Showing papers on "Benzoic acid published in 2007"
TL;DR: The oxidative coupling of benzoic acids with internal alkynes effectively proceeds in the presence of [Cp*RhCl2]2 and Cu(OAc)2 x H2O as catalyst and oxidant, respectively, to produce the corresponding isocoumarin derivatives.
Abstract: The oxidative coupling of benzoic acids with internal alkynes effectively proceeds in the presence of [Cp*RhCl2]2 and Cu(OAc)2 x H2O as catalyst and oxidant, respectively, to produce the corresponding isocoumarin derivatives. The copper salt can be reduced to a catalytic quantity under air. Interestingly, by using [Cp*IrCl2]2 in place of [Cp*RhCl2]2, the substrates undergo 1:2 coupling accompanied by decarboxylation to afford naphthalene derivatives exclusively. In this case, Ag2CO3 acts as an effective oxidant.
475 citations
TL;DR: In this paper, the synthesis of acrolein by catalytic gas-phase dehydration of biomass-derivate glycerol was studied over various solid catalysts with a wide range of acid base properties.
326 citations
TL;DR: In this article, the effect of various operating parameters using titanium based dimensionally stable anode (DSA) was investigated to degrade a textile dye namely Reactive Blue 19 (RB-19).
297 citations
TL;DR: In this paper, a series of compounds having hydrazide groups was prepared and evaluated as nucleating agent for poly(L-lactic acid) by differential scanning calorimetry.
Abstract: A series of compounds having hydrazide groups was prepared and evaluated as nucleating agent for poly(L-lactic acid) by differential scanning calorimetry. Hydrazide compounds derived from benzoic acid, 2-hydroxybenzoic acid, 3-tert-butylbenzoic acid, and 2-aminobenzoic acid, where two of hydrazide compounds connected by four methylene chain were evaluated in series. Benzoylhydrazide type was found to be more effective on the enhancement of crystallization of poly(L-lactic acid). Effects of connecting length of methylene chain numbers between two of benzoylhydrazide on the nucleation ability were also evaluated. Benzoylhydrazide-type compound having 10 methylenes, that is, decamethylenedicarboxylic dibenzoylhydrazide demonstrated excellent nucleation ability, and the resulted crystallization temperature and enthalpy of PLA with the compound of 1 wt % loading were 131°C and 46 J g−1. The achieved crystallization temperature and enthalpy were over 10°C and over 10 J g−1 higher than PLA with conventional nucleating agents, such as talc and ethylenebis (12-hydroxystearylamide). Thus, the improvement in processability, productivity, and heat resistance of PLA is suggested to be achieved by using decamethylenedicarboxylic dibenzoylhydrazide as a nucleating agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 198–203, 2007
196 citations
TL;DR: In this paper, the polyphenol contents of the seed coat fraction of the millet were extracted with different polar and non-polar solvents, and it was observed that 1% HCl-methanol was very effective for extraction of the MILlet polyphenols.
196 citations
TL;DR: In this paper, five Cu(II)/benzoate/4,4‘-bipy complexes were synthesized through hydrothermal reaction of copper(II) nitrate, benzoic acid, and 4,4'bipyridine under different pH conditions, showing the marked sensitivity of the structural chemistry of the aromatic carboxylate ligand to synthesis conditions.
Abstract: Five Cu(II)/benzoate/4,4‘-bipy complexes, namely, [Cu(H2O)(benzoate)2(4,4‘-bipy)2](benzoic acid)2·(4,4‘-bipy) (1), [Cu2(H2O)2(benzoate)4(4,4‘-bipy)3]·(H2O)9 (2), [Cu2(benzoate)4(4,4‘-bipy)3] (3), [Cu3(H2O)4(benzoate)6(4,4‘-bipy)4.5]·(4,4‘-bipy)·(H2O)5 (4), and [Cu3(OH)2(H2O)2(benzoate)4(4,4‘-bipy)2] (5) (4,4‘-bipy = 4,4‘-bipyridine), have been synthesized through hydrothermal reaction of copper(II) nitrate, benzoic acid, and 4,4‘-bipyridine under different pH conditions. The diverse product structures show the marked sensitivity of the structural chemistry of the aromatic carboxylate ligand to synthesis conditions. Complex 1, which exhibits a zero-dimensional (0D) structure of mononuclear copper(II), is formed at pH = 5.5. At pH = 6.0, dimeric copper(II) complexes of 2 and 3 are formed. Reaction at pH = 7 leads to a one-dimensional (1D) structure of 4. A further increase of the pH to 8.0 results in a two-dimensional (2D) structure of 5. Crystal data are monoclinic, space group P2/n, a = 13.992(4) A, b = 5...
160 citations
TL;DR: The aim was to compare the production of antifungal metabolites in silage with the production in liquid cultures previously studied in the laboratory, and it was concluded that other metabolites, e.g., p-hydrocoumaric acid, hydroferulic acid, and p-coumarIC acid, were released from the grass by the added LAB strains.
Abstract: The metabolite production of lactic acid bacteria (LAB) on silage was investigated. The aim was to compare the production of antifungal metabolites in silage with the production in liquid cultures previously studied in our laboratory. The following metabolites were found to be present at elevated concentrations in silos inoculated with LAB strains: 3-hydroxydecanoic acid, 2-hydroxy-4-methylpentanoic acid, benzoic acid, catechol, hydrocinnamic acid, salicylic acid, 3-phenyllactic acid, 4-hydroxybenzoic acid, (trans, trans)-3,4-dihydroxycyclohexane-1-carboxylic acid, p-hydrocoumaric acid, vanillic acid, azelaic acid, hydroferulic acid, p-coumaric acid, hydrocaffeic acid, ferulic acid, and caffeic acid. Among these metabolites, the antifungal compounds 3-phenyllactic acid and 3-hydroxydecanoic acid were previously isolated in our laboratory from liquid cultures of the same LAB strains by bioassay-guided fractionation. It was concluded that other metabolites, e.g., p-hydrocoumaric acid, hydroferulic acid, and p-coumaric acid, were released from the grass by the added LAB strains. The antifungal activities of the identified metabolites in 100 mM lactic acid were investigated. The MICs against Pichia anomala, Penicillium roqueforti, and Aspergillus fumigatus were determined, and 3-hydroxydecanoic acid showed the lowest MIC (0.1 mg ml−1 for two of the three test organisms).
154 citations
TL;DR: The reactions of benzoic acid derivatives with (N-isocyanimino)triphenylphosphorane proceed smoothly at room temperature to afford 2-aryl-1,3,4-oxadiazoles in high yields as mentioned in this paper.
125 citations
TL;DR: In this paper, the photocatalytic oxidation of different benzene derivatives has been investigated in order to understand how the substituent group affects the selectivity to hydroxylated compounds.
124 citations
TL;DR: The behavior of addition of aromatic acids and their sodium salts on the micellar morphological changes in cationic gemini surfactant solutions is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive.
Abstract: In this paper, we are reporting the influence of addition of aromatic acids (anthranilic and benzoic acid) and their sodium salts on the micellar morphological changes in three cationic gemini surfactant solutions, viz. 5 mM tetramethylene-1,4-bis(N-hexadecyl-N,N-dimethylammonium bromide), 10 mM pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium bromide), and 10 mM hexamethylene-1,6-bis(N,-hexadecyl-N,N-dimethylammonium bromide). The solubilization site of the counterions (obtained from the additives) near the micellar surface are inferred by 1H NMR. The behavior is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive.
122 citations
TL;DR: Direct head-space analysis of the gaseous components formed during quercetin oxidation in aqueous solution at ambient temperature indicates that the ratio of carbon dioxide/carbon monoxide in the gas phase after acidification of the reaction media is 96:4%.
Abstract: Oxidation of quercetin by air oxygen takes place in water and aqueous ethanol solutions under mild conditions, namely in moderately-basic media (pH approximately 8-10) at ambient temperature and in the absence of any radical initiators, without enzymatic catalysis or irradiation of the reaction media by light. The principal reaction products are typical of other oxidative degradation processes of quercetin, namely 3,4-dihydroxy-benzoic (proto-catechuic) and 2,4,6-trihydroxybenzoic (phloroglucinic) acids, as well as the decarboxylation product of the latter--1,3,5-trihydroxybenzene (phloroglucinol). In accordance with the literature data, this process involves the cleavage of the gamma-pyrone fragment (ring C) of the quercetin molecule by oxygen, with primary formation of 4,6-dihydroxy-2-(3,4-dihydroxybenzoyloxy)benzoic acid (depside). However under such mild conditions the accepted mechanism of this reaction (oxidative decarbonylation with formation of carbon monoxide, CO) should be reconsidered as preferably an oxidative decarboxylation with formation of carbon dioxide, CO2. Direct head-space analysis of the gaseous components formed during quercetin oxidation in aqueous solution at ambient temperature indicates that the ratio of carbon dioxide/carbon monoxide in the gas phase after acidification of the reaction media is ca. 96:4%. Oxidation under these mild conditions is typical for other flavonols having OH groups at C3 (e.g., kaempferol), but it is completely suppressed if this hydroxyl group is substituted by a glycoside fragment (as in rutin), or a methyl substituent. An alternative oxidation mechanism involving the direct cleavage of the C2-C3 bond in the diketo-tautomer of quercetin is proposed.
TL;DR: Both the rate of permeation and potassium transfer significantly increase when hydrophilic surfactants are present and there was no relationship observed between potassium cation transfer from the internal phase and emulsion stability in the storage test.
Abstract: The effects of various commercial and model surfactants of different structure and hydrophilicity were studied on water-in-oil (w/o) emulsion stability, potassium cation leakage and permeation of 6-nitro-3-phenylacetamide benzoic acid in a model system using Penicillin acylase (EC 35111) immobilized in a liquid membrane Both emulsion stability, potassium leakage and permeation of organic substances depend upon hydrophilicity of surfactants Hydrophilic surfactants may be used to stabilize emulsions only in mixtures with hydrophobic emulsifiers Additions of small quantities of hydrophilic surfactants to the system in which permeation occurs together within an enzymatic process may be advantageous Both the rate of permeation and potassium transfer significantly increase when hydrophilic surfactants are present There was no relationship observed between potassium cation transfer from the internal phase and emulsion stability in the storage test
TL;DR: In this paper, the authors used oxovanadium(IV) exchanged zeolite-Y with the Schiff base derived from salicylaldehyde and 2-aminomethylbenzimidazole (Hsal-ambmz) in refluxing methanol followed by aerial oxidation leads to the formation of encapsulated dioxovanadium (V) complex, [VO2(sal-ambermz)]-Y(1).
Abstract: Interaction of oxovanadium(IV) exchanged zeolite-Y with the Schiff base derived from salicylaldehyde and 2-aminomethylbenzimidazole (Hsal-ambmz) in refluxing methanol followed by aerial oxidation leads to the formation of encapsulated dioxovanadium(V) complex, [VO2(sal-ambmz)]-Y(1). Similar reaction with copper(II) exchanged zeolite-Y followed by its treatment with aqueous NaCl gave encapsulated copper(II) complex, [Cu(sal-ambmz)Cl]-Y(2). These encapsulated complexes have been characterized by spectroscopic studies, thermal analysis and scanning electron micrographs (SEMs) as well as X-ray diffraction patterns. 3D model structure generated for neat complex [VO2(sal-ambmz)] suggests that zeolite-Y can accommodate these complexes in its nano-cavity without any strain. The encapsulated materials are active catalysts for the oxidation of phenol, styrene and methyl phenyl sulfide using H2O2 as an oxidant. Under the optimised reaction conditions about 42% conversion of phenol was obtained with these catalysts where the selectivity of catechol varied in the order: 2 (73.9%) >1 (65.2%). With the conversion of 97.0% with 1 or 56.7% with 2, the oxidation of styrene gave styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde as major products. A maximum of 96.1% (with 1) conversion of methyl phenyl sulfide was observed in which the selectivity of major product methyl phenyl sulfoxide was found to be ca. 98%.
TL;DR: Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated and high reaction temperatures are an advantage because under these conditions smaller amounts of byproducts are formed.
Abstract: Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Careful control of the reaction conditions is necessary because ammonium hexanitratocerate(IV) dissolved in an ionic liquid can transform benzyl alcohol not only into benzaldehyde but also into benzyl nitrate or benzoic acid. The selectivity of the reaction of cerium(IV) triflate with benzyl alcohol in dry ionic liquids depends on the degree of hydration of cerium(IV) triflate: anhydrous cerium(IV) triflate transforms benzyl alcohol into dibenzyl ether, whereas hydrated cerium(IV) triflate affords benzaldehyde as the m...
TL;DR: The cyclization of amino-alkynes 1 in which an amino group is attached to the aromatic ring, proceeded smoothly using a catalytic amount of Pd(PPh3)4 and benzoic acid in toluene at 120 degrees C, leading to the formation of the 2-substituted tetrahydroquinolines 2.
Abstract: The cyclization of amino-alkynes 1 in which an amino group is attached to the aromatic ring, proceeded smoothly using a catalytic amount of Pd(PPh3)4 and benzoic acid in toluene at 120 °C, leading to the formation of the 2-substituted tetrahydroquinolines 2. An asymmetric variant of the reaction using the chiral palladium catalyst (prepared in situ by mixing Pd2(dba)3·CHCl3 and (R,R)-RENORPHOS) was also explored. The absolute configuration of the enantiomerically enriched tetrahydroquinolines, obtained in this way, was determined by converting them to the known compounds and was found to be R. The alkaloids such as (±)-galipinine, (±)-angustureine, and their optically active form were synthesized by using this reaction as a key step.
TL;DR: In this article, the preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr)3 and KMnO4 with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof.
TL;DR: In this paper, a polymer-anchored 2-(2′-hydroxyphenyl)benzimidazole (Hhpbmz) has been covalently bonded to the chloromethylated polystyrene cross-linked with 5% divinylbenzene.
Abstract: Monobasic bidentate ligand 2-(2′-hydroxyphenyl)benzimidazole (Hhpbmz) has been covalently bonded to the chloromethylated polystyrene cross-linked with 5% divinylbenzene. Treatment of the resulted chelating resin, abbreviated as PS-Hhpbmz, with [VO(acac)2], [MoO2(acac)2] (Hacac = acetylacetone) and Cu(CH3COO)2·H2O, gave polymer-anchored complexes PS-[VO(hpbmz)2], PS-[MoO2(hpbmz)2] and PS-[Cu(hpbmz)2], respectively. The corresponding neat complexes with Hhpbmz have also been prepared similarly. Structures of these complexes have been established on the basis of elemental analyses, scanning electron micrographs and spectroscopic (infrared and electronic) as well as thermogravimetric studies. These complexes have been tested as catalyst for the oxidation of styrene, ethylbenzene and methyl phenyl sulfide. Reaction conditions for the maximum oxidation of these substrates have been optimised by considering the concentration of oxidant, amount of catalyst, volume of solvent and temperature of the reaction mixture. Under the optimised conditions styrene gave a maximum of 58.9% conversion with five reaction products namely styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid, and phenylacetaldehyde. Oxidation of ethylbenzene gave 47.7% conversion where benzaldehyde, phenyl acetic acid, styrene, 1-phenylethane-1,2-diol and benzoic acid have been obtained as major oxidation products. A maximum of 76.5% conversion of methyl phenyl sulfide, catalysed by PS-[VO(hpbmz)2], has been achieved. Catalyst, PS-[MoO2(hpbmz)2] has shown comparable (75.1%) catalytic activity while only 44.8% conversion has been achieved with PS-[Cu(hpbmz)2]. Irrespective of their catalytic performances, the selectivity for the formation of sulfoxide is almost similar (ca. 75%) for all these catalysts. These catalysts do not leach metal ions during catalytic activity and are recyclable.
TL;DR: The diffusion profiles obtained for SA in the different solvents were very similar when compared with those obtained for BA but the permeation rates were higher for BA than for SA, which results from the similar chemical structure and lipophilicity.
TL;DR: It has been found that salicylic acid can be removal effectively at the lower temperature of 140 degrees C on perovskite-type oxide LaFeO3 catalyst in the catalytic wet air oxidation (CWAO) process, which confirms further the key role of intramolecular H-bonding in the CWAO.
TL;DR: A series of lanthanide metal−organic frameworks, [Ln2 (Suc)0.5(BC)3(OH)2] have been synthesized by the reaction of nitrate salts of Ln(III) with succinic acid and benzoic acid under hydrothermal conditions and were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction.
Abstract: A series of lanthanide metal−organic frameworks, [Ln2 (Suc)0.5(BC)3(OH)2] (Ln = Tb (1), Eu (2), Sm (3), Pr (4); H2Suc = succinic acid; HBC = benzoic acid), have been synthesized by the reaction of nitrate salts of Ln(III) with succinic acid and benzoic acid under hydrothermal conditions and were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analyses reveal that they exhibit the same two-dimensional (2D) architecture and crystallized in triclinic space group P1 for complexes 1−4. Infinite inorganic walls were formed by lanthanide ions, μ3-OH, and an edge-sharing “...Ln−O−C−O−Ln...” chain, which link to each other through the carbon atoms of the succinate anions on the [110] plane and phenyl groups of the benzoic acid ligands on the [101] plane, leading to a two-dimensional open framework structure. The thermogravimetric analysis of 1−4 and photoluminescent properties of 1 and 2 are discussed in detail.
TL;DR: In this article, the adsorption of benzoic acid from water on cetyl trimethylammonium exchanged montmorillonite (CTAB-montmorillonites) is reported.
TL;DR: In this article, the molecular diffusion coefficient data were obtained for 2-naphthol, benzoic acid, salicylic acid, camphor, and cinnamic acid in water at temperatures that differ significantly from ambient value.
Abstract: Molecular (or tracer) diffusion coefficient data were obtained for 2-naphthol, benzoic acid, salicylic acid, camphor, and cinnamic acid in water at temperatures that differ significantly from ambient value. Experimental values were determined for the dissolution of 2-naphthol in water at 283 to 368 K, of benzoic acid in water at 283 to 338 K, of salicylic acid in water at 283 to 343 K, of camphor in water at 283 to 318 K, and of cinnamic acid in water at 283 to 318 K. Empirical correlations are presented for the prediction of molecular diffusion coefficient over the entire range of temperatures studied, and they are shown to predict the obtained data with very good accuracy.
TL;DR: It was found that the enthalpic contribution is negligible and that the changes in surface pKa values are entropically controlled, which suggests that solvent ordering/disordering around the interface strongly influences the observed pKa value, which then reflects the relative hydrophobicity/hydrophilicity of the different graphitic surfaces.
Abstract: The difference between the values of 4-carboxyphenyl groups, covalently attached to either graphite (BAcarbon) or glassy carbon (BA-GC) surfaces, and benzoic acid in solution is explored using potentiometric titration and cyclic voltammetry. In solution, benzoic acid has a pKa of 4.20 at 25 °C. However, the observed pKa value on the graphitic surfaces shows significant deviations, with BAcarbon exhibiting a large shift to higher pKa values (pKa = 6.45) in contrast to BA-GC, which is shifted to lower pKa values (pKa = 3.25). Potentiometric titrations at temperatures between 25 and 50 °C allowed us to determine the surface pKa of these materials at each temperature studied and hence to determine the enthalpy, entropy, and Gibbs' energy changes associated with the ionization of the carboxylic acid groups. It was found that the enthalpic contribution is negligible and that the changes in surface pKa values are entropically controlled. This suggests that solvent ordering/disordering around the interface strong...
TL;DR: In this paper, the solubility of benzoic acid and phthalic acid in acetic acid + water solvent mixtures is determined by a static method, and the experimental data was correlated by the NRTL activity coefficient model.
Abstract: The solubilities of benzoic acid and phthalic acid in acetic acid + water solvent mixtures are determined by a static method. The experimental temperature ranges from (298.3 to 367.9) K, and the mass fraction of acetic acid in the solvent mixtures ranges from 0.8 to 1.0. The experimental results show that, within the temperature range of the measurements, the solubility of benzoic acid and phthalic acid in all the mixtures shows an increasing trend as the temperature increases. The solubility of benzoic acid decreases with increasing mass fraction of water. For the solubility of phthalic acid in acetic acid + water within the solvent composition range of the measurements, below 325.2 K, the higher the mass fraction of water, the less the solubility. However, above 325.2 K the higher the mass fraction of water, the greater the solubility. A simple explanation was given for this “maximum-solubility effect”. The experimental data was correlated by the Non-Random Two Liquids (NRTL) activity coefficient model,...
TL;DR: In this paper, the polyphenols epicatechin and epigallocatechin gallate (EGCG) were evaluated for their efficiency in regenerating α-tocopherol from α -tocopheroxyl radical in comparison with ascorbyl palmitate.
Abstract: Benzoic acid-derived phenolics (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, vanillic acid, syringic acid, and gallic acid) and the polyphenols epicatechin and epigallocatechin gallate (EGCG) were evaluated for their efficiency in regenerating α-tocopherol from α-tocopheroxyl radical in comparison with ascorbyl palmitate, which is known to regenerate α-tocopherol. Ethanolic solutions of phenolic compounds were added to a homogeneous hexane medium containing α-tocopheroxyl radical generated by reaction of α-tocopherol in molar excess with 1,1-diphenyl-2-picrylhydrazyl radical, and the α-tocopheroxyl radical was monitored by electron spin resonance spectroscopy. p-Hydroxybenzoic acid, vanillic acid, and syringic acid (400 μM) did not exhibit a significant effect on α-tocopheroxyl radical concentration (0.6−0.7 μM). In contrast, 3,4-dihydroxybenzoic acid and gallic acid were able to reduce the concentration of α-tocopheroxyl radical by 16 and 64%, respectively. Epicatechin showed a reduction of α-tocoph...
TL;DR: In this article, an aromatic diazirine-containing benzoic acid has been prepared via the key intermediate, and it has been shown that irradiation of the simple ester yields the methanol insertion product 24.
TL;DR: An application of solid phase extraction (SPE) for high-performance liquid chromatography (HPLC) analysis was developed for the rapid determination of benzoic acid and sorbic acid in Thai rice wine and distillate products as mentioned in this paper.
TL;DR: Inhibition studies revealed that the proposed electrochemical biosensor was applicable for monitoring benzoic acid in real sample such as milk, yoghurt, sprite and cola, and investigated the effects of temperature, pH value of solution on the inhibition and the interferences.
TL;DR: The fast co-oxidation of the alcohol means that HO2* gradually takes over the role of benzylperoxyl as principal chain carrier, which drastically changes the autoxidation mechanism and, among other things, causes a sharp decrease in the hydroperoxide yield.
Abstract: Aerobic oxidation of toluene (PhCH3) is investigated by complementary experimental and theoretical methodologies. Whereas the reaction of the chain-carrying benzylperoxyl radicals with the substrate produces predominantly benzyl hydroperoxide, benzyl alcohol and benzaldehyde originate mainly from subsequent propagation of the hydroperoxide product. Nevertheless, a significant fraction of benzaldehyde is also produced in primary PhCH3 propagation, presumably via proton rather than hydrogen transfer. An equimolar amount of benzyl alcohol, together with benzoic acid, is additionally produced in the tertiary propagation of PhCHO with benzylperoxyl radicals. The "hot" oxy radicals generated in this step can also abstract aromatic hydrogen atoms from PhCH3, and this results in production of cresols, known inhibitors of radical-chain reactions. The very fast benzyl peroxyl-initiated co-oxidation of benzyl alcohol generates HO2* radicals, along with benzaldehyde. This reaction also causes a decrease in the overall oxidation rate, due to the fast chain-terminating reaction of HO2*with the benzylperoxyl radicals, which causes a loss of chain carriers. Moreover, due to the fast equilibrium PhCH2OOH+HO2* right harpoon over left harpoonPhCH2OO* + H2O2, and the much lower reactivity of H2O2 compared to PhCH2OOH, the fast co-oxidation of the alcohol means that HO2* gradually takes over the role of benzylperoxyl as principal chain carrier. This drastically changes the autoxidation mechanism and, among other things, causes a sharp decrease in the hydroperoxide yield.
TL;DR: The developed method was shown to be suitable for the routine monitoring of benzoic and sorbic acids in various types of food samples and reproducibility was tested by evaluating the intra- and interday precisions.
Abstract: A simple, rapid and sensitive on-line method for the simultaneous determination of benzoic and sorbic acids in food was developed by coupling in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC) with UV detection. The diethylamine-modified poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolithic capillary selected as the extraction medium exhibited a high extraction capability towards benzoic and sorbic acids. To obtain optimum extraction performance, several in-tube SPME parameters were investigated, including pH value, inorganic salt, and the organic solvent content of the sample matrix. After simple dilution with 0.02 mol/L phosphate solution (pH 4.0), carbonated drink, juice drink, sauce and jam samples could be directly injected for extraction. For succade samples, a small amount of acetonitrile was required to extract analytes prior to dilution and subsequent extraction. The linearity of the method was investigated over a concentration range of 5–20000 ng/mL for both analytes, and the correlation coefficients (R
2 values) were higher than 0.999. The detection limits for benzoic and sorbic acids were 1.2 and 0.9 ng/mL, respectively. The method reproducibility was tested by evaluating the intra- and interday precisions; relative standard deviations of less than 4.4 and 9.9%, respectively, were obtained. Recoveries of compounds from spiked food samples ranged from 84.4 to 106%. The developed method was shown to be suitable for the routine monitoring of benzoic and sorbic acids in various types of food samples.