On-line HPLC–MS–DPPH assay for the analysis of phenolic antioxidant compounds in fruit wine: Antidesma thwaitesianum Muell.

A reversed phase high performance liquid chromatography (RP-HPLC) separation coupled with an electrospray ionisation mass spectrometry detection (ESI-MS) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used for the screening of multiple antioxidant compounds in Antidesma thwaitesianum Muell. fruit wine. The active compounds were identified by comparison with authentic standards and published mass spectra. With the help of the multidimensional information of LC–ESI-MS/MS and DPPH assay, the compounds with different chemical structures could be determined in one run successfully. The antioxidant compounds were separated and identified as gallic acid, cyanidin-3-sophoroside, monogalloyl glucoside, delphinidin-3-sambubioside, catechin, caffeic acid, and pelargonidin-3-malonyl glucoside. This result shows that an on-line HPLC–MS–DPPH assay can be a powerful technique for the rapid characterisation of antioxidant compounds in plant extracts.     

Partial extraction method for the rapid analysis of total lipids and γ-oryzanol contents in rice bran

Total lipids and γ-oryzanol in rice bran were determined by a partial extraction method. The results agreed well with the conventional total extraction methods. The proposed method uses fewer hazardous organic solvents, takes a shorter extraction time and requires no special extraction apparatus. Total lipids and γ-oryzanol in nine rice bran varieties were analysed by the developed technique. Daw Dum 5647 had the highest total lipids and γ-oryzanol while the lowest content was found in KD XBT 313-19-1-1 and SP XBT 43-7, respectively. The adsorption coefficient (K_d) of the lipids and γ-oryzanol, between hexane and bran, at 30 °C are between 1.16 and 2.00 and 2.02 and 2.65, respectively (depending on the moisture content of the bran). From the K_d values, it was estimated that about 92–95% of the lipids and 95–96% of the γ-oryzanol were extracted into hexane at a 10:1 (v/w) ratio of hexane to bran. The effect of solvents on the extraction of γ-oryzanol from rice bran was also studied. It was found that isopropanol was the most suitable solvent for extraction and determination of γ-oryzanol in rice bran. It showed better agreement with the total extraction method.     

Characterisation of phenolic antioxidants in aqueous extract of Orthosiphon grandiflorus tea by LC–ESI-MS/MS coupled to DPPH assay

Aqueous extract from Orthosiphon grandiflorus tea was on-line screened for its antioxidant components based on their capacity to scavenge free DPPH (1,1-diphenyl-2-picrylhydrazyl) radical after separation by a LC gradient. The structural elucidation of the active compounds was achieved by negative ionisation LC–ESI-MS/MS. Based on their mass spectra and fragmentation patterns related to antioxidant activity trace, seven compounds showing strong DPPH scavenging were identified to be danshensu, caffeic acid, caftaric acid, rosmarinic acid, caffeic acid derivative, sagerinic acid and salvianolic acid B. It is noted that danshensu, caftaric acid, sagerinic acid and salvianolic acid B have been reported in O. grandiflorus for the first time. In addition, the quantification of antioxidant compounds was performed using LC–MS/MS in multiple reaction monitoring (MRM) mode. Rosmarinic acid was found as a major component responsible for the antioxidant activity of this plant extract.     

Improved geopolymerization of bottom ash by incorporating fly ash and using waste gypsum as additive

This research studied the improvement of the geopolymerization of bottom ash (BA) by incorporating fly ash (FA) and using flue gas desulfurization gypsum (FGDG) as additive. The BA:FA ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 were used as the blended source materials. The source materials were then replaced with 0%, 5%, 10%, and 15% of FGDG. NaOH, sodium silicate and temperature curing were used to activate the geopolymer. Test results indicated that the increase in FA content in the BA–FA blends improved the strengths of geopolymer mortars owing to the high glassy phase content and high reactivity of FA compared to those of BA. The use of up to 10% of FGDG as additive also significantly increased the strengths of geopolymer. In this case, the compressive strength enhancement was due to the increase in the Al³⁺ leached from BA in the presence of ${\text{SO}}_4^{2-}$ and the formation of additional calcium silicate hydrate.     

Gas Chromatographic Separation and Identification of Jacaric and Punicic 2-Ethyl-1-Hexyl Esters

The present study demonstrates the separation of a critical pair of conjugated linolenic acid (CLN) isomers—jacaric acid (JA; c8, t10, c12-18:3) and punicic acid (PA; c9, t11, c13-18:3)—on a 60-m conventional Supelcowax 10 column. The alkyl esters of different alcohols (C₁–C₈) of JA and PA were prepared and analyzed isothermally at 220, 230 and 240 °C. The adequacy of their separation was determined from the separation factors (α) and peak resolutions (R _s). Acceptable resolution (R _s = 1.01) of JA and PA was obtained with their 2-ethyl-1-hexyl ester derivatives at a column temperature of 230 °C. In addition, the Gibbs energy of transfer from solution to gas of the three double bonds \((\Delta_{\text{sln}}^{\text{g}} G_{\text{u}}\)) could be used to describe the interactions of the double bond with the stationary phase. Characterization of 2-ethyl-1-hexyl esters of Jacaranda mimosifolia seed oil at 230 °C demonstrates that the oil contains JA and α- and β-calendic acid as a CLN without the presence of PA. The results suggested that JA could be resolved from PA on a 60-m Supelcowax 10 column as the ethyl hexyl ester.     

Separation and Determination of Wax Content Using 100-Å Phenogel Column

Rice bran wax (RBW) is a by product of rice bran oil refinery. Crude RBW from refineries in Thailand had only 20–40% of the wax ester. The major impurity was triglyceride (TG). Purification of RBW requires a rapid and reliable method of analysis. In this study, a modified size exclusion HPLC column (100-Å Phenogel) was reported. Degree swellings of the gel matrix were controlled by isooctane–toluene mobile phase ratio. With pure toluene as the mobile phase, the gel matrix is fully swollen. Wax and TG could not be separated. With 65:35 (v/v) of isooctane–toluene, wax and TG as well as other lipids were baseline separated. The resolution (Rs) between wax and TG was greater than 1.5. Acetic acid (0.1% or higher) in the mobile phase could suppress peak tailing and improved separation of the lipid containing active hydroxyl groups such as free fatty acid, diglyceride and monoglyceride without affecting retention times of the wax and the TG. Separation of lipids in crude RBW could be completed in a single run on the modified Phenogel column (100 Å) with the total analysis time less than 15 min. The relationship between the amount of wax in the sample and the peak area was linear with the R ² greater than 0.98.     

A Mathematical Model for Estimating Molecular Compressibility of Fatty-Acid Methyl Ester and Biodiesel

In this study, the molecular compressibility (k_m) of a fatty-acid methyl ester (FAME) or a biodiesel is correlated with ΔG, , via the Gibbs energy additivity method, where MW is the molecular weight of the FAME or the average MW of the biodiesel. The Gibbs energy associated with molecular compressibility () is further correlated with the structure of FAME. Thus, the relationship between the structure (of a FAME or a biodiesel) and the physical property (k_m) is established. Thus, k_m of a FAME at different temperatures can be easily estimated from the carbon numbers of fatty acid (z) and the number of double bonds (n_d) with good accuracy. For biodiesel, k_m is calculated from the same equation with the average z (z_(ave)) and average n_d (n_d(ave)). k_m is not temperature independent and a slight change in k_m depends on the structure of the FAME and biodiesel. For FAME having 14 carbon atoms or less in the fatty acid, k_m decreases as temperature is increased. On the other hand, for FAME with a longer chain length (16 or higher), k_m increases as temperature is increased. Similarly, a double bond in the long-chain FAME is more sensitive to temperature than the saturated FAME.     

Correlating the Speed of Sound with the Gibbs Energy and Estimating the Speed of Sound in Fatty Acid Methyl Ester and Biodiesel

The relationship between the speed of sound (u) in biodiesel and the change in Gibbs energy (ΔG) has not been described in the literature. With the Gibbs energy additivity method, the relationship between u and ΔG can be expressed as ln(u²) = ΔG/RT + A, where R is the universal gas constant, T is the absolute temperature, and A is a constant. The molecule of fatty acid methyl ester (FAME) was arbitrarily sub-divided into groups of atoms and a ΔG was assigned to each group of atoms. A new model correlating the speed of sound to the structure of fatty acid was derived. The proposed model was good for estimation of the speed of sound in both FAME and biodiesel at various temperatures with good accuracy. The absolute average deviations for the speed of sound in FAME (65 data points) and in biodiesel (175 data points) were 0.23% and 0.36%, respectively. Only the number of double bonds and carbon atoms of the fatty acid are required for the calculation.     

Rapid screening and identification of antioxidants in aqueous extracts of Houttuynia cordata using LC–ESI–MS coupled with DPPH assay

Houttuynia cordata Thunb. has been used traditionally as immune stimulant and anticancer agent. An aqueous extract of H. cordata tea showed high radical scavenging activity determined by off-line DPPH assays. Then, it was screened for its antioxidant components via an on-line DPPH radical scavenging technique coupled with a liquid chromatography–electrospray ionization mass spectrometer (LC–ESI–MS). Based on their mass spectra and fragmentation patterns; the antioxidant compounds were identified as quinic acid derivative, caffeic acid derivatives, procyanidin B, neo-chlorogenic acid, catechin, chlorogenic acid, crypto-chlorogenic acid and quercetin hexoside. LC–MS/MS in multiple reactions monitoring (MRM) mode was used to quantify these antioxidant compounds. Chlorogenic acid was found to be a major component in H. cordata tea.     

Formaldehyde degradation by photocatalytic Ag-doped TiO2 film of glass fiber roving

The photocatalytic Ag doped TiO2 porous films were prepared by sol-gel method and dip coated on glass fiber roving. The sol composed of titanium (IV) isopropoxide, triethanolamine, ethanol and nitric acid followed by calcination of the film at 500 degrees C for 1 hour with a heating rate of 3 degrees C/min. The surface morphology and properties of synthesized TiO2 films were characterized by X-ray diffraction, atomic forced microscope and scanning electron microscope. A laboratory photocatalytic reactor was set up to carry out photoactivity of the prepared catalysts. The results show that TiO2-Ag and TiO2-Ag-TEA porous films give highest rate of formaldehyde gas degradation. It can be noted that triethanolamine exhibits two effects on TiO2 composite films; one is its effect on porous film structure and second is a reverse effect of hindrance of anatase growth.