30 mg/m 3 ( r = 0.9990, n = 7), and the detection limit (3 σ ) was 0.01 mg/m 3 . There was no or weak response to foreign substances, such as benzene, ethanol, chloroform, carbon tetrachloride, toluene, dimethylbenzene and n -hexane. This proposed formaldehyde gas sensor showed the high sensitivity, rapid response, good stability, and allowed on-line monitoring of formaldehyde in air.

Determination of picomole amounts of formaldehyde in air and bio-fluids based on its enhanced myoglobin-luminol chemiluminescence reaction

A rapid and sensitive chemiluminescence determination of formaldehyde with the flow injection technique was presented. It was found that the specific binding of myoglobin with formaldehyde could accelerate the electron transfer between myoglobin and luminol, thus producing quicker and more efficient chemiluminescence at 425 nm than with the myoglobin–luminol reaction. The increased chemiluminescence intensity was linear with the formaldehyde concentration in the range of 1–3000 pmol L−1, and the limit of detection was 0.3 pmol L−1 with a relative standard deviation of less than 5.0% (3σ). At a flow rate of 2.0 mL min−1, including sampling and washing, the assay could be accomplished in 0.5 min. It was also found that there was a linear relationship between the vapour pressure of formaldehyde and temperatures of 291.5–315.0 K. The proposed method has been applied successfully for the determination of formaldehyde in air and human serum.

Continuous chemiluminescence determination of formaldehyde in air based on Trautz–Schorigin reaction

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5 L min −1 (absorption liquid flow rate of 336 μL min −1). The limit of detection (S/N = 3) is 0.60 μg m −3 HCHO (0.49 ppb). The calibration graph is linear up to 300 μg m −3 HCHO (244 ppb). The relative standard deviations of chemiluminescence method for 1 × 10 −6 and 5 × 10 −6 M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.

On-line monitoring of formaldehyde in air by cataluminescence-based gas sensor

A rapid and sensitive cataluminescence (CTL)-based gas sensor using nanosized V 2Ti 4O 13 as a probe was proposed for the determination of formaldehyde in air. The gas sensor showed high selectivity for formaldehyde at 490 nm and satisfying activity at 370 °C. The linear range of the CTL intensity versus concentration of formaldehyde was 0.1–40 mg/m 3 ( γ = 0.9995), and the detection limit (3 σ) was 0.06 mg/m 3. No interference was observed while the foreign substances, such as ammonia, ethanol, benzene, carbon monoxide and sulfur dioxide, were passing through the sensor. The gas sensor displayed good stability for continuously introducing formaldehyde over 80 h, and allowed on-line monitoring of formaldehyde in air.

Spectrophotometric Method with Silica‐Gel Beads for Determination of Trace Formaldehyde in Air

A novel method is described for the determination of formaldehyde, with sensitivity enhancement based on the Hantzsch reaction, which involves the cyclization of ammonium, formaldehyde, and 2,4‐pentanedione (PD) in Nash's reagent to form the yellow compound 3,5‐diacetyl‐1,4‐dihydrolutidine (DDL) at pH 6. Silica‐gel beads are added into solution, and the reaction completes within 55 min at room temperature without heating. The silica‐gel beads not only catalyze the reaction process but also increase the sensitivity of the analysis. The proposed method is simple and convenient. The absorbance at 412 nm is proportional to the concentration of formaldehyde over the range of 0.1–2.0 g · mL−1. The detection limit is 0.1 g · mL−1. This method has been applied to the determination of formaldehyde in air with satisfactory results. This paper was invited as a contribution to a special issue of the journal concerning Chemical Spectroscopy in China. It was presented at Sichuan University, Chengdu China, October 17–24, 2003; the 6th International Symposium on Green Chemistry in China.

Continuous fluorescence determination of formaldehyde in air

A flow method for the determination of formaldehyde in air is presented. A cylindrical wet effluent diffusion denuder (CWEDD) is used for continuous collection of formaldehyde from air into distilled-deionized water as denuder liquid. Collected formaldehyde in the denuder concentrate is on-line determined by fluorescence 2,4-pentandione method. The collection efficiency of HCHO is quantitative at the air flow rate of 0.5 l min −1. The calibration graph is linear in the range 2–300 μg m −3 HCHO. The limit of detection is 1.6 μg m −3 HCHO. The relative standard deviations for 2 × 10 −6 and 1 × 10 −5 M HCHO are 2.57 and 1.06%, respectively. Acetaldehyde, acetone, formic acid and acetic acid do not interfere. Delay of the signal is 2.5 min.

Spectrofluorimetric determination of formaldehyde in air after collection onto silica cartridges coated with Fluoral P

In the present work, a sensitive and selective fluorimetric method for formaldehyde determination in air samples is described. The method is based in the reaction between formaldehyde and Fluoral P producing 3,5-diacetyl-1,4-dihydrolutidine, which, when excited at 410 nm, emits fluorescence at 510 nm. The Fluoral P was prepared by the reaction of 0.3 ml of acetic acid, 0.2 ml of acetylacetone and 15.4 g of ammonium acetate. Then, the volume was completed to 100 ml with deionized water. The Fluoral P obtained, if stored under refrigeration in the dark, can be used, safely, for 60 days. The calibration curve obtained with concentrations of formaldehyde in the range of 12 to 192 ng ml −1 ( n=9) was Intensity=1.11 C+0.06 ( R 2=0.9920). In the quantification of formaldehyde, air samples were passed at 1 l min −1, during 120 min, through glass impingers containing 40 ml of Fluoral P, followed by direct fluorescence measuring, or through two SEP PAK silica cartridges, coated with Fluoral P. The cartridges were eluted with 10 ml of Fluoral P solution and quantified by spectrofluorimetry. Under these conditions, the detection limit (S/N=3) obtained was 2.0 ng ml −1. The new methodology was validated by comparison with a well-known HPLC method in which formaldehyde was collected into SEP PAK C18 cartridges coated with 2,4 dinitrophenylhydrazine. The application of the t 95% test did not show significant differences between the HPLC and either fluorimetric methodologies. This method has been used in the determination of gas phase formaldehyde in both indoor and outdoor sites. For the indoor site, the measured concentrations were in the range of 9.0 to 67.7 μl l −1, while for the outdoor site they were in the range of 16.8 to 38.8 μl l −1. Further, due to the ease of handling in field studies, the SEP PAK cartridges coated with Fluoral P were used. The formaldehyde concentrations thus determined, in outdoor sites, were in the range of 2.09 to 25.1 μl l −1. The main advantage of this analytical procedure is its selectivity for formaldehyde, without interferences from bisulfite and other aldehydes, especially acetaldehyde, and low blank level, resulting in low detection limits. In addition, very little sample preparation is required.

Catalytic Determination of Trace Formaldehyde with a Flow Injection System Using the Indicator Reaction between Crystal Violet and Bromate

A sensitive flow injection method is proposed for the determination of formaldehyde based on its catalytic action upon the redox reaction between crystal violet and potassium bromate in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of crystal violet injected at the maximum absorption wavelength of 600 nm. A calibration graph from 0.018 to 1.400 µg mL−1 is obtained, and the detection limit is 0.007 µg mL−1 in a sample volume of 30 µL. Up to 15 samples can be analyzed per hour with a relative standard deviation of 1.2 and 2.3%, respectively, for the determination of 1.0 and 0.1 µg mL−1 of formaldehyde. The method is free from most interference. This method has been applied to the determination of formaldehyde in air, decoration boards and paints, and the results compare well with those provided by iodimetry.

On-site Analysis of Trace Amounts of Formaldehyde in Ambient Air Using Batchwise Collection/Concentration Method and Portable Flow Injection System

A simple and rapid method for the determination of formaldehyde (HCHO) in air was developed by using a portable flow injection analysis (FIA) system installed with a detector consisting of a light emitting diode (LED) as a light source, and a flow cell and with a heating system. The method was used for on-site measurement by coupling with a simple batchwise absorption collection method. HCHO in air was collected quantitatively on-site in a 50-ml syringe (volume: 7 1.92k0.43 ml) containing 3 ml of purified water as an absorbing solution, which was subsequently introduced into the carrier stream of the FIA system. The amounts of HCHO in the absorbing solution were measured at 450 nm after reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 6.0 or with a fluoral P solution of 0.4 M phosphate buffer (pH 6.0). A calibration graph with standard HCHO aqueous solutions could be adopted for the determination of formaldehyde in air. The relative standard deviation (RSD) was 0.63% for lx10-~ M (n = 12) and with the limit of detection (LOD) was 2.7x10-' M (0.8 ppb) in aqueous solution (SN =3), which corresponds to 35 pptv of HCHO in air. The proposed method was successfhlly applied to air samples

Preconcentration with membrane cell and adsorptive polarographic determination of formaldehyde in air

The present paper describes a procedure that formaldehyde in air was preconcentrated in a membrane cell and its content was determined by adsorptive polarography. First the formaldehyde in air samples was preconcentrated in a membrane cell using water, then the formaldehyde reacted with 2,4-dinitrophenyl hydrazine to form 2,4-dinitrophenyl hydrazone, which can be adsorbed at the mercury electrode and yields a sensitive adsorptive polarographic wave. Over the range 6.0×10 −10–5.0×10 −6 M, the peak currents are linearly proportional to the concentration of formaldehyde, the detection limit is 2.0×10 −10 M.

A new fluorimetric method for the determination of formaldehyde in air based on the liquid droplet sampling technique.

A new, simple, sensitive, selective and in-field fluorimetric method for the determination of formaldehyde is proposed. The reaction of formaldehyde with hydralazine in acidic medium, heating on a boiling water-bath for 25 min, produces s-triazolo[3,4-a]phthalazine (Tri-P). The fluorescence intensity of the product formed (Tri-P) was determined at lambda em = 389 nm with lambda ex = 236 nm. The fluorescence intensity is linear over a formaldehyde concentration range of 1.2-33.0 micrograms l-1. The proposed method was applied successfully to the determination of formaldehyde sampled from the atmosphere using the liquid droplet technique. Formaldehyde vapour in a wind tunnel was produced by a mean of permeater. A linear curve was obtained between the concentration in the wind tunnel and that in the droplet. The detection limit for formaldehyde was 2.0 micrograms l-1 with RSDs varying from 3 to 12% in ambient air, using a droplet correction solution (boric acid and hydralazine). The effect of interfering substances on the determination shows that most cations and anions did not interfere. The results obtained were satisfactory compared with a reference method.

Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid

A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 microL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a light emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is approximately 2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min-1. The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.

Gas chromatographic determination of formaldehyde in air using solid-phase microextraction sampling

The optimization of in situ derivatization and preconcentration of formaldehyde in air using solid phase microextraction with gas chromatographic determination was investigated. A dimethylpolysiloxane coating (7 μm) solid-phase microextraction needle was used in the final procedure as a support for derivatizing reagents such as 2,4-dinitrophenylhydrazine and acetylacetone. Standard concentrations of formaldehyde in air were obtained using a headspace technique and equilibrium concentrations of formaldehyde in air were calculated using Henry's law. After derivatization on the fiber, the derivative was thermally desorbed in the injector of a gas chromatograph and analyzed using an electron capture detector. A detection limit of 0.17 mg m−3 was obtained. Calibration was done at 296 K. Reproducibility of the method was 9.6%. Some real air samples were also analyzed. The method is very convenient and ideal for the rapid determination of formaldehyde in air.

Determination of formaldehyde in air by ion-exclusion and ion-exchange chromatography with pulsed amperometric detection

A method is presented for the determination of formaldehyde in air sample extracts containing aqueous sodium hydrogensulfite. Utilizing the unique properties of its hydrogensulfite complex, formaldehyde is separated from other sample components by ion-exclusion and ion-exchange chromatography, then selectively detected by amperometry at a silver electrode. Optimum sensitivity of detection was found to occur at +0.10 V versus a silver wire reference electrode using a strongly basic background electrolyte. Using ribose as an internal standard, a linear response (r2 > 0.99) was observed for aqueous formaldehyde concentrations in the range 0.02–10.0 mg l–1; detection limits of <1 ng for formaldehyde were obtained using a 50 µl sample loop. The short-term reproducibility was better than 5%(as RSD). Analysis of laboratory air by collection in impingers containing aqueous NaHSO3 yielded results consistent with previous literature values.

Selective Monitoring of Formaldehyde in Air by Use of the Stopped-Flow Technique

Abstract Two kinetic methods based on the stopped-flow technique are proposed for the determination of formaldehyde in air by reaction with 3-methyl-2-benzothiazolone hydrazone (MBTH), followed by photometric detection at 620 nm, and with acetylacetone, followed by fluorimetric detection at δcx = 410 nm and δcm = 510 nm. Kinetic methodology considerably shortens the formaldehyde analysis time (measurements can be obtained within a few seconds) relative to existing methods based on these reactions and equilibrium measurements (ca. 30 and 60 min are needed for equilibrium to be reached in the photometric and fluorimetric method, respectively). One additional advantage of the kinetic methodology is its high selectivity, which was checked by studying the effect of various organic and inorganic species. Calibration graphs were linear over the ranges 20–600 and 20–1000 ng ml−1 formaldehyde for the photometric and fluorimetric methods, respectively. Both methods were applied to the determination of formaldehyde in air from urban- areas; the accuracy of the results was confirmed by comparing them with those provided by the standard chromotropic acid method. The poposed kinetic methods were found to be more sensitive, rapid, reproducible and easier to use than the widely accepted standard method.