Photometric stopped-flow determinations of butylated hydroxyanisole

Summary A kinetic study of the colour reactions between butylated hydroxyanisole (BHA) and Gibbs and Ehrlich reagents carried out with a stopped-flow system is reported. Kinetic methods for the determination of BHA were developed with both reagents. The parameters used were the initial rate and the signal amplitude. The use of a diode-array photodetector allowed the application of an amplification method with a decreased detection limit. The different kinetic methods developed were satisfactorily applied to the determination of BHA in different commercial oil samples. Analytical recovery data are also reported.

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Photometrische Stopped-Flow Bestimmung von butyliertem Hydroxyanisol

     

Protective role of butylated hydroxytoluene and certain carotenoids in photocarcinogenesis

Butylated hydroxytoluene (BHT) and certain carotenoid pigments have been found to inhibit photocarcinogenesis in animal models. In addition, BHT protects against UV-B-induced erythema and UV-B induction of ornithine decarboxylase. Studies on the photoprotective mechanism(s) of BHT suggested that changes in the physico-chemical properties of the keratin of the stratum corneum layer of skin occurred, leading to increases in UV absorption of that tissue. These changes might be exerted via the anti-radical action of BHT that retards oxidation and prevents cross-linking of the keratin chains, resulting in a diminution of UV-B radiation reaching potential target sites. The carotenoids beta-carotene, canthaxanthin and phytoene also inhibit UV-B carcinogenesis. beta-Carotene and canthaxanthin are excellent quenchers of singlet oxygen, and all three pigments can quench free radicals. beta-Carotene and canthaxanthin have been shown to quench singlet oxygen/free radical reactions in the skin of porphyric mice, and these two pigments as well as phytoene have been found to quench excited species formed on irradiation of mouse skin by UV-B.     

Effects of butylated hydroxytoluene upon PUVA-tumorigenesis and induction of ornithine decarboxylase activity in the mouse

Psoralen photochemotherapy (PUVA) is widely used in the treatment of psoriasis. Some therapy regimen have been associated with increased risk of skin cancer. Free radical species are thought to play a role in psoralen phototoxicity and photocarcinogenesis. It has been reported that the antioxidant butylated hydroxytoluene (BHT) inhibits acute phototoxicity by PUVA but does not reduce therapeutic efficacy. It has also been shown that BHT inhibits UVB-induced erythema, tumorigenesis and induction of ornithine decarboxylase (ODC) activity--ODC activity is thought by some to be associated with tumor promotion. Therefore, we have investigated the effect of BHT on psoralen tumorigenesis and PUVA-induced epidermal ODC activity. SKH-Hr-1 hairless albino mice were treated with topically applied 8-MOP and exposed to UVA (3X weekly) for 31 weeks with and without BHT administered either in the diet or topically. Induction of ODC activity was determined in similar experimental groups 24 h after a single exposure to UVA. Neither route of BHT administration had any effect on 8-MOP phototumorigenesis. However, BHT when administered in the diet reduced induction of ODC activity by 40% (p less than 0.05). These data indicate different mechanisms for UVB- and PUVA-induced carcinogenesis and again bring into question the relationship between induction of ODC activity and photocarcinogenesis.     

Solid-phase ultraviolet absorbance spectrophotometric multisensor for the simultaneous determination of butylated hydroxytoluene and co-existing antioxidants

Continuous flow injection and UV spectrophotometric detection have been proposed for simultaneous determination of the two binary mixtures, butylated hydroxytoluene (BHT)/n-propyl gallate (n-PG) and butylated hydroxytoluene (BHT)/butylated hydroxyanisole (BHA), in food and cosmetics samples. The method is based on the different residence times of each antioxidant when the flow cell is packed to a height of 25 mm with silica C₁₈ using methanol-water 50:50% (v/v) as a carrier with a flow rate of 1.25 and 1.10 ml min⁻¹, respectively. The determination of each antioxidant is based on the measurement of its absorbance at its maximum wavelengths using a DAD detector at 30 and 180 s for the mixture n-PG-BHT and 90 and 220 s for BHA-BHT. Calibration graphs were linear over the range 10.0-300.0 μg ml⁻¹ for each antioxidant in both mixtures. The relative standard deviations were 2.5% for BHT and 2.0% for the co-existing antioxidant. Resolution of the n-PG-BHT mixture in ratios between 1:8 and 8:1 and the BHA-BHT mixture in ratios between 1:10 and 10:1 is possible. The method was applied to the determination of both antioxidants in fat foods and cosmetics samples with recoveries ranging between 101 and 105%.     

Molecular inclusion of butylated hydroxyanisole (BHA) into alpha and beta cyclodextrins

BHA (butylated hydroxyanisole) was complexed with ??- and ??-cyclodextrins with the objective of characterizing the thermal stability. From phase solubility diagrams, the association constants for the complexes of ??-CD:BHA and ??-CD:BHA were found as 49.3 and 585 L mol^?1, respectively. To increase the thermal stability of BHA, its molecular encapsulation in ??-CD and ??-CD, was tested using molar ratios of 1:1 and 1:2 (BHA:CD) and the complex preparation techniques of kneading and physical mixture. The products of complexation were characterized by differential scanning calorimetry and thermogravimetry, indicating the formation of a BHA:??-CD complex and showing that the release of the complexed BHA occurs in the temperature range of 280?C350 °C, well above the temperature at which BHA sublimates. Dissolution tests have shown that the BHA: ??-CD complex produced by kneading has high efficiency of dissolution and partition coefficient experiments demonstrated that the presence of ??-CD leads to higher concentration of BHA in the organic phase.     

Preconcentration and differential pulse voltammetry of butylated hydroxyanisole at a carbon paste electrode

Butylated hydroxyanisole (BHA) and other tocopherols are shown to accumulate very strongly onto carbon paste, with the surface species retaining their characteristic electroactivity. This accumulation serves as a preconcentration step which improves the voltammetric measurement with respect to the sensitivity and selectivity. After 5-min preconcentration, a detection limit near 2 × 10^?8 M BHA is obtained. Enhanced selectivity is achieved if the electrode is transferred into an electrolytic blank solution between the preconcentration and measurement steps. The accumulated analyte can then be quantified in the presence of a 10³-fold amount of a solution species with similar redox potential. The differential pulse stripping response is evaluated with respect to concentration dependence, reproducibility, preconcentration period, detection limit, and other variables. The preconcentration/medium exchange approach is exploited for selective detection of BHA in a flow injection system. Applicability to various real samples is illustrated.     

Binding of thermo-sensitive and pH-sensitive butylated poly(allylamine)s with lysozyme

Butyl modified poly(allylamine)s with butyl substitution degrees of 15%to 70%were prepared.The polymers show pH sensitive property and lower critical solution temperature(LCST)behavior.The LCST appears at lower temperature,lower pH and lower polymer concentration for the polymer with higher butylated degree.The binding of native lysozyme with the polymers depends on the hydrophobicity of the polymers at the pH range that the protein and the polymer carry the same positive charges.The increase of polymer hydrophobicity can increase the binding with lysozyme,but the self-aggregation of the polymer decreases the binding.The bound lysozyme molecules can recover their native activity completely after the dissociation of the complexes.Compared with native lysozyme,the denatured one which exposes the hydrophobic residues can increase the binding with the polymer and form stable complex nanoparticles.     

Capillary electrophoresis-amperometric determination of antioxidant propyl gallate and butylated hydroxyanisole in foods.

Capillary electrophoretic separation coupled with end-column amperometric detection for the simultaneous quantification of butylated hydroxyanisole (BHA) and propyl gallate (PG) in food was developed. Important factors affecting separation and detection, such as the running buffer, separation voltage, and detection potential, were investigated in detail. An improved working electrode preparation method was used, where a carbon disk of 33 microm in diameter was sealed in a tip and positioned opposite the outlet of a capillary. The experiments indicated that the preparation method was simple, and the obtained electrode exhibited good flexibility and stability for the determination of phenolic antioxidants. The separation was carried out within 5 min using a 50 cm length capillary, with a solution containing 5 mM phosphate and 5 mM borax of pH 8.84 as a separation buffer, and a separation potential of 20 kV. Amperometric detection was achieved with an applied potential of 0.70 V versus Ag|AgCl| saturated KCl. There was excellent linearity between the peak current and the concentrations of the analytes in the range of 1.8 - 180.2 microg/mL for BHA and 10.6 - 212.2 microg/mL for PG, respectively. Relative standard deviations of 4.92% for BHA and 5.27% for PG were obtained, respectively. The developed method was successfully applied for the determination of antioxidants in several commercial foods.     

Application of solid-phase microextraction combined with gas chromatography-mass spectrometry to the determination of butylated hydroxytoluene in bottled drinking water

Butylated hydroxytoluene (BHT) is an antioxidant utilized as additive in foods and packaging plastic. Its presence in drinking water is possible if it is used as an antioxidant in the packaging plastic because it may migrate into the package's contents. A method for the determination of BHT in water by means of solid-phase microextraction and gas chromatography-mass spectrometry has been developed and evaluated with respect to the time of fiber exposure, limits of detection and quantitation, linearity and precision. Finally, the method was applied to evaluate the presence of this substance in samples of mineral and mineralized bottled drinking water, and it appeared to be present in seven out of a total of fifteen commercial brands.     

FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular geometry of butylated hydroxy toluene

The FT-IR spectrum of 2,6-di-tert-butyl-4-methylphenol [butylated hydroxy toluene] was recorded in the region 4000-400 cm(-1). The FT-Raman spectrum of butylated hydroxy toluene was also recorded in the region 3500-50 cm(-1). The molecular structure and vibrational frequencies of butylated hydroxy toluene (BHT) have been investigated with combined experimental and theoretical study. Two stable conformers of the title compound were obtained from the result of geometry optimizations of these possible conformers. The conformer 1 is (approximately 2.6 kcal/mol) more stable than conformer 2. Geometry optimizations and vibrational frequency calculations were performed by BLYP and B3LYP methods using 6-31G(d), 6-31G(d,p) and 6-31+G(d,p) as basis sets. The scaled frequencies were compared with experimental spectrum and on the basis of this comparison; assignments of fundamental vibrational modes were examined. Comparison of the experimental spectra with harmonic vibrational wavenumbers indicates that B3LYP/6-31G(d) results are more accurate. Predicted electronic absorption spectra of BHT from TD-DFT calculation have been analyzed and compared with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.     

In situ formation of silver nanoparticles in PMMA via reduction of silver ions by butylated hydroxytoluene

Silver nanoparticles (Ag NPs) were efficiently generated by in situ reduction of silver ions via butylated hydroxytoluene (BHT), in poly(methyl methacrylate). The characterization of Ag/PMMA by TEM, SEM, XRD, and FTIR indicated that Ag NPs with a face center cubic (fcc) crystal structure and a mean diameter of about 30 nm were dispersed in PMMA matrix with a relatively uniform distribution. In addition, the results of UV–Vis spectroscopy indicated that optical properties of the nanocomposite appeared mainly dependent on the reaction time and temperature. Increasing the reaction time and temperature make higher yield of Ag NPs. A provisional reduction mechanism was also proposed for the formation of the Ag NPs.     

Detection of antioxidant butylated hydroxytoluene (BHT) in Antarctic krill (Euphausia superba Dana)

In this study, butylated hydroxytoluene (BHT) was separated and prepared from Antarctic krill. BHT was separated from the volatile oil of Antarctic krill using high performance thin layer chromatography (HPTLC) with petroleum ether/ethyl acetate/hexane (4:1:0.5, v/v/v) was used as the developing solvent. The content of BHT in volatile oil was 9.20?mg/g and the content of BHT in dried Antarctic krill was 0.35?mg/g (0.070?mg/g in frozen whole Antarctic krill). The linearity, accuracy, stability, and recovery of the analysis showed that HPTLC is the most suitable method for the determination of BHT in Antarctic krill. The BHT crude sample was obtained by scraping the separated spot in the thin layer chromatography plate, which was then analyzed using high performance liquid chromatography (HPLC). The resulting sample was identified with 96.05% purity based on the HPLC analysis. The structure of BHT was determined using gas chromatography–mass spectrometry (GC–MS). The results of the HPLC and GC–MS analysis validated the HPTLC method. BHT is a widely used antioxidant in food, pharmaceuticals, and in industrial production. The exploitation and utilization of BHT in Antarctic krill is of great economic value.     

Fast and direct determination of butylated hydroxyanisole in biodiesel by batch injection analysis with amperometric detection

We report here, for the first time, application of batch injection analysis (BIA) with amperometric detection for determination of the phenolic antioxidant butylated hydroxyanisole (BHA) in biodiesel. A sample plug was directly injected onto a boron-doped diamond electrode immersed in 50% v/v hydroethanolic solution with 0.1 mol L⁻¹ HClO₄ using an electronic micropipette. Importantly, the only preparation step required for biodiesel analysis is dilution in the same hydroethanolic electrolyte solution. Our proposed method has several advantages for routine biodiesel analysis, including: a low relative standard deviation between injections (0.29%, n = 20), high analytical frequency (120 h⁻¹), adequate recovery values (93-101%) for spiked samples, satisfactory accuracy (based on comparative determinations by high-performance liquid-chromatography), and a low detection limit (100 ng of BHA per g of biodiesel). Finally, our method can be adapted for the determination of other antioxidants in biodiesel samples.