Monitor for measuring the total concentration of reactive hydrocarbons in ambient air based on their chemiluminescence reaction with oxygen atoms

The monitor functions by measuring the intensity of the chemiluminescence radiation at 309 nm which is emitted during the reaction of hydrocarbons with O(³p) atoms. The system comprises a specially-developed stable source of atomic oxygen, a detection unit for measuring the intensity of the chemiluminescence radiation and a device for preconcentration of the hydrocarbons to be determined. The sensitivity of the monitor depends on the concentration and reactivity of the hydrocarbons, and is greatest for unsaturated compounds. For butadiene, the detection limit is 3 ppb, and response is linear over the range 0–2500 ppb. The monitor can also serve as a detector for unsaturated hydrocarbons in gas chromatography.     

An integrated enzyme-linked immunosorbent assay system with an organic light-emitting diode and a charge-coupled device for fluorescence detection

A fluorescence detection system for a microfluidic device using an organic light-emitting diode (OLED) as the excitation light source and a charge-coupled device (CCD) as the photo detector was developed. The OLED was fabricated on a glass plate by photolithography and a vacuum deposition technique. The OLED produced a green luminescence with a peak emission at 512 nm and a half bandwidth of 55 nm. The maximum external quantum efficiency of the OLED was 7.2%. The emission intensity of the OLED at 10 mA/cm(2) was 13 μW (1.7 mW/cm(2)). The fluorescence detection system consisted of the OLED device, two band-pass filters, a five microchannel poly(dimethylsiloxane) (PDMS) microfluidic device and a linear CCD. The fluorescence detection system was successfully used in a flow-based enzyme-linked immunosorbent assay on a PDMS microfluidic device for the rapid determination of immunoglobulin A (IgA), a marker for human stress. The detection limit (S/N=3) for IgA was 16.5 ng/mL, and the sensitivity was sufficient for evaluating stress. Compared with the conventional 96-well microtiter plate assay, the analysis time and the amounts of reagent and sample solutions could all be reduced.     

Investigations on laser ablation–microwave induced plasma–atomic emission spectrometry using polymer samples

The potential of laser ablation–microwave induced plasma–atomic emission spectrometry (LA–MIP–AES) for the analysis of plastic materials has been investigated. A Nd/YAG laser, operated in its fundamental mode at 1064 nm, was used to ablate small amounts of various plastics. The sample atoms were transported and excited in a closely neighbored continuously running microwave induced plasma (MIP) operated in argon or helium at reduced pressure. A 0.5-m échelle spectrometer, equipped with an intensified charge coupled device (ICCD) as a detector was used for recording the spectra. The amount of ablated material was found to be strongly dependent on the matrix (10–190 ng/shot). Signals for some metals often used as additives in polymers (Al, Ca, Cu, Sb, Ti) and for the elements F, Cl, Br, J, and P in various polymers were recorded in the spectral range 250–840 nm. The estimated detection limits were found to be in the range 0.001–0.08% for metals and 0.05–0.7% for non-metals. Spectral lines of fluorine and iodine could only be measured in the helium MIP. For high concentrations of chlorine and carbon in the samples (polyvinylchloride), a memory effect was observed.     

Trace analysis of pollutants in water using the photothermal interferometry as HPLC detector

A new procedure including high performance liquid chromatography in combination with photothermal interference spectroscopy as detection device (HPLC/PIS) has been proposed, optimized and its figures of merit for pesticide residue analysis are shown. The flowing sample under study is set in one arm of a Mach-Zehnder interferometer, and its refractive index is modulated by a periodically chopped continuous wave argon ion laser. As chopper, an acousto optical modulator has been introduced to switch the excitation laser beam between different lines (457 nm, 488 nm, 514 nm) simultaneously. Thus a multi component analysis can be realized either by using an HPLC-system in front of the PIS device or by a multi line Ar(+)-laser, directly. The limit of detection of the HPLC/PIS system reached 71 microg/l of the pesticide di-nitro-ortho-cresol (DNOC).     

Tungsten coil atomic emission spectrometry

A tungsten coil atomic emission spectrometer is described and evaluated. The system employs a single tungsten coil as a combined atomizer and excitation source for the determination of metals by atomic emission spectrometry. The tungsten coil is extracted from a 150 W, 15 V commercial slide projector light bulb. A simple, laboratory constructed, computer-controlled power supply provides a constant current to the coil. A high-resolution Czerny–Turner monochromator with a charge coupled device detector completes the system. Simultaneous, multi-element analyses are possible within a 4 nm spectral window. Eleven test elements are used to characterize the system: Al (396.1 nm), Co (353.0 nm), Cr (427.1 nm), Dy (404.6 nm), Ga (403.3 nm), K (404.4 nm), Mn (403.1 nm), Pb (405.8 nm), Rb (420.2 nm), Sc (404.8 nm), and Yb (398.7 nm). Tungsten coil atomic emission detection limits are reported for these elements for the first time: 0.02 ng Al, 0.7 ng Co, 0.003 ng Cr, 0.01 ng Dy, 0.7 ng Ga, 0.3 ng K, 0.04 ng Mn, 10 ng Pb, 0.07 ng Rb, 1 ng Sc, and 0.003 ng Yb. The precision for the new technique is better than 13% relative standard deviation for all metals at concentrations two orders of magnitude above the detection limit. Aluminum, Cr, Mn, and K are determined in a standard reference material (trace elements in water) after simple dilution with water, and found values varied from certified values by up to 26%. The average tungsten coil lifetime was found to be 265 heating cycles. The elimination of the external radiation source needed for atomic absorption measurements results in an emission system that could be quite portable.     

An echelle polychromator for inductively coupled plasma optical emission spectroscopy with vacuum ultraviolet wavelength coverage and charge injection device detection

The development and evaluation of a simultaneous inductively coupled plasma optical emission spectrometer with vacuum ultraviolet (VUV) wavelength coverage and charge injection device (CID) detection are described. The spectrometer is an echelle polychromator with a magnesium fluoride prism as a cross-disperser. A thin coating of Lumogen, used as a wavelength conversion phosphor, is applied to the surface of the CID detector. The Lumogen coating increases sensitivity in the VUV region dramatically. Wavelengths between 130 and 800 nm can be measured by this spectrometer. A measured spectral bandwidth of 0.006 nm at 134.724 nm is achieved. The analytical performance in radial viewing mode is evaluated. The 3σ detection limit measured for Cl at 134.724 nm in aqueous solution is 100 ng ml⁻¹.     

Analytical evaluation of an air-cooled 1 l min argon ICP

The analytical capabilities of an air-cooled ICP that runs on 1 l min⁻¹ argon and 600–900 W generator power are demonstrated. Improvements in the cooling device allow the use of conventional r.f. coils and unattended operation at generator powers up to 1 kW. Although plasmas can be maintained on generator powers as low as 400 W, an increased power-level is necessary for the sensitive detection below 250 nm, for the application of organic solvents and for the use of the hydride generation technique. In all cases the detection power is comparable to that of a conventional ICP. The analysis of reference samples shows that the air-cooled plasma can be used for real applications.     

Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices.

The fabrication and performance of an electrophoretic separation chip with integrated optical waveguides for absorption detection is presented. The device was fabricated on a silicon substrate by standard microfabrication techniques with the use of two photolithographic mask steps. The waveguides on the device were connected to optical fibers, which enabled alignment free operation due to the absence of free-space optics. A 750 microm long U-shaped detection cell was used to facilitate longitudinal absorption detection. To minimize geometrically induced band broadening at the turn in the U-cell, tapering of the separation channel from a width of 120 down to 30 microm was employed. Electrical insulation was achieved by a 13 microm thermally grown silicon dioxide between the silicon substrate and the channels. The breakdown voltage during operation of the chip was measured to 10.6 kV. A separation of 3.2 microM rhodamine 110, 8 microM 2,7-dichlorofluorescein, 10 microM fluorescein and 18 microM 5-carboxyfluorescein was demonstrated on the device using the detection cell for absorption measurements at 488 nm.     

Biochemical Imaging of Human Atherosclerotic Plaques with Fluorescence Lifetime Angioscopy

A prototype angioscopy system with fluorescence lifetime imaging microscopy (FLIM) capabilities was built and applied for biochemical imaging of human coronary atherosclerotic plaques. The FLIM angioscopy prototype consisted of a thin flexible angioscope suitable for UV-excited autofluorescence imaging, and a FLIM detection system based on a pulse sampling approach. The angioscope was composed of an imaging bundle attached to a gradient index objective lens and surrounded by a ring of illumination fibers (2 mm outer diameter, 50 μm spatial resolution). For FLIM detection based on the pulse sampling approach, a gated-intensified charge-couple device camera (200 ps temporal resolution) was used. Autofluorescence was excited with a pulsed UV laser (337 nm) and FLIM images were acquired at three emission bands (390/40 nm, 450/40 nm, 550/88 nm). The system was characterized on standard fluorophores and then used to image postmortem human coronary arteries. The FLIM angioscope allowed us to distinguish elastin-dominant plaques (peak emission at 450 nm, ∼1.5 ns lifetimes) from collagen-dominant plaques (peak emission at 390 n, ∼2–3 ns lifetimes) based on their intrinsic fluorescence spectral and lifetime differences. This study demonstrates the potential of FLIM angioscopy for biochemical imaging of human coronary atherosclerotic plaques.     

Improvements in drug purity determination by capillary electrophoresis using UV-absorption and LIF-detection with a UV-laser

Summary In drug purity determinations by capillary electrophoresis using UV-detection generally a relative high concentration of the main compound has to be injected. Principles how to handle overloading effects are described. NXX-066 is a drug with a native fluorescence which made it possible to use of CE system equipped with a LIF-detection unit. Monitoring drug purity determination with LIF detection results in an improved limit of quantification of the impurities and/or opens a possibility to avoid an overloaded main peak. A frequency doubled (FRED) argon ion laser set at 244 nm was used as excitation source in drug purity determination with the LIF-detection unit and the chemicals used were therefore carefully chosen in order to minimize the background noise level, which easily is enhanced when fluorescence detection is performed in the UV-range. The separation of the fluorescent NXX-066 analogues proved to be a difficult task, but an adequate resolution was obtained when β- and γ-cyclodextrins was added as structural selectors and the separation window was expanded by the use of a repressed/reversed electroosmotic flow. A comparison of the separation capability for the UV-detection system and the laser induced fluorescence detection system was performed, showing that the overloading effects of the main peak can be removed using the CE-LIF system and thereby obtain a substantially improved resolution of the analogues. A comparison of LC-UV and CE-UV for drug purity determination of a crude product from, synthesis of NXX-066 is also included in this paper where a good correlation of the results were obtained. Presented at the 8th. International Symposium on High Performance Capillary Electrophoresis, Jan. 21–25 1996, Orlando, USA.     

Determination of ultratrace nitrogen in pure argon gas by dielectric barrier discharge-molecular emission spectrometry

A dielectric barrier discharge (DBD) was used as a new atmospheric optical emission detector for the determination of trace nitrogen in pure argon gas in this work. The whole system was composed of an ac ozone generation device for power supply, a six-way valve, a laboratory-built DBD device and a USB2000 charge coupled device (CCD). Trace nitrogen in argon was detected at nitrogen molecular emission line of 337 nm. This method features with several advantages: atmospheric working condition, low power consumption (≤ 12 W), simple and cheap instrumentation, fast response and high sensitivity and accuracy. Under the optimized conditions, the limits of detection can be down to 34 ppb.     

Computerized chromatographic peak detection using the trigg tracking signal. An application devised for use with an online analog to digital converter connected between an amino acid analyser and a personal computer

Manual integration of the amino acid peaks from physiological samples produced by conventional anion exchange liquid chromatography is a time-consuming process. This paper describes a combined unit, consisting of an analog to digital converter and a personal computer, which was connected in parallel with the chart recorder and the analyser's 570 nm channel of the colorimeter. The computer was programmed to log the digitized data, detect the start, maximum and end of each chromatographic peak, calculate the area under the peak and its retention time and provide a printout of the results at the end of the elution program. The computer program successfully exploited the Trigg Tracking Signal as both a peak detection and as a moving baseline monitoring device. This approach proved to have an equivalent performance to the manual method for 17 out of the 19 amino acids normally quantitated in physiological samples. The automated detection and quantitation of arginine was unsatisfactory due to its characteristically low profile peak shape, and proline was not measured because the device was not connected to the 440 nm channel of the colorimeter. The automated system provided economic and analytically acceptable solutions to the problem of providing an online integrator versatile enough to be used with the 255 min long amino acid analysis of physiological fluids.     

Trace analysis of pollutants in water using the photothermal interferometry as HPLC detector

A new procedure including high performance liquid chromatography in combination with photothermal interference spectroscopy as detection device (HPLC/PIS) has been proposed, optimized and its figures of merit for pesticide residue analysis are shown. The flowing sample under study is set in one arm of a Mach-Zehnder interferometer, and its refractive index is modulated by a periodically chopped continuous wave argon ion laser. As chopper, an acousto optical modulator has been introduced to switch the excitation laser beam between different lines (457 nm, 488 nm, 514 nm) simultaneously. Thus a multi component analysis can be realized either by using an HPLC-system in front of the PIS device or by a multi line Ar⁺-laser, directly. The limit of detection of the HPLC/PIS system reached 71 g/l of the pesticide di-nitro-ortho-cresol (DNOC).     

Automated liquid-solid extraction of pyrene from soil on centrifugal microfluidic devices

Organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) are present in the environment in increasing concentrations and so are of growing concern. Monitoring these species, particularly on-site, can be both difficult and expensive. This paper presents a novel miniaturised magnetically actuated liquid-solid extraction unit integrated in tandem with a filtration unit and a detection unit on a single centrifugal microfluidic device. A demonstration analyte, pyrene, was rapidly extracted and quantified by UV-absorbance from multiple soil samples. The system showed excellent performance for a system designed for field use. Characterization of two types of passive valves was performed along with an extraction time efficiency study. The system provides a factor of 150 reduction in sample weights and extraction solvent volumes and provides statistically similar recoveries to the conventional method with a pyrene detection limit of 1 ppm (0.03 μg absolute detection limit). The reduction in time and solvent and the potential for field use suggest that this device type may be valuable for environmental monitoring.     

Incorporation of a 2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione unit into a donor–acceptor triad: synthesis and ion recognition features

A novel directly-linked donor–acceptor–donor (D–A–D) type system, which is based on 2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione as the A unit and thiophene as the D units, respectively, is designed, synthesized, and characterized by spectroscopic methods. This novel D–A–D system can be used for the fluorogenic detection of Cu²⁺ among other ions.     

Thermal lens detection device

A thermal lens detection device was developed to realize an easy-to-use, portable and sensitive detector for nonfluorescent molecules. Two laser diodes (658 nm for excitation and 785 nm for probe) were made coaxial in an optical unit and were coupled to a single-mode optical fiber. On a microfluidic chip, a small holder for the optical fiber was fixed, and micro-lenses (numerical aperture of 0.2) were also integrated inside the holder. The micro-lenses were designed to realize an adequate chromatic aberration (50 μm), which was essential for sensitive thermal lens detection. Compared with conventional thermal lens detection systems which required very laborious and accurate optical alignment with the microchannel, the new device needed just attachment-detachment of the optical fiber, which was important for practical application. The lower limit of detection was 10 nM for nickel(II) phthalocyaninetetrasulfonic acid tetrasodium salt solutions (model sample), and the absorbance was 9 × 10(-6) AU. The absolute number of molecules detected was less than 200 zmol. The coefficient of variance for 5-time attachment-detachment of the optical probe was as small as 3.6%. The technical development allowed integration of the thermal lens detection devices inside a microsystem (e.g. enzyme-linked immuno-sorbent assay system), and practical microsystems were realized with sensitivities several-orders higher than absorptiometry.     

In situ synthesis Bismarck brown R reductive products-immobilised AgNPs assisted by catalytic activity of AgNPs as colorimetric probe for Hg2+ detection in water

A novel, selective and sensitive colorimetric detection method for Hg²⁺ is developed using Bismarck brown R (BBR) reductive products-immobilised silver nanoparticles (BBR products-AgNPs) as a sensing probe. In this research, the BBR reductive products were synthesised in situ and immediately immobilised on the surface of AgNPs. A surface plasmon resonance band of BBR products-AgNPs was observed at 396 nm. The absorbance at 396 nm gradually decreased, and a remarkable blue shift from 396 to 368 nm and a colour change from yellow to colourless by increasing the Hg²⁺ concentration were observed. This observation is due to the oxidation of Ag° to Ag⁺ and the reduction of Hg²⁺ to Hg° during the process, and thus Ag–Hg nanoalloy is formed. In addition, an exploratory study of the designed system is done by chemometrics approaches with the aim of making a clear perspective from the reaction system. The effective parameters for detection of Hg²⁺ based on the BBR products-AgNPs as optical probe were optimised. Under optimal conditions, the sensor exhibited a high selectivity and sensitivity with limit of detection of 6.1 nM (1.66 µg L^?1) and the linear range from 0.01–19.0 µM (2.72–5160 µg L^?1). The proposed method was simple, rapid and cost-effective without any complicated operation. Finally, it was successfully used for detection of Hg²⁺ in water samples with recoveries ranges of 86.7–103.6% and relative standard deviation slower than 10.1%.     

A parallel diffusion-based microfluidic device for bacterial chemotaxis analysis

We developed a multiple-channel microfluidic device for bacterial chemotaxis detection. Some characteristics such as easy operation, parallel sample adding design and fast result readout make this device convenient for most biology labs. The characteristic feature of the design is the agarose gel channels, which serve as a semi-permeable membrane. They can stop the fluid flow and prevent bacteria getting across, but permit the diffusion of small molecules. In the device fabrication process a novel thermal-based method was used to control the shape of agarose gel in the microfluidic channel. The chemical gradient is established by diffusion which can be precisely controlled and measured. Combined with an 8-channel pipette, different attractants, repellent chemicals or different bacteria were analyzed by a two step operation with a readout time of one hour. This device may be useful in the high throughput detection of chemotaxis related molecules and genes.     

Helium–hydrogen microplasma device (MPD) on postage-stamp-size plastic–quartz chips

A new design of a miniaturized, atmospheric-pressure, low-power (e.g., battery-operated), self-igniting, planar-geometry microplasma device (MPD) for use with liquid microsamples is described. The inexpensive MPD was a hybrid, three-substrate quartz–plastic–plastic structure and it was formed on chips with area the size of a small postage stamp. The substrates were chosen for rapid prototyping and for speedy device-geometry testing and evaluation. The ~700-µm (diameter) and 7-mm (long) He–H₂ (3% H₂) microplasma was formed by applying high-voltage ac between two needle electrodes. Operating conditions were found to be critical in sustaining stable microplasma on plastic substrates. Spectral interference from the electrode materials was not observed. A small-size, electrothermal vaporization system was used for introduction of microliter volumes of liquids into the MPD. The microplasma was operated from an inexpensive power supply. And, operation from a 14.4-V battery has been demonstrated. Microplasma background emission in the spectral range between 200 and 850 nm obtained using a portable, fiber-optic spectrometer is reported. Analyte emission from microliter volumes of dilute single-element standard solutions of Cd, Cu, K, Li, Mg, Mn, Na, Pb, and Zn is documented. Element-dependent precision was between 10–25% (the average was 15%) and detection limits ranged between 1.5 and 350 ng. The system was used for the determination of Na in diluted bottled-water samples.     

Autonomous Portable Solar Ultraviolet Spectroradiometer (APSUS) – a New CCD Spectrometer System for Localized,Real‐Time Solar Ultraviolet (280–400 nm) Radiation Measurement

Terrestrial solar ultraviolet (UV) radiation has significant implications for human health and increasing levels are a key concern regarding the impact of climate change. Monitoring solar UV radiation at the earth's surface is therefore of increasing importance. A new prototype portable CCD (charge‐coupled device) spectrometer‐based system has been developed that monitors UV radiation (280–400 nm) levels at the earth's surface. It has the ability to deliver this information to the public in real time. Since the instrument can operate autonomously, it is called the Autonomous Portable Solar Ultraviolet Spectroradiometer (APSUS). This instrument incorporates an Ocean Optics QE65000 spectrometer which is contained within a robust environmental housing. The APSUS system can gather reliable solar UV spectral data from approximately April to October inclusive (depending on ambient temperature) in the UK. In this study the new APSUS unit and APSUS system are presented. Example solar UV spectra and diurnal UV Index values as measured by the APSUS system in London and Weymouth in the UK in summer 2012 are shown.