Application of a xenon arc lamp as a light source for evaporative light scattering detection

The standard tungsten-halogen light source used in a commercial evaporative light scattering detector (ELSD) was replaced with a 180 W xenon arc lamp. The xenon arc lamp possesses a broader spectrum in the UV region than the halogen source. The influence of the UV transmittance of five selected solvents was studied with a size-exclusion chromatography column. This solvent parameter was not observed to influence the ELSD response between the two light source settings. With the solvents studied, better sensitivity was obtained with the xenon arc lamp than the halogen lamp. This high-energy source was applied to ceramide III analysis with an octadecyl-grafted silica column and methanol:tetrahydrofuran 97:3 as the mobile phase, and the sensitivity of the quantification of ceramide III increased 16-fold for injected amounts of 14∼140 ng. The molecular species in a sample of naturally occurring ceramides was analyzed using two C18 columns at 40 °C and gradient elution from 100% acetonitrile to 100% isopropanol in 30 min. The increased ELSD sensitivity achieved when using the xenon arc lamp allowed both the minor and major ceramide species to be observed, in contrast to the results achieved when the halogen lamp was used, where the increased photomultiplier voltage needed to observed the signals from the minor species caused the signals from the major ceramide species to occur above the detector response window.     

Spectrometer with microreaction chamber and tri-colour light emitting diode as a light source

This paper describes a tri-colour light emitting diode (LED)-photoresistor (PR)-based in situ spectrometer with geometry that differs from the previously presented and allows for small volumes of test solution (350 μl) and effective homogenisation of reagents. The emission maximums of the tri-colour LED (TC-LED) are at 470, 565 and 660 nm. The basic measuring characteristics of the prototype were evaluated. The prototype was tested for determination of calcium in natural waters with the o-cresolphtalein complexon and was proved to be useful for real life applications. The in situ spectrometer with microreaction chamber enables the rapid optimisation of experimental conditions, as was demonstrated on the example of oxidation of alcohols with potassium dichromate. The drop-based experimental approach to the ruggedness test is fast, economic and gives reliable results with the minimum waste production. The prototype, connected to the computer, functions as a kinetic microreactor suitable also for following rapid changes. In spite of the manual addition of the initialising reagent, the data are lost only during the first 3 s.     

Polyester microchannel chip for electrophoresis - incorporation of a blue LED as light source

A blue-light-emitting diode was incorporated as a fluorescence-excitation light source into a polyester microchannel chip fabricated by in situ polymerization. Placing the light-emitting facet of the diode close to the microchannel obviated any need for an additional optical arrangement. Fluorescence from the sample was transmitted by an optical fiber incorporated into the microchip perpendicular to the LED. FITC labeled amino acids were separated in the presence of 5 mM SDS by using the microchip and were detected by LED-induced fluorescence.     

Mechanoluminescent light source for a fluorescent probe molecule

We have demonstrated an innovative ability of mechanoluminescent (ML) material as a light source for the first time. By appropriate smart size control and nondestructive mechanical stimulation, the ML particle can be considered a promising candidate of in situ light source for bio-imaging and photo-therapy even in a human body.     

Paramagnetic Oxygen as Contrast Agent for a Potential PDT Treatment MRI Monitoring

As a proof of concept, we demonstrate in this preliminary study that ³O₂ could be used as magnetic Contrast Agent (CA) to monitor photodynamic treatments (PDT). In this purpose, and using a well-studied Photo-Sensitizer (PS) from our team ( Ruteg ), we highlighted that the combined action of the PS and irradiation led to significant changes in T₁ (and R₁) values of the protons of the water molecules. We assume that with these conclusive results using relaxometric measurements, transposition to Magnetic Resonance Imaging (MRI) in pertinent conditions (oxygen concentration, magnetic field) should be achievable.     

Exploring BODIPY Derivatives as Singlet Oxygen Photosensitizers for PDT

This minireview is devoted to honoring the memory of Dr. Thomas Dougherty, a pioneer of modern photodynamic therapy (PDT). It compiles the most important inputs made by our research group since 2012 in the development of new photosensitizers based on BODIPY chromophore which, thanks to the rich BODIPY chemistry, allows a finely tuned design of the photophysical properties of this family of dyes to serve as efficient photosensitizers for the generation of singlet oxygen. These two factors, photophysical tuning and workable chemistry, have turned BODIPY chromophore as one of the most promising dyes for the development of improved photosensitizers for PDT. In this line, this minireview is mainly related to the establishment of chemical methods and structural designs for enabling efficient singlet oxygen generation in BODIPYs. The approaches include the incorporation of heavy atoms, such as halogens (iodine or bromine) in different number and positions on the BODIPY scaffold, and also transition metal atoms, by their complexation with Ir(III) center, for instance. On the other hand, low-toxicity approaches, without involving heavy metals, have been developed by preparing several orthogonal BODIPY dimers with different substitution patterns. The advantages and drawbacks of all these diverse molecular designs based on BODIPY structural framework are described.     

Computer screen as a programmable light source for visible absorption characterization of (bio)chemical assays

Visible absorption features suitable for color recognition and micro-plate reading of a standard bioassay are performed by the combination of a computer screen used as a programmable light source and a web camera as detector. The method provides in this way a highly available platform for 'home tests' or 'self-tests', where the requirement is to monitor well defined assays and the use of economical instrumentation is advantageous.     

Metal phthalocyanine as photosensitizer for photodynamic therapy (PDT)

A series of sulfonated (S) phthalimidomethyl (P) zinc phthalocyanines (Pc) was synthesized in a reaction, in which both kinds of substituents were introduced to ZnPc simultaneously. The products were separated by HPLC. The five different fractions obtained were further purified by a membrane separation method, and then characterized by UV/Vis, IR, element analysis and the abilities to generate singlet oxygen upon irradiation by light as well as a preliminary determination ofin vitro antitumor activities. The results show that one of the five separating parts with formula of ZnPcS₂P₂ exhibited rather good PDT activity. The compound was further characterized by NMR, MS and thermal analysis. Studies onin vivo antitumor activities of ZnPcS₂P₂ as photosensitizer show that its inhibitory rate was up to 89.8% and 90.8% for S₁₈₀ and U₁₄ solid tumors transplanted in mice respectively when the dosage of drug was 2 mg/kg and the dosage of laser light with 670 nm wavelength was 72 J/cm². Several structural factors influenced on the PDT activities were discussed.     

Whole column fluorescence imaging on a microchip by using a programmed organic light emitting diode array as a spatial-scanning light source and a single photomultiplier tube as detector

A novel miniaturized, integrated whole-column imaging detection (WCID) system on a microchip is presented. In this system, a program controlled organic light emitting diode (OLED) array was used as a spatial-scanning light source, to achieve imaging by the time sequence of the excited fluorescence. By this mechanism, a photomultiplier tube (PMT) instead of a charge coupled detector (CCD) can be applied to the imaging. Unlike conventional systems, no lenses, fibers or any mechanical components are required either. The novel flat light source provides uniform excitation light without size limitations and outputs a stronger power by pulse driving. The scanning mode greatly reduced the power consumption of the light source, which is valuable for a portable system. Meanwhile, this novel simplified system has a broader linear range, higher sensitivity and higher efficiency in data collection. Isoelectric focusing of R-phycoerythrin (PE) and monitoring of the overall process with WCID were performed on this system. The limit of detection (LOD) was 38 ng mL(-1) or 3.2 pg at 85 nL per column injection of PE. The system provides a technique for WCID capillary isoelectric focusing (cIEF) on chip and can be used for throughput analysis.     

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.     

Application of a modulated Grimm-type glow discharge plasma as primary light source for simultaneous reading atomic absorption spectrometry

Summary The Grimm-type glow discharge lamp (GDL) working in a modulated way can be used as primary light source for atomic absorption measurements. The number of element radiations is given by the composition of the target (sample on GDL) which becomes sputtered. Its composition can be adopted to the analytical problem to be solved. It is easy to change the target.The glow discharge source generated at relatively low power (10–24 W) is burning stable for >20 min on the same spot. This is time enough to operate atomic absorption measurements of 10 samples simultaneously, for example, by using the normal flame technique or the graphite tube furnace or the atomsource sputter method to generate atoms of the sample material. The monochromator device of an AA spectrometer has to be replaced by a polychromator one.The spectral behaviour of the glow discharge source compared to that of the hollow cathode lamps of the elements studied is described here by using a double beam two channel AA spectrometer for simultaneous reading of both the signals. In most cases the glow discharge source is the better one. Home-made targets are used to measure first analytical results.

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Einsatz einer modulierten Glimmentladungslampe als Primärlichtquelle zur simultan messenden Atomabsorptionsspektrometrie

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We have to thank the Spectruma company and Bernhard Bogdain especially for supporting this work.     

Visible fluorescence spectrometry using second harmonic emission self-induced in semiconductor laser as a light source

Second harmonic emission (416 or 453 nm) self-induced in a nearinfrared semiconductor laser (832 or 906 nm) is used as a light source for excitation of the fluorescent molecules which have absorption bands in the visible region. The conversion efficiency from fundamental to second harmonic emission is 1.7 × 10^–11 (0.5 pW) for a continuous wave (CW) laser, when it is operated at 30 mW. This value is further improved for a pulsed laser operated at a peak power of 10 W. Perylene is used as a standard sample for construction of an analytical curve. The detection limit is 10^–6 M for CW laser excitation. The present fluorimetric system is used for measurements of pH dependence of the fluorescence intensity for 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS). Neutralization titration is demonstrated by using HPTS as a pH indicator.     

Optical-fiber sensor based on the second-harmonic emission of a near-infrared semiconductor laser as light source

Second-harmonic emission from a near-infrared semiconductor laser is used as the light source for fluorimetry. The efficiency of the second-harmonic generation is 2.5×10^?6; at 390 nm, the power achieved is 50 nW when a 20-mW semiconductor laser (780 nm) is used. For fluorimetric determination of 7-diethylamino-4-methylcoumarin, the calibration plot is linear in the range 0–8×10^?7 M, the detection limit being 5×10^-∞ M (S/N=3 ). The generated ultraviolet emission is used with benzo (ghi)perylene in an optical-fiber sensor for oxygen (0–15%).     

A microfluidic device using a green organic light emitting diode as an integrated excitation source

A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively.     

Mapping the light field of the Waldmann PDT 1200 lamp: potential for wide-field low light irradiance aminolevulinic acid photodynamic therapy

A quantitative assessment of the light field produced by a Waldmann PDT 1200 lamp is presented. A photodiode detector array capable of measuring a beam diameter of 30 cm was used to map the light field. The irradiance was measured as a function of voltage. For lamp-detector distances of 10 cm (central axis irradiance = 250 mW/cm2), the spatial profile of irradiance was typically Gaussian. For lamp-detector distances of 30 cm (central axis irradiance = 79 mW/cm2), the spatial profile appeared more hemispherical in shape but with some asymmetry. The relative percentage variation between the maximum and minimum irradiance with respect to the central axis irradiance was approximately 13% and 3%, respectively, for a beam width of 12 cm. Beyond a lamp-detector distance of 50 cm (central axis irradiance = 32 mW/cm2), the spatial profile of irradiance was observed to become more crater-like in structure, with a minimum on the central axis and an approximately symmetric peak at a radial distance of 9 cm from the center. The relative percentage variation of this peak irradiance with respect to the central axis irradiance was approximately 17%. At lamp-detector distances of 70 and 90 cm (central axis irradiance = 19 and 13 mW/cm2, respectively), the beam's profile was asymmetric, and the irradiance was observed to increase from the center to a radial distance of 15 cm (beam width 30 cm). For a lamp-detector distance of 70 and 90 cm, the relative percentage variation between the maximum irradiance and the central axis irradiance was approximately 25% and 35%, respectively.     

Cerenkov light as a source of photochemical reactions in irradiated solutions of nitrile of malachite green

Experimental data on photochemical activity of Cerenkov light are presented. Malachite green leucocyanide (MGCN) was used to detect the photochemical effects. The G value of Cerenkov light from the region 200–300 nm (number of quanta normed per 100 eV absorbed energy of ionizing radiation) in ethanol was estimated to be in the range 0.0027–0.049.     

Determination of phosphorus by electrothermal atomic absorption spectrometry with a phosphorus hollow-cathode lamp as light source

Graphite tubes are pre-heated with a 10% (w/v) zirconium solution, and a 1% (w/v) zirconium solution is injected prior to each phosphorus sample solution. The calibration graph is linear up to ca. 100 ng P, and the detection limit is 5 ng. Phosphorus in water-soluble organic and inorganic compounds can be determined directly by the proposed method, which is also suitable for the determination of phosphorus in NBS standard reference plant materials and in green tea leaves.