HPLC determination of neopterin in biological liquids for clinical purposes

A HPLC method is proposed for determining neopterin in biological liquids. The method was realized using a standard chromatographic instrumentation. Neopterin was isolated from blood serum and urine by solid-phase extraction on cartridges containing 30 mg of supercrosslinked polystyrene. The separation was carried out on an Irica chromatograph (Japan) equipped with means of UV (350 nm) and fluorimetric (es350-em430 nm) detection. The degree of extraction was 96–113%, and the sensitivity of UV and fluorimetric detection was 0.1 and ～0.03 ng, respectively (at signal-to-noise ratio 3). It is shown that the method is suitable for use in routine clinical analysis of neopterin in biological liquids.     

不相交主成分分析(PCA)和遗传算法(GA)用于差异表达基因的识别

建立了一种基于不相交主成分分析(Disjoint PCA)和遗传算法(GA)的特征变量选择方法, 并用于从基因表达谱(Gene expression profiles)数据中识别差异表达的基因. 在该方法中, 用不相交主成分分析评估基因组在区分两类不同样品时的区分能力; 用GA寻找区分能力最强的基因组; 所识别基因的偶然相关性用统计方法评估. 由于该方法考虑了基因间的协同作用更接近于基因的生物过程, 从而使所识别的基因具有更好的差异表达能力. 将该方法应用于肝细胞癌(HCC)样品的基因芯片数据分析, 结果表明, 所识别的基因具有较强的区分能力, 优于常用的基因芯片显著性分析(Significance analysis of microarrays, SAM)方法.     

Ion-exchange measurement in biological samples by (p,X) and (p,p) reactions

A method of analysis by ion-exchange in biological samples using (p, X) reactions and back-scattering of charged particles is proposed. Sensitivity and rapidity are the principal qualities of this method.     

A Simple and Highly Selective Determination of Telmisartan at Sodium Dodecyl Sulfate Modified Pyrolytic Graphite Surface

A simple, facile, selective and cost effective electrochemical method is proposed for the determination of telmisartan (TMS); a drug used for hypertension. A sodium dodecyl sulfate (SDS) modified edge plane pyrolytic graphite (EPPG) is prepared by simple immersion of EPPG in SDS solution at concentration greater than critical micelle concentration (CMC). The modified sensor exhibited superior sensing properties towards the oxidation of TMS. The modified surface was characterized by using the Energy dispersive X‐ray analysis, Field Emission Scanning Electron Microscopy, Electrochemical Impedance Spectroscopy and cyclic voltammetry. The quantitative investigations of the TMS were performed by applying the square wave voltammetry. The micelles of SDS form a pseudo complex with cation radical of TMS and catalyse the oxidation. The proposed sensor shows the linear calibration plot in the concentration range of 5–100 μM with sensitivity 0.2983 μA/μM and the limit of the detection of the sensor was found to be 0.082 μM. The specificity of the developed sensor was also evaluated in the presence of commonly present interfering substances in biological samples. The amount of TMS excreted in urine of the patients undergoing treatment has also been determined. The proposed method can be effectively applied for the investigation of TMS in pharmaceutical formulations and biological samples.     

气相色谱-质谱法测定生物检材中毒鼠强的含量

采用气相色谱-质谱提取离子的方法测定了生物检材中毒鼠强的含量。毒鼠强的线性范围为0.05-50ng，检出限为0.01ng，以苯为溶剂，毒鼠强的提取回收率为93.5%，RSD为4.96%(n=5)。方法准确、快速，适用于生物检材中毒鼠强的测定。     

Speciation analysis of aluminium(III) in natural waters and biological fluids by complexing with various catechols followed by differential pulse voltammetry detection

The biological effects of aluminium have received much attention in recent years. Speciation of Al is of basic relevance as it concerns its reactivity and bioavailability. A differential pulse voltammetry (DPV) procedure is proposed for speciation analysis of Al(III) in natural waters and biological fluids using six catechols (L-dopa, dopamine, epinephrine, norepinephrine, caffeic acid and o-benzenediol) as electroactive ligands. The decrease of the DPV anodic peak current for each catechol ligand is linear with the increase of Al concentration. This speciation analysis idea is based on the measurement of the complexation capacity, namely, different affinities of Al(III) for catechols and organic ligands under two pH conditions. The labile monomeric Al fraction (mainly inorganic aluminium) is determined at pH 4.6, while the total monomeric Al fraction is determined at pH 8.5. The principle for Al(III) speciation analysis by an electrochemical method is discussed. This sensitive and simple fractionation method is successfully applied to the speciation analysis of Al in natural waters and the results agree well with those of Driscoll's method. The speciation analysis of Al in biological fluids is also explored and the results are compared with those obtained by ultrafiltration and dialysis. Compared with other speciation protocols the electrochemical method possesses some remarkable advantages: rapidity, high sensitivity, cheap instrumentation and a simple operation procedure.     

Differential pulse polarographic determination of ofloxacin in pharmaceuticals and biological fluids

A sensitive method is described for the determination of ofloxacin in its pure form, dosage forms and biological fluids. The proposed method depends upon the polarographic activity of ofloxacin in Britton Robinson buffers, whereby a well-defined cathodic wave is produced over the pH range 4.1-10.3. The wave was characterized as being irreversible, diffusion-controlled with limited adsorption properties. The current-concentration relationship was found to be rectilinear over the range 5x10(-5)-5x10(-4) M and 1x10(-5)-5x10(-4) M using the DC(t) and DPP modes respectively, with a minimum detectability (S/N=3) of 3x10(-7) M. The proposed method was successfully applied to the determination of ofloxacin in tablets and biological fluids. The results obtained were found to be in agreement with those obtained by a reference method.     

A new integrated statistical approach to the diagnostic use of two-dimensional maps

Two-dimensional (2-D) electrophoresis is a very useful technique for the analysis of proteins in biological tissues. The complexity of the 2-D maps obtained causes many difficulties in the comparison of different samples. A new method is proposed for comparing different 2-D maps, based on five steps: (i) the digitalisation of the image; (ii) the transformation of the digitalised map in a fuzzy entity, in order to consider the variability of the 2-D electrophoretic separation; (iii) the calculation of a similarity index for each pair of maps; (iv) the analysis by multidimensional scaling of the previously obtained similarity matrix; (v) the analysis by classification or cluster analysis techniques of the resulting map co-ordinates. The method adopted was first tested on some simulated samples in order to evaluate its sensitivity to small changes in the spots position and size. The optimal setting of the method parameters was also investigated. Finally, the method was successfully applied to a series of real samples corresponding to the electrophoretic bidimensional analysis of sera from normal and nicotine-treated rats. Multidimensional scaling allowed the separation of the two classes of samples without any misclassification.     

Clustering of time-course gene expression data using functional data analysis

Clustering of gene expression data collected across time is receiving growing attention in the biological literature since time-course experiments allow one to understand dynamic biological processes and identify genes governed by the same processes. It is believed that genes demonstrating similar expression profiles over time might give an informative insight into how underlying biological mechanisms work. In this paper, we propose a method based on functional data analysis (FNDA) to cluster time-dependent gene expression profiles. Consideration of clustering problems using the FNDA setting provides ways to take time dependency into account by using basis function expansion to describe the partially observed curves. We also discuss how to choose the number of bases in the basis function expansion in FNDA. A synthetic cycle data and a real data are used to demonstrate the proposed method and some comparisons between the proposed and existing approaches using the adjusted Rand indices are made.     

Spectrofluorometric determination of ketorolac tromethamine via its oxidation with cerium(IV) in pharmaceutical preparations and biological fluids

A simple and sensitive fluorometric method for determination of ketorolac tromethamine was studied. The method depends on oxidation of the drug with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at lambda(em) 365 nm after excitation at 255 nm. Different variables affecting the reaction conditions, such as the concentrations of cerium(IV), sulfuric acid concentration, reaction time, and temperature, were carefully studied and optimized. Under the optimum conditions, a linear relationship was found between the relative fluorescence intensity and the concentration of the investigated drug in the range of 0.1-0.8 microg/mL. No interferences could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drug in its pure form, pharmaceutical preparations, and biological fluids with good accuracy and precision. The recoveries for pharmaceutical formulations ranged from 99.8-101.0 +/- 0.6% for tablets, 98.5-101.0 +/- 1.0% for ampoules, and 99.0-100.5 +/- 0.7% for eye drops. The results obtained by the proposed method were satisfactory compared with those obtained by the official method. The recoveries for biological fluids were 99.1-100.4 +/- 0.7 and 99.0-100.0 +/- 0.5% for plasma and urine, respectively.     

Simultaneous Quantification of 25 Fentanyl Derivatives and Metabolites in Oral Fluid by Means of Microextraction on Packed Sorbent and LC–HRMS/MS Analysis

Fentanyl and fentalogs’ intake as drugs of abuse is experiencing a great increase in recent years. For this reason, there are more and more cases in which it is important to recognize and quantify these molecules and related metabolites in biological matrices. Oral fluid (OF) is often used to find out if a subject has recently used a psychoactive substance and if, therefore, the person is still under the effect of psychotropics. Given its difficulty in handling, good sample preparation and the development of instrumental methods for analysis are essential. In this work, an analytical method is proposed for the simultaneous determination of 25 analytes, including fentanyl, several derivatives and metabolites. OF was collected by means of passive drool; sample pretreatment was developed in order to be fast, simple and possibly semi-automated by exploiting microextraction on packed sorbent (MEPS). The analysis was performed by means of LC–HRMS/MS obtaining good identification and quantification of all the analytes in less than 10 min. The proposed method was fully validated according to the Scientific Working Group for Forensic Toxicology (SWGTOX) international guidelines. Good results were obtained in terms of recoveries, matrix effect and sensitivity, showing that this method could represent a useful tool in forensic toxicology. The presented method was successfully applied to the analysis of proficiency test samples.     

Simultaneous determination of cefepime and vancomycin in plasma and cerebrospinal fluid by MEKC with direct sample injection and application for bacterial meningitis

A simple MEKC with UV detection at 214 nm for simultaneous analysis of cefepime and vancomycin in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of cefepime and vancomycin from biological matrices was performed at 25 degrees C using a BGE consisting of a Tris buffer with SDS and methanol as the electrolyte solution. Under optimal MEKC conditions for biological samples, good separations with high efficiency and short analysis time are achieved. Several parameters affecting the separation of the drugs from biological matrices were studied, including methanol, pH, and concentrations of the Tris buffer and SDS. The linear ranges of the method for the determination of cefepime and vancomycin in plasma and in CSF using imidazole or cefazolin as an internal standard, respectively, were all over the range of 1-30 microg/mL; the detection limits of cefepime and vancomycin in biological matrices (injection 10 kV, 15 s) were 0.3 and 0.5 microg/mL, respectively. The applicability of the proposed method for the determination of cefepime and vancomycin in plasma and CSF collected after intravenous administration of the drugs in patients with meningitis was demonstrated.     

A pre-irradiation separation procedure based on ion-exchange chromatography for gallium determination in biological and environmental materials by neutron activation analysis

A pre-irradiation separation procedure, for gallium determination in biological and environmental materials by neutron activation analysis (NAA) is reported. The proposed method, based on ion-exchange chromatography, allows to eliminate the radiation risk, while taking the advantages of high sensitivity of NAA. The single comparator method is employed for gallium quantitative evaluation. Since no standard reference materials with certified gallium contents were available, the reliability of the proposed method was extensively investigated by various approaches. Four biological and one environmental standard reference materials, with gallium contents ranging from 54 g/g-3 ng/g, have been analyzed.     

Instrumental neutron-activation determination of phosphorus in biological materials by bremsstrahlung measurement

The determination of phosphorus in biological materials by instrumental neutron-activation analysis by the reaction (31)P (n, lambda)(32)p is described. The bremsstrahlung produced by (32)P is measured in a well-type NaI(T1) detector. The samples are measured in the polyethylene irradiation container with no additional handling between irradiation and measurement. The sources of error have been studied and the proposed method has been applied to the determination of phosphorus in ten internationally cerfified materials.     

A closer look at "social" boundary genes reveals knowledge to gene expression profiles

As social network analysis is gaining popularity in modeling real world problems, the task of applying the social network model concepts and notions to biological data is still one of the most attractive research problems to be addressed. According, our work described in this paper focuses on a particular set of genes that reside on the community boundaries in gene co-expression networks. Stemmed from community mining problem in social networks, peripheries of communities (i.e., boundaries) can be used to aid certain biological analysis. The proposed method consists of three parts: 1) Finding communities of gene co-expression networks through clustering. 2) Analyzing stability of community structures by Monte Carlo method. 3) Designing of dynamic adoption of boundaries using geometric convexity. We validated our findings using breast cancer gene expression data from various studies. Our approach contributes to the new branch of applying social network mechanisms in biological data analysis, leading to new data mining strategies implied by witnessing social behaviors in gene expression analysis.     

High performance liquid chromatography of glucose using a post-column reactor of immobilized enzyme followed by electrochemical detection (glucose-LCEC)

A sensitive and selective, reasonably fast method for the determination of glucose content has been developed. A glucose oxidase immobilized column was coupled to a small-size anion exchange column/borate buffer chromatograph. The hydrogen peroxide produced in the enzyme reaction was detected directly by an amperometric detector using a platinum working electrode. The detection limit was 0.03 ppm (1.5 x 10(-7) M, 3 pmol/injection). The linear dynamic range was three orders of magnitude at least. The system was stable and reproducible both in short- and long-term operation. The proposed method is suitable for analysis of complicated matrices of biological samples because of its good selectivity and sensitivity.     

Using Gaussian model to improve biological sequence comparison

One of the major tasks in biological sequence analysis is to compare biological sequences, which could serve as evidence of structural and functional conservation, as well as of evolutionary relations among the sequences. Numerous efficient methods have been developed for sequence comparison, but challenges remain. In this article, we proposed a novel method to compare biological sequences based on Gaussian model. Instead of comparing the frequencies of k‐words in biological sequences directly, we considered the k‐word frequency distribution under Gaussian model which gives the different expression levels of k‐words. The proposed method was tested by similarity search, evaluation on functionally related genes, and phylogenetic analysis. The performance of our method was further compared with alignment‐based and alignment‐free methods. The results demonstrate that Gaussian model provides more information about k‐word frequencies and improves the efficiency of sequence comparison. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Microwave treatment of biological samples for methylmercury determination by high performance liquid chromatography-cold vapour atomic fluorescence spectrometry

A simple and rapid microwave-assisted alkaline digestion procedure was developed in combination with high performance liquid chromatography-ultraviolet post-column oxidation-cold vapour atomic fluorescence spectrometric detection for methylmercury determination in biological tissues. Since the stability of methylmercury in methanolic potassium hydroxide solution under microwave irradiation was verified, the microwave-assisted extraction procedure was optimized in terms of quantitative recovery of methylmercury and minimum time required. The alkaline extracts were subjected to clean-up steps with dichloromethane and hydrochloric acid in order to reduce matrix interferences in methylmercury determination. The effects of matrix interferences were checked by comparison of the slopes corresponding to calibration and standard addition curves. The accuracy of the method was evaluated by the analysis of two biological certified reference materials, NRC TORT-2 and BCR 463. The results obtained by the proposed method were in good agreement with the certified values of methylmercury concentration in both materials. The detection limit was 10 microg kg(-1) and the relative standard deviation was < 8% for methylmercury concentrations ranging from 0.15 to 3.0 mg kg(-1).     

Polymer monolithic capillary microextraction combined on‐line with inductively coupled plasma MS for the determination of trace rare earth elements in biological samples

A rapid and sensitive method based on polymer monolithic capillary microextraction combined on‐line with microconcentric nebulization inductively coupled plasma MS has been developed for the determination of trace/ultratrace rare earth elements in biological samples. For this purpose, the iminodiacetic acid modified poly(glycidyl methacrylate‐trimethylolpropane trimethacrylate) monolithic capillary was prepared and characterized by SEM and FTIR spectroscopy. Factors affecting the extraction efficiency, such as sample pH, sample flow rate, sample/eluent volume, and coexisting ions were investigated in detail. Under the optimal conditions, the LODs for rare earth elements were in the range of 0.08 (Er) to 0.97 ng/L (Nd) with a sampling frequency of 8.5 h^?1, and the RSDs were between 1.5% (Sm) and 7.4% (Nd) (c = 20 ng/L, n = 7). The proposed method was successfully applied to the analysis of trace/ultratrace rare earth elements in human urine and serum samples, and the recoveries for the spiked samples were in the range of 82–105%. The developed method was simple, rapid, sensitive, and favorable for the analysis of trace/ultratrace rare earth elements in biological samples with limited sample volume.     

Determination of Trace Amounts of Lorazepam by Adsorptive Cathodic Differential Pulse Stripping Method in Pharmaceutical Formulations and Biological Fluids

Abstract

A new adsorptive cathodic differential pulse stripping voltammetry method for the direct determination of lorazepam at trace levels in pharmaceutical formulations and biological fluids is proposed. The procedure involves an adsorptive accumulation of lorazepam on a hanging mercury drop electrode (HMDE), followed by reduction of adsorbed lorazepam by voltammetric scan using differential pulse modulation. The optimum conditions for the analysis of lorazepam are pH=2 using Britton‐Robinson (B‐R) buffer, accumulation potential of ?0.2 V (vs. Ag/AgCl), and accumulation time of 40 sec. The peak current is proportional to the concentration of lorazepam, and a linear calibration graph is obtained at 0.05–1.15 µg mL^?1. A relative standard deviation of 2.41% (n=3) was obtained, and the limit of detection was 0.019 µg mL^?1. The capability of the method for the analysis of real samples was evaluated by determination of lorazepam in pharmaceutical preparations and biological (urine and plasma) fluids with satisfactory results.