Determination of formaldehyde in fruit juice based on magnetic strong cation-exchange resin modified with 2,4-dinitrophenylhydrazine

Chromatographic Methods and Sample Pretreatment Techniques for Aldehydes, Biogenic Amine, and Carboxylic Acids in Food Samples

This review paper critically examines the current state of research concerning the analysis and derivatization of aldehyde, aromatic hydrocarbons and carboxylic acids components in foods and drinks samples, with a specific focus on the application of Chromatographic techniques. These diverse components, as vital contributors to the sensory attributes of food, necessitate accurate and sensitive analytical methods for their identification and quantification, which is crucial for ensuring food safety and compliance with regulatory standards. In this paper, High-Performance Liquid Chromatography (HPLC) and Gas Chromatographic (GC) methods for the separation, identification, and quantification of aldehydes in complex food matrices were reviewed. In addition, the review explores derivatization strategies employed to enhance the detectability and stability of aldehydes during chromatographic analysis. Derivatization methods, when applied judiciously, improve separation efficiency and increase detection sensitivity, thereby ensuring a more accurate and reliable quantification of aldehyde aromatic hydrocarbons and carboxylic acids species in food samples. Furthermore, methodological aspects encompassing sample preparation, chromatographic separation, and derivatization techniques are discussed. Validation was carried out in term of limit of detections are highlighted as crucial elements in achieving accurate quantification of compounds content. The discussion presented by emphasizing the significance of the combined HPLC and GC chromatography methods, along with derivatization strategies, in advancing the analytical capabilities within the realm of food science.

Determination of Four PAHs and Formaldehyde in Traditionally Smoked Chicken Products

The present study was conducted to analyze the level of four priority polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (BaP), chrysene (Chr), benzo[a]anthracene (BaA), and benzo[b]fluoranthene (BbF), in traditionally smoked chicken products marketed in China. The results show that the amount of ƩPAH4 (the sum of four different PAHs: BaP, Chr, BaA, and BbF) was 30.43-225.17 and 18.75-129.54 µg/kg in the skin and meat of smoked chicken products, respectively. The content of ƩPAH4 in the smoked skin was significantly higher as compared to the smoked meat (p < 0.05). The calculation of MOE (margin of exposure) results suggested the possibilities of ingestion risk associated with the consumption of smoked chicken skin. Furthermore, the formaldehyde content in the skin of smoked chicken was 2.17-6.84 mg/kg and 0.86-2.95 mg/kg in the smoked meat. These results indicate that optimization or alternative methods for food processing should be developed to reduce the high level of harmful substances formed during processing to ensure the safety of smoked chicken products. Moreover, along with harmful substances, the moisture content and color of traditionally smoked chicken were analyzed to provide a practical reference for healthy, safe and green processing technology for smoked chicken.

Shape memory luminescent cellulose/chitosan hydrogel for high sensitive detection of formaldehyde

Hybrid hydrogels containing biomacromolecules have been widely used in sensors, fluorescent probes, and other fields due to their high biocompatibility and nontoxicity. In this paper, tough hydrogels with interconnected macro-pores have been fabricated by freeze-induced chemical cross-linking of microfibrillated cellulose (MFC) and organic modified chitosan (CS). In this hydrogel materials, three-dimensional networks were formed by abundant hydrogen bonds and chemical cross-linking. Luminescent lanthanide complexes were covalently bonded to the hydrogel networks through coordination of Eu³⁺ ions with 2, 3-pyridine dicarboxylic acid modified chitosan. The luminescence of hydrogel materials was further improved by the replacement of coordination water with 2-thiophenyltrifluoroacetone (TTA). The prepared hydrogels showed excellent shape memory properties both under water and in air. The stress of the hybrid hydrogel at 80 % strain can reach 159 kPa, which is much higher than that of the traditional microfibrillated cellulose-based hydrogels. The obtained luminescent hybrid hydrogels exhibited an excellent fluorescence detection effect on formaldehyde. The detection limit for formaldehyde is 45.7 ppb, which is much lower than the WHO standard (80 ppb for indoor air). The novel, facile preparing procedure may extend the potential applications of hybrid lanthanide luminescent hydrogel as fluorescence probes for pollution monitoring, especially for formaldehyde and other organic aldehydes.

Quantum dot assisted precise and sensitive fluorescence-based formaldehyde detection in food samples

Formaldehyde has an extremely reactive carbonyl group, commonly used as an antibacterial agent to sterilize and prevent food to spoil. This article describes an efficient and rapid detection method of formaldehyde from an aqueous solution by synthesizing 3-Aminopropyltriethoxysilane (APTES) quantum dots (Nano A) which react with formaldehyde to generate a Schiff base reaction. The photoinduced electron transfer produced by the quantum dots themselves results in fluorescence quenching to detect formaldehyde. The detection limit can reach 10^-9 M, and it can further be used to detect formaldehyde content in foods, such as baby vegetables, mushrooms, and vermicelli among other daily foods.

Cost-effective formaldehyde assay platform for multi-sample analysis in one run based on pervaporation coupled with a biodegradable sensor and a simple heat control unit

A novel, cost-effective platform using a biodegradable sensor and a simple heat control unit was proposed for multi-sample formaldehyde (FA) assay in one run based on pervaporation. The biodegradable sensor was a composite starch gel attached to paper and immobilized with a mixture of color agents of modified 4-amino-3-hydrazino-5-mercapto-1,2,4-triazol (AHMT). The sensor was situated on the cap of a vial that served for pervaporation. Two types of heat control units were specially designed using the concepts of aluminum block and water bath heating. With these two designs, multi-sample assays together with standard calibration could be performed in the same run under the same conditions. An FA solution was placed in the vial of the pervaporation unit. After a heating period, FA vapor would change the color of the sensor to purple due to the reaction between AHMT and FA. As a result, the color intensity was proportional to the FA concentration. The change of the color (green or G intensity) was monitored using a smartphone camera and image processing software. Factors affecting the sensitivity of the assay, pervaporation time, pervaporation temperature, FA solution volume, and humidity, were studied. Under the chosen condition, the developed procedure, with a calibration of G intensity = 7.93[FA] + 198, R² = 0.98, was applied to analyze real samples of seafood and mushrooms available in local markets in Thailand. As there were 24 pervaporation units in the proposed platform, 5 working standards and 9 samples with duplicates could be included in a 1-run assay either in the laboratory or on-site. The developed assay offers green chemical analysis with a simple, cost-effective approach. This serves the UN-SDGs of #2, #3, #7, #10, and #12.

RGB color analysis of formaldehyde in vegetables based on DNA functionalized gold nanoparticles and triplex DNA

A highly sensitive and selective RGB color analysis for the detection of formaldehyde (FA) was developed by using a DNA functionalized gold nanoparticle (AuNPs-DNA) probe. When complementary oligonucleotides (oligo 2 and oligo 3) and a silver ion (Ag⁺) were added to the AuNPs-DNA solution, triplex DNA was formed, resulting in the aggregation of AuNPs, and accompanied by a solution color change from red to purple. With the addition of formaldehyde, it reacted with Ag⁺, decreased the stability of triplex DNA between AuNPs-DNA, induced the dispersion of AuNPs, and the color of AuNPs recovered to red. Therefore, the formaldehyde concentration could be estimated with the RGB (red, green, blue) values of the AuNP solution by using a smartphone application (APP). The R value of the system was proportional to the concentration of formaldehyde within the range of 0.23-4.50 mg L^-1, with a detection limit of 0.14 mg L^-1. The method has been successfully applied to detect the residues of formaldehyde in vegetable samples and has the potential of the on-site determination of formaldehyde.

Novel Method of Analysis for the Determination of Residual Formaldehyde by High-Performance Liquid Chromatography

Formaldehyde is commonly used as an alkylating agent in the pharmaceutical industry. Consequently, its residual level in drug substances and/or their intermediates needs to be accurately quantified. Formaldehyde is a small, volatile molecule with a weak chromophore (the carbonyl group), and its direct analysis by GC-FID and HPLC-UV is difficult. For these reasons, the majority of papers found in the literature are based upon a derivatisation process (most commonly using the desensitised explosive 2,4-dinitrophenylhydrazine) prior to the analysis of formaldehyde. A novel high-performance liquid chromatography (HPLC) method with UV detection for its quantification in a pharmaceutical is described in this paper. The method proposed herein is based upon a derivatisation reaction between formaldehyde and 4-methylbenzenesulfonohydrazide (MBSH) before analysis by HPLC-UV. Selectivity, linearity, limit of quantification, accuracy, repeatability, intermediate precision, and solution stability were successfully assessed as per ICH guideline Q2(R1), and the method has also been validated in a good manufacturing practice (GMP) laboratory in the UK.

Modified Natural Rubber as a Simple Chemical Sensor with Smartphone Detection for Formaldehyde Content in a Seafood Sample

A new biodegradable platform-based sensor for formaldehyde assay is proposed. Natural rubber latex was modified to polylactic acid–chloroacetated natural rubber polymer blend sheets. The polymer blend sheet was grafted using a water-based system with amine monomers as a platform, with a spot exhibiting positive polarity for immobilizing with anionic dye (Acid Red 27). The sensor was exposed to formaldehyde. The color intensity of the dye on the sensor spot would decrease. Using a smartphone with image processing (via ImageJ program), the color intensity change (∆B) could be followed. A linear calibration, ∆B intensity = 0.365 [FA] + 6.988, R² = 0.997, was obtained for 10–150 mM FA with LOD and LOQ at 3 and 10 mM, respectively (linear regression method). The precision was lower than 20% RSD. Application to real seafood samples was demonstrated. The ready-to-use sensor with the proposed method was cost-effective, was portable for on-site analysis, and demonstrated green chemical analysis.

Application of Silicon Quantum Dots in the Detection of Formaldehyde in Water and Organic Phases

Background:

Formaldehyde is widely acknowledged as a carcinogen, but as an important organic reagent, it has also been widely employed in the fields of chemical synthesis, industrial production and biomedicine. It is therefore of great practical significance for the detection of formaldehyde in food, clothing, daily necessities, construction materials and environments.

Methods:

The two silicon QDs, that are, DAMO-Si-QDs (with N-[3-(Trimethoxysilyl) propyl] ethylenediamine as silicon source) and APTMS-Si-QDs (with (3-Aminopropyl) trimethoxysilane as silicon source) as the fluorescence probe to detect formaldehyde in both water and organic phases.

Results:

Silicon QDs prepared by different silicon sources exhibit an obvious difference in their tolerances to the environment and the responses to formaldehyde. However, APTMS-Si-QDs show better selectivity in both water and organic phases. In Tris-HCl solution (20.00mmol•L-1, pH=5), the formaldehyde concentration maintains an excellent linear relationship with the fluorescence intensity of APTMS-Si-QDs in the range of 3.125×10-7-3.125×10-5 mol•L-1, with correlation coefficient R2= 0.9998. In methanol, the formaldehyde concentration maintains an excellent linear relationship with the fluorescence intensity of APTMS-Si-QDs in the range of 1.563×10-7-3.125×10-5 mol•L-1, with correlation coefficient R2= 0.9992.

Conclusion:

It is found that DAMO-Si-QDs show poor response to the presence of formaldehyde, while APTMS-Si-QDs got a strong, sensitive and selective response to that in both aqueous and organic phases. In the Tris-HCl buffer (20 mmol•L-1, pH=5), the linear range for formaldehyde detection reaches 3.125×10-7-3.125×10-5 mol•L-1, and for the detection in the organic phase, the linear range reaches 1.563×10-7-3.125×10-5 mol•L-1, in methanol solution. The paper provides a sensitive, selective and simple means for formaldehyde detection in both aqueous and organic phase

SERS-based chip for discrimination of formaldehyde and acetaldehyde in aqueous solution using silver reduction

A method is described for surface-enhanced Raman scattering (SERS) discrimination of formaldehyde (FA) and acetaldehyde (AA) in aqueous sample solutions. It is based on the use of a paper strip containing 4-aminothiophenol (Atp)-modified reduced graphene oxide (rGO)/[Ag(NH₃)₂]⁺ (rGO/[Ag(NH₃)₂]⁺/Atp). The addition of FA or AA induces the conversion of [Ag(NH₃)₂]⁺ complex to silver nanoparticles (AgNPs) because of aldehyde-induced silver reduction reaction. The AgNPs possess strong SERS activity. The average interparticle gaps between the AgNPs can be fine-tuned by controlling the experimental conditions, this leading to the formation of optimized SERS hot spots. It is also found that the changes in the spectral shapes and the relative intensity ratio of the bands at 1143 and 1072 cm^-1 result from the difference in the pH value of the surrounding solution. This effect enables the selective discrimination of FA and AA. The paper strip can be used as a SERS dipstick and swab for on-site determination of FA or AA in wine and human urine via the differences in the intensity of the SERS peaks. The assay works over a wide range of concentrations (0.45 ng·L^-1 to 480 μg·L^-1) for FA and AA, and the respective detection limits are 0.15 and 1.3 ng·L^-1. Graphical abstract Schematic presentation of the preparation procedure of 4-aminothiophenol (Atp)-modified reduced graphene oxide (rGO)/[Ag(NH₃)₂]⁺ hybrid paper and its surface-enhanced Raman scattering discrimination of formaldehyde and acetaldehyde based on silver reduction.

Determination of Formaldehyde in Water Samples by High-Performance Liquid Chromatography with Methyl Acetoacetate Derivatization

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).

4-hydrazinobenzoic acid as a derivatizing agent for aldehyde analysis by HPLC-UV and CE-DAD

Aldehydes are relevant analytes in a wide range of samples, in particular, food and beverages but also body fluids. Hydrazines can undergo nucleophilic addition with aldehydes or ketones giving origin to hydrazones (a group of stable imines) that can be suitably used in the identification of aldehydes. Herein, 4-hydrazinobenzoic acid (HBA) was, for the first time, used as the derivatizing agent in analytical methodologies using liquid chromatography aiming the determination of low-molecular aldehydes. The derivatization reaction was simultaneously performed along with the extraction process, using gas-diffusion microextraction (GDME), which resulted in a clean extract containing the HBA-aldehyde derivates. The corresponding formed imines were determined by both high-performance liquid chromatography (LC) with UV spectrophotometric detection (HPLC-UV) and capillary electrophoresis with diode array detection (CE-DAD). HBA showed to be a rather advantageous derivatization reagent due to its stability, relatively high solubility in water and other solvents, high selectivity and sensibility, reduced impurities, simple preparation steps and applicability to different separation and/or different detection techniques. Limits of detections (LODs) of the optimized methodologies (in terms of time and pH among other experimental variables) were all below 0.5 mg L^-1, using both instrumental techniques. Furthermore, for the first time, the HBA-aldehyde derivatives were analyzed by LC with mass spectrometry (LC-MS), demonstrating the possibility of identification by MS of each compound. The developed methodologies were also successfully applied in the analysis of formaldehyde and acetaldehyde in several alcoholic beverages. This was also the first time GDME was combined with CE, showing that it can be a valuable sample preparation tool for electrophoresis, in particular by eliminating the interference of ions and inorganic constituents present in the samples.

A novel mass spectrometric method for formaldehyde in children's personal-care products and water via derivatization with acetylacetone

RATIONALE

New legislation in the state of Minnesota prohibits the sale of children's personal-care products (PCPs) that contain more than 500 ng/mg formaldehyde. Previous attempts to quantify formaldehyde in PCPs use nonspecific derivatization procedures that employ harsh reagents and/or nonspecific detection. Derivatization of formaldehyde by acetylacetone occurs under mild conditions and is specific for formaldehyde but it has not been investigated using high-performance liquid chromatography/tandem mass-spectrometry (HPLC/MS/MS).

METHODS

To determine formaldehyde, PCPs were dissolved and then interferences were minimized by graphitized-carbon solid-phase extraction. Formaldehyde was derivatized to 3,5-diacetyl-1,4-dihydrolutidine (DDL) using an acetylacetone solution. Post-derivatization, samples were diluted and analyzed by HPLC/MS/MS. Quantification was performed by isotopic dilution. Product-ion spectra were acquired for DDL and D₁₂ -DDL. The mass shifts between the two product-ion spectra were used to assign fragment structures. To confirm molecular formulas, high-resolution accurate-mass analysis of the DDL product ions was performed by quadrupole time-of-flight MS.

RESULTS

Structures were proposed for all product ions of DDL above 10% relative intensity. Method accuracy ranged between 96-104% for all matrices at all concentrations tested. Method precision was less than 4% relative standard deviation. The reporting limit was 10 ng/mg in PCPs and 100 μg/L in water. Twenty children's PCPs were tested to demonstrate the method and formaldehyde was reported in five from 23-1500 ng/mg. Of those five, two samples contained formaldehyde above the Minnesota regulatory limit.

CONCLUSIONS

The developed method allows for the accurate quantification of formaldehyde in PCPs at levels below those required by a new regulation on children's products in Minnesota. The method includes a derivatization procedure that is newly adapted to HPLC/MS/MS; therefore, structures were proposed for the product ions of the derivative (DDL). Copyright © 2017 John Wiley & Sons, Ltd.

Multi-pesticides residue analysis of grains using modified magnetic nanoparticle adsorbent for facile and efficient cleanup

A facile, rapid sample pretreatment method was developed based on magnetic nanoparticles for multi-pesticides residue analysis of grains. Magnetite (Fe₃O₄) nanoparticles modified with 3-(N,N-diethylamino)propyltrimethoxysilane (Fe₃O₄-PSA) and commercial C18 were selected as the cleanup adsorbents to remove the target interferences of the matrix, such as fatty acids and non-polar compounds. Rice was used as the representative grain sample for method optimization. The amount of Fe₃O₄-PSA and C18 were systematically investigated for selecting the suitable purification conditions, and the simultaneous determination of 50 pesticides and 8 related metabolites in rice was established by liquid chromatography-tandem mass spectrometry. Under the optimal conditions, the method validation was performed including linearity, sensitivity, matrix effect, recovery and precision, which all satisfy the requirement for pesticides residue analysis. Compared to the conventional QuEChERS method with non-magnetic material as cleanup adsorbent, the present method can save 30% of the pretreatment time, giving the high throughput analysis possible.

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.

Extraction and preconcentration of formaldehyde in water by polypyrrole-coated magnetic nanoparticles and determination by high-performance liquid chromatography

In this study, a simple and rapid extraction method based on the application of polypyrrole-coated Fe3 O4 nanoparticles as a magnetic solid-phase extraction sorbent was successfully developed for the extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4-dinitrophenylhydrazine. The analyses were performed by high-performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 μL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10-500 μg/L), correlation coefficient (R(2) ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 μg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.

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.