Matrix effects in the gas chromatographic-mass spectrometric determination of brominated analogues of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone

Brominated analogues (BMXs) of the strong drinking water mutagen MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) were found to be subject to strong matrix induced chromatographic response enhancement effects. We evaluated different ways to reduce errors in quantification including comparison of gas chromatographic inlet systems, improved clean up of sample extracts, and preparation of calibration standards in the sample matrix. The best quantitative accuracy and long term performance were achieved when the calibration standards were prepared in sample matrix, samples were cleaned up with C18-resin in conjunction with solid phase extraction (SPE) with Oasis HLB cartridges, and gas chromatography with PTV splitless injection was used. This method enables the determination of MX and BMXs from 500 ml water sample with quantitation limits of 1 ng/l or less.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Retrieval of Optical Constants from Magnetoreflectance by Maximum Entropy Model

Phase retrieval, and thereby retrieval of optical constants, from magnetoreflectance data is performed using the maximum entropy model for spectra analysis. The applicability of the analysis is tested by using the Lorentz model for the permittivity of a nonmagnetic insulator in a case of Faraday configuration.     

Development of supercritical fluid extraction with a solid-phase trapping for fast estimation of toxic load of polychlorinated dibenzo-p-dioxins-dibenzofurans in sawmill soil

A method consisting of automated supercritical fluid extraction (SFE) with simultaneous cleanup by a solid-phase trap was developed for fast analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in soil. SFE was optimised to replace conventional liquid-based methods in routine analyses of PCDD/PCDFs in sawmill soil contaminated by a chlorophenol formulation. PCDD/PCDFs were quantitatively extracted in 60 min using CO2 at 400 atm and 100 degrees C without a modifier. A trap containing a small amount of activated carbon mixed with Celite efficiently collected PCDD/PCDFs after SFE. After SFE co-extracted impurities were eluted out from the trap with 4 ml of hexane and PCDD/PCDFs were eluted with 10 ml of toluene. The concentrations and TCDD-equivalent of PCDD/PCDFs corresponded to the results of traditional solvent extraction method (Soxhlet) in six sawmill soils tested. The performance of the trap was maintained over a long period of time (nearly 100 extractions).     

Analysis and some chemical properties of MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone), the potent drinking water mutagen

Summary The solubility of the potent drinking water mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in water (50.8, 44.7, 43.7, and 51.0 mg/ml at pH values 2, 5, 7, and 9, respectively) was only slightly dependent on pH, on the contrary to octanol/water partition (log P_ow 1.13, 0.84, –0.44, and –1.02 at pH 2, 5, 7, and 9, respectively). MX was stable in ethyl acetate and acidic water solutions. The recovery of MX during isolation from water or urine samples was about 100% but about 73–82% in the methylation process. The alternative isolation and derivatization methods tested for MX did not give better results.     

Efficient decomposition of quantum gates

Optimal implementation of quantum gates is crucial for designing a quantum computer. We consider the matrix representation of an arbitrary multiqubit gate. By ordering the basis vectors using the Gray code, we construct the quantum circuit which is optimal in the sense of fully controlled single-qubit gates and yet is equivalent with the multiqubit gate. In the second step of the optimization, superfluous control bits are eliminated, which eventually results in a smaller total number of the elementary gates. In our scheme the number of controlled NOT gates is O(4(n)) which coincides with the theoretical lower bound.     

Dissipative dispersion-managed soliton 2 μm thulium/holmium fiber laser

We report a first dissipative dispersive-managed soliton fiber laser operating at 2?μm. The cavity comprised of all-anomalous-dispersion fiber employs chirped fiber Bragg grating, which ensures net-normal cavity dispersion and semiconductor saturable absorber for mode-locking.