摘要：Various methods have been proposed for smoothing and denoising data sets, but a distinction is seldom made between the two procedures. Here, We distinguish be- tween them in the signal domain and its transformed domain. Smoothing removes components (of the trans- formed signal) occurring in the high end of the trans- formed domain regardless of amplitude.
摘要：Near-infrared spectroscopy in the wavelength region 800- 1100 nm has been applied to the measurement of aqueous solutions of hydrofluoric acid over the concentra- tion range 0.01-2.65 M and the pH range 2-13. The analysis is based on the detection of subtle perturbations of the water spectrum which result from the presence of the acid and other species in solution .
摘要：A novel chiral stationary phase that contains a new chiral selector based on L-valine-3, 5-dimethylanilide attached to monodisperse poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads has been prepared. The polymeric separation medium provides greatly enhanced enantionse- lectivities and reduced retention times when compared to the analogous silica-based chiral stationary phase in the separation of the enantiomers of 3, 5-dinitrobenzamido derivatives of α-amino acids under normal-phase HPLC conditions.
摘要：Amethod for the direct determination of dissolved silica in seawater by ion exclusion chromatography in combina- tion with inductively coupled plasma mass spectrometry is described. This method was developed as a second, independent method to complement the usual colorimet- ric procedure in the determination of a certified concen- tration of dissolved silica in a planned seawater reference material.
摘要：A mechanical method for the direct determination of boric acid in shellfish is proposed. The sample is weighed, placed in a sample vessel inserted in the flow system, and treated with warm water in order to release the analyte, which is extracted into the aqueous solution. The solution is then continuously filtered to clean the aqueous solution and obtain a clear medium that is processed in the flow system to determine boric acid by spectrophotometrically monitoring its reaction with azomethine H.
摘要：An apparatus for real-time MS/MS analysis of individual airborne microparticles by laser ablation in an ion trap is described. The performance has been demonstrated by the detection of tributyl phosphate and bis(2-ethylhexyl) phosphate on silicon carbide and kaolin microparticles.
摘要：A bacterial sensing system that responds selectively to antimonite and arsenite has been investigated. The bacteria used in these studies have been genetically engineered to produce the enzyme β-galactosidase in response to these ions. This is accomplished by using a plasmid that incorporates the gene for β-galactosidase (reporter gene) under the control of the promoter of the ars operon.
摘要：Sample introduction systems have been developed to significantly extend existing isotope ratio monitoring gas chromatography/mass spectrometry techniques to allow the simultaneous determination of the concentration and stable carbon isotopic ratio of methane from low-concen- tration aqueous and gaseous samples.
摘要：Most mass spectrometers employ destructive detection, so that it is necessary to repeat an experiment in order to vary even one parameter. In contrast, Fourier transform ion cyclotron resonance mass spectrometry offers non- destructive detection, So that ions remain available for further manipulation and redetection. Here, we show for the first time how to perform mass spectrometry interac- tively.
摘要：An organic-inorganic hybrid sol-gel matrix was used as host for tridodecylmethylammonium chloride(TDMAC), which is an ionophore for chloride. The sol-gel precursor was prepared by the reaction of (3-isocyanopropyl)- triethoxysilane with 1, 4-butanediol. On mixing with TD- MAC, the sol-state precursor slowly gelled, to give a TDMAC-containing membrane.
摘要：A significant fraction of the total analysis time (injection- to-injection)in capillary electrophoresis is dedicated to a rigorous between-run capillary rinsing/regeneration pro- cedure. This is of particular importance with CE-based assays developed for high-throughput analysis of clinical Samples. In this study, we examine the necessity of a between-run rinsing step when detergent is present in the separation buffer.
摘要：A novel method for the production of coated capillaries for capillary zone electrophoresis-electrospray mass spec- trometry (CZE-ESMS), operating at 100-200 nL/min flow rates is described. Electrophoretic conditions con- ducive to the simultaneous operation of ESMS were investigated for microsparayers of different inner diam- eters. The ruggedness and reliability of the CZE columns with microsprayers of 20μm i.d. were investigated over 6h of uninterrupted operation.
摘要：Research in this laboratory has focused on the cytokinetic effect of taxanes on nonmammalian systems. Taxanes are a class of natural products that includes the well-known anticancer compound, paclitaxel(Taxol). Our methodol- ogy for the study of fungal growth in liquid medium amended with paclitaxel included membrane solid phase extraction (SPE) of the fungal broth. This was followed by elution of paclitaxel from the SPE membrane using methanol.
摘要：The physical properties of a porous medium impregnated by a Liquid or vapor are dictated in part by the spatial distribution of these phases within the solid host matrix and by physicochemical interactions at the solid-Liquid- vapor boundaries. We report on a novel 3-D imaging technique based on the high spatial resolution and chemi- cal specificity of the confocal Raman microscope, which allows for the first time the in situ study and ivsualization of these processes.
摘要：A method is described to synchronize the scans of the first and second double-focusing mass spectrometers of a tandem double-focusing mass spectrometer. The scans are synchronized by scanning the first mass spectrometer with voltages instead of the magnetic field. The method is demonstrated with scans that provide all of the precur- sor ions that produce a selected product ion (precursor ion scan).
摘要：The use of enhanced-fluidity liquid mixtures of tetrahy- drofuran (THF)/CO_2 for liquid chromatography at the critical condition is described. For polystyrene polymers, the molecular weight range that can be analyzed at the critical condition was compared for using THF/CO_2 and other common liquid mixtures. Because enhanced-fluid- ity liquids are highly compressible, it was possible to reach the critical condition by changing the pressure of the THF/CO_2 mixture.
摘要：Heterogeneous electron transfer Kinetics for reduction of Fe(H2o)_6~3+ at Pt electrodes in the presence of equimolar F_e(H2o)_6~2+ in noncoordinating 1.0 M HCLO_4 have been studied during irradiation with high-intensity ultrasound at 20 kHz both in the presence and in the absence of small Solid particles. Increases in heterogeneous rate constants have been measured during sonication in the presence of 1-μm particles of Al_2O_3.
摘要：Nitrous oxide generated by the electrochemical reduction of nitrite on a polycrystalline platinum electrode in aque- ous 0.1 M HCLO_4 was monitored by in situ potential difference Fourier transform infrared reflection absorption spectroscopy. An analysis of the intensity of the N_2O asymmetric stretch band at 2231 cm~-1, A(N_2O), moni- tored during a slow linear potential (E) sweep in the range 0.8＞E＞-0.32V vs SCE, indicated that N_2O begins to form at E～0.5V vs SCE, reaches a maximum at E～0.05 V, and disappears completely for E＜-0.1V.
摘要：Trace analysis of fatty acids in water and/or air was enhanced by coupling solid-phase microextraction(SPME) with derivatization of the target analytes to less polar and more volatile species prior to GC analysis. Derivatization was performed in three ways: in the sample matrix, in the SPME fiber coating, and in the GC injector port. Derivatization converts polar analytes into less polar analogues, therefore increasing their coating/water of coating/gas partition coefficients and improving SPME efficiency and method sensitivity.
摘要：The amount of a sample compound extracted into a 1-μL drop of n-octane suspended in a stirred aqueous solution from the tip of a microsyringe needle is measured by gas chromatography(GC) as a function of time. The observed extraction rate curve is first order and yields the overall mass transfer coefficient for the sample compound, β_o. For a given compound, β_o varies linearly with stirring rate.