Sunanta Wangkarn

Determination of linear alkylbenzene sulfonates in water samples by liquid chromatography–UV detection and confirmation by liquid chromatography–mass spectrometry

A high-performance liquid chromatographic (HPLC) method was developed for the separation and determination of individual (C(10)-C(13)) linear alkylbenzene sulfonates (LAS). New sets of conditions have been established for routine analysis of individual chemical forms of four LAS surfactants, i.e. C(10)-C(13) LAS. Under a condition set using a mobile phase containing 1.5mM ammonium acetate in methanol/water 80:20 (v/v) mixture, detection limits obtained were in the range 1.5 ppb (for C(10) LAS) to 11.5 ppb (for C(13) LAS). This offers the advantages of significant improvement in resolution, short separation time and using less amount of common salt under isocratic condition. In addition, the use of simple mobile phase containing a simple low amount of salt cannot deposit at the entrance of mass spectrometric detector. The method is applicable to the simultaneous determination of LAS surfactants in various water samples. LAS surfactants presented in these samples were also successfully confirmed by using electrospray mass spectrometry.

Sequential injection spectrophotometric determination of zinc(II) in pharmaceuticals based on zinc(II)-PAN in non-ionic surfactant medium

A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amounts of zinc(II) with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the zinc(II)-PAN chelate solubilized with a non-ionic surfactant, Triton X-100, no extraction procedure is required in the proposed method, yielding a pink colored complex at pH 9.5 with absorption maximum at 553nm. The SIA parameters that affect the signal response have been optimized in order to get the better sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and concentration was obtained in the concentration range of 0.1-1.0microg ml(-1). The limit of detection (LOD, defined as 3sigma) and limit of quantification (LOQ, defined as 10sigma) were 0.02 and 0.06microg ml(-1), respectively. The sample throughput about 40 samples/h was obtained. The repeatability were 1.32 and 1.24% (n=10) for 0.1 and 0.5microg ml(-1), respectively. The proposed method was successfully applied to the assay of zinc(II) in three samples of multivitamin tablets. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric method and with the claimed values by the manufactures. The t-test showed no significant difference at 95% confidence level.

Investigation of plant hormone level changes in shoot tips of longan (Dimocarpus longan Lour.) treated with potassium chlorate by liquid chromatography–electrospray ionization mass spectrometry

The endogenous levels of indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA) and cytokinins (CKs) and their changes were investigated in shoot tips of ten longan (Dimocarpus longan Lour.) trees for off-season flowering until 60 days after potassium chlorate treatment in comparison with those of ten control (untreated) longan trees. These analytes were extracted and interfering matrices removed with a single mixed-mode solid phase extraction under optimum conditions. The recoveries at three levels of concentration were in the range of 72-112%. The endogenous plant hormones were separated and quantified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Detection limits based on the signal-to-noise ratio ranged from 10 ng mL(-1) for gibberellin A4 (GA4) to 200 ng mL(-1) for IAA. Within the first week after potassium chlorate treatment, dry weight (DW) amounts in the treated longan shoot tips of four gibberellins, namely: gibberellin A1(GA1), gibberellic acid (GA3), gibberellin A19 (GA19) and gibberellin A20 (GA20), were found to increase to approximately 25, 50, 20 and 60 ng g(-1) respectively, all of which were significantly higher than those of the controls. In contrast, gibberellin A8 (GA8) obtained from the treated longan was found to decrease to approximately 20 ng g(-1)DW while that of the control increased to around 80 ng g(-1)DW. Certain CKs which play a role in leaf bud induction, particularly isopentenyl adenine (iP), isopentenyl adenosine (iPR) and dihydrozeatin riboside (DHZR), were found to be present in amounts of approximately 20, 50 and 60 ng g(-1)DW in the shoot tips of the control longan. The analytical results obtained from the two-month off-season longan flowering period indicate that high GA1, GA3, GA19 and GA20 levels in the longan shoot tips contribute to flower bud induction while high levels of CKs, IAA and ABA in the control longan contribute more to the vegetative development.

Prediction of liquid chromatographic retention behavior based on quantum chemical parameters using supervised self organizing maps.

Self organizing maps (SOMs) in a supervised mode were applied for prediction of liquid chromatographic retention behavior of chemical compounds based on their quantum chemical information. The proposed algorithm was simple and required only a small alteration of the standard SOM algorithm. The application was illustrated by the prediction of the retention indices of bifunctionally substituted N-benzylideneanilines (NBA) and the prediction of the retention factors of some pesticides. Although the predictive ability of the supervised SOM could not be significantly greater than that of some previously established neural network methods, such as a radial basis function (RBF) neural network and a back-propagation artificial neural network (ANN), the main advantage of the proposed method was the ability to reveal non-linear structure of the model. The complex relationships between samples could be visualized using U-matrix and the influence of each variable on the predictive model could be investigated using component planes-which can provide chemical insight.

A cost-effective assay for antioxidant using simple cotton thread combining paper based device with mobile phone detection

A cost-effective assay for antioxidant using simple cotton thread combining paper based device with mobile phone detection has been investigated. Standard and sample solutions flow along a bunch of cotton thread treated with sodium hydroxide via microfluidic behaviors without external pumping. The analyte solution reacts with the reagents that have been immobilized on the paper strip fixed at the end of the cotton bunch. The developed platforms were used for the assays of total phenolic content and antioxidant capacity by employing Folin-Ciocalteu and 2, 2-diphenyl-1-picryhydrazyl (DPPH) respectively. Simple detection can be made by employing a mobile phone camera (iPhone 4S) with Image J or Photoshop for image processing and evaluation. Gallic acid was used as a reference standard in this work, as its polyphenol structures can be found in many plants. The total phenolic content is expressed as gallic acid equivalents (GAE) (mg/g material). Inhibition capacity is calculated by the equation: % I = [(Io - Is)/ Io] × 100, where Is is the relative magenta intensity (CMYK mode) of sample, and Io the relative magenta intensity of DPPH•. IC50 inhibition can be estimated from the graph and can be used for the antioxidant capacity consideration. Applications to the assay green tea samples were demonstrated. The total phenolic contents in the green tea samples were found to be 48-105mg/g, with %RSD of less than 10 for that of higher 50 GAE mg/g and IC50 values of the samples studied were 25-50mg/L. The results obtained by the developed methods agree with that of the standard methods.

Chemical diversity and anti-acne inducing bacterial potentials of essential oils from selected Elsholtzia species

Abstract Essential oils from the aerial parts of four Elsholtzia species; Elsholtzia stachyodes, Elsholtzia communis, Elsholtzia griffithii and Elsholtzia beddomei were obtained by steam distillation and their chemical components were analysed by gas chromatography-mass spectrometry (GC-MS). Principle Component Analysis was used to identify the chemical variations in the essential oils from these plants, which could be categorised into two groups according to their main chemical components which are acylfuran derivatives and oxygenated monoterpenes. Additionally, the anti-acne inducing bacterial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. The oil from E. stachyodes was the most efficacious against the growth of S. aureus and S. epidermidis having MIC values of 0.78 and 1.56 μL/mL, respectively, and exhibited five times more effective than erythromycin (standard antibiotic).

Chemical Variation and Potential of Kaempferia Oils as Larvicide Against Aedes aegypti

Abstract The essential oil constituents of the Kaempferia species, specifically K. angustiflora, K. marginata and the three varieties of K. galanga, i.e., K. galanga 1, K. galanga 2 and K. galanga 3 from Chiang Mai Province, Thailand, were studied using gas chromatography-mass spectrometry (GC-MS). Monoterpene hydrocarbons and cinnamate derivatives were identified as the phytochemical markers of these Kaempferia species. The chemical variation of these oils was investigated using Principle Component Analysis (PCA). Cinnamate derivatives were found to be the main components in the three varieties of K. galanga, whereas K. marginata and K. angustiflora consisted of monoterpene hydrocarbons. Comparing the chemical variation between Kaempferia species in this research and other areas in previous reports revealed similar constituents in different quantities. Additionally, the three varieties of K. galanga showed significant larvicidal activity, with LC50 values ranging from 49.03 to 53.48 μg/ml. Based on partial least squares (PLS) regression, δ-3-carene, E-ethyl cinnamate, ethyl-p-methoxycinnamate, γ-cadinene and n-pentadecane are the dominant compounds and contributed positively to the larvicidal activity.