Kinetic Monitoring of Electrophoretically Induced Solute Reaction by Axial Absorption Detection with Liquid-Core Waveguide

Dynamic Mass Transfer of Hemoglobin at the Aqueous/Ionic-Liquid Interface Monitored with Liquid Core Optical Waveguide

Protein transfer from aqueous medium into ionic liquid is an important approach for the isolation of proteins of interest from complex biological samples. We hereby report a solid-cladding/liquid-core/liquid-cladding sandwich optical waveguide system for the purpose of monitoring the dynamic mass-transfer behaviors of hemoglobin (Hb) at the aqueous/ionic liquid interface. The optical waveguide system is fabricated by using a hydrophobic IL (1,3-dibutylimidazolium hexafluorophosphate, BBimPF6) as the core, and protein solution as one of the cladding layer. UV-vis spectra are recorded with a CCD spectrophotometer via optical fibers. The recorded spectra suggest that the mass transfer of Hb molecules between the aqueous and ionic liquid media involve accumulation of Hb on the aqueous/IL interface followed by dynamic extraction/transfer of Hb into the ionic liquid phase. A part of Hb molecules remain at the interface even after the accomplishment of the extraction/transfer process. Further investigations indicate that the mass transfer of Hb from aqueous medium into the ionic liquid phase is mainly driven by the coordination interaction between heme group of Hb and the cationic moiety of ionic liquid, for example, imidazolium cation in this particular case. In addition, hydrophobic interactions also contribute to the transfer of Hb.

Analytical devices based on light-emitting diodes--a review of the state-of-the-art

A general overview of the development of the uses of light-emitting diodes in analytical instrumentation is given. Fundamental aspects of light-emitting diodes, as far as relevant for this usage, are covered in the first part. The measurement of light intensity is also discussed, as this is an essential part of any device based on light-emitting diodes as well. In the second part, applications are discussed, which cover liquid and gas-phase absorbance measurements, flow-through detectors for chromatography and capillary electrophoresis, sensors, as well as some less often reported methods such as photoacoustic spectroscopy.

Absorbance characteristics of a liquid-phase gas sensor based on gas-permeable liquid core waveguides

The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas-permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r(2)>0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min(-1), the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC=0.0267c+0.0351 (AU min(-1)), with r(2)=0.9922 within concentrations of 0.5-3.0 mg L(-1). The relative error for 0.5 mg L(-1) benzene (n=6) is 7.4±3.7%, and the LOD is 0.04 mg L(-1). This research can provide theoretical and practical guides for liquid-phase gas sensor design and development based on a gas-permeable Teflon AF 2400 LCW.

Real-time monitoring of chemical reactions by mass spectrometry utilizing a low-temperature plasma probe

Real-time and in-situ monitoring of ongoing chemical reactions by mass spectrometry was achieved by simply directing the low-temperature plasma (LTP) to the surface of the reaction system for analyte desorption and ionization without any sample pretreatment.

Water-ice chip with liquid-core waveguide functionality. Toward lab on ice

A liquid-core waveguide is fabricated with water-ice, which has lower refractive index than most of the solvents, as cladding, and provides a possibility as an ice chip for flow analyses.

Liquid-core waveguide in CE

Liquid-core waveguide (LCW) brings about several advantages in CE. This review discusses some aspects of fundamental and practical importance involved in this method. Sensitivity in absorption and fluorescence detection is in general improved by more than one order of magnitude over usual crossbeam detection arrangements; the improvements come from the long light path in absorption detection and low light scattering in fluorescence detection. Versatile instrumental arrangements are another advantage of LCW in CE, leading to several detection schemes, some of which provide information that is not gained by usual capillary-end crossbeam detection, e.g. whole-capillary imaging, simultaneous monitoring of multicapillary separation, and kinetic evaluation. The high potential and perspectives of LCW in CE are discussed based on the state-of-the-art developments.

Photochemical Behavior of Lysozyme-4-(2-pyridylazo)-resorcinol Polymolecular Complex and Its Analytical Applications

It was first found that 4-(2-pyridylazo)-resorcinol (PAR) can combine with lysozyme forming a polymolecular complex, with the molar ratio of 1:12 (lysozyme/PAR) in the medium of acetate buffer (pH 6.0). The fluorescence spectra suggested that PAR molecules may produce self-aggregation, and it was suggested that there are interactions between lysozyme and PAR possibly mainly on the cooperation of hydrophobic, electrostatic actions and chelate bond. The coordination complex of lysozyme-PAR can cause an enhanced resonance light scattering (RLS) signal with the scattering peak located at 521 nm. The increment of RLS intensity was linear with the concentration of lysozyme over the range from 1 ng mL(-1) to 30.0 mug mL(-1), with the limit of detection of 0.3 ng mL(-1) (3sigma, n = 5). Effect of experimental conditions, including temperature, pH, concentration of PAR, and the ionic strength on RLS were also tested. The proposed RLS method was successfully applied to analyze lysozyme in hen egg white, human saliva and tear samples without any special pretreatment. Compared with other methods, the proposed procedure is of high sensitivity and selectivity.