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Abstract: A versatile, simple, liquid core waveguide (LCW)-based fluorescence detector design is described for capillary systems. A Teflon AF coated fused silica capillary serves as the LCW. The LCW is transversely excited. The light source can be a conventional or high power (HP) light emitting diode (LED) or a laser diode (LD). The source can be coupled to the LCW directly or via an optical fiber. Fiber coupling is convenient if a high power (necessarily heat sink mounted) emitter is used. The LCW is concentrically placed within a slightly larger opaque jacket tube and the LCW terminates just short of the jacket terminus, which is sealed with an optical window. The influent liquid thus exits the LCW tip, flows back around the LCW through the jacket annulus to exit via an aperture on the jacket tube. The problem of coupling the emitted light efficiently to the photodetector is thus solved by placing the tip of the annular tubular assembly directly on the detector. For excitation wavelengths of 365nm (LED/HPLED) and 405nm (LD), the tris(8-hydroxyquinoline-5-sulfonic acid (sulfoxine)) chelate of aluminum (λ em,max ∼500nm) and Coumarin 30 were respectively used as the model analyte. For source–detector combinations comprising (a) a UV LED (∼1.5mW @ 15mA) and a photodiode, (b) a LD (∼5mW, abstracted from a “Blu-Ray” recorder) and a miniature photomultiplier tube (mPMT), and (c) a high power (210mW @ 500mA) surface-mount HPLED–mPMT, the S/N=3 LODs were, respectively, 1.7pmol Al, 3–100fmol Coumarin 30 (depending on laser intensity and integration time), and 4fmol Al. In the last case, the relative standard derivation (R.S.D.) at the 20fmol level was 1.5% (n =10). [Copyright &y& Elsevier]

Abstract: In the present work, the use of surfactants and oil-in-water (O/W) microemulsions as alternative extractants in accelerated solvent extraction (ASE) for the extraction of polycyclic aromatic hydrocarbons (pyrene and phenanthrene) from soils was investigated. In particular, the effect of each individual component within the microemulsions, i.e., oil phase, surfactant and co-surfactatnt, and extraction conditions on the percentage recovery was systematically studied. When compared to the water and organic solvent, the important findings were that the common surfactant solutions at the concentrations above their critical micelle concentrations (CMC) were shown to enhance the percentage recovery at the lower extraction temperature. Moreover, the highest percentage recovery can be obtained using microemulsion as the extractant. The chemical component within the microemulsions and relative amounts of the oil phase appeared to play a much more significant role in ensuring high percentage recovery. Finally, an overall comparison between the percentage recoveries obtained with ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and ASE using organic solvents, surfactants and microemulsions as extractants was exhibited. [Copyright &y& Elsevier]

Abstract: The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) was previously based on the use of a cotton-packed column to entrap the analyte-containing surfactant aggregates after salt-induced CPE, and then the preconcentrated analyte was eluted into a separate detection cell for subsequent chemiluminescence (CL) detection (via the peroxyoxalate CL reaction). In the work, the on-line CPE/FIA technique was improved by the following: (1) sample preconcentration and CL detection were both carried out directly inside the collection column, thus avoiding the decrease in detection sensitivity due to sample dispersion and dilution, and (2) CL detection was performed through the reaction between nitrite and hydrogen peroxide, which is compatible with aqueous samples and should allow for chemical excitation to occur more efficiently inside the collection column. In addition to more effective sample preconcentration, the CL detection of the entrapped analytes directly inside the collection column, i.e., a unique heterogeneous microenvironment in which analyte-containing surfactant aggregates were embedded within the densely packed filtering material, may also contribute to the overall increase in CL intensity (e.g., a CL enhancement factor of ca. 1000). Under optimum experimental conditions, the calibration curve was found to be linear for the CL detection of bilirubin (5 to 120μgL−1), the limit of detection (S/N=3) was 1.8μgL−1, and the R.S.D. was ca. 2.6% (n =30) for 20μgL−1 bilirubin. Good agreements were obtained for the determination of total bilirubin in certified reference human serum samples between the present approach and an established clinical method. [Copyright &y& Elsevier]

Abstract: This review extensively covers information on chemiluminescence-detection systems for five reactive oxygen species, including superoxide radical, singlet oxygen, hydroxyl radical, hydrogen peroxide and peroxynitrite. We evaluate in detail the current state and the limitations of different chemiluminescence systems. We give some pointers to the likely directions of future developments and prospects. [Copyright &y& Elsevier]

Abstract: A capillary electrophoresis method with ultraviolet (UV) detection was developed and optimized for the enantiomer separation of norepinephrine (NE), epinephrine (EP) and isoprenaline (IP) using dual cyclodextrins (CDs) of 2-hydroxypropyl-β-CD (HP-β-CD) and heptakis (2,6-di-o-methyl)-β-CD (DM-β-CD) as chiral selectors. Optimal separation was obtained using a running buffer of 50mM phosphate containing 30mM HP-β-CD and 5mM DM-β-CD at pH 2.90 and a field strength of 20kV in 45cm×75μm (40cm effective length) uncoated capillary. The UV absorbance detection was set at 205nm. A 0.1% (w/w) polyethylene glycol or 0.1% (v/v) acetonitrile was used to enhance the detection sensitivity. There was a wide and excellent linear calibration graph for each enantiomer in the range 1.0×10−3 to 1.0×10−6 M and the detection limit (S/N=3) was found from 8.5×10−7 to 9.5×10−7 M. The method has been applied for the determination of isoprenaline in isoprenaline hydrochloride aerosol and to the analysis of serum samples. The recoveries of NE and EP in serum and IP in drug were ranged from 90 to 110%. The relative standard deviations of all the analyte peaks were less than 2.8% for migration time and less than 4.8% for peak area. [Copyright &y& Elsevier]

Describes the simultaneous determination of catechins and caffeine in green, black tealeaves and canned tea-drink using micellar electrokinetic chromatography. How the catechins analyzed include (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate; Use of UV absorption method at 280 nm to determine the limits of detections of catechins and caffeine; How the extraction of these compounds from the tealeaves with hot water is compared under different temperatures; Reference to how the effects of temperature on the amount of catechins and caffeine extracted show that (-)-epigallocatechin gallate is the most easiest to be extracted at 100°C; Stability of catechins and caffeine in stocking solution of tea-drink at 4°C; Contents of catechins and caffeine in green and black teas; Difference of the content between different tealeaves can provide a reference for the assessment of tea quality.

Abstract: A novel on-line liquid chromatography–photodiode array detection–mass spectrometry (LC–DAD–MS) system was established with restricted-access media (RAM) pre-column and dilution line combined with a column-switching valve. The serum samples were injected directly onto pre-column under diluted condition by dilution line. After elution of proteins in the serum, the analytes were backflushed onto an ODS analytical column using a six-port column-switching device. The influence of the composition of the mobile phase, for instance, organic modifer, ionic strength, pH, dilution times and the rotation time of the switching valve have been investigated using bisphenol A (BPA) and 4-octyphenol (4-OP) as analytes. The evaluations for peak responses and sensitivity were conducted by MS, and proteins were removed by RAM-column with DAD monitoring at 280nm. The peak shape was improved by adding a dilution line, especially in the case of large volume injection (LVI), which increased the sensitivity of the analysis. The selective and sensitive quantification of BPA and 4-OP in serum sample could be finished within 25min. The method had linearity in the range 0.1–500ng/mL with a limit of quantification for BPA and 4-OP of 0.1 and 0.5ng/mL, respectively. The recoveries were in the range of 80–101% with less than 9.0% RSDs. This on-line LC–MS method demonstrates potential application to evaluating the exposure and risk of BPA and 4-OP in human. [Copyright &y& Elsevier]