Quantification of flavonoids in black rice by liquid chromatography-negative electrospray ionization tandem mass spectrometry.

Systematic identification and structural characterization of flavonoids and their glycosides in bran extracts of seven Thai black rice varieties were performed by sequential uses of reversed-phase HPLC with a photodiode array detector and a combined electrospray ionization tandem mass spectrometer. Eleven flavonoids were detected, and six of these were found for the first time in rice bran. These were taxifolin-7-O-glucoside, myricetin-7-O-glucoside, isorhamnetin-3-O-acetylglucoside, isorhamnetin-7-O-rutinoside, 5,6,3',4',5'-pentahydroxyflavone-7-O-glucoside, and 5,3',4',5'-tetrahydroxyflavanone-7-O-glucoside. The quantitative results revealed that different rice varieties possessed flavonoids in different concentrations. The most abundant glycoside derivative of flavonoids widely distributed among the rice varieties was monoglucoside, such as quercetin-3-O-glucoside, isorhamnetin-3-O-glucoside, and isorhamnetin-3-O-glucoside.

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.

Seasonal variation, risk assessment and source estimation of PM 10 and PM10-bound PAHs in the ambient air of Chiang Mai and Lamphun, Thailand.

Daily PM10 concentrations were measured at four sampling stations located in Chiang Mai and Lamphun provinces, Thailand. The sampling scheme was conducted during June 2005 to June 2006; every 3 days for 24 h in each sampling period. The result revealed that all stations shared the same pattern, in which the PM10 (particulate matters with diameter of less than 10 microm) concentration increased at the beginning of dry season (December) and reached its peak in March before decreasing by the end of April. The maximum PM10 concentration for each sampling station was in the range of 140-182 microg/m(3) which was 1.1-1.5 times higher than the Thai ambient air quality standard of 120 microg/m(3). This distinctly high concentration of PM10 in the dry season (Dec. 05-Mar. 06) was recognized as a unique seasonal pattern for the northern part of Thailand. PM10 concentration had a medium level of negative correlation (r = -0.696 to -0.635) with the visibility data. Comparing the maximum PM10 concentration detected at each sampling station to the permitted PM10 level of the national air quality standard, the warning visibility values for the PM10 pollution-watch system were determined as 10 km for Chiang Mai Province and 5 km for Lamphun Province. From the analysis of PM10 constituents, no component exceeded the national air quality standard. The total concentrations of PM10-bond polycyclic aromatic hydrocarbons (PAHs) are calculated in terms of total toxicity equivalent concentrations (TTECs) using the toxicity equivalent factors (TEFs) method. TTECs in Chiang Mai and Lamphun ambient air was found at a level comparable to those observed in Nagasaki, Bangkok and Rome and at a lower level than those reported at Copenhagen. The annual number of lung cancer cases for Chiang Mai and Lamphun Provinces was estimated at two cases/year which was lower than the number of cases in Bangkok (27 cases/year). The principal component analysis/absolute principal component scores (PCA/APCS) model and multiple regression analysis were applied to the PM10 and its constituents data. The results pointed to the vegetative burning as the largest PM10 contributor in Chiang Mai and Lamphun ambient air. Vegetative burning, natural gas burning & coke ovens, and secondary particle accounted for 46-82%, 12-49%, and 3-19% of the PM10 concentrations, respectively. However, natural gas burning & coke ovens as well as vehicle exhaust also deserved careful attention due to their large contributions to PAHs concentration. In the wet season and transition periods, 42-60% of the total PAHs concentrations originated from vehicle exhaust while 16-37% and 14-38% of them were apportioned to natural gas burning & coke ovens and vegetative burning, respectively. In the dry period, natural gas burning & coke ovens, vehicle exhaust, and vegetative burning accounted for 47-59%, 20-25%, and 19-28% of total PAHs concentrations. The close agreement between the measured and predicted concentrations data (R(2) > 0.8) assured enough capability of PCA/APCS receptor model to be used for the PM10 and PAHs source apportionment.

Greener analytical method for the determination of copper(II) in wastewater by micro flow system with optical sensor.

Greener analytical method using micro flow system for the determination of Cu(II) in wastewater samples was designed and investigated. The micro flow system consisted of a planar glass chip with poly(dimethylsiloxane) (PDMS) top plate and fixed with fiber optic probe as optical sensor for monitoring of Cu(II) that reacted with 2-carboxy-2'-hydroxy-5'-sulfoformazyl benzene (zincon) on the chip at 605nm. This design gave a satisfied sensitivity with a linear calibration graph over the range of 0.1-3.0mugmL(-1) of Cu(II) and correlation coefficient 0.9991. The percentage relative standard deviation was 2.5 for 10-replicate measurements and the limit of detection (LOD) was 0.1mugmL(-1). This system has been successfully applied to the determination of Cu(II) in wastewaters from electroplating industry with less reagents and samples consumption and diminutive waste generation.

The development of sequential injection analysis coupled with lab-on-valve for copper determination.

A sequential injection analysis (SIA) using lab-on-valve with air segmentation and spectrophotometric detection was designed for copper(II) determination. It is based on the reaction of copper(II) and 2-carboxy-2'-hydroxy-5'-sulfoformazyl benzene (Zincon) in a weak alkaline solution between the air zones. Beer's Law was obeyed over the range of 0.1-2.0mgL(-1) copper(II) with a correlation coefficient 0.9985 and a slope of 0.2893 absorbance unit/mgL(-1). The relative standard deviation was 2.0% for a series of 10 measurements of 0.5mgL(-1) copper(II) solution. The detection limit (3 S/N) and the limit of quantification (LOQ) were 0.05 and 0.17mgL(-1) respectively. This method has been successfully applied to determination of copper(II) in wastewater with a sample throughput of 120h(-1). The method is superior to the batchwise method in that it provides fully automation, rapidity, less reagents and sample consumption with little waste generation.

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.

Flow injection in-valve-mini-column pretreatment combined with ion chromatography for cadmium, lead and zinc determination.

A flow injection (FI) in-valve-mini-column packed with Chelex-100 resin is proposed for on-line sample pretreatment for some metal ions, namely, Cd(II), Pb(II) and Zn(II), prior to simultaneous determination using ion chromatography (IC). A solution containing a mixture of the cations was first passed through the in-valve-mini-column, followed by on-line elution. The eluate was then flowed further to an injection valve and was injected into an ion chromatograph. Conditions of the system were optimized. A single standard calibration was possible. The recoveries of cations were found to be in the range of 95-105%. The developed method was applied to the accurate analysis of zinc ore samples.

Characterization and use of a Raman liquid-core waveguide sensor using preconcentration principles.

A novel Raman sensor using a liquid-core optical waveguide is reported, implementing a Teflon-AF 2400 tube filled with water. An aqueous analyte mixture of benzene, toluene and p-xylene was introduced using a 1000 microl sample loop to the liquid-core waveguide (LCW) sensor and the analytes were preconcentrated on the inside surface of the waveguide tubing. The analytes were then eluted from the waveguide using an acetonitrile-water solvent mixture injected via a 30 microl eluting solvent loop. The preconcentration factor was experimentally determined to be 14-fold, in reasonable agreement with the theoretical preconcentration factor of 33 based upon the sample volume to elution volume ratio. Raman spectra of benzene, toluene and p-xylene were obtained during elution. It was found that analytically useful Raman signals for benzene, toluene and p-xylene were obtained at 992, 1004 and 1206 cm(-1), respectively. The relative standard deviation of the method was 3% for three replicate measurements. The limit of detection (LOD) was determined to be 730 ppb (parts per billion by volume) for benzene, exceptional for a system that does not resort to surface enhancement or resonance Raman approaches. The Raman spectra of these test analytes were evaluated for qualitative and quantitative analysis utility.

Enhanced sensitivity and selectivity in the detection of polycyclic aromatic hydrocarbons using sequential simplex optimization, the addition of an organic modifier and wavelength programming.

Optimized separation of a mixture of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) by high performance liquid chromatography (HPLC) using the sequential simplex optimization method was accomplished by varying the starting and ending compositions of acetonitrile and water, linear gradient time, mobile phase flow rate, column temperature and holding time of the final mobile phase composition. Focusing on the two sets of difficult-to-separate pairs (acenaphthene-fluorene and benzo[g,h,i]perylene-indeno[1,2,3-c,d]pyrene), analysis time was reduced by about ten percent through the use of an organic modifier (isopropanol or methanol), under both optimum and near-optimum conditions, while maintaining good separation of the remaining PAHs. High sensitivity for all of the 16 PAHs was achieved by wavelength programming during elution using five wavelengths (224, 235, 254 270 and 296 nm), depending upon the molar absorptivities of the individual compounds. Detection limits (DLs) ranging from 0.002 (benzo[a]pyrene) to 0.140 mug ml(-1) (acenaphthene) were achieved for this set of 16 standard compounds.

Optimization of high-performance liquid chromatographic parameters for the determination of capsaicinoid compounds using the simplex method.

A high-performance liquid chromatographic method was developed for the analysis of capsaicinoid compounds, the pungent principles of capsicum fruits. A sequential simplex method was applied to optimize the chromatographic response function used to assess the quality of separation by varying the chromatographic parameters. The separation was achieved in 11 min using a C-8 column of 15-cm length and 4.6 mm diameter using a UV detector. A flow rate of 1.15 ml min(-1) at a column temperature of 43.5 degrees C using 63.7% methanol in water gave the most efficient separation. The method was found to be suitable for the determination of the major capsaicinoid compounds in the capsicum samples.

A reverse-flow injection analysis method for the determination of dissolved oxygen in fresh and marine waters.

A reverse flow injection method (rFIA) based on the Winkler titration chemistry, is reported for the determination of dissolved oxygen (DO) in natural waters. Manganese(II) sulfate is injected into a continuously flowing stream of sample and subsequently merges with a reagent stream of sodium hydroxide and sodium iodide. Manganese(II) hydroxide that is formed reacts with DO in the sample to form an oxidized manganese hydroxyoxide floc. Addition of 10% sulfuric acid dissolves this floc, and under acidic conditions, the triiodide ion formed is detected by photometry in a flow through cell at a wavelength of 440 nm. The method is rapid (48 measurements per h), repeatable (R.S.D. ca. 3%, n=3), and has a calculated detection limit of 0.25 mg l(-1) (P=0.001). No interference from nitrite or ferrous ions was observed at concentrations typically found in natural waters. The method has been successfully applied to on-line measurement of DO in sediment respiration reactors.