KINETIC STUDIES ON CHEMILUMINESCENCE OF CHLOROPLASTS INDUCED BY CHANGES IN ION CONCENTRATION

Abstract— Acid-base, acid-, and salt-induced chemiluminescences of chloroplasts were investigated in relation to their dependences upon several time parameters:

• 1 The dependence of the three chemiluminescences on the preillumination time was similar; the luminescences rose to a maximum and then decayed to a steady-state This behaviour depends on the preillumination level and the length of the dark time following the preillumination. Analysis of the above indicates the formation of quenching entities during the preillumination which react with the luminescence precursors mainly in the dark. In contrast, the delayed light measured after 22 msec from the preillumination, showed a much slower but smooth rise to the steady-state with no subsequent drop.
• 2 During the dark period following preillumination the ability of the system to chemi-luminescence decayed with a first order rate.
• 3 During emission the above chemiluminescences decayed with a first order law. The total emission in different experiments was also proportional to the maximum emission, in agreement with a first order law of decay.
• 4 The comparison of the kinetic behaviour of the three types of chemiluminescence indicates common precursors of luminescence for at least the acid-base and the salt types. The delayed emission at 22 msec however, seems to have separate precursors than the three chemiluminescences.

     

Yb ion as a sensitizer for the upconversion luminescence in nanocrystalline Gd3Ga5O12:Ho

The effect of Yb³⁺ co-doping on the upconversion luminescence in nanocrystalline Gd₃Ga₅O₁₂:Ho³⁺ was examined. Strong and efficient NIR to green anti-Stokes luminescence was noted in nanocrystalline Gd₃Ga₅O₁₂:Ho³⁺, Yb³⁺ after excitation into the ²F_5/2 level of Yb³⁺ with 978 nm radiation. Weaker blue, red and NIR anti-Stokes luminescence was also observed after 978 nm excitation. An enhancement of the red ⁵F₅ → ⁵I₈ luminescence was observed in the anti-Stokes spectrum compared to the Stokes emission spectrum. This enhancement was attributed to two distinct energy transfer upconversion (ETU) mechanisms which preferentially populate the (⁵F₄, ⁵S₂) and ⁵F₅ levels.     

Photo-luminescence of Risø B3 and PVB films for application in radiation dosimetry

Risø B3 film dosimeters (23 μm) prepared from poly(vinyl butyral) (PVB) incorporating pararosaniline cyanide, as the radiation-sensitive element and PVB films (25 μm) prepared from PVB without any additives are investigated for γ-radiation measurement using spectrofluorimetry based on their emission properties. The unirradiated Risø B3 film when excited at 554 nm shows an emission band at 602 nm while PVB film shows an emission band at 305 nm when excited at 235 nm wavelength. The fluorescence intensity of both emission bands decreases with the increase of absorbed dose due to the damage caused by ionizing radiation. The useful dose range of Risø B3 film extends up to 120 kGy while that of PVB film extends up to 60 kGy. The response of Risø B3 film increases with the increase of relative humidity during irradiation while that of PVB has less effect in the humidity range of 20–70%. The percent uncertainty associated with the measurement of the dose response was found to be ±3% (1σ) for both films. Risø B3 and PVB films show good post-irradiation stability in dark and indirect daylight where the deviation in the response overall a 2-month storage period was found to be ±5% for Risø B3 and ±2% for PVB.     

Analysis of acrylamide in coffee and dietary exposure to acrylamide from coffee

An analytical method for analysing acrylamide in coffee was validated. The analysis of prepared coffee includes a comprehensive clean-up using multimode solid-phase extraction (SPE) by automatic SPE equipment and detection by liquid chromatography tandem mass spectrometry using electrospray in the positive mode. The recoveries of acrylamide in ready-to-drink coffee spiked with 5 and 10 μg l⁻¹ were 96±14% and 100±8%, respectively. Within laboratory reproducibility for the same spiking levels were 14% and 9%, respectively. Coffee samples (n = 25) prepared twice by coffee machines and twice by a French Press Cafetière coffee maker contained 8±3 μg l⁻¹ and 9±3 μg l⁻¹ acrylamide. Five ready-to-drink instant coffee prepared twice contained 8±2 μg l⁻¹. Hence, the results do not show significant differences in the acrylamide contents in ready-to-drink coffee prepared by coffee machine, French Press or from instant coffee. Medium roasted coffee contained more acrylamide (10 μg l⁻¹) than dark roasted coffee (5 μg l⁻¹). Males aged 35–45 years, drinking on average 1.1 l coffee per day are exposed to the highest doses of acrylamide from coffee. The dietary intake of acrylamide from coffee comprises, on an average, 10 μg day⁻¹ for males and 9 μg day⁻¹ for females aged 35–45 years. Probabilistic modelling of the exposure of Danish consumers (all adults) to acrylamide from coffee shows a mean exposure of 6.5 μg day⁻¹ and a 95 percentile of 18 μg day⁻¹.     

Optically stimulated luminescence techniques in retrospective dosimetry

Optically stimulated luminescence signals from natural quartz and feldspar are now used routinely in dating geological and archaeological materials. More recently they have also been employed in accident dosimetry, i.e. the retrospective assessment of doses received as a result of a nuclear accident. Since 1990 the exploration of this wide variety of applications has driven an intensive investigation and development programme at Risø, in measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including (i) optimisation of stimulation and emission windows, and detection sensitivity, (ii) experience with various stimulation light sources, including filtered incandescent lamps (420–550 nm) and high intensity light emitting diodes (470 nm) and laser diodes (830–850 nm). We also discuss recently developed high-precision single-aliquot measurement protocols. These offer exciting possibilities in dating and accident dosimetry, and are already leading to new demands on measurement techniques and facilities.     

Determination of bisphenol A (BPA) in the presence of phenol by first-derivative fluorescence following micro liquid-liquid extraction (MLLE)

Bisphenol A (BPA) in the presence of phenol is determined using a method based on first-derivative spectrofluorimetry. The proposed method involves a micro liquid–liquid extraction of sodium chloride saturated water samples with diethyl ether followed by direct fluorimetric analysis of extracts. The excitation spectra of both compounds in diethyl ether are recorded between 200 and 290 nm, with the emission wavelength at 306 nm. The first-derivative spectra were calculated, measuring the analytical signal for BPA at 239 nm. The concentration range over which the method was applied was 0.5–10.0 μg·l⁻¹ of BPA with relative standard deviations of 2.9% for a concentration of 4.0 μg·l⁻¹ of BPA. The detection limit was 0.07 μg·l⁻¹. The proposed method was applied satisfactorily to the determination of BPA in synthetic mixtures and water samples from different sources previously spiked with different amounts of these chemicals. Recovery values ranging from 93% to 112% were obtained for water samples.     

Preparation of visible-light-excited luminescence enhancement solutions for time-resolved luminescence detection of europium biolabel

Dissociation enhanced lanthanide fluoroimmunoassay (DELFIA) technique based on EDTA-Eu(3+) derivative biolabels is the most widely used time-resolved luminescence bioassay technique for clinical diagnosis, but its major drawback is that the conventional luminescence enhancement solution of EDTA-Eu(3+) requires UV excitation (<360 nm). In this work, three new visible-light-excited luminescence enhancement solutions are developed and their luminescence response behaviors to EDTA-Eu(3+) are systematically investigated. The new solutions were prepared by co-dissolving a newly synthesized tetradentate β-diketone, 1,2-bis[8'-(1',1',1',2',2',3',3'-heptafluoro-4',6'-hexanedion-6'-yl)-naphth-2'-yl]-benzene (BHHNB), and one of three derivatives of triazine, 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (DPBT), 2-(N,N-diethylanilin-4-yl)-4,6-bis(3-methylpyrazol-1-yl)-1,3,5-triazine (MPBT) or 2-(N,N-diethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine (BPT), in a weakly acidic aqueous buffer at pH 3.2 containing 0.1% Triton X-100. These solutions showed sensitive and rapid luminescence responses to non-luminescent EDTA-Eu(3+) by the formation of the ternary Eu(3+) complexes, BHHNB-Eu(3+)-DPBT, BHHNB-Eu(3+)-MPBT and BHHNB-Eu(3+)-BPT. These complexes have long luminescence lifetimes (>500 μs) and a wide excitation wavelength range from UV to visible light with the excitation peaks at 390, 400 and 420 nm, respectively, which enabled the solutions to be used as visible-light-excited luminescence enhancement solutions for the highly sensitive time-resolved luminescence detection of EDTA-Eu(3+).     

Ultrafast luminescence in Ir(ppy)3

A femtosecond luminescence and transient absorption study of fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)₃] is reported. An emission with a lifetime component of 230 fs in the spectral region 500–560 nm is assigned to the population equilibration between electronic substates of the lowest excited triplet state, with energy dissipation by intramolecular vibrational redistribution. At shorter wavelengths a strong emission with a faster decay was observed and is attributed to a state with a higher admixture of singlet character. A slower decay on a 3 ps time scale is attributed to vibrational cooling. The results contribute to an understanding of the photophysics of transition metal complexes.     

1.54 and 1.75 μm infrared luminescence of Y2O3:Er

A new 1.75 μm infrared emission transition of Y₂O₃:Er³⁺ is assigned to the ⁴S_3/2 → ⁴I_9/2 transition of Er³⁺ ions situated at the C₂ sites of cubic RE₂O₃ (RE = Y, Gd, Lu). The intensities of features in the 1.54 μm ⁴I_15/2–⁴I_13/2 absorption transition due to Er³⁺ at S₆ and C₂ sites are consistent with the site occupation ratio and the relative magnetic dipole–electric dipole intensity contributions of Er³⁺ at the different sites. The 1.54 μm emission lines are predominantly from Er³⁺ ions at C₂ sites. The different behaviours of the emission intensities 1.75 and 1.54 μm groups with change in Er³⁺ dopant ion concentration, preparation technique, Yb³⁺ co-doping, temperature change and different excitation line are rationalized.     

Excited species in the FBX dosimeter system

In the FBX dosimeter solution, the excitation of xylenol orange (XO) produces maximum emission at 550–575 nm both at room and liquid nitrogen temperatures (about 85%) having a lifetime of 0.20–0.36 ns. In addition, at room temperature there is an emission at 350 nm for the excitation at 260 nm (about 15%) having a longer lifetime of 3.71–4.01 ns. Benzoic acid (BA) has excitation at 284–295 nm and emission at 320–365 nm having a lifetime of 1.38 ns. In an aqueous solution containing 5×10⁻³ mol dm⁻³ BA, 2×10⁻⁴ mol dm⁻³ XO and 0.04 mol dm⁻³ H₂SO₄ there is no XO emission at 550 nm due to UV absorption at 260 nm by BA. In this solution, 2 emissions are observed near 350–360 nm, having lifetimes of 1.25 ns (89%) and 2.86 ns (11%). The wavelengths for the emission of XO and absorption of ferric-XO complex are nearly the same. Excited XO produces oxidation of ferrous ions and BA increases the chain length.     

Highly efficient blue up-conversion of Tm in Nd–Yb–Tm co-doped ZrF4-based fluoride glass

Up-conversion luminescence and energy-transfer processes in Nd³⁺, Yb³⁺ and Tm³⁺ co-doped ZrF₄-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm³⁺:¹G₄→³H₆ transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF₃-concentration dependence. Among the Nd³⁺, Yb³⁺ and Tm³⁺, Nd³⁺ and Tm³⁺ have ground state absorption bands due to the (²H_9/2,⁴F_5/2)←⁴I_9/2 and ³F₄←³H₆ transitions, respectively, which can be directly pumped by 800 nm radiation. However, no emissions were observed in Tm³⁺ singly-doped and Tm³⁺–Yb³⁺ doubly-doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: energy-transfer firstly occurs from Nd³⁺ to Yb³⁺ when Nd³⁺ is excited by 800 nm light, then the energy is transferred from Yb³⁺ to Tm³⁺ which is in the excited state and, finally, blue up-conversion emission of Tm³⁺ is observed through the Tm³⁺:¹G₄→³H₆ transition.     

Pd encapsulated and nanopore hollow fiber membranes: Synthesis and permeation studies

New types of supported Pd membranes were developed for high temperature H₂ separation. Sequential combinations of boehmite sol slip casting and film coating, and electroless plating (ELP) steps were designed to synthesize “Pd encapsulated” and “Pd nanopore” membranes supported on -Al₂O₃ hollow fibers. The permeation characteristics (flux, permselectivity) of a series of unaged and aged encapsulated and nanopore membranes with different Pd loadings were compared to those of a conventional 1 μm Pd/4 μm γ-Al₂O₃/-Al₂O₃ hollow fiber membrane. The unaged encapsulated membrane exhibited good performance with ideal H₂/N₂ separation factors of 3000–8000 and H₂ flux 0.4 mol/m² s at 370 °C and a transmembrane pressure gradient of 4 × 10⁵ Pa. The unaged Pd nanopore membranes had a lower initial flux and permselectivity, but exhibited superior performance with extended use (200 h). At the same conditions the unaged 2.6 μm Pd nanopore membrane had a H₂ flux of 0.16 mol/m² s and separation factor of 500 and the unaged 0.6 μm Pd nanopore membrane had a H₂ flux of 0.25 mol/m² s and separation factor of 50. Both nanopore membranes stabilized after 40 h of operation, in contrast to a continued deterioration of the permselectivity for the other membranes. An analysis of the permeation data reveals a combination of Knudsen and convective transport through membrane defects. A phenomenological, qualitative model of the synthesis and resulting structure of the encapsulated and nanopore membranes is presented to explain the permeation results.     

Enantioseparation and quality control of biperiden in pharmaceutical formulations by capillary electrophoresis

An original capillary electrophoretic method has been developed and applied for the enantioselective analysis of the antiparkinson drug biperiden in pharmaceutical formulations, using a modified cyclodextrin as the chiral selector. Baseline enantioseparation of the racemic compound was achieved in less than 7 min using an uncoated fused silica capillary (50 μm i.d. and 48.5, 40.0 cm, total and effective length, respectively), filled with a background electrolyte consisting of a 50 mM phosphate buffer at pH 3.5 supplemented with 3% (w/v) β-cyclodextrin sulphate and applying a voltage of 20 kV, reversed polarity. Samples were injected by pressure (50 mbar, 90 s) at the cathodic end of the capillary and detection wavelength was 195 nm (bandwidth: 10 nm). A simple and fast pre-treatment procedure allowed the complete extraction of the drug from commercial formulations (sustained release tablets and ampoules for injections) without any interference from the matrix. Good linearity was found in the 1–50 μg/mL concentration range; the limit of quantitation was 1 μg/mL and the limit of detection was 0.4 μg/mL. Precision and accuracy were good, with R.S.D. values always lower than 2.8% and a mean recovery value of 101.1%. The method was suitable for the quality control of biperiden in commercial formulations.     

Fast 5d → 4f luminescence of Pr in Lu2SiO5 single crystal host

Absorption and photoluminescence spectra including the decay kinetics of the Pr³⁺-doped Lu₂SiO₅ were measured. Fast luminescence originating from the radiative 5d → 4f transition of Pr³⁺ center is revealed with the maximum at 273 nm at room temperature. Low temperature photoluminescence decay is governed by the 25 ns decay, while substantial shortening to 6–7 ns occurs at room temperature. With the help of slow decay measurement in the millisecond time scale we evidence the thermal ionization of the relaxed excited 5d₁ state of Pr³⁺. The ionization can explain the observed temperature dependences of the decay times and emission intensity.     

Ultraviolet laser-induced fluorescence detection strategies in capillary electrophoresis: determination of naphthalene sulphonates in river water

Various UV-laser-induced fluorescence detection strategies for capillary electrophoresis (CE) are compared, i.e. two UV-laser systems (a pulsed laser providing up to 25 mW of tunable emission, applied at 280, 290 and 325 nm, and a continuous wave (cw) laser providing up to 100 mW of 257 nm emission) and different methods to collect the fluorescence emission signal and to reduce the background. Attention is focused on the determination of amino- and hydroxy-substituted naphthalene sulphonates (NS) in river water; these analytes exhibit native fluorescence upon UV excitation. Optimum results were obtained by applying only a minor portion of the available (average) laser powers, viz. 0.7 mW at 280 nm for the pulsed laser, and 5 mW for the cw laser. For emission collection, the most favourable results were obtained with a mirror-based microscope objective, which facilitates efficient spatial filtering and does not produce impurity fluorescence upon UV-laser irradiation. For standard solutions, the cw laser gave around 20-fold better detection limits (10⁻⁹–10⁻¹⁰ M) than the pulsed laser. For river water, excitation of interferences (presumably humic acids, which exhibit native fluorescence) could be much better suppressed if the pulsed laser was used with selective excitation at 280 nm. Therefore, for real-sample analysis the latter combination is to be preferred. The set-up was used for the identification and quantification (at the 1–35 μg l⁻¹ level) of NS in a river Elbe sample.     

Implementation of flow-through multi-sensors with bead injection spectroscopy: fluorimetric renewable surface biparameter sensor for determination of berillium and aluminum

For the first time a new, sensitive, and simple bead injection spectroscopy–flow injection analysis (BIS–FIA) system with spectrofluorimetric detection is described for the sequential determination of two metals. The sensor is based on the alternate use of two carriers and a commercially available flow cell (Hellma 176-QS). The flow cell is filled by injecting in the flow system 500 μl of a homogeneous bead suspension of an appropriate solid support (Sephadex QAE A-25) previously loaded with the fluorogenic reagent morin (2′,3,4′,5,7-pentahydroxyflavone). A sequential reaction of Al(III) and Be(II) with morin (immobilized on beads) to form their fluorescent complexes is performed on the bead sensing support and their respective fluorescence emission monitored, after doing two successive injections from the mixture solution. Firstly, Al(III) could be determined in the sample using 0.5 M NaCl/HCl, pH 6 as carrier. Then, the carrier solution was changed (0.3 M NaCl/NaOH, pH 12) making possible the elution of Al(III) and the restoration of the baseline, then allowing the reaction of Be(II). At the end of the analysis, beads are automatically discarded from the flow cell, by reversing the flow, and transported out of the system. The analytical signals are measured at an excitation wavelength of 440 nm and an emission wavelength of 520 nm. Using a sample volume of 600 μl, the analytical signal showed a very good linearity in the range 0.1–8 ng ml⁻¹ and 0.1–1 μg ml⁻¹ with detection limits of 0.024 ng ml⁻¹ and 0.010 μg ml⁻¹ for Be(II) and Al(III), respectively. R.S.D.s (%) lower than 5% were obtained for both analytes and the selectivity was improved using EDTA as masking reagent. The sensor was satisfactorily applied to the determination of these metals in waters and simulated alloy samples.     

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with PX. The signal for PX–EU is monitored at λ_ex=358 nm and λ_em=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu³⁺ which allows the determination of 100–2000 ppb of pX in batch method and 100–1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.     

Investigation of the hydrothermal stability of cross-linked liquid silicone rubber (LSR)

We investigate the hydrothermal stability of cross-linked liquid silicone rubber (LSR) in water at 100 °C up to period of two years. Optical microscopy of cross-sections of the exposed samples reveal that only the outer 100 μm of the surface layer is affected after two years. However, the surface chemistry of the material after prolonged exposure becomes significantly modified, as monitored by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR), which probes depths of 10 nm and 1 μm, respectively. In addition, changes to the bulk physical properties of the rubber samples, prior to and after the exposure, were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Micro-hardness analysis showed that surface roughness of the two year exposed sample increased from 60 (IRHD) to 75 (IRHD). Furthermore, the volume change (%) measurement showed a significant decrease in the course of exposure at prolonged time. The results provide the experimental basis for development of LSR materials suitable for numerous technical applications.     

Sensitive absorption detection for micro-column liquid chromatography by ultraviolet forward-scattering degenerate four-wave mixing

The performance of forward-scattering degenerate four-wave mixing (F-D4WM) in the mid-ultraviolet (UV) region (351 nm) as a detection technique for micro-column liquid chromatography (μLC) is studied, using nitro-substituted polycyclic aromatic hydrocarbons (NO₂-PAHs) and amino-substituted anthraquinones (AAQs) as test compounds. When using round capillaries, the concentration limits of detection (LOD) for the NO₂-PAHs were 20–70-fold better compared with absorption detection using a U-shaped detector cell. The final result is influenced by photochemical degradation during 351 nm F-D4WM detection. Furthermore, it is demonstrated that the use of recently commercially available square capillaries (i.e., capillaries with both a square cross section and a square bore) instead of round ones is quite suitable for F-D4WM detection. The square capillary (internal dimensions, 75×75 μm²; external dimensions 300×300 μm²) did not cause significant chromatographic band broadening in μLC. The angle of incidence of the laser light should be 56°, thus fulfilling the Brewster condition at the air–quartz boundary. Using this approach for the AAQs, compounds not prone to significant photodegradation under the experimental conditions, a further 4-fold improvement was achieved. As a result, the overall gain in concentration LOD for 2-amino-9,10-anthraquinone (molar absorptivity 4000 M⁻¹ cm⁻¹ at 351 nm) was from 4 to 0.05 μM, and baseline irregulations were reduced.     

Red luminescence in MgO-GeO<Subscript>2</Subscript> gel glasses and glass ceramics doped with Mn ions prepared by sol-gel method

To obtain red luminants, MgO-GeO₂ gel glasses and glass ceramics doped with manganese ions were prepared by a sol-gel method and their properties were investigated by measuring X-ray diffraction (XRD), electron spin resonance (ESR), and luminescence and excitation spectra. Under UV irradiation at 254 nm, the gel glasses and glass ceramics showed red luminescence at 620–665 nm, the intensity of which became strong with increasing the heat-treatment temperature. A glass ceramic with the composition 1.0MnO-25MgO-75GeO₂ heat treated at 1000°C exhibited the strongest red luminescence at 661 nm. From the results of XRD and ESR, this luminescence is found to be due to the transition from the ⁴T_1g to the ⁶A_1g state of octahedrally coordinated Mn²⁺ ions located in MgGeO₃ polycrystals. The luminescence wavelength of the glass ceramics (∼665 nm) is long compared with Eu³⁺-containing phosphors (612 nm), therefore the glass ceramics can be expected for red luminants.