Determination of formaldehyde in bovine milk using a high sensitivity HPLC-UV method

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.

Green infant formula analysis: Optimizing headspace solid-phase microextraction of carbonyl compounds associated with lipid peroxidation using GC-MS and pentafluorophenylhydrazine derivatization

The refinement and optimization of a method combining headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS) was successfully performed for the first time to determine seven carbonyl and dicarbonyl compounds, including glyoxal, methylglyoxal, dimethylglyoxal, and malondialdehyde in infant formulae, related to lipid peroxidation. HS-SPME was utilized for simultaneous extraction and derivatization with pentafluorophenylhydrazine (PFPH). Critical parameters such as temperature, pH, extractive phase, and salting-out were meticulously investigated and fine-tuned by an asymmetrical 2232//9 screening design to ensure the method's efficacy and reliability. Optimal conditions included a PFPH concentration of 5 g/L, pH 5.0, head-space extraction at 60 °C within 10 min, utilizing a DVB/CAR/PDMS coating, and a 20% w/w salting-out. The analytical validation of this method, compliant with FDA guidelines, demonstrated exceptional linearity, sensitivity, specificity, precision (RSD ≤13.8%), and accuracy (84.8% ≤ recovery ≤111.5%). The metric approach AGREEprep confirms its eco-friendliness, marking a significant step towards an environmentally conscious approach in infant formula analysis. An occurrence study conducted on 25 infant formula samples revealed widespread carbonyl and dicarbonyl compounds in both powdered and liquid variants. ANOVA results exhibited variations in compound concentrations among different sample groups. Clustering analyses delineated distinct groups based on carbonyl content, indicating the potential of these compounds as markers for lipid peroxidation and food quality assessment. This method serves as a valuable tool for evaluating infant formula quality, stability towards oxidation, and safety.

Fluorimetric determination of aqueous formaldehyde employing heating and ultrasound-assisted approach through its derivatization with a ß-diketone-nickel(2+) complex immobilized in a PMMA flow cell

Formaldehyde (FA) is a highly toxic substance present in many matrices, including freshwater as well as found in natural mechanisms such as rainfall and combustion of organic matter. Consumption of water contaminated with high levels of FA can cause severe short-term or long-term health problems. Due to these health risks, procedures are necessary to determine and quantify FA in aqua sources This paper reports on a study of fluorimetric determination of FA using a nickel(2 + )-diketonate coordination compound immobilized as a solid precursor. The compound was characterized by electronic absorption, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetry (TG), optical microscopy (OM), and scanner electron microscopy (SEM). The methodology was based on the reaction of the synthesized compound with an ammoniacal buffer generating a selective reagent for formaldehyde: fluoral-P. The product of the reaction generates 3,5-diacetyl-1,4-dihydrolutidine (DDL), which is responsible for the fluorescence of the system. Several parameters such as temperature, duration of heating time, and dilution effect with the best effects were studied to carry out FA determination. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg/L FA (R = 0.997 and n = 10), and a detection (3σ criterion) and quantification (10 σ criterion) limit estimated at 0.129 and 0.389 mg/L, respectively were achieved. The FA analysis was able to be conducted in 05 min with a relative standard deviation estimated at 1.10 %.

UV-vis spectroscopic detection of formaldehyde and its analogs: A convenient and sensitive methodology

Formaldehyde is deemed to be an indispensable industrial product that has been widely applied in manufacture of resins, drugs, building materials, etc. It has been widely accepted that, nevertheless, residual formaldehyde will cause pathogen reactions, even leading to cancers like leukemia. Thus, a facile and efficient approach has been designed to achieve the determination of formaldehyde by ultraviolet and visible (UV-vis) spectrophotometry in liquid media. In detail, O-(carboxymethyl) hydroxylamine (C₂H₅NO₃·0.5HCl) is chosen as the detection reagent for the specific recognition of formaldehyde on account of its unique aminooxy (-O-NH₂) which can react with formaldehyde to form oxime bonds (O-NCH₂), accompanied with the only by-product of H₂O. Likewise, this simple and sensitive detection approach based on the chemical detection reagent C₂H₅NO₃·0.5HCl can also be applied to the determination of other aldehyde homologs with carbonyl groups including acetaldehyde, acetone, benzaldehyde, 1, 4-phthalaldehyde. As a result, all the UV absorbances of analytes display remarkable linear detection relationships. The limits of detection (LOD) and limits of quantitation (LOQ) values are in the range of 0.03-1.16 ppm and 0.03-5.81 ppm respectively, with RSDs of 3.27-3.75 %, evidencing the feasibility of our method to determine formaldehyde and its homologs by UV-vis spectrophotometry and auspicious prospects of practical applications.

Development of a Portable and Modular Gas Generator: Application to Formaldehyde Analysis

This work aims at developing and validating under laboratory-controlled conditions a gas mixture generation device designed for easy on-site or laboratory calibration of analytical instruments dedicated to air monitoring, such as analysers or sensors. This portable device, which has been validated for formaldehyde, is compact and is based on the diffusion of liquid formaldehyde through a short microporous interface with an air stream to reach non-Henry equilibrium gas–liquid dynamics. The geometry of the temperature-controlled assembly has been optimised to allow easy change of the aqueous solution, keeping the microporous tube straight. The formaldehyde generator has been coupled to an on-line formaldehyde analyser to monitor the gas concentration generated as a function of the liquid formaldehyde concentration, the temperature, the air gas flow rate, and the microporous tube length. Our experimental results show that the generated gaseous formaldehyde concentration increase linearly between 10 and 1740 µg m−3 with that of the aqueous solution ranging between 0 and 200 mg L−1 for all the gas flow rates studied, namely 25, 50 and 100 mL min−1. The generated gas phase concentration also increases with increasing temperature according to Henry’s law and with increasing the gas–liquid contact time either by reducing the gas flow rate from 100 to 25 mL min−1 or increasing the microporous tube length from 3.5 to 14 cm. Finally, the performances of this modular formaldehyde generator are compared and discussed with those reported in the scientific literature or commercialised by manufacturers. The technique developed here is the only one allowing to operate with a low flow rate such as 25 to 100 mL min−1 while generating a wide range of concentrations (10–1000 µg m−3) with very good accuracy.

Enzyme decorated dendritic bimetallic nanocomposite biosensor for detection of HCHO

In recent times, bi- and tri-metallic nanocomposites are being extensively studied to improve the catalytic surface and sensitivity of detection. In this study, we designed a formaldehyde dehydrogenase decorated Cys-AuPd-ErGO nanocomposite with fern like AuPd dendrites deposited on reduced graphene oxide (ErGO) on screen printed electrode (SPE) for determination of NADH and successfully demonstrated its application for detection of HCHO. This biosensor exhibited direct electron transfer by lowering the oxidation potential of NADH from +0.63 V to 0.32 V vs Ag/AgCl, avoiding usage of electron mediators. The sensor LOD was 0.3 μM HCHO with excellent sensitivity of 70 μA/μM/cm² and linear detection range between 1 μM and 100 μM during chronoamperometric studies at applied over potential of +0.35 V vs Ag/AgCl. The sensor was tested for its performance in simulated HCHO adulterated samples of fish and milk, and appreciable recoveries (88-104%) at tested concentrations indicated good sensor performance. It was also validated against conventional method of HPLC with highly acceptable correlation coefficient of 0.99, indicating successful fabrication of a simple, "on site" disposable sensor for HCHO detection. The developed biosensor can also find wide application in quantitative measurement of NADH and analytes involved in reactions with the co-enzyme.

A derivatization and microextraction procedure with organic phase solidification on a paper template: Spectrofluorometric determination of formaldehyde in milk

A derivatization and air-assisted dispersive liquid-liquid microextraction procedure with organic phase solidification on a paper template was developed for the first time. The procedure was used for the spectrofluorometric determination of formaldehyde in milk samples. The Hantzsch reaction of formaldehyde with acetylacetone in the presence of ammonia to form a derivative (3,5-diacetyl-1,4-dihydrolutidine) was implemented for the microextraction and detection of analyte. Thymol was investigated as the extraction solvent for the air-assisted dispersive liquid-liquid microextraction for the first time. In the developed procedure, molten thymol was added to the thermostated aqueous sample solution containing reagents for formaldehyde derivatization, and cloudy solution of fine thymol droplets was formed by air bubbling. After separation of phases the liquid extract phase was withdrawn with a dispenser and distributed on the black paper template in a thin layer to be solidified. The solidified extract phase on the template was inserted to a sample holder of a spectrofluorometer and fluorescence intensity was measured without using cuvettes. Under optimal experimental conditions the linear detection range was found to be 45-500 µg L^-1 with LOD calculated from a blank test, based on 3σ, 15 µg L^-1. The developed procedure does not require the dilution of the solid extract phase in organic solvent to be introduced in an analytical instrumentation and the use of cuvettes for spectrofluorometric detection.

Determination of DDT in honey samples by liquid-liquid extraction with low-temperature purification (LLE-LTP) combined to HPLC-DAD

Honey is widely consumed worldwide, however, this food can be contaminated by chemical contaminants, such as the insecticide dichlorodiphenyltrichloroethane (DDT). Despite legal restrictions on DDT use, this organochlorine pesticide has been detected in honey collected in several developed and developing countries, representing risks to human health, animals, and the environment due to its high environmental persistence, potential carcinogenicity, and ecotoxicological effects. Thus, the development of an analytical method for DDT monitoring in this matrix is important to ensure food security. Therefore, this study aimed to optimize and validate a simple, low-cost, and efficient method using the liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine DDT in honey samples by high-performance liquid chromatography with diode array detector (HPLC-DAD). The proposed method was validated according to SANTE guidelines, being considered selective, precise, accurate, and linear in the range of 8.0-160 μg kg^-1. The limits of detection (LOD) and quantification (LOQ) achieved were 4.0 and 8.0 μg kg^-1, respectively. This LOQ value is lower than the maximum residue limit established by the Brazilian and European Union legislation. Therefore, the LLE-LTP combined to HPLC-DAD allows the routine analysis of DDT in honey samples and can be widely applied in studies to monitor this pesticide, especially in developing countries, where DDT use is still allowed.

Simple click chemistry-based derivatization to quantify endogenous formaldehyde in milk using ultra-high-performance liquid chromatography/tandem mass spectrometry in selected reaction monitoring mode

RATIONALE

Formaldehyde (FA) exposure via environmental pollution or through the food chain poses a serious threat to human health, especially in developing countries like India. Although the addition of FA to food is proscribed, it is often illegally added to foods such as milk to increase the shelf-life. There are challenges in differentiating the endogenous FA content in milk from externally added FA.

METHOD

We have developed a simple method using ultra-high-performance liquid chromatography/tandem mass spectrometry in selected reaction monitoring mode (UHPLC/MS/SRM) for the absolute quantification of endogenous FA in milk. The steps include fat removal, protein precipitation using acid, and spiking with labelled FA (FA*), followed by simple click chemistry-based derivatization using Girard P reagent (GP) and final analysis.

RESULTS

A standard curve with FA* was constructed and used for the calculation of endogenous FA in milk. The optimal conditions for the derivatization reaction using 500 μL of milk were: GP, 50 μg; temperature, 37°C; time, 60 min; and 0.1% HCl. The validation parameters such as accuracy (95.84 to 99.73%), precision (2.84 to 8.02%) and spiked recovery (>95%) are within the FDA guidelines. This method is highly sensitive [limit of detection (LOD) of 1 ng/mL] with a dynamic range of 3.12 to 200 ng/mL. The endogenous FA level in pasteurized cow milk is 70 ng/mL (n = 60). The FA content in raw milk samples from cow, goat and buffalo (each n = 10) varied from 134 to 255 ng/mL.

CONCLUSIONS

This method is precise and sufficiently sensitive to quantify endogenous FA in milk samples using a minimal sample volume. As it involves simple sample preparation steps, it can be used routinely to quantify endogenous FA.

On-Line Gaseous Formaldehyde Detection Based on a Closed-Microfluidic-Circuit Analysis

This paper describes a compact microfluidic analytical device in a closed-circuit developed for the detection of low airborne formaldehyde levels. The detection is based on the passive trapping of gaseous formaldehyde through a microporous tube into the acetylacetone solution, the derivative reaction of formaldehyde with acetylacetone to form 3,5-Diacetyl-1,4-dihydrolutidine (DDL) and the detection of DDL by fluorescence. The recirculation mode of the analytical device means that the concentration measurement is carried out by quantification of the signal increase in the liquid mixture over time, the instantaneous signal increase rate being proportional to the surrounding gaseous formaldehyde concentration. The response of this novel microdevice is found to be linear in the range 0–278 µg m−3. The reagent volume needed is flexible and depends on the desired analytical resolution time and the concentration of gaseous formaldehyde in the environment. Indeed, if either the gaseous concentration of formaldehyde is high or the reagent volume is low, the fluorescence signal of this recirculating liquid solution will increase very rapidly. Consequently, the sensitivity simultaneously depends on both the reagent volume and the temporal resolution. Considering a reagent volume of 6 mL, the hourly and daily detection limits are 2 and 0.08 µg m−3, respectively, while the reagent autonomy is more than 4 days the airborne formaldehyde concentration does not exceed 50 µg m−3 as it is usually the case in domestic or public indoor environments.

Quantitative Characteristics of Toxic Compounds According to the Solvent Type

The quantitative analysis of target substances is an important part of assessing the toxicity of diverse materials. Usually, the quantitation of target compounds is conducted by instrumental analysis such as chromatography and capillary electrophoresis. If solvents are used in the pretreatment step of the target analyte quantification, it would be crucial to examine the solvent effect on the quantitative analysis. Therefore, in this study, we assessed the solvent effects using four different solvents (methanol, hexane, phosphate buffered saline (PBS), and dimethyl sulfoxide (DMSO)) and three toxic compounds (benzene, toluene, and methylisothiazolinone (MIT)). Liquid working standards containing the toxic compounds were prepared by dilution with each solvent and analyzed by gas chromatography-mass spectrometry (GC-MS). As a result, we found that the response factor (RF) values of the target analytes were different, depending on the solvent types. In particular, benzene and toluene exhibited their highest RF values (33,674 ng^-1 and 78,604 ng^-1, respectively) in hexane, while the RF value of MIT was the highest (9,067 ng^-1) in PBS. Considering the correlation (R ²) and relative standard deviation (RSD) values, all target analytes showed fairly good values (R ² > 0.99 and RSD < 10%) in methanol and DMSO. In contrast, low R ² (0.0562) and high RSD (10.6%) values of MIT were detected in hexane, while benzene and toluene exhibited relatively low R ² and high RSD values in PBS (mean R ² = 0.9892 ± 0.0146 and mean RSD = 13.3 ± 4.1%). Based on these findings, we concluded that the results and reliability of the quantitative analysis change depending on the analyte and solvent types. Therefore, in order to accurately assess the toxicity of target compounds, reliable analytical data should be obtained, preferentially by considering the solvent types.

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.