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1.
    
A dispersive liquid–liquid microextraction procedure was developed to extract nine fluoroquinolones in porcine blood, six of which were quantified using a univariate calibration method. Extraction parameters including type and volume of extraction and dispersive solvent and pH, were optimized using a full factorial and a central composite designs. The optimum extraction parameters were a mixture of 250 μL dichloromethane (extract solvent) and 1250 μL ACN (dispersive solvent) in 500 μL of porcine blood reached to pH 6.80. After shaking and centrifugation, the upper phase was transferred in a glass tube and evaporated under N2 steam. The residue was resuspended into 50 μL of water–ACN (70:30, v/v) and determined by CE method with DAD, under optimum separation conditions. Consequently, a tenfold enrichment factor can potentially be reached with the pretreatment, taking into account the relationship between initial sample volume and final extract volume. Optimum separation conditions were as follows: BGE solution containing equal amounts of sodium borate (Na2B4O7) and di‐sodium hydrogen phosphate (Na2HPO4) with a final concentration of 23 mmol/L containing 0.2% of poly (diallyldimethylammonium chloride) and adjusted to pH 7.80. Separation was performed applying a negative potential of 25 kV, the cartridge was maintained at 25.0°C and the electropherograms were recorded at 275 nm during 4 min. The hydrodynamic injection was performed in the cathode by applying a pressure of 50 mbar for 10 s.  相似文献   

2.
    
The current state of affairs in the drug discovery and development process is briefly summarized and then ways to take advantage of the ever‐increasing fundamental knowledge and technical knowhow in chemistry and biology and related disciplines are discussed. The primary motivation of this Essay is to celebrate the great achievements of chemistry, biology, and medicine and to inform and inspire students and academics to enter the field of drug discovery and development while, at the same time, continue to advance the fundamentals of their disciplines. It is also meant to encourage and catalyze multidisciplinary partnerships between academia and industry as scientists attempt to merge their often complementary interests and expertise to achieve new improvements and breakthroughs in their respective fields, and the common goal of applying them to the discovery and invention of new and better medicines, especially in areas of unmet needs.  相似文献   

3.
    
A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in‐syringe dispersive liquid–liquid microextraction, coupled as a front end to GC–MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly. The denser‐than‐water organic droplets released in the extraction step, were accumulated at the head of the syringe, where the sedimented fraction was transferred to a rotary micro‐volume injection valve where finally was introduced by an air stream into the injector of the GC through a stainless‐steel tubing used as interface. Factors affecting the microextraction efficiency were optimized using multivariate optimization. Figures of merit of the proposed method were evaluated under optimal conditions, achieving a detection limit in the range of 0.03–0.10 μg/L, while the RSD% value was below 5% (n = 5). A good linearity (0.9956 ≥ r2 ≥ 0.9844) and a broad linear working range (0.5–120 μg/L) were obtained. The method exhibited enrichment factors and recoveries, ranging from 14.11–16.39 and 88–102%, respectively.  相似文献   

4.
    
Inferable from the significance of solvent mixtures in practical chemistry, toluene (TL) and butanol (BL) mixtures are used to study fluorescence behavior of coumarin dye C1 namely 3‐hydroxy‐3‐[2‐oxo‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐ethyl]‐1,3‐dihydro‐indol‐2‐one. Bimolecular quenching reaction studies of C1 with aniline as quencher are made in mixtures of TL–BL to know the effect of viscosity and dielectric constant variation at room temperature. The quenching process is studied in all solvent mixtures by steady state method. Quenching is characterized by Stern–Volmer (S–V) plots having upward curvature. Analysis of modified S–V equations which accounts both static and dynamic quenching allows calculating bimolecular quenching rate constant. The bimolecular quenching reactions are found to be significantly larger. Further finite sink approximation model is invoked so as to check whether reactions are diffusion limited. The extents of these rate parameters demonstrate that positive deviations in the S–V plot are because of the presence of apparent static and dynamic quenching process.  相似文献   

5.
    
A novel method for the simultaneous determination of sulfonamides (SAs) in water samples has been developed by using dispersive liquid–liquid microextraction (DLLME) coupled with CE. Orthogonal and Box–Behnken designs were employed together to assist the optimization of DLLME parameters, including volumes of extraction and disperser solvents, ionic strength, extraction time, and centrifugation time and speed as variable factors. Under the optimum extraction and detection conditions, successful separation of the five SAs was achieved within 5 min, and excellent analytical performances were attained, such as good linear relationships (R>0.980) between peak area and concentration for each SA from 0.5 to 50 μg/mL, low limits of detection for the five SAs between 0.020 and 0.570 μg/mL and the intra‐day precisions of migration time below 0.80%. The method recoveries obtained at fortified 10 μg/mL for three water samples ranged from 53.6 to 94.0% with precisions of 1.23–5.60%. The proposed method proved highly sensitive and selective, rapid, convenient and cost‐effective, showing great potential for the simultaneous determination of SAs in water samples.  相似文献   

6.
    
This work deals with the optimization of a rapid, cost‐effective, and eco‐friendly gas chromatography with mass spectrometry method for the simultaneous determination of four endocrine disruptor compounds in water matrices: estrone, 17β‐estradiol, 17α‐ethinylestradiol, and bisphenol A, that are currently considered to be of main concern in the field of water policy and that could became candidates for future regulations. The method involves simultaneous derivatization and extraction of compounds by dispersive liquid–liquid microextraction followed by gas chromatography with mass spectrometry analysis. Derivatization and extraction parameters were optimized with the aid of experimental design approach. An excellent linear response was achieved for all analytes (r2 ≥ 0.999). Limits of detection and quantification are 0.003–0.005 and 0.0094–0.0164 μg/L, respectively. Intraday precision ranged between 1.1 and 12.6%, whereas interday precision ranged between 0.5 and 14.7%. For accuracy, bias values varied between –15.0 and 13.7%. Recoveries at three concentration levels ranged from 86.4 to 118.2%. The proposed method can be applied to the routine analysis of groundwater, river, sea, tap, and mineral water samples with excellent sensitivity, precision, and accuracy.  相似文献   

7.
    
A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid–liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001–10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.  相似文献   

8.
    
This paper describes a new chromatographic method for the determination of polyphenolic compounds in wines. The method is based on the separation of analytes by reversed-phase mode in a C18 column (2.6 μm particle size) and UV absorption spectroscopy. The elution gradient is generated from 0.1% formic acid aqueous solution and acetonitrile as an organic modifier. Experimental conditions including pH, percentage of organic modifier and elution gradient profile have been thoroughly optimized using experimental design. A multi-objective function has been defined as a criterion for obtaining a satisfactory compromise among number of compounds separated, resolution and analysis time. Multi-detection at 280, 310 and 370 nm has been utilized in order to work under the most appropriate wavelengths for each compound. Figures of merit including linearity ranges, precisions, detection limits and recoveries have been established under selected experimental conditions using synthetic standards and commercial red wines. The method has been applied to analyze red wines from various Spanish regions.  相似文献   

9.
Commercial zeolite USY (CBV500, Si/Al = 2.6) was dealuminated with oxalic acid, desilicated with ammonium hydroxide assisted by cetyltrimethylammonium bromide, and acid washed with lactic acid for obtaining hierarchical zeolite Y. The samples were characterized by X-ray diffraction, N2-physisorption, temperature programmed desorption of NH3, transmission electronic microscopy and diffuse reflectance infrared Fourier transform spectroscopy Ppyridine adsorption. A central composite experimental design was used for obtaining the influence of the concentration of the three solutions used in each step of the synthesis, on the relative crystallinity (%RC), mesopore volume (Vmeso), and total acidity of the synthesized materials. All the materials conserved the %RC and total acidity between 51-89% and 51–80%, respectively; modified materials showed an increase of up to 300 m2/g of external surface area and 0.17 cm3/g of the Vmeso with respect to the CBV500 sample. The statistical analysis showed that all the properties are influenced by oxalic acid concentration, whereas ammonium hydroxide concentration affects Vmeso, and lactic acid concentration affects %RC and total acidity in the modified samples. According to the optimization of the process, the material synthesized and labeled as MZ-OP, showed a %RC = 82%, Vmeso = 0.21 cm3/g, and total acidity of 1.430 mmol/g. The catalytic cracking of n-dodecane was tested over CBV500, MZ-OP, and MZ-10-100-500 and the obtained conversion at 300 min was 65%, 95% and 82%, respectively. Deactivation rate of the modified samples was significantly lower than the values obtained with CBV500, showing that the modified samples were more stable under tested reaction conditions.  相似文献   

10.
    
Optimization of alcoholic‐assisted dispersive liquid–liquid microextraction of pentachlorophenol (PCP) and determination of it with high‐performance liquid chromatography (UV‐Vis detection) was investigated. A Plackett‐Burman design and a central composite design were applied to evaluate the alcoholic‐assisted dispersive liquid–liquid microextraction procedure. The effect of seven parameters on extraction efficiency was investigated. The factor studied were type and volume of extraction and dispersive solvents, amount of salt, and agitation time. According to Plackett‐Burman design results, the effective parameters were type and volume of extraction solvent and agitation time. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 170‐μL 1‐octanol and 5‐min agitation time. The enrichment factor of PCP was 242 with limits of detection of 0.04 μg L?1. The linearity was 0.1–100 μg L?1 and the extraction recovery was 92.7%. RSD for intra and inter day of extraction of PCP were 4.2% and 7.8%, respectively for five measurements. The developed method was successfully applied for the determination of PCP in environmental water samples.  相似文献   

11.
    
《Electrophoresis》2017,38(8):1122-1129
In the previously published part of this study, we detailed a novel strategy based on dispersive liquid–liquid microextraction to extract and preconcentrate nine fluoroquinolones in porcine blood. Moreover, we presented the optimized experimental conditions to obtain complete CE separation between target analytes. Consequently, this second part reports the validation of the developed method to determine flumenique, difloxacin, enrofloxacin, marbofloxacin, ofloxacin, ciprofloxacin, through univariate calibration, and enoxacin, danofloxacin, and gatifloxacin through multivariate curve resolution analysis. The validation was performed according to FDA guidelines for bioanalytical assay procedures and the European Directive 2002/657 to demonstrate that the results are reliable. The method was applied for the determination of fluoroquinolones in real samples. Results indicated a high selectivity and excellent precision characteristics, with RSD less than 11.9% in the concentrations, in intra‐ and interassay precision studies. Linearity was proved for a range from 4.00 to 30.00 mg/L and the recovery has been investigated at four different fortification levels, from 89 to 113%. Several approaches found in the literature were used to determinate the LODs and LOQs. Though all strategies used were appropriate, we obtained different values when using different methods. Estimating the S/N ratio with the mean noise level in the migration time of each fluoroquinolones turned out as the best studied method for evaluating the LODs and LOQs, and the values were in a range of 1.55 to 4.55 mg/L and 5.17 to 9.62 mg/L, respectively.  相似文献   

12.
    
The objective of the present study was to investigate whether analysis of carbon dioxide, acetone and/or butanol present in human breath can be used as a simple and noninvasive diagnosis method for obstructive sleep apnea syndrome (OSAS). For this purpose, overnight changes in the concentrations of these breath molecules were measured before and after sleep in 10 patients who underwent polysomnography and were diagnosed with OSAS, and were compared with the levels of these biomarkers determined after sleep in 10 healthy subjects. The concentrations of exhaled carbon dioxide were measured using external cavity laser‐based off‐axis cavity enhanced absorption spectroscopy, whereas the levels of exhaled acetone and butanol were determined using thermal desorption gas chromatography mass spectrometry. We observed no significant changes in the levels of exhaled acetone and carbon dioxide in OSAS patients after sleep compared with pre‐sleep values and compared with those in healthy control subjects. However, for the first time, to our knowledge, analyses of expired air showed an increased concentration of butanol after sleep compared with that before sleep and compared with that in healthy subjects. These results suggest that butanol can be established as a potential biomarker to enable the convenient and noninvasive diagnosis of OSAS in the future.  相似文献   

13.
    
《中国化学会会志》2017,64(10):1227-1234
This paper describes an optimized method for the quick screening of low levels of haloacetonitriles (HANs), a nitrogenous disinfection byproduct. The method is especially geared toward screening of water used for drinking and in swimming pools. The method is based on vortex‐assisted liquid–liquid microextraction (VALLME), which is carried out before determination of the gathered samples by gas chromatography‐mass spectrometry (GC‐MS). Factors that can potentially affect the extraction efficiency of the desired trace chemicals from the gathered sample were enhanced using the Box–Behnken design method. The optimal VALLME parameters for a 10‐mL water sample (pH 4, containing 3 g of sodium sulfate), according to the Box–Behnken design method, are extractant 160 μL dichloromethane and vortex extraction time of 1 min at the maximum speed (2500 rpm). The limits of quantitation calculated were 16–35 ng/L. Precision for both intra‐ and inter‐day analysis was also calculated, which was less than 11% on three concentration levels. Mean extraction recovery, otherwise known as trueness, was between 71 and 92%. The developed method was applied successfully to extract HANs from drinking and swimming pool water samples.  相似文献   

14.
    
Marjoram extracts have been separated into polar and nonpolar parts using liquid–liquid extraction. Both polar and nonpolar parts of the extracts were further fractionated by flash chromatography. The obtained fractions (90 polar and 45 nonpolar fractions) were investigated for their antioxidant activities by 2,2‐diphenylpicrylhydrazyl and ferric ion reducing antioxidant power assays. A direct, positive, and linear relationship between antioxidant activity and total phenolic content of the fractions was observed. Based on antioxidant and total phenolic content data, the three fractions with the high antioxidant activities from polar and nonpolar part of the extract were analyzed for their constituent polyphenols by liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Compounds were identified by matching the mass spectral data and retention time with those of authentic standards. Identification of the compounds for which there were no “in‐house” standards available was carried out by accurate mass measurement of the precursor ions and product ions generated from collision‐induced dissociation. Rosmarinic acid was found to be the strongest antioxidant polyphenol conferring the highest antioxidant activity to fractions 47 and 17 of polar and nonpolar part of the extract, respectively. The identification of the rosmarinic acid was further confirmed by 1H NMR spectroscopy.  相似文献   

15.
    
In the present study, dispersive liquid–liquid microextraction followed by high performance liquid chromatography‐diode array detection has been developed as simple, rapid, accurate, and efficient sample preparation method for simultaneous determination of seven organic UV filters in urine samples. The influence of the main effects as well as their interactions was studied through a 2(6–2) fractional factorial design. The candidate parameters were: type and volume of dispersant and extraction solvents, sample pH, and salt concentration. Under final optimal conditions, the analytes were extracted from 5 mL of samples by addition of 0.5 mL of acetonitrile (dispersing solvent) containing 70 μL of carbon tetrachloride (extraction solvent), without modifying the pH of the solution and applying the (+1) level of salt concentration (10% w/v NaCl). The assay was linear (R2 > 0.997), relative recoveries ranged from 86.9 up to 97.3% and the LOQs between 3 and 45 ng mL?1 were obtained. The intra‐ and interday RSDs were lower than 5 and 8% at the middle point of the linear range, respectively. The proposed method was successfully applied to different volunteer urine samples and it was shown that the extraction efficiency was not affected by the type of urine samples.  相似文献   

16.
    
By using a fluorescent exonuclease assay, we reported unusual electrophoretic mobility of 5′‐indocarbo‐cyanine 5 (5′‐Cy5) labelled DNA fragments in denaturing polyacrylamide gels. Incubation time and enzyme concentration were two parameters involved in the formation of 5′‐Cy5‐labelled degradation products, while the structure of the substrate was slightly interfering. Replacement of positively charged 5′‐Cy5‐labelled DNA oligonucleotides (DNA oligos) by electrically neutral 5′‐carboxyfluorescein (5′‐FAM) labelled DNA oligos abolished the anomalous migration pattern of degradation products. MS analysis demonstrated that anomalously migrating products were in fact 5′‐labelled DNA fragments ranging from 1 to 8 nucleotides. Longer 5′‐Cy5‐labelled DNA fragments migrated at the expected position. Altogether, these data highlighted, for the first time, the influence of the mass/charge ratio of 5′‐Cy5‐labelled DNA oligos on their electrophoretic mobility. Although obtained by performing 3′ to 5′ exonuclease assays with the family B DNA polymerase from Pyrococcus abyssi, these observations represent a major concern in DNA technology involving most DNA degrading enzymes.  相似文献   

17.
We investigated the influence of arachidic acid/cadmium dication (AA/Cd(2+)) as a transfer promoter for the deposition of dicyanopyrazine-linked porphyrin (2-DCPP) Langmuir-Blodgett (LB) films on both hydrophobic and hydrophilic substrates. In the case of LB deposition on a hydrophilic substrate, the presence of AA/Cd(2+) does not improve 2-DCPP LB deposition. The poor transfer in the case of the hydrophilic surface is believed to be due to 2-DCPP not wetting the surface during the down-stroke deposition, and this is not improved by the transfer agent. However, on a hydrophobic substrate, deposition of 2-DCPP is significantly improved by the presence of AA/Cd(2+). Comparison of the UV-visible spectrum of a 2-DCPP LB film with that of 2-DCCP dissolved in chloroform reveals that the Soret and Q bands for the 2-DCPP LB film are broadened and red-shifted due to aggregation of porphyrin rings in the LB film. UV-visible spectral changes and ellipsometry as a function of the number of deposition layers suggest continuous transfer of 2-DCPP/AA onto the hydrophobic substrate and reproducibility in the deposition process. The Soret and Q bands of the 2-DCPP LB film upon acid vapor exposure have also been investigated, and these measurements may have chemical sensor applications.  相似文献   

18.
    
A simple, rapid, and sensitive method for the determination of naproxen and ibuprofen in complex biological and water matrices (cow milk, human urine, river, and well water samples) has been developed using ultrasound‐assisted magnetic dispersive solid‐phase microextraction. Magnetic ethylendiamine‐functionalized graphene oxide nanocomposite was synthesized and used as a novel adsorbent for the microextraction process and showed great adsorptive ability toward these analytes. Different parameters affecting the microextraction were optimized with the aid of the experimental design approach. A Plackett–Burman screening design was used to study the main variables affecting the microextraction process, and the Box–Behnken optimization design was used to optimize the previously selected variables for extraction of naproxen and ibuprofen. The optimized technique provides good repeatability (relative standard deviations of the intraday precision 3.1 and 3.3, interday precision of 5.6 and 6.1%), linearity (0.1–500 and 0.3–650 ng/mL), low limits of detection (0.03 and 0.1 ng/mL), and a high enrichment factor (168 and 146) for naproxen and ibuprofen, respectively. The proposed method can be successfully applied in routine analysis for determination of naproxen and ibuprofen in cow milk, human urine, and real water samples.  相似文献   

19.
    
A sensitive technique to determinate naproxen in hair samples was developed using hollow‐fiber micro‐solid‐phase combined with fluorescence spectrophotometry. The incorporation of multi‐walled carbon nanotubes modified with a Keggin polyoxometalate into a silica matrix prepared by the sol–gel method was reported. In this research, the Keggin carbon nanotubes /silica composite was used in the pores and lumen of a hollow fiber as the hollow‐fiber micro‐solid‐phase extraction device. The device was used for the microextraction of the analyte from hair and water samples under the optimized conditions. An orthogonal array experimental design with an OA24 (46) matrix was employed to optimize the conditions. The effect of six factors influencing the extraction efficiency was investigated: pH, salt, volume of donor and desorption phase, extraction and desorption time. The effect of each factor was estimated using individual contributions as response functions in the screening process. Analysis of variance was employed for estimating the main significant factors and their contributions in the extraction. Calibration curve plot displayed linearity over a range of 0.2–10 ng/mL with detection limits of 0.072 and 0.08 ng/mL for hair and aqueous samples, respectively. The relative recoveries in the hair and aqueous matrices ranged from 103–95%. The relative standard deviation for fiber‐to‐fiber repeatability was 3.9%.  相似文献   

20.
An efficient micellar electrokinetic chromatography (MEKC) method has been developed for the analysis of nine anthraquinones and bianthrones in rhubarb. A chemometric approach was used to search for the optimum conditions of separation. Those factors which were found to be significant with a screening design were further optimized with a central composite face-centered (CCF) design. Acetonitrile concentration was found to be the most influential, not only in resolution, but also in analysis time and peak asymmetry. With the optimized conditions: 15 mM sodium tetraborate/15 mM sodium dihydrogenphosphate buffer, 30 mM sodium deoxycholate, pH 8.6, 17 vol.% acetonitrile and 28 kV, nine tested analytes were baseline-separated within 14 min. The method was validated to analyze the rhubarb material. Solid-phase extraction (SPE) was manipulated to remove interfering substances. Five anthraquinones and two glycosidic bianthrones were detected and quantificated. The method should be suitable for determining these major active principles in rhubarb crude drugs.  相似文献   

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