回归正交评价指标智能筛选法用于色谱分离条件的快速优化

建立了一种可用于色谱分离条件快速优化的回归正交评价指标智能筛选法。以串行色谱响应函数作为色谱条件优化指标,利用回归正交试验设计建立回归模型,并通过最优解智能筛选程序对综合性优化指标进行筛选,最终实现色谱分离条件的最优化。结果表明:实验测定值与预测值的平均相对偏差为0.18%,优化结果理想。     

Inner filter effect and the onset of concentration dependent red shift of synchronous fluorescence spectra

The phenomenon of concentration dependent red shift, often observed in synchronous fluorescence spectra (SFS) of monofluorophoric as well as multifluorophoric systems at high chromophore concentrations, is known to have good analytical advantages. This was previously understood in terms of large inner filter effect (IFE) through the introduction of a derived absorption spectral profile that closely corresponds to the SFS profile. Using representative monofluorophoric and multifluorophoric systems, it is now explained how the SF spectral maximum changes with concentration of the fluorophore. For dilute solutions of monofluorophores the maximum is unchanged as expected. It is shown here that the onset of red shift of SFS maximum of both the mono as well as the multifluorophoric systems must occur at the derived absorption spectral parameter value of 0.32 that corresponds to the absorbance value of 0.87. This value is unique irrespective of the nature of the fluorophore under study. For monofluorophoric systems, the wavelength of derived absorption spectral maximum and the wavelength of synchronous fluorescence spectral maximum closely correspond with each other in the entire concentration range. In contrast, for multifluorophoric systems like diesel and aqueous humic acid, large deviations were noted that could be explained as to be due to the presence of non-fluorescing chromophores in the system. This work bridges the entire fluorophore concentration range over which the red shift of SFS maximum sets in; and in the process it establishes the importance of the derived absorption spectral parameter in understanding the phenomenon of concentration dependent red shift of SFS maximum.     

Homotopy analysis method to study a quadrupole mass filter

The homotopy analysis method (HAM) is applied to study the behavior of a hyperbolic rods of quadrupole mass filter and a sinusoidal potential form V_ac cos(Ωt). Numerical computation method of a 20th‐order HAM is employed to compare the physical properties of the confined ions with fifth‐order Runge–Kutta method. Also, comparison is made for the first stability region, the ion trajectories in real time, the polar plots, and the ion trajectory in x ? y plan. The results show that the two methods are fairly similar; therefore, the HAM method has potential application to solve linear and nonlinear equations of the charge particle confinement in quadrupole field. Copyright © 2012 John Wiley & Sons, Ltd.     

Analytical evaluation of enzyme-linked immunosorbent assay for neonicotinoid dinotefuran for potential application to quick and simple screening method in rice samples

The analytical performance of a kit-based enzyme-linked immunosorbent assay (ELISA) for the determination of a neonicotinoid insecticide dinotefuran residue in rice samples is addressed. The sensitivity (I₅₀ value) was 5.4 ng/mL, with the limit of detection, 0.6 ng/mL and the dynamic range from 1.0 to 30 ng/mL. The ELISA showed substantially high specificity toward dinotefuran besides clothianidin (184%). For rice samples, dinotefuran was extracted with methanol and the extracts were directly determined with the ELISA because of no significant matrix interference. Good recoveries were observed and ranged from 92.5% to 113.2% with coefficients of variation below 10%. The results obtained with the ELISA correlated well with those by the HPLC method for rice samples (r > 0.98). These findings strongly indicate that the evaluated and validated ELISA has a potential utility in a quick, simple, and reliable residue analysis, especially a screening method before shipment contributing to food safety.     

A new fluorescent probe with ultralow background fluorescence for imaging of endogenous cellular selenol under oxidative stress

A new fluorescent probe (Rhod-Sec) for selenol detection with ultralow background fluorescence have been developed in this paper, which showed a 380-fold off-on fluorescence response, and can be applied to visualize the fluctuation of selenol in HepG2 cells through LPS-induced cells oxidation resistance.     

Stability indicating method for the determination of paracetamol in its pharmaceutical preparations by TLC densitometric method

Simple, sensitive and accurate thin layer procedure was described for a quantitative determination of paracetamol in its bulk powder and in its pharmaceutical dosage forms in the presence of its degradation product. The method consists of dissolving the drug in methanol and then spotting the solution on a thin layer of silica gel G254. Paracetamol was separated on silica gel using the mixture of the mobile phase, ethyl acetate: benzene: acetic acid in a ratio (1:1:0.05 v/v/v).Absorbance measurements (detection of reflectance) of the separated drug were carried out at 250 nm. Calibration curves were established in the concentration range of 5–20 mcg/spot for paracetamol. Quantitation is achieved by comparing the area under the peaks obtained from scanning the thin layer chromatographic plates in a spectrodensitometer. The method has been successfully applied to pharmaceutical preparations (capsules) and the results obtained were statistically compared with those obtained by applying the reference method.     

The water-soluble indolium-based fluorescence probes for detection of the extreme acidity or extreme alkalinity

In this work, 3,3′-(((1E,1′E)-(H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diyl)bis(ethene-2,1-diyl))bis(1,1-dimethyl-1H-benzo[e]indole-3-ium-2,3-diyl))bis(propane-1-sulfonate) (1), 3,3’-(((1E,1′E)-(6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diyl)bis(ethene-2,1-diyl))bis(3,3-dimethyl-3H-indole-1-ium-2,1-diyl))bis(propane-1-sulfonate) (2), 2,2’-((1E,1′E)-(6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diyl)bis(ethene-2,1-diyl))bis(1,3,3-trimethyl-3H-indol-1-ium) iodide (3) and 2,2’-((1E,1′E)-(6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diyl)bis(ethene-2,1-diyl))bis(1,1,3-trimethyl-1H-benzo[e]indol-3-ium) iodide (4) were designed and synthesized by ethylene bridging of the N-substituted indolium salts and the Tröger’s Base (TB) framework. The probes exhibited a longer absorption and emission wavelength and the emission wavelength of them in dichloromethane (DCM) was more than 600 nm, performed a red fluorescence. All of the probes could work on the extreme acidic and the extreme alkaline environments and showed a good liner response in the working pH range. Especially, 2 and 4 were soluble in water and manifested a good pH sensing in a water system. Also, ¹H NMR analysis illustrated how these dyes worked as the pH-sensitive fluorescence probes. In addition, they performed excellent reversibility, high selectivity and good photostability.     

Arsenic fractionation in agricultural soil using an automated three-step sequential extraction method coupled to hydride generation-atomic fluorescence spectrometry

A fully automated modified three-step BCR flow-through sequential extraction method was developed for the fractionation of the arsenic (As) content from agricultural soil based on a multi-syringe flow injection analysis (MSFIA) system coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS). Critical parameters that affect the performance of the automated system were optimized by exploiting a multivariate approach using a Doehlert design. The validation of the flow-based modified-BCR method was carried out by comparison with the conventional BCR method. Thus, the total As content was determined in the following three fractions: fraction 1 (F1), the acid-soluble or interchangeable fraction; fraction 2 (F2), the reducible fraction; and fraction 3 (F3), the oxidizable fraction. The limits of detection (LOD) were 4.0, 3.4, and 23.6 μg L⁻¹ for F1, F2, and F3, respectively. A wide working concentration range was obtained for the analysis of each fraction, i.e., 0.013–0.800, 0.011–0.900 and 0.079–1.400 mg L⁻¹ for F1, F2, and F3, respectively. The precision of the automated MSFIA–HG-AFS system, expressed as the relative standard deviation (RSD), was evaluated for a 200 μg L⁻¹ As standard solution, and RSD values between 5 and 8% were achieved for the three BCR fractions. The new modified three-step BCR flow-based sequential extraction method was satisfactorily applied for arsenic fractionation in real agricultural soil samples from an arsenic-contaminated mining zone to evaluate its extractability. The frequency of analysis of the proposed method was eight times higher than that of the conventional BCR method (6 vs 48 h), and the kinetics of lixiviation were established for each fraction.     

Determination of L-phenylalanine by cucurbit[7]uril sensitized fluorescence quenching method

The determination method of L-phenylalanine（LPA） by fluorescence quenching was developed.The assay was based on the combination of the cucurbit[7]uril（CB[7]） with palmatine hydrochloride（PAL） reaction.In the presence of CB[7],the fluorescence of PAL was quenched by LPA which can be employed to detect LPA.Under the optimal conditions,a linear range 3.63×10^-8- 9.68×10^-6mol/L and a detection limit 1.27×10^-8mol/L of LPA were obtained.The relative standard deviation（R.S.D） was 1.8%obtained from a series of 11 standards each containing 6.05×10^-6 mol/L of LPA.This paper also discusses the mechanism of fluorescence indicator probe.     

Efficient removal of unwanted signals in NMR spectra using the filter diagonalization method

It is often desirable to selectively remove corrupting or uninteresting signals from complex NMR spectra without disturbing overlapping or nearby signals. For biofluids in particular, removal of solvent and urea signals is important for retaining quantitative accuracy in NMR‐based metabonomics. This article presents a novel algorithm for efficient filtering of unwanted signals using the filter diagonalization method (FDM). Unwanted signals are modeled in the time domain using FDM. This modeled signal is subtracted from the original free induction decay. The resulting corrected signal is then processed using established workflow. The algorithm is found to be reliable and fast. By eliminating large, broad, uninteresting signals, many spectra can be subjected to fully automated absolute value processing, allowing objective preparation of spectra for pattern recognition analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

喹啉酮-香豆素类Hg2+比色荧光探针的合成及应用

设计合成了新型喹啉酮-香豆素类比色荧光探针7-二乙氨基-3-[3-(7-二乙氨基)香豆素基-3-氧代丙烯基]喹啉-2-酮(QCO), 用于检测水溶液中的Hg²⁺. 探针QCO对Hg²⁺表现出高选择性和强抗干扰性. 此外, Hg²⁺引起探针QCO溶液的颜色变化明显, 可裸眼识别. 比色法中, 吸收值比(A₅₀₀/A₃₈₀)与Hg²⁺浓度呈良好的线性关系, 其检出限为2.62×10^-8 mol/L. 荧光法中, 探针QCO对Hg²⁺的检出限为5.42×10^-8 mol/L. 经等摩尔变化( Job’s Plot)法、 质谱及红外光谱验证, 探针QCO与Hg²⁺形成络合比为1∶1(摩尔比)的络合物. 硅胶板实验和加标回收率实验结果表明, 探针QCO可用于检测实际水样中的Hg²⁺.     

基于发光金纳米粒子荧光增强法测定溶菌酶

参照文献方法合成了BSA修饰的水溶性发光金纳米粒子,并考察了其与溶菌酶之间的相互作用.依据溶菌酶对金纳米粒子的发光增强现象,建立了测定溶菌酶的荧光新方法.考察了发光金纳米粒子的浓度、pH值、反应时间及共存物质对测定的影响.优化条件为:发光金纳米粒子浓度4.0×10(-6)mol/L,pH 7.0、反应时间10 min....     

Preparation and FT-IR spectra of calcium bilirubinate

In this investigation two calcium bilirubinates compounds, Ca(HBR)₂·H₂O and Ca(BR)·2H₂O, were prepared. Their Fourier transform infrared spectra were measured in KBr discs and in fluorolube and nujol mulls, respectively. The results suggest that it is better to identify the Ca(HBR)₂·H₂O and Ca(BR)·2H₂O with fluorolube and/or nujol mulls when examining mixtures (e.g. gallstone).     

The inner filter effects and their correction in fluorescence spectra of salt marsh humic matter

The inner filter effects in synchronous fluorescence spectra (Δλ = 60 nm) of sedimentary humic substances from a salt marsh were studied. Accordingly to their type and the influence of plant colonization, these humic substances have different spectral features and the inner filter effects act in a different manner. The fluorescence spectra of the humic substances from sediments with colonizing plants have a protein like band (λ_exc = 280 nm) which is strongly affected by primary and secondary inner filter effects. These effects were also observed for the bands situated at longer wavelengths, i.e., at λ_exc = 350 nm and λ_ex = 454 nm for the fulvic acids (FA) and humic acids (HA), respectively. However, they are more important for the band at 280 nm, causing spectral distortions which can be clearly seen when the spectra of solutions 40 mg L⁻¹ of different samples (Dissolved Organic Carbon – DOC ∼ 20 mg L⁻¹) are compared with and without correction of the inner filter effects. The importance of the spectral distortions caused by inner filter effects has been demonstrated in solutions containing a mixture of model compounds which represent the fluorophores detected in the spectra of sedimentary humic samples. The effectiveness of the mathematical correction of the inner filter effects in the spectra of those solutions and of solutions of sedimentary humic substances was studied. It was observed that inner filter effects in the sedimentary humic substances spectra can be mathematically corrected, allowing to obtain a linear relationship between the fluorescence intensity and humic substances concentration and preventing distortions at concentrations as high as 50 mg L⁻¹ which otherwise would obscure the protein like band.     

A gold-based nanobeacon probe for fluorescence sensing of organophosphorus pesticides

A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples.     

Evidence for covalent binding of epicocconone with proteins from synchronous fluorescence spectra and fluorescence lifetimes

Synchronous fluorescence and time-resolved fluorescence spectroscopic studies that reveal the interaction of epicocconone with human serum albumin is significantly different from its interaction with surfactant assemblies. This observation, along with steady-state fluorescence data, indicates ground-state interaction between the fluorophore epicocconone and the protein. Similarity in fluorescence properties with the adduct of the fluorophore with n-butylamine indicates that bonding occurs at the N-terminus of the protein.     

Two highly selective fluorescence probes for imaging Pd2+ in cells and mice

Two rhodamine-based probes were designed and prepared, which exhibited highly sensitive and selective fluorescence enhancement upon binding to Pd²⁺ by UV–vis and fluorescence spectroscopies. Meanwhile the distinct color changes and rapid switch-on fluorescence also provided “naked-eyes” detection for Pd²⁺ over a broad pH range. The recognition mechanism was explored through Job’s plot, MS data, IR spectra and related theoretical calculations. Furthermore, the probes were applied for biological imaging to confirm that they can be used for monitoring Pd²⁺ in living cells (L929 and A549 cells) and living mice with satisfying results, which further demonstrated their value of practical applications in environmental and biological systems.     

A fluorescence turn-on probe for cysteine and homocysteine based on thiol-triggered benzothiazolidine ring formation

We synthesized a new coumarin-based probe TP, containing a disulfide moiety, to detect biothiols in cells. A fluorescence turn-on response is induced by the thiol–disulfide exchange of the probe, with subsequent intramolecular benzothiazolidine ring formation giving rise to a fluorescent product. The probe exhibits an excellent selectivity for cysteine (Cys) and homocysteine (Hcy) over glutathione (GSH) and other amino acids. The fluorescent probe also exhibits a highly sensitive fluorescence turn-on response to Cys and Hcy with detection limits of 0.8 μM for Cys and 0.5 μM for Hcy. In addition, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that the probe TP could be an efficient fluorescent detector for thiols in living cells.