Study on mode-filtered light sensor for methane detection

A novel mode-filtered light gas sensor has been reported.It was constructed by inserting an optical fiber deposited by a thin silicone cladding of cryptophane A into a fused-silica capillary.When different concentration of methane gas was introduced to the sensor,the phenomenon that mode-filtered light intensity decreased with the increasing concentration of methane was observed. And a linear relationship was obtained within the methane concentration range of 0.0-16.0%(v/v).The detection limit was 0.06% ...     

Dual-light source excitation for mode-filtered light detection

The sensitivity of a multi-channel mode-filtered light detection system has been enhanced by using a dual-light source irradiation technique. The detection system was constructed from an annular column consisting of a bare optical fibre inserted into a capillary. Sample was introduced through the gap between the fibre and the capillary. A multi-channel charge-coupled device was set on the side of the capillary at which four detection windows could be simultaneously monitored. The changes in the intensities of the mode-filtered light on exposure to various concentrations of ethanol samples from each detection window were monitored. The theoretical studies on the sensitivity of detection of the detection system using dual-light source irradiation have been described. The sensitivity of detection was enhanced when a dual-light source instead of a single-light source was employed. The working concentration range for ethanol was 0-80% (v/v) ethanol. The limit of detection was determined to be 1% (v/v) ethanol. The proposed method has been successfully applied to the determination of ethanol contents of some wine samples. The results were satisfactory compared with values obtained from a standard reference method.     

Mixed C18 and C1 modification on an optical fiber for chromatographic sensing

An optical fiber-chromatographic sensor, aiming at simultaneous and selective response to multiple components following a chromatographic separation, is described. We report an improved approach for immobilization of octadecyl (C(18)) and methyl (C(1)) moieties as stationary phase on an optical fiber suitable as a sensing phase for organic solutes. By this approach, the stability and lifetime of the sensing layer as well as the detectability and retention behavior of the chromatographic sensor could be improved. Infrared spectroscopy was employed to confirm the presence of C(18) and C(1) moieties on the modified surface of the optical fiber. The chromatographic sensor was applied, with good sensitivity and chemical selectivity, to the simultaneous separation and detection of bromobenzene and toluene, using water as the mobile phase.     

A novel sensor of potassium ions based on mode-filtered light detection

<正>A novel potassium ions sensor based on mode-filtered light detection was reported.The analyzer was consisting of an optical fiber immobilized with a dye of bromocresol green and a fused-silica capillary.It was found that mode-filtered light intensity decreased with the concentration of potassium ions and a linear detection range of 0.25-20 mmol/L(R~2 = 0.9977) was obtained with a detection limit of 9×10~(-5) mol/L as well as fast response,good reproducibility and reversibility in the working concentration range.     

Synchronization of separation and determination based on multichannel mode-filtered light detection with capillary electrophoresis.

A novel method for the synchronization of separation and determination is described, in which a mode-filtered light detector is used as an online detector in capillary electrophoresis. An instrument is described which has been developed for this purpose. The round capillary used in conventional capillary electrophoresis is replaced by an annular column, which is constructed from a naked optical fibre inserted into a fused-silica capillary. In fact, the annular electrophoresis column itself forms part of the mode-filtered light sensor. Along the side of the annular column are several detection channels for gathering and transmitting the mode-filtered light to a charge-coupled device (CCD). Every channel provides information on the sample from the point at which it is located. Using capillary isotachophoresis incorporating the annular column, the analytes in a sample containing alanine (10.0 mM) and glycine (9.7 mM) were simultaneously separated and determined using multichannel mode-filtered light detection with a detection limit of 1.5 mM.     

Separation and determination synchronously by multichannel mode-filtered light capillary electrochromatography

Mode-filtered light capillary electrophoresis (CE) was developed for capillary electrochromatography (CEC) by applying annular columns of different size (250, 320, and 530 micro m) and a bovine serum albumin (BSA)-modified chiral stationary phase. BSA was encapsulated on the pretreated surface of an optic fiber and the inner wall of a capillary using sol-gel technique with a resultant larger active stationary phase area. The coating was examined by atomic force microscopy (AFM) and Fourier transform infrared (FT-IR). The separation of DL-tryptophan (10 mM) was investigated under different voltage/current conditions.     

Gas chromatographic detection of organometallic compounds by reactive-flow photometry

The response of the reactive flow detector (RFD) toward organometallic compounds of several transition metals has been explored, and several of its strong elemental responses have been characterized in detail. The RFDs minimum detectable flow (measured in picograms of metal per second at S/N_p-t-p=2) is 0.1 for ruthenium, 3 for chromium, 10 for manganese, 5 for nickel, 15 for iron, and 2 for osmium. Typically, the linearity of response spans four orders of magnitude, with atomic selectivity of metal versus carbon ranging from 2 to 3 orders. Response quenching by co-eluting hydrocarbons is not observed. As a demonstration experiment, the common analysis of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline is carried out on an RFD system modified for dual-channel operation. The results show that dual-channel operation of the RFD can increase the native elemental selectivity of manganese over carbon by a factor of 100, in accordance with earlier results obtained on a special version of the flame photometric detector (FPD). Significant differences exist between the optical spectra of carbon flame species resulting from various combustion modes carried out in the RFD capillary, and also between conventional FPD and typical RFD spectra. Consideration of these spectral differences suggests that the virtual absence of in the reactive flow may be the primary reason why analyte response quenching by hydrocarbons, while prominent in the FPD, is not observed in the RFD.     

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber

This paper reports the enhancement of sensitivity of detection for in‐column fiber optic‐induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF‐CE and COF‐CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF‐CE was ca. ten times that of COF‐CE. In addition, the detection performance of four excitation light source‐fiber configurations including Laser‐TOF, Laser‐COF, LED‐TOF, and LED‐COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source–fiber configurations. The results demonstrate that the sensitivity obtained by LED‐TOF is close to that of Laser‐COF. Both Laser‐TOF and LED‐TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED‐TOF without focusing lens is just same as that of LED‐COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED‐TOF‐CE and LED‐COF‐CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic‐induced fluorescence detection system in CE is an ideal tool for trace analysis.     

Gas chromatographic determination of volatile alkenes by on-column bromination and electron-capture detection

A method is described for the GC-electron-capture detection determination of ultra trace quantities of alkenes via on-column bromination reactions. Copper bromide coated onto a non-polar solid support, Gas Chrom Q (100–120 mesh) acted as the bromine source. At a temperature of 90–110°C, steel wool may be used to remove selectively up to 90% of the bromine bleed from the reactor. The conversion efficiency of an alkene to the dibrominated derivative is extremely high, up to 90% for ethene, propene, butene and pentene. The bromination of acetylene is also possible, but is not as efficient.     

Fluorescence-based aluminum ion sensing using a surface-functionalized microstructured optical fiber

The first microstructured optical fiber-based sensor platform for aluminum ions using a surface-attached derivative of lumogallion (3), a known fluorescence-based indicator, has been fabricated. These fibers allow for strong evanescent field interactions with the surrounding media because of the small core size while also providing the potential for real-time and distributed measurements. The fluorescence response to aluminum ions was first demonstrated by applying the procedure to glass slides. This was achieved through the covalent attachment of the fluorophore to a polyelectrolyte-coated glass surface and then to the internal holes of a suspended-core microstructured optical fiber to give an effective aluminum sensor. Whereas the sensor platform reported is fabricated for aluminum, the approach is versatile, with applicability to the detection of other ions.     

Microfluidic flow rate detection based on integrated optical fiber cantilever

We demonstrate an integrated microfluidic flow sensor with ultra-wide dynamic range, suitable for high throughput applications such as flow cytometry and particle sorting/counting. A fiber-tip cantilever transduces flow rates to optical signal readout, and we demonstrate a dynamic range from 0 to 1500 microL min(-1) for operation in water. Fiber-optic sensor alignment is guided by preformed microfluidic channels, and the dynamic range can be adjusted in a one-step chemical etch. An overall non-linear response is attributed to the far-field angular distribution of single-mode fiber output.     

Single nucleotide polymorphism detection by optical DNA-based sensing coupled with whole genomic amplification

The work presented here deals with the optimization of a strategy for detection of single nucleotide polymorphisms based on surface plasmon resonance imaging. First, a sandwich-like assay was designed, and oligonucleotide sequences were computationally selected in order to study optimized conditions for the detection of the rs1045642 single nucleotide polymorphism in the gene ABCB1. Then the strategy was optimized on a surface plasmon resonance imaging biosensor using synthetic DNA sequences in order to evaluate the best conditions for the detection of a single mismatching base. Finally, the assay was tested on DNA extracted from human blood which was subsequently amplified using a whole genome amplification kit. The direct detection of the polymorphism was successfully achieved. The biochip was highly regenerable and reusable for up to 20 measurements. Furthermore, coupling these promising results with the multiarray assay, we can foresee applying this biosensor in clinical research extended to concurrent analysis of different polymorphisms.     

Acid-base titrations using fluorescent indicators and fiber optical light guides

Summary A report is given on acid-base titrations with fluorescent indicators whose colour changes are followed with the help of fibre optical light guides. Acids as well as bases can be titrated using the almost ideal pH-indicator, 1-hydroxypyren-3, 6,8-trisulphonate. The method offers some principal advantages over electrochemical ones: (a) No reference signals are required; (b) there are no interferences by electrochemical potentials; (c) relatively inexpensive components may be used; (d) solutions harmful to glass electrodes may be titrated as well. The sensitivity of the method towards daylight is a disadvantage, so that titrations have to be performed in diffuse light or, even better, in the dark.

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Säure-Basen-Titrationen mit Hilfe fluorescierender Indicatoren und faseroptischer Lichtleiter

Zusammenfassung Es wird über die Möglichkeit von SäureBasen-Titrationen mit Hilfe eines Fluorescenzindicators unter Verwendung faseroptischer Lichtleiter berichtet. Säuren und Basen lassen sich, auch in Gegenwart farbiger oder fluorescierender Störstoffe, mit Hilfe des als ideal angesehenen pH-Indicators 1-Hydroxypyren-3,6,8-trisulfonat titrieren. Das Verfahren bietet gegenüber elektrochemischen Verfahren einige prinzipielle Vorteile: (a) Es werden keine Referenzmessungen benötigt; (b) es können keine Störungen durch elektrische Potentiale auftreten; (c) die Titrationen werden mit Hilfe kostengünstiger Elemente durchgeführt; (d) es können auch Lösungen titriert werden, die Glaselektroden angreifen würden. Nachteilig ist die Empfindlichkeit gegenüber dem Umgebungslicht, so daß entweder bei diffusem Licht oder überhaupt im Dunkeln gearbeitet werden muß.

     

Wavelength dispersion in fiber optical detection of time-resolved fluorescence

Summary Fiber optical recorded time-resolved fluorescence emission spectra distorted by wavelength dispersion have been investigated. Calculated and measured transit times for long fibers (50 m) are in good agreement. A simple correction algorithm was proposed resulting in time-resolved spectra of second-order, bilinear structure. Two different deconvolution algorithms using either an entire spectrum or single fluorescence decay curves from different wavelengths were used to calculate the lifetimes of rhodamine B and anthracene.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

A method for the detection of alcohol vapours based on optical sensing of magnesium 5,10,15,20-tetraphenyl porphyrin thin film by an optical spectrometer and principal component analysis

In this work we have proposed a method for the detection of alcohol vapours, i.e. methanol, ethanol and isopropanol, based on the optical sensing response of magnesium 5,10,15,20-tetraphenyl porphyrin (MgTPP) thin films, as measured by optical spectrometry with the assistance of chemometric analysis. We have implemented a scheme which allows a laboratory UV–vis spectrometer to act as a so-called “electronic nose” with very little modification. MgTPP thin films were prepared by a spin coating technique, using chloroform as the solvent, and then subjected to thermal annealing at 280 °C in an argon atmosphere. These MgTPP optical gas sensors presented significant responses with methanol compared to ethanol and isopropanol, based on the dynamic flow of alcohol vapours at the same mol% of alcohol concentration. Density functional theory (DFT) calculations were performed to model the underlying mechanism of this selectivity. The performance of the optical gas sensors was optimised by varying the fabrication parameters. It is hoped that the MgTPP thin film together with an off-the-shelf optical spectrometer and a simple chemometrics algorithm can be a valuable tool for the analysis of alcoholic content in the beverage industry.     

Photosensitizer drug delivery via an optical fiber

An optical fiber has been developed with a maneuverable mini-probe tip that sparges O(2) gas and photodetaches pheophorbide (sensitizer) molecules. Singlet oxygen is produced at the probe tip surface which reacts with an alkene spacer group releasing sensitizer upon fragmentation of a dioxetane intermediate. Optimal sensitizer photorelease occurred when the probe tip was loaded with 60 nmol sensitizer, where crowding of the pheophorbide molecules and self-quenching were kept to a minimum. The fiber optic tip delivered pheophorbide molecules and singlet oxygen to discrete locations. The 60 nmol sensitizer was delivered into petrolatum; however, sensitizer release was less efficient in toluene-d(8) (3.6 nmol) where most had remained adsorbed on the probe tip, even after the covalent alkene spacer bond had been broken. The results open the door to a new area of fiber optic-guided sensitizer delivery for the potential photodynamic therapy of hypoxic structures requiring cytotoxic control.