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[Display omitted] • A novel approach for quantifying HSAD's mass transfer was proposed. • In the mixing process, feedstock tended to accumulate around the 1st stage impeller. • HSAD's mixing homogeneity remained unachieved after 4 h. • Prolonging the mixing time could not significantly improve the mass transfer. • The novel measuring approach visualized the mass transfer in HSAD. High solid anaerobic digestion (HSAD) is a promising technology for the treatment of organic waste. Mixing process in HSAD is quite difficult with long mixing time, poor homogenization, significant short-circuiting and stagnant zones. However, the mass transfer in mixing process in HSAD has not been visualized due to the lack of a proper method. In this study, a novel approach for experimentally quantifying the mass transfer in HSAD's mixing process was proposed in a mixing tank equipped with multistage impellers by means of the Laser Induced Fluorescence (LIF) technique. Flow field was investigated for better illustrating the mass transfer, thus Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) technique were conducted for flow field measurement. The obtained results revealed that the feedstock tended to accumulate around the impeller in the HSAD system, especially near the 1st stage. The tracer diffused rapidly around the 1st impeller in t = 10 s, but the diffusion around the 2nd impeller was quite tough even after 4 h 08 min 23 s. And prolonging mixing time could not significantly improve the flow pattern along with the mixing. In this study, new insight was thrown into the visualization of the mass transfer in mixing process within a HSAD reactor. The visualization of mass transfer in the mixing process in HSAD could offer reference information to the study of the mixing process of HSAD even in full-scale. [ABSTRACT FROM AUTHOR]

Nowadays scientific study of Cultural Heritage accompanies most of the time historical artistic evaluation and an assessment of the conservation state by humanistic experts and restorers. Several laboratory methods with high sensitivity are well established (ICP-MS, FTIR,...), and many methods for in situ rough characterization of large surface are widely diffused (thermovision, UV photography,...), in addition to instrumentation for punctual analysis to be applied also in field (XRF, colorimetry,...). However, the request for systems that can provide rapid detailed characterization on large surface in any storage conditions is still a hot topic. This is combined with the ever-increasing demand for digital material for documentation, fruition and study. Laser-based systems, and in particular Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy and Raman spectroscopy, due to the characteristics of these sources and the detectors to which they can be coupled, respond well to these needs. The TECFIS-DIM (Diagnostic and Metrology) Laboratory of the ENEA center of Frascati (Rome, Italy) in the last decade has put an effort to develop more and more compact and efficient laser systems for in situ material characterization on cultural heritage surfaces. Here two prototypal LIF systems have been used to characterize marble surfaces treated with ancient and modern materials and a rapid recognition and mapping method has been developed and tested thanks to the individuation of discriminant spectral features. Results are reported on test samples created in lab with known substances and in situ on real artworks. [ABSTRACT FROM AUTHOR]

• Bladder cancer is one of the most common malignant tumors in humans. • White light cystoscopy is the gold standard for detection of bladder cancer. • Autofluorescence (AFE) and photodynamic diagnostics (PDD) are the new techniques for early bladder cancer diagnosis. • High sensitivity and specificity of AFE/PDD in bladder cancer diagnosis. Bladder cancer is one of the most common Genito-urinary malignant tumors in humans. Improved diagnostic and therapeutic methods that aim to reduce rates of recurrence and progression of bladder cancer are needed. In current publications, one can find information on such methods as Raman spectroscopy, ultraviolet autofluorescence microscopy, confocal laser endoscopy, photoacoustic imaging, molecular imaging, multi-photon microscopy and many other new diagnostic techniques. These methods do not show significant adverse effects and are procedures well tolerated by patients as they use mostly physical phenomena that are neutral towards the human body. This review highlights the techniques of autofluorescence (AF) or laser induced fluorescence (LIF) and photodynamic diagnostics (PDD) which have been widely clinically studied for many years as a complement to cystoscopy. These methods can be performed during standard cystoscopy and they can be used in routine practice. This review shows that Autofluorescent and Photodynamic diagnostics are effective and have great potential in enhancing the diagnosis of bladder cancer. However, more research should be performed to help realize their full potential. [ABSTRACT FROM AUTHOR]

Abstract A multiwavelength laser induced fluorescence (LIF) LIDAR system, which can be employed around the clock for detecting oil spills in a marine environment, has been developed. The system incorporates a pulsed Nd: YAG laser, Nd: YAG laser amplifier and two KD*P crystals for generating 266 nm, 355 nm and 532 nm. Additionally, the LIF LIDAR system incorporates a nitrogen laser pumped dye laser system operating at 428 nm (Stilbene 420 dye), a Newtonian telescope, motorized monochromator, a photomultiplier detection system and a data acquisition system. Fluorescence intensity measurements collected from fresh and weathered oil samples using the LIF LIDAR system are presented. Strong fluorescence spectra were detected from refined and crude oils when excited with 266 nm. Finally, a brief description for the principle components algorithm used for identifying and classifying unknown oil samples is provided. [ABSTRACT FROM AUTHOR]

Highlights • A novel elliptic capsule is suggested for the large scale latent thermal energy storage. • Motion of PCM lump in elliptic capsule is reported which improved the heat transfer rate. • Elliptical capsule decreases the charging/discharging time by 50% and 35%, respectively. • Test for 1000 L of water reveals charging/discharging time of 4.8 and 6.25 h, respectively. Abstract A latent heat thermal energy storage (LHTES) system is an efficient thermal battery using a phase change material (PCM) for key applications of intermittent renewable energy. In this study, a flexible elliptical-shaped capsule is investigated and subsequently proposed as a container of the PCM used for LHTES. The novel elliptical PCM capsule is made of polyethylene and designed to achieve maximum enhancement of heat transfer. The thermal flow inside the capsule is analyzed via the combined methods of particle image velocimetry and laser induced fluorescence. In the present study, the upward and downward motion of a solid PCM lump in an elliptical capsule are reported for the first time. This is shown to increase the heat transfer rate by more than twice that of a spherical capsule. A prototype heat storage tank with 1000 L of water and 500 kg of the PCM is fabricated for application as a large-scale thermal battery. Consequently, the developed PCM capsule exhibits a decrease of 50% and 35% in the charging and discharging process time, respectively. [ABSTRACT FROM AUTHOR]

Ammonia is considered a promising alternative fuel for reducing CO 2 emissions. However, the nitriding effect induced by ammonia flames poses a significant challenge that hinders its practical application in various industries. In the present study, to investigate the effects of temperature on the nitriding of stainless steel induced by ammonia flames, experiments were conducted by exposing SUS310S test plates to ammonia flames at different wall temperatures ranging from 550 °C to 850 °C. The distributions of chemical species in ammonia flames were obtained experimentally by means of the laser-induced fluorescence (LIF) technique and chemiluminescence measurement. Numerical simulations were also performed to estimate the ammonia flame structures with the consideration of surface reaction on the wall. In addition, the distributions of surface hardness and nitrogen atom concentration in the wall material were quantified by employing a nano-indenter and wavelength dispersive spectroscopy method (WDS), respectively. The LIF data for NH and NH 3 concentration are in good agreement with the numerical results, highlighting the necessity of considering the surface reaction to accurately estimate the ammonia flame structure near the wall. It is also observed that both the surface hardness and the diffusion depth of nitrogen atoms into the wall decrease with increasing wall temperature, indicating a weakened nitriding effect at high wall temperatures. Notably, the NH 3 concentration at the wall surface was identified as the most dominant parameter for the nitriding effect, while NH 2 radicals also partially contribute to the nitriding. It is also found that the water vapor also hinders the nitriding. [ABSTRACT FROM AUTHOR]

Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s 2 4s 2 S 1/2 → 3s 2 3p 2 P° 3/2 ) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure ( p o ) in the atmospheric pressure environment using N 2 as the makeup gas was varied from 0 to 400 Torr O 2 . 2D–fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume. [ABSTRACT FROM AUTHOR]

We present development and performance tests of a new single particle bio-detector (BARDet – Bio-AeRosol Detector) for real time air monitoring. The instrument uses single CW laser at 375 nm and measures scattering signal intensity and fluorescence of individual particles in seven spectral bands. The device is integrated into a single compact enclosure and allows remote operation on mobile platform. The bio-aerosol detector is equipped with internal computer and SSD (Solid State Drive) for real time data acquisition and analysis. The final result is sent to the remote operator. Classification of aerosols with known fluorescence properties was performed using Principal Component Analysis (PCA). It showed that pollens are well separated from flours, riboflavin and culture media. The classification effectiveness of particular groups of substances varied from 88 to 98%. We demonstrated a new technological approach to air monitoring combining laser induced fluorescence particle characterization technique with internal computer that performs real-time data analysis and classification. In consequence the BARDet could be used as a remote sensor integrated with the robot. This introduces a new quality and improves versatility of air monitoring. [ABSTRACT FROM AUTHOR]

Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a ) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio ( F 690 / F 730 ) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F 690 / F 730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit. [ABSTRACT FROM AUTHOR]

Confined impinging jet reactors (CIJMs) are very efficient mixing devices. Due to the generation of high turbulent dissipation and, thus, intensive mixing of two colliding liquid flows CIJMs are widely used in laboratory applications. Besides low construction effort, these mixers enable a sensitive control of fast reactions, an efficient initial homogenization of educts and consequently a rapid build-up of supersaturation as the driving force for precipitation and crystallization. The understanding of fluid mechanics and mixing in those CIJMs is of fundamental interest for a proper description of parallel or consecutive processes. Therefore, this paper gives an insight into characteristic procedures, with the main focus on the turbulent flow regime in a T- and Y-CIJM. Experimental investigation on the local mixing behavior of liquid-phase impinging jets in static mixers is carried out by using an optical laser induced fluorescence (LIF) and particle image velocimetry (PIV) setup. In order to avoid optical measurement errors due to the cylindrical geometry, a refractive index correction of fluids with the ionic additive NH 4 SCN has been carried out. Due to poor information in literature, important properties of the corrected aqueous solution are listed. Another main focus of this work lies in the mathematical modeling of the flow field based on computational fluid dynamics (CFD) methods. The transient hybrid Detached Eddy-SST- k – ω turbulence approach is introduced as a computational cost-efficient highly accurate method to calculate flow conditions in turbulent CIJMs. LIF and PIV as well as pressure drop measurements provide a wide set of data that serve to validate CFD simulations. [ABSTRACT FROM AUTHOR]

Highlights: [•] The favorable effect of ultrasound (US) on preliminary and sample preparation steps in metabolomics is emphasized. [•] The beneficial effect of US on a number of metabolomics subdisciplines is shown. [•] Major use of US in targeted than in untargeted analysis is shown. [Copyright &y& Elsevier]

Studies have been performed to evaluate a direct laser induced fluorescence (LIF) technique for measurements of atmospheric sulfur dioxide (SO2). The technique is novel in that it uses a nontunable laser source that is spectrally coincident with absorption of the SO2 molecule near 223 nm that allows sensitive measurements at environmentally relevant concentrations. In this report, the spectral characteristics and analytical capabilities of the nontunable LIF approach have been evaluated and preliminary measurements of ambient SO2 are reported. The current limit of detection is 0.5 ppb and compares well to other analytical spectroscopy methods used for atmospheric measurements of SO2. The results indicate strong feasibility for the nontunable LIF approach for SO2 measurements and suggest ways for method improvement. [ABSTRACT FROM PUBLISHER]

Abstract: This study describes the development of a novel fluorescent tag, O-2-[aminoethyl]fluorescein, for the separation of sugars by capillary electrophoresis with fluorescence detection using an argon ion laser. The tag was synthesised using three consecutive steps namely: esterification, alkylation and hydrolysis, specifically designed to offer a flexible way in which to make an assortment of fluorescent tags from cheap and readily available starting reagents (typically less than $1perg of fluorescent tag). Via this flexible synthetic pathway, O-2-[aminoethyl]fluorescein was designed and synthesised with a spacer group to lower steric effects between the fluorescein backbone and the reducing end of the carbohydrate which were anticipated to improve the reactivity of the tag. The newly synthesised tag, O-2-[aminoethyl]fluorescein was evaluated against structurally similar commercial fluorescent motifs namely fluorescent 5-aminomethylfluorescein and non-fluorescent 5-aminofluorescein. Kinetic studies indicated that O-2-[aminoethyl]fluorescein showed similar labeling efficiencies as 5-aminomethylfluorescein, but were achieved in only 30min, supporting the notion of improved reactivity of the spacer group. The sensitivity of O-2-[aminoethyl]fluorescein was evaluated using maltoheptaose with a detection limit of 1nM obtained, which was slightly higher than that of 0.3nM obtained with 5-aminomethylfluorescein, and was due to its lower quantum yield (0.24) when conjugated to the sugar. The separation performance of the tag was also benchmarked with the two commercial reagents using a range of corn syrup oligosaccharides, from 4 to 10 glucose units, typically found in rice starch. Separations were performed using an electrolyte containing 100mM boric acid, tris at pH 8.65 as background electrolyte, 30kV applied voltage, 50μm I.D.×40cm (30cm effective length) capillary. The novel tag showed better resolution of small oligosaccharides, G3 and G4, than the other two reagents, but slightly worse resolution for the longer oligosaccharides, most likely due to the monovalent charge state of the O-2-[aminoethyl]fluorescein compared to the divalent charge of the other two tags. [Copyright &y& Elsevier]

Abstract: The auto-ignition process during transient injection of gaseous dimethyl ether (DME) in a constant high-pressure atmosphere is studied experimentally by laser-optical methods and compared with numerical calculations. With different non-intrusive measurement techniques jet properties and auto-ignition are investigated at high temporal and spatial resolution. The open jet penetrates a constant pressure oxidative atmosphere of up to 4 MPa. During the transient evolution, the fuel jet entrains air at up to 720 K. The subsequent auto-ignition of the ignitable part of the jet occurs simultaneously over a wide spatial extension. The ignition delay times are not affected by variation of the nozzle exit velocity. Thus, the low-temperature oxidation is slow compared with the shorter time scales of mixing, so that chemical kinetics is dominating the process. The typical two-stage ignition is resolved optically with high-speed shadowgraphy at a sampling rate of 10 kHz. The 2D fields of jet velocity and transient mixture fraction are measured phase-coupled with Particle Image Velocimetry (PIV) and Tracer Laser Induced Fluorescence (LIF) during the time-frame of ignition. The instationary Probability Density Functions (PDF) of mixture fraction are described very well by Beta functions within the complete area of the open jet. Additional 1D flamelet simulations of the auto-ignition process are computed with a detailed reaction mechanism for DME [S. Fischer, F. Dryer, H. Curran, Int. J. Chem. Kinet. 32 (12) (2000) 713–740; H. Curran, S. Fischer, F. Dryer, Int. J. Chem. Kinet. 32 (12) (2000) 741–759]. Calculated ignition delay times are in very good agreement with the measured mean ignition delay times of 3 ms. Supplemental flamelet simulations address the influence of DME and air temperature, pressure and strain. Underneath a critical strain rate the air temperature is identified to be the most sensitive factor on ignition delay time. [Copyright &y& Elsevier]

In this paper, we describe the experimental approaches to understand the microdischarge physics of an alternating current plasma display panel (ac PDP) cell. We discuss the experimental techniques to explore the major parameters to understand the operation of ac PDP such as the vacuum ultra violet (VUV) emission and wall charge variation. Regarding the discharge dynamics, the detailed VUV emission characteristics were measured and explained by the gas reaction modeling and the microdischarge characteristics during the ramp reset period were compared with the simulation result. The wall voltage and wall charge distribution were measured by laser induced fluorescence (LIF) and electro-optic modulation method. The slight increase of the wall voltage by Xe addition to pure He discharge gas was observed by LIF. And the existence of self-erasing discharge results in the drastic decrease of wall charge near discharge gap. [ABSTRACT FROM PUBLISHER]

Abstract: Simultaneous measurements of temperature and velocity fields have been performed by applying combined laser induced fluorescence (LIF) and particle image velocimetry (PIV) techniques to natural convection in a die cast model. A 10cm×10cm×3cm U-shape rectangular die casting model has been filled with pure water and the cell walls have been continuously cooled between 41 and 6°C. The resulting natural convection pattern and temperature field have been measured with PIV and LIF. Furthermore, the convection pattern has been simulated in 2D and 3D using the commercial CFD software FLUENT. The comparison of the experimental and numerical results given in this work shows good agreement both qualitatively and quantitatively. [Copyright &y& Elsevier]

Abstract: The potential of the commercially available dye sypro orange for in-capillary derivatization was evaluated for the detection of insulin and one gastrointestinal peptide (Arg-Arg-gastrin) by capillary electrophoresis with laser induced fluorescence (CE–LIF). The fluorescent emission intensity (λ ex =488nm, λ em =610nm) of this probe is very low in aqueous medium, and increases strongly in less polar solvent, e.g. methanol. The hydrophobic character of the two analyzed peptides is too low to induce sufficient interaction with the fluorescent probe for good sensitivity when the latter is alone in the background electrolyte. Thus, the potential of several neutral, zwitterionic, cationic and anionic surfactants to favor probe/peptide interactions has been evaluated. It was demonstrated that a borate buffer (pH 8.5) containing tetradecyltrimethylammonium bromide (TTAB) in sub-micellar conditions can be considered as the most suitable buffer for insulin CE–LIF analysis. In addition, the method showed a good linearity between insulin concentration and the peak area of the labeled insulin, allowing quantitative measurements. The sensitivity achieved so far is comparable with that achieved with UV absorption detection, but even at this level it is interesting for microchip analysis, in which fluorescence detection is much more commonly available than UV absorption detection. [Copyright &y& Elsevier]

Corona-induced fluorescence (CIF) of nitric oxide (NO) reveals that NO(A²Σ+) is primarily excited through N2 (A³Σu+) produced in a pulsed corona rector (PCR). The charge voltage in PCR, the time delay of the high-voltage pulse applied to the reactor, and its time jitter vary from gas composition to gas composition. This is because the reactor electric equivalent resistance in an OFF state has different values for different gas components. The PCR pulse jitter, typically a few tenths of a microsecond, for the same gas composition, varies with the frequency of high-voltage pulses due to changes in feed composition. A precise lime synchronization of CIF with the laser induced fluorescence (LIF), the intensified charge-coupled device (ICCD) detector and the PCR pulse reveals that NO molecules stay in the vibrational levels of the ground state for about 700 μs. [ABSTRACT FROM AUTHOR]

To characterize intermittency phenomena in the impeller jet, digital particle image velocimetry (DPIV) was used to measure the near-instantaneous flow fields in baffled, stirred reactor, equipped with a Rushton turbine (RT) impeller of large impeller and reactor diameter ratio. From the transient velocity fields obtained by DPIV, characterized by a chaotic movement of the jet axis in a fan section in the plane of laser sheet, effective intermittency phenomena in the impeller stream were identified for lower rotational speed. To gain insight into the nature of the intermittency phenomena, the impeller discharge angle corresponding to the near-instantaneous velocity field was calculated and its time series were constructed and analyzed via frequency count and power spectral density function (PSD). The macro-instability (MI) behavior of the reactor was investigated and its presence in the bulk flow was verified via spectral analysis of time series of the spatially averaged vorticity for lower rotational speed (namely 30, 60 and 120 min-1). Coherent spectral analysis was introduced to determine the cause of the intermittency phenomenon in the impeller stream as well as the relationship between the intermittency phenomenon and MI in the bulk flow. Results show that intermittency in the impeller stream is linearly related to MI in the reactor. The influence of MI should not be neglected in study of impeller stream intermittency phenomena. [Copyright &y& Elsevier]

A review is presented on the CE analysis of colloidal/nano particles. Topics discussed include the CE separation of polymeric, inorganic, microbial (i.e. viruses, bacteria, fungi, and whole cells), and sub-cellular particles (i.e. mitochondria and nuclei). Several of the encountered difficulties in analysis are presented as well as the methods employed to overcome them. [Copyright &y& Elsevier]

A competitive immunoassay for detecting morphine in bio-samples was established by capillary zone electrophoresis combined with laser-induced fluorescence detection (CZE-LIF). The antigen of morphine was labeled with isothiocyano-fluorescein (FITC) and then incubated with morphine monoclonal antibody and samples. The linear range was 50–1000 ng/mL, which was suitable for clinical and forensic applications. The detection limit can reach 40 ng/mL, based on S/N = 2. The recoveries of morphine from serum were satisfactory. [ABSTRACT FROM AUTHOR]

A square jet with mixing tabs was investigated using laser induced fluorescence and laser Doppler anemometer (LDA). The triangular tabs were tilted either downstream (i.e., at an inclination, θ=45°) or upstream (i.e., at θ=135°). With four tabs, the jet flow was bifurcated into a four-finger structure and there was a “mushroom” structure behind each tab for θ=135°. Secondary velocity vector measurements using LDA in the y–z plane for the θ=45° and 135° with tabs at x=0.25DH and 0.075DH respectively showed a vortex pair formed behind each tab. These streamwise vortices spread the jet fluids “outward” along the diagonal direction of the jet cross-section, resulting in the four-finger structure. At the two corners of each finger, a pair of streamwise vortices, which were the legs of weaker horseshoe vortices, were also found. For θ=135°, a third pair of streamwise vortices proposed by Reeder and Samimy [J. Fluid Mech. 311 (1996) 73] was observed at the tip of each tab, which explained the existence of the unique mushroom structure. LDA measurements of mean velocity contours on the two tabbed jets confirmed the flow visualization results that the jet core had bifurcated into a four-finger structure. Furthermore, with tabs at x=0.75DH and 1.25DH, the downstream tilted tab jet produced a larger cross-sectional area of the jet core than the jet with θ=135° and the jet without tab. Downstream tilted tabs were thus more efficient in mixing enhancement than upstream tilted tabs. [Copyright &y& Elsevier]

[Display omitted] • Efficient and sensitive FITC labeling process was optimized using DoE approach. • The optimized labeling process could be easily implemented for pharmaceuticals. • DoE combined with multivariate statistical modeling was used to optimize the process. • Variance component analysis was integrated to DoE to estimate process variability. Fluorescence, especially laser induced fluorescence (LIF), is a powerful detection technique thanks to its specificity and high sensitivity. The use of fluorescence detection hyphenated to separation technique often requires the labeling of analytes with suitable fluorescent dye, such as FITC for the labeling of molecules presenting amino groups. Nevertheless, the labeling of analytes could be a tedious, time consuming and a non-robust step of the analytical workflow. In this context, the objective of the present work was to propose a robust and reliable FITC labeling process. Primary and secondary amino compounds (i.e. synthetic cathinones) were selected as model compounds because they are representative of a large proportion of pharmaceutical small molecules. Based on prior knowledge, DoE combined with multivariate statistical modeling was performed to optimize the process. Reaction time and pH of reaction buffer were highlighted as the most critical parameters to control the process. The study showed also the benefit of short reaction time to maximize the labeling efficiency. Indeed, optimal condition was defined as reaction time of 32 min with ratio between FITC and analytes of 40.4 and the buffer reaction pH of 9.7. In addition, variance component analysis was integrated to the DoE to estimate the variability of process and to evaluate its applicability for quantitative purpose. These chemometric approaches helped to develop an efficient labeling process able to reach high sensitivity for CE-LIF analysis (i.e. 10 nM) with good precision (i.e. intermediate precision values lower or close to 5 %). [ABSTRACT FROM AUTHOR]

• The mixture of RdB fluorophore and RBC species are excited at 532 nm to record various LIF spectra. • RdB + RBCs fluorescence emissions of different blood types demonstrate certain values of Stern-Volmer coefficient. • There is a correlation between Stern-Volmer coefficient and corresponding spectral shift for ABO blood group. • Specific sugar on RBCs membrane exhibit key factor for photon path length elongation, reabsorption and corresponding spectral shift. In this work, the optical properties of Rhodamine B (RdB) are investigated in the attendance of various red blood cells (RBCs). RdB fluorophores, as biological markers, is excited using SHG-CW Nd:YAG laser at 532 nm. In fact, the addition of biomolecules of interest to the reference fluorophore notably changes the fluorescence properties of the suspension. Here, laser induced fluorescence (LIF) spectrophotometry based on Stern-Volmer quenching formalism and field emission scanning electron microscope (FESEM) are employed here. According to the given fluorescence spectra, the spectral shift of emissions as well as quenching coefficients are assessed subsequently. The Stern-Volmer formalism is used to determine the quenching coefficients. In fact, RdB + RBCs suspensions contain a plenty of bioconjugates leading to the signal reduction and notable red shift in RdB fluorescence emissions. Furthermore, it is demonstrated that the positive blood type RBCs exhibit the higher quenching coefficients and the larger red shifts against those of negative blood types. This mainly arises from the nature of specific sugar antigens available on the RBC membranes as to N-acetylgalactosamine and galactose attached to the O-antigen terminal would enhance further quenching of the species. Moreover, a significant correlation appears between Stern-Volmer coefficients and the corresponding RBCs. In fact, distinct discrepancy takes place in quenching coefficients in terms various positive/negative blood types to envisage a facile method of blood typing. [ABSTRACT FROM AUTHOR]

Dual detection, which simultaneously employs two complementary detection methods, is a useful approach to enhance the selectivity and sensitivity of capillary electrophoresis (CE). Through dual detection, multiple classes of analytes with different structural and chemical characteristics can be sensitively detected using a single CE method. In addition, the comigrating peaks can be distinguished by comparing the signal outputs of two detectors with different selectivities. Typically, dual detection is achieved by coupling two detectors in series along a capillary. However, in this approach, it is inconvenient to evaluate the signal outputs of the two detectors. The two detectors present differences in their corresponding effective capillary lengths and dead volumes of the detection cell. Therefore, detectors that combine two or three detection methods in a single detection point are proposed to address this issue. In this work, to fabricate a combined detector in a simple and low-cost manner, multimaterial 3D printing technology is employed. A two-in-one detection cell that combines capacitively coupled contactless conductivity detection (C 4 D) and confocal laser-induced fluorescence (LIF) detection was fabricated by 3D printing functional materials. In 3D printing, conductive composite polylactic acid (PLA, Proto-pasta) filaments and normal nonconductive PLA filaments were employed. The conductive material was used to build a C 4 D shielding layer that was electrically grounded. The nonconductive PLA was used as an electrical insulator placed between the shielding layer and C 4 D electrodes, which were two stainless-steel tubes (0.4 mm i.d. and 5 mm length). To embed the electrodes into the nonconductive material, a "print-pause-print" approach was applied. After building two chambers for housing electrodes using nonconductive PLA, the 3D printing was paused, following which the two electrodes were manually installed. Printing was then resumed, and the remaining part was built. The two electrodes were 2 mm apart, and the gap between them was filled with a conductive material for shielding to eliminate stray capacitance. A through-hole (1 mm i.d.) was placed between the middle conductive shielding layer for LIF detection. The size of the detection cell was 60 mm×29 mm×7.2 mm. The cell was screwed onto an XYZ stage to precisely align the light path of LIF detection, which was realized using a TriSep TM -2100LIF detector equipped with a 473 nm laser. C 4 D detection was achieved using a TraceDec detector equipped with a ChipCE adaptor. The two-in-one detector was coupled with a lab-made CE system that had a flow-through injection interface. Use of the detection cell allows the simultaneous detection of inorganic cations and fluorescein isothiocyanate (FITC)-labeled amino acids. The C 4 D excitation frequency and buffer concentration were then optimized. A mixture of 10 mmol/L 3-( N -morpholino)propanesulfonic acid (MOPS) and 10 mmol/L bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (Bis-Tris) was selected as the background electrolyte as a compromise of C 4 D signal-to-noise ratio ( S/N ) and separation efficiencies of amino acids. The C 4 D excitation frequency was set to 77 kHz with S/N =233±8 for 200 μmol/L Na + . The baseline separation of Na + , K + , Li + , FITC, fluorescein, histidine (His), lysine (Lys), tryptophan (Trp), phenylalanine (Phe), alanine (Ala), and glycine (Gly) was achieved with a 25 μm i.d.×365 μm o.d.×45 cm (35 cm effective length) capillary and -10 kV separation voltage. The limits of detection (LODs) of C 4 D for Na + , K + , and Li + were 2.2, 2.0, and 2.6 μmol/L, respectively. The LODs of LIF for fluorescein and FITC were 7.6 and 1.7 nmol/L, respectively. The relative standard deviations (RSDs) of the two detection methods were within the range of 0.3%-4.5% ( n =3). The r 2 of the calibration curves was ≥0.9904. Thus, 3D printing technology is a simple and low-cost approach to implement complex designs, including those that are difficult to fabricate by traditional "workshop" technologies.

In this work, the fluorescence properties of Phycocyanin (PC) and the corresponding quenching effects are investigated in attendance of human serum albumin (HSA). At first, PC is excited at 532 nm using CW SHG Nd:YAG laser, then the emission wavelength, Stokes shift, quantum yield, extinction constant and self-quenching coefficient are obtained based on the modified Beer-Lambert equation. It is shown that a notable red shift appears in terms of PC concentration. According to the fluorescence spectra, the addition of HSA in PC solution leads to a significant reduction in the fluorescence signal via quenching events, however a lucid blue shift takes place in the same time. Stern-Volmer formalism is used to determine the quenching constant (K S), the number of binding sites (n) between PC and HSA as well as the association constant K a for the purpose of facile transportation to the target in the context of drug delivery. Eventually, temperature dependent coefficients and corresponding spectral shifts are investigated over a wide range of temperatures at a couple of distinct PC concentrations to attest the dominant static quenching takes place. The rate of conjugate formations elevates at low temperatures leading to a certain blue shift. Furthermore, large K S is measured in the course of signal reduction, particularly at low PC populations. In fact, PC conjugation to HSA is essential interaction to enhance chemo drug transportation. Here, at the body temperature, the quenching coefficient decreases to facilitate the drug release. Moreover, the spectral shift of fluorescence emission can be useful for simultaneous monitoring and drug delivery treatment. Unlabelled Image • Fluorescence signal emission and spectral red shift of PCB versus PC concentration • Assessment of static quenching mechanism via Stern-Volmer formalism • Correlation between spectral blue shift and the quenching coefficient in HSA-PC conjugates over a wide range of temperature • Potential of HSA-PC conjugate as a carrier/antioxidant for drug delivery and cancer therapy [ABSTRACT FROM AUTHOR]