Low Molecular Aldehydes Research Articles

A novel methodology and strategy to detect low molecular aldehydes in beer based on charged microdroplet driving online derivatization and high resolution mass spectrometry

The concentration of aldehydes is one of the important indicators in the food quality and safety. To efficiently analyze the four aldehydes (methanal, ethanal, propanal and n-butanal) in beer, charged microdroplet driving online derivatization apparatus coupled with high resolution mass spectrometry was firstly developed. Utilizing the high-speed reaction accelerated by microdroplets, the offline derivative of aldehydes with 2,4-dinitrophenylhydrazine in bulk was transferred into online derivatization. The developed method featured acceptable linearities (R2 ≥ 0.95), high sensitivities (LODs at ng mL−1 level) and qualified precisions (RSDs ≤ 8.4 %) for target compounds. Four aldehydes with trace amount were successfully determined in beer. The results indicated that the novel online analytical strategy did not require complex sample preparation and could conduct simple, rapid, sensitive detection of small molecule aldehydes with high throughput in beer or even other food samples.

Production of acetonitrile via catalytic fast pyrolysis of biomass derived polylactic acid under ammonia atmosphere

In this study, a series of catalysts including different metal oxides loading on HZSM-5(Si/Al = 25) and cobalt oxides loading on different supports were synthesized to catalyze fast pyrolysis (CFP) of biomass derived polylactic acid (PLA) to produce acetonitrile under ammonia atmosphere. Both the metal and the acid of the catalyst had a crucial influence on the yield of acetonitrile and Co/HZSM-5(25) produced most acetonitrile. Other factors that might affect the product distribution including cobalt loading, reaction temperature, resident time and NH3 flow rate have been investigated systematically. Under the optimized CFP condition (650 ℃; resident time 2.4 s; NH3 flow rate 80 ml/min), the carbon yield and selectivity of acetonitrile in liquid product reached 50.2% and 83.6%, respectively. The possible reaction pathway from PLA to acetonitrile was also studied and proposed. PLA firstly cracked into lactic acid through thermal decomposition and formed lactide at the same time. Then lactic acid and lactide cracked into low-molecular aldehydes, ketones and acids. These aldehydes and ketones reacted with ammonia to form imines, acids to amides, and finally to acetonitrile and small amount of proponitrile under the catalysis of Co/HZSM-5 catalyst.

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.

Application of Single Drop Extraction (SDE) Gas Chromatography Method for the Determination of Carbonyl Compounds in Spirits and Vodkas

The application of single drop extraction (SDE) for isolation and enrichment of carbonyl compounds after derivatization with O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine in spirits and vodkas is discussed. The optimal parameters (extraction volume, drop volume, content of ethyl alcohol, sample volume, temperature and time of extraction) for isolation and preconcentration of C1–C6 aldehydes from alcoholic matrices were established. The developed SDE‐gas chromatography (GC)‐electron capture detection (ECD), an extraction method, allows the determination of low molecular aldehydes at level lower than 1 µg dm−3. The overall analysis time without derivatization is 35 minutes. The procedure was applied for the determination of aldehydes in real alcoholic beverages (vodkas). The simplicity and cost‐effectiveness of the proposed procedure makes it a good alternative to solid phase microextraction (SPME) and other more labor‐intensive methods.

Origin and Conditions of Ketoacid Formation During Ozonation of Natural Organic Matter in Water

Abstract The batch ozonation of some fractions of aqueous humic substances (humic, fulvic and hydrophilic acids) extracted from natural waters is studied. The reaction leads to oxidation byproducts such as low molecular aldehydes and ketoacids. Formation conditions and origin of some of them (glyoxylic, pyruvic and ketomalonic acids) regarding the extracted fraction of natural organic matter is established.

Cooked odor of antarctic krills. Part VI. Basic and neutral compounds in the cooked odor from antarctic krill.

The cooked odor concentrate from precooked krill was obtained by a simultaneous distillation and extraction system. The resulting odor concentrate was separated into basic, carbonyl and carbonyl-free fractions. Each fraction was analyzed by gas chromatography and gas chromatography-mass spectrometry. Fifty seven compounds, including 3 pyridines, 10 pyrazines, 6 thiazoles, 3 dihydro-4H-1,3,5-dithiazines, 11 aldehydes, 10 ketones, 4 alcohols, 6 hydrocarbons and 4 other compounds were identified. Twenty two of these compounds were newly found as the odor components of krill. The low molecular aldehydes, which are known to be a part of the precursors of the secondary formation of the cooked odor, were also investigated by thin layer chromatography. Ethanal, propanal and butanal were newly detected.

FLUORESCENCE HISTOCHEMISTRY OF BIOGENIC MONOAMINES A STUDY OF THE CAPACITY OF VARIOUS CARBONYL COMPOUNDS TO FORM FLUOROPHORES WITH BIOGENIC MONOAMINES IN GAS PHASE REACTIONS

The capacity of biogenic amines to form fluorophores in histochemical gas phase reactions has been tested with 20 compounds having a carbonyl group (> C = O) as a common characteristic. Significant visible fluorescence was induced from catecholamines and indolamines with aldehydes, ketones, α-keto acids and carboxylic acids, suggesting that all of these compounds can enter fluorophore-forming cyclization reactions under the histochemical gas phase conditions. The most "reactive" reagents are found among the low molecular aldehydes, and formaldehyde and glyoxylic acid seem to be the most suitable reagents, combining high reactivity with good selectivity. Fluorescence, interesting for the histochemical demonstration of N-acetylated indolamines, was obtained from melatonin and N-acetyl-5-hydroxytryptamine with some acid reagents (glyoxylic acid, formic acid, acetic acid and pyruvic acid). A direct cyclodehydration according to the classical Bischler-Napieralski reaction is the most likely mechanism underlying this fluorophore formation. The usefulness of the various carbonyl reagents for the fluorescence histochemical demonstration of other biologically interesting amines, such as histamine, p-tyramine and octopamine, has been specially investigated.