An SPE-assisted BODIPY fluorometric paper sensor for the highly selective and sensitive determination of Cd²âº in complex sample: rice.

By using sensing technology, the individual component analysis at trace level in complex samples remains problematic simply because of various interfering species. For example, the determination of Cd(2+) in rice is difficult due to the co-existing interfering metal cations at thousands or even millions of times higher concentrations. In this study, a heavy-metal ion sensitive BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)-based fluorometric paper sensor with assistance of solid phase extraction (SPE) was developed for the highly selective and sensitive determination of trace Cd(2+) in rice. SPE column packed with prepared sulfonated PS-DVB microspheres was employed to enrich trace Cd(2+) and meanwhile remove most interfering heavy-metal ions in simulated complex rice sample with oxalic acid as eluent, which was theoretically selected on the basis of f values. Mn(2+), as a major coexistent heavy-metal ion, could not be easily removed by SPE, but showed little fluorescent response for BODIPY fluorometric paper sensor even in excess amounts. Combining the separation and enrichment capability of SPE column with the selectivity of BODIPY-based fluorometric paper sensor, we were able to detect trace Cd(2+) in complex samples. The response of fluorometric paper sensor was linearly related with Cd(2+) concentrations in the range of 0.5-4 µM, with a detection limit of 0.5 µM. Twelve real rice samples spiked with Cd(2+) were analysed using this method and the results are in good agreement with ICP-MS measurements.

Development, validation, and application of a liquid chromatography-tandem mass spectrometry method for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in human hair.

The tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a valuable biomarker for human exposure to the carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in tobacco and tobacco smoke. In this work, an efficient and sensitive method for the analysis of NNAL in human hair was developed and validated. The hair sample was extracted by NaOH solution digestion, purified by C(18) solid-phase extraction (SPE) and molecularly imprinted solid-phase extraction, further enriched by reverse-phase ultrasound-assisted dispersive liquid-liquid microextraction (USA-DLLME) into 1.0 % aqueous formic acid, and finally analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry. Good linearity was obtained in the range of 0.24-10.0 pg/mg hair with a correlation coefficient of 0.9982, when 150 mg hair was analyzed. The limit of detection and lower limit of quantification were 0.08 and 0.24 pg/mg hair, respectively. Accuracies determined from hair samples spiked with three different levels of NNAL ranged between 87.3 and 107.7 %. Intra- and inter-day relative standard deviations varied from 4.1 to 8.5 % and from 6.9 to 11.3 %, respectively. Under the optimized conditions, an enrichment factor of 20 was obtained. Finally, the developed method was applied for the analysis of NNAL in smokers' hair. The proposed sample preparation procedure combining selectivity of two-step SPE and enrichment of DLLME significantly improves the purification and enrichment of the analyte and should be useful to analyze NNAL in hair samples for cancer risk evaluation and cancer prevention in relation to exposure to the tobacco-specific carcinogen NNK.

Small-volume fiber-optic evanescent-wave absorption sensor for nitrite determination.

A novel small-volume fiber-optic evanescent-wave absorption sensor based on the Griess-Ilosvay reaction has been developed and evaluated for nitrite determination. The sensor was constructed by inserting a decladded optical fiber into a transparent capillary to form an annular column microchannel. The Evanescent wave (EW) field produced on the optical fiber core surface penetrated into the surrounding medium and interacted with the azo dye, which was generated by the reaction of nitrite and nitrite-sensitive reagents. The detector was designed to be parallel to the axis of the optical fiber. The defined absorbance was linear with the concentration of nitrite in the range from 0.05 to 10 mg L(-1), and the detection limit was 0.02 mg L(-1) (3sigma) with the relative standard deviation (RSD) of 2.6% (n = 8). The present sensor was successfully used to determine nitrite in real samples of mineral water, tap water, rain water, and seawater. The results were consistent with the data obtained by standard spectrophotometric method, showing potential of the proposed sensor for practical application.

A fiber-optic evanescent wave sensor for dissolved oxygen detection based on novel hybrid fluorinated xerogels immobilized with [Ru(bpy)3]2+.

We have prepared a novel fiber-optic evanescent wave sensor (FEWS) for dissolved oxygen (DO) detection. The sensor fabrication was based on coating a decladded portion of an optical fiber with a microporous coating, which was prepared from 3,3,3-trifluoropropyltrimethoxysilane and n-propyltrimethoxysilane. The fluorophores were immobilized in the porous coating and excited by the evanescent wave field produced on the core surface of the optical fiber. The sensitivity of the sensor was quantified by the ratio of the fluorescence intensities in pure deoxygenated (I (0)) and in pure oxygenated environments (I). Results show that the quenching response of DO is increased with the enhancement of the coating surface hydrophobicity using the presented hybrid fluorinated ORMOSILs. The calibration curve of I (0)/I to [O(2)] is linear from 0 to 40 ppm and the detection limit is 0.05 ppm (3sigma) with a short response time of 15 s for DO detection.

[A novel light-emitting diode-induced fluorescence detector for micro-scale flow analysis system].

A compact light-emitting diode-induced fluorescence detector based on collinear scheme is described. The detector was assembled by all-solid-state optical-electronic components and easily coupled with micro-scale flow analysis system by on-column detection mode. Fluorescein isothiocyanate (FITC) and FITC-labeled amino acids were used as test analytes to evaluate the detector performance by capillary electrophoresis and flow injection analysis techniques. The concentration limit of detection was 10(-8) mol x L(-1) for FITC-labeled phenylalanine at a signal-to-noise ratio (S/N) of 3 (on-column, 0.05 mm i.d.). The system exhibited a good linear response in the range of 1 x 10(-7) -2 x 10(-5) mol x L(-1) (r2 = 0.999). The relative standard deviation (RSD) of 6 repetitive injections on peak heights is less than 3%.

The calibration of cellphone camera-based colorimetric sensor array and its application in the determination of glucose in urine.

In this work, a novel approach that can calibrate the colors obtained with a cellphone camera was proposed for the colorimetric sensor array. The variations of ambient light conditions, imaging positions and even cellphone brands could all be compensated via taking the black and white backgrounds of the sensor array as references, thereby yielding accurate measurements. The proposed calibration approach was successfully applied to the detection of glucose in urine by a colorimetric sensor array. Snapshots of the glucose sensor array by a cellphone camera were calibrated by the proposed compensation method and the urine samples at different glucose concentrations were well discriminated with no confusion after a hierarchical clustering analysis.

BODIPY-based fluorometric sensor for the simultaneous determination of Cys, Hcy, and GSH in human serum.

Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are interconnected and play essential roles for regulating the redox balance of biological processes. However, finding a simple and effective method for the simultaneous determination for these three biothiols in biological systems is always a challenge. In this work, we report a method for the simultaneous quantitative determination of three biothiols in a mixture using a monochlorinated boron dipyrromethene (BODIPY)-based fluorometric sensor. At a specified period of time, after reacting with excess sensor, Hcy and GSH form predominantly sulfur-substituted BODIPY, while Cys generates sulfur-amino-diBODIPY due to a fast substitution-rearrangement-substitution reaction. A significant difference in polarities of these respective major products simplifies their separation by TLC, thus leading to the simultaneous determination of Cys, Hcy, and GSH readily. The sensor was successfully applied for the simultaneous quantitative detection of three biothiols in human serum, and the results were in good agreement with those obtained via high performance liquid chromatography (HPLC).

A fluorometric paper-based sensor array for the discrimination of heavy-metal ions.

A fluorometric paper-based sensor array has been developed for the sensitive and convenient determination of seven heavy-metal ions at their wastewater discharge standard concentrations. Combining with nine cross-reactive BODIPY fluorescent indicators and array technologies-based pattern-recognition, we have obtained the discrimination capability of seven different heavy-metal ions at their wastewater discharge standard concentrations. After the immobilization of indicators and the enrichment of analytes, identification of the heavy-metal ions was readily acquired using a standard chemometric approach. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative estimation of the heavy-metal ion concentration was obtained by comparing color changes with a set of known concentrations. The sensor array was tentatively investigated in spiked tap water and sea water, and showed possible feasibility for real sample testing.

BODIPY-based fluorometric sensor array for the highly sensitive identification of heavy-metal ions.

A BODIPY(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)-based fluorometric sensor array has been developed for the highly sensitive detection of eight heavy-metal ions at micromolar concentration. The di-2-picolyamine (DPA) derivatives combine high affinities for a variety of heavy-metal ions with the capacity to perturb the fluorescence properties of BODIPY, making them perfectly suitable for the design of fluorometric sensor arrays for heavy-metal ions. 12 cross-reactive BODIPY fluorescent indicators provide facile identification of the heavy-metal ions using a standard chemometric approach (hierarchical clustering analysis); no misclassifications were found over 45 trials. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative interpolation of the heavy-metal concentration is obtained by comparing the total Euclidean distance of the measurement with a set of known concentrations in the library.

[Study on correlation between HPV57 infection and the etiology of IP].

OBJECTIVE: To study correlation between HPV infection and the etiology of human papilloma and uncover the effects of HPV57 infection on IP, in order to provide a new way for IP precaution and treatment. METHOD: Sixty formalin-fixed, paraffin-embedded specimens of IP were definitely diagnosed by pathologists. They were examined by the polymerase chain reaction (PCR) technique to amplify HPV DNA with HPV L1 consensus primer and HPV57 type-specific primer. Ten specimens of chronic sinusitis were taken as control group. RESULT: All of the sixty IP specimens showed negative after amplification by HPV 1.1 consensus primer MY09/11. There were forty-seven specimens(47/60, 78.3%) showed positive for HPV type 57 after amplification by HPV57 type-specific primer. CONCLUSION: Our findings suggest a possible role for HPV type 57 in the pathogenesis of nasal inverted papilloma.

A windowless flow cell-based miniaturized fluorescence detector for capillary flow systems.

A miniaturized fluorescence detector utilizing a three-dimensional windowless flow cell has been constructed and evaluated. The inlet and outlet liquid channels are collinear and are located in the same plane as the excitation paths, while the optical fiber used to collect the emission light is perpendicular to this plane. The straightforward arrangement of the flow path minimizes band dispersion and eliminates bubble formation or accumulation inside the cell. The use of high-brightness light-emitting diodes (LEDs) as the excitation source and a miniaturized metal package photomultiplier tube (PMT) results in a compact and sensitive fluorescence detector. The detection limit obtained from the system for fluorescein isothiocyanate (FITC) in flow injection mode is 2.6 nmol/L. The analysis of riboflavin and FITC by packed capillary liquid chromatography is demonstrated.

[Application of electroosmotic pump on micro column liquid chromatography].

An electroosmotic pump(EOP) was designed and evaluated, which could replace the mechanical pump. The EOP could generate 2.0 MPa-6.0 MPa output pressure and tens of nL/min-3 microL/min flow rate. A test mixture containing naphthalene, anthracene and phenanthrene was separated on a 14 cm x 320 microns i.d., 5 microns, C18 micro column with acetonitrile/water as a mobile phase, which demonstrated the applicability of the EOP.

[New technologies of solid-phase microextraction].

Solid-phase microextraction (SPME) is a technology with functions of sampling, extraction and concentration based on adsorption/absorption-desorption equilibrium between coating and sample. The recent development of SPME is reviewed. Studies on the in-tube-SPME technology, novel extraction probes and its coupling with other analytical technologies are summarized.

[Design and evaluation of a confocal laser-induced fluorescence detector].

A portable laser-induced fluorescence detector, based on confocal configuration detection system has been developed. This is assembled from commercially available components. All the components of the detector are domestic, which makes it low cost. The routine alignment procedure is simplified by using a skillful and visual alignment system and requires minimal experience for operation. The module design makes it possible for high performance liquid chromatographic, capillary electrophoretic and microfluid chip applications. The performance of the detector, including the sensitivity, noise, linear range and detection limit, was evaluated by capillary electrophoresis and flow injection analytical technique using a red-absorbing cyanine derivative (Cy5) and Cy5 labeled tryptophan as test samples. The results show that the background signal is very low and the peak-to-peak noise level is 0.002 mV. The detection limit and the linear dynamic range are 3.7 nmol/L and 10(3), respectively.

Gas chromatographic analysis of aromatic hydrocarbons in gasoline by column switching-back flushing technique and normalization method.

A simple and efficient method based on the technique of capillary column switching-back flushing was developed for the detailed analysis of aromatic hydrocarbons in gasoline. The early eluting components from a pre-column and the components of interest eluting from an analytical column are all directed to a flame ionization detector through a tee piece, which facilitates the quantitation of aromatic hydrocarbons in gasoline by normalization method. Real samples were analyzed and RSD < or = 3%. The operation is simple and easy, and the switching time window is +/- 5 s.