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SPE
Terms modified by SPE Selected AbstractsHistorical review of sample preparation for chromatographic bioanalysis: pros and consDRUG DEVELOPMENT RESEARCH, Issue 3 2007Min S. Chang Abstract Sample preparation is a major task in a regulated bioanalytical laboratory. The sample preparation procedure significantly impacts assay throughput, data quality, analysis cost, and employee satisfaction. Therefore, selecting and optimizing an appropriate sample preparation method is essential for successful method development. Because of our recent expertise, this article is focused on sample preparation for high-performance liquid chromatography with mass spectrometric detection. Liquid chromatography with mass spectrometric detection (LC-MS) is the most common detection technique for small molecules used in regulated bioanalytical laboratories. The sample preparation technologies discussed are pre-extraction and post-extraction sample processing, protein precipitation (PPT), liquid,liquid extraction (LLE), offline solid-phase extraction (SPE), and online solid-phase extraction. Since all these techniques were in use for more than two decades, numerous applications and variations exist for each technique. We will not attempt to categorize each variation. Rather, the development history, a brief theoretical background, and selected references are presented. The strengths and the limitations of each method are discussed, including the throughput improvement potential. If available, illustrations from presentations at various meetings by our laboratory are used to clarify our opinion. Drug Dev Res 68:107,133, 2007. ©2007 Wiley-Liss, Inc. [source] Macro,micro analysis method for wave propagation in stochastic mediaEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2006T. Ichimura Abstract This paper presents a new analysis method, called macro,micro analysis method (MMAM) for numerical simulation of wave propagation in stochastic media, which could be used to predict distribution of earthquake strong motion with high accuracy and spatial resolution. This MMAM takes advantage of the bounding medium theory (BMT) and the singular perturbation expansion (SPE). BMT can resolve uncertainty of soil and crust structures by obtaining optimistic and pessimistic estimates of expected strong motion distribution. SPE leads to efficient multi-scale analysis for reducing a huge amount of computation. The MMAM solution is given as the sum of waves of low resolution covering a whole city and waves of high resolution for each city portion. This paper presents BMT and SPE along with the formulation of MMAM for wave propagation in three-dimensional elastic media. Application examples are presented to verify the validity of the MMAM and demonstrate potential usefulness of this approach. In a companion paper (Earthquake Engng. Struct. Dyn., this issue) application examples of earthquake strong motion prediction are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Disposable Amperometric Sensors for Thiols with Special Reference to GlutathioneELECTROANALYSIS, Issue 18 2008Dipankar Bhattacharyay Abstract The antioxidant ,reduced glutathione' tripeptide is conventionally called glutathione (GSH). The oxidized form is a sulfur-sulfur linked compound, known as glutathione disulfide (GSSG). Glutathione is an essential cofactor for antioxidant enzymes; it provides protection also for the mitochondria against endogenous oxygen radicals. The ratio of these two forms can act as a marker for oxidative stress. The majority of the methods available for estimation of both the forms of glutathione are based on colorimetric and electrochemical assays. In this study, electrochemical sensors were developed for the estimation of both GSH and GSSG. Two different types of transducers were used: i) screen-printed three-electrode disposable sensor (SPE) containing carbon working electrode, carbon counter electrode and silver/silver chloride reference electrode; ii) three-electrode disposable system (CDE) consisting of three copper electrodes. 5,5,-dithiobis(2-nitrobenzoic acid) (DTNB) was used as detector element for estimation of total reduced thiol content. The enzyme glutathione reductase along with a co-enzyme reduced nicotinamide adenine dinucleotide phosphate was used to estimate GSSG. By combining the two methods GSH can also be estimated. The detector elements were immobilized on the working electrodes of the sensors by bulk polymerization of acrylamide. The responses were observed amperometrically. The detection limit for thiol (GSH) was less than 0.6,ppm when DTNB was used, whereas for GSSG it was less than 0.1,ppm. [source] Development of a Rapid Single-Drop Analysis Biosensor for Screening of Phenanthrene in Water SamplesELECTROANALYSIS, Issue 20 2004Abstract Detection techniques for biosensors often require bulky instruments or cells that are not feasible for in-field analysis. Our single-drop cell design, optimized in this work, comprised a screen-printed three-electrode (SPE), strip in horizontal position onto which a volume of 100,,L of sample or substrate solution was placed to ensure electrical contact (complete circuit). Together with optimized linear sweep voltammetry (LSV), parameters for the detection of the enzyme alkaline phosphatase (AP), the system was applied to a biosensor for the analysis of polycyclic aromatic hydrocarbons (PAHs), in environmental samples. A limit of detection (LOD), of 0.15,ppb was achieved for a model system with an IC50 value of 0.885 ppb and a linear range (LR), of 0.2,10,ppb. Application of the single drop analysis (SDA), format to a PAH biosensor gave a LOD of 1.4,ppb for detection of phenanthrene with an IC50 value of 29.3,ppb and linear range of 2,100,ppb. Proof of concept is shown with spiked sample analysis of phenanthrene in matrices such as sea, river and tap water. [source] CEC-ESI ion trap MS of multiple drugs of abuseELECTROPHORESIS, Issue 7 2010Zeineb Aturki Abstract This article describes a method for the separation and determination of nine drugs of abuse in human urine, including amphetamines, cocaine, codeine, heroin and morphine. This method was based on SPE on a strong cation exchange cartridge followed by CEC-MS. The CEC experiments were performed in fused silica capillaries (100,,m×30,cm) packed with a 3,,m cyano derivatized silica stationary phase. A laboratory-made liquid junction interface was used for CEC-MS coupling. The outlet capillary column was connected with an emitter tip that was positioned in front of the MS orifice. A stable electrospray was produced at nanoliter per minute flow rates applying a hydrostatic pressure (few kPa) to the interface. The coupling of packed CEC columns with mass spectrometer as detector, using a liquid junction interface, provided several advantages such as better sensitivity, low dead volume and independent control of the conditions used for CEC separation and ESI analysis. For this purpose, preliminary experiments were carried out in CEC-UV to optimize the proper mobile phase for CEC analysis. Good separation efficiency was achieved for almost all compounds, using a mixture containing ACN and 25,mM ammonium formate buffer at pH 3 (30:70, v/v), as mobile phase and applying a voltage of 12,kV. ESI ion-trap MS detection was performed in the positive ionization mode. A spray liquid, composed by methanol,water (80:20, v/v) and 1% formic acid, was delivered at a nano-flow rate of ,200,nL/min. Under optimized CEC-ESI-MS conditions, separation of the investigated drugs was performed within 13,min. CEC-MS and CEC-MS2 spectra were obtained by providing the unambiguous confirmation of these drugs in urine samples. Method precision was determined with RSDs values ,3.3% for retention times and ,16.3% for peak areas in both intra-day and day-to-day experiments. LODs were established between 0.78 and 3.12,ng/mL for all compounds. Linearity was satisfactory in the concentration range of interest for all compounds (r2,0.995). The developed CEC-MS method was then applied to the analysis of drugs of abuse in spiked urine samples, obtaining recovery data in the range 80,95%. [source] Improved disc SDS-PAGE for extraction of low molecular weight proteins from serumELECTROPHORESIS, Issue 6 2010Tiechun Li Abstract The low molecular weight proteins can provide a lot of valuable information of biomarkers. To study these proteins, the high abundance and high molecular weight proteins must be removed prior to analysis. In this work, a simple and inexpensive disc SDS-PAGE to extract low molecular weight proteins from human serum and cutoff proteins larger than 30,kDa was developed. Some experimental conditions were examined. The experimental results obtained by plate SDS-PAGE and MALDI-TOF MS showed that the molecular weight of extracted proteins was about in the range from 0.3 to 28,kDa. Some experiments, including precipitation of proteins in organic solvents, SPE and cytochrome C test, were carried out and the experimental results demonstrated successful recovery of proteins/peptides with molecular weight from several hundreds of dalton to about 30,kDa. The experimental results obtained by plate SDS-PAGE indicated the repeatability was satisfactory. [source] Integrated microdevice for preconcentration and separation of a wide variety of compounds by electrochromatographyELECTROPHORESIS, Issue 3 2009Gaelle Proczek Abstract An integrated microdevice was developed to couple on-chip SPE to separation by channel electrochromatography. An acrylate-based monolith was synthesized within a glass microdevice by photoinitiated polymerization. It was used for both separation and preconcentration by direct injection on the head of the stationary phase or by confining the preconcentration step in a given zone of the stationary phase. The composition of the polymerization mixture was chosen to achieve a monolithic material containing both hydrophobic and charged moieties to ensure an electroosmotic flow for separation. As a consequence the extraction procedure occurs via hydrophobic and ionic interactions. Neutral, ionizable and charged compounds were successfully preconcentrated and separated within the microdevice through electrochromatographic mechanisms, highlighting the versatility of this device. The performance of the integrated microdevice was demonstrated with the preconcentration and separation of a mixture of PAHs for which a signal enhancement factor (SEF) of 270 was achieved within 120,s of preconcentration. In the case of charged and ionizable compounds, according to the electrolyte composition, contributions of both reverse-phase and ion-exchange mechanisms were used to perform effective electrochromatographic preconcentration. A SEF of 250 was obtained for the model-charged compound within 20,s of preconcentration. Finally, the potentials of on-chip preconcentrate and separate both neutral and ionized compounds have been demonstrated using a mixture of model compounds. [source] The combination of flow injection with electrophoresis using capillaries and chipsELECTROPHORESIS, Issue 1 2009Wen-juan Lü Abstract The technique of combined flow injection CE (FI-CE) integrates the essential favorable merits of FI and CE. It utilizes the various excellent on-line sample pretreatments and preconcentration (such as cloud point extraction, SPE, ion-exchange, dynamic pH junction and head-column field-amplified sample stacking technique) of FI, which has the advantages of high speed, accuracy, precision and avoiding manual handling of sample and reagents. Therefore, the coupling of FI-CE is an attractive technique; it can significantly expand the application of CE and has achieved many publications since its first appearance. The basic principles, instrumental developments and applications of FI-CE system from 2006 to 2008 are reviewed. [source] SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: Comparison of direct injection to SPE-MEKCELECTROPHORESIS, Issue 21 2008Rade Injac Abstract A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco® LC-8, LC-18, LC-SCX, and LC-WCX, as well as StrataÔ-X and X-C). DOX was determined on a 56,cm (effective length 50,cm)×50,,m id fused-silica capillary. The BGE was 20,mM borate buffer, pH 9.3, containing 80,mM SDS and 7.5%,v/v of methanol (30,s×50,mbar), and the temperature and voltage were 25°C and 30,kV, respectively. The analytical wavelength was set at 210,nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1,,g/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80,mM of SDS, 10%,v/v of methanol and 40,mM borate buffer (pH 9.3; 30,s×50,mbar; 25°C; 30,kV; 350,nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition. [source] Carbon nanotube disposable detectors in microchip capillary electrophoresis for water-soluble vitamin determination: Analytical possibilities in pharmaceutical quality controlELECTROPHORESIS, Issue 14 2008Agustín G. Crevillén Abstract In this work, the synergy of one mature example from "lab-on-chip" domain, such as CE microchips with emerging miniaturized carbon nanotube detectors in analytical science, is presented. Two different carbon electrodes (glassy carbon electrode (GCE) 3,mm diameter, and screen-printed electrode (SPE) 0.3,mm×2.5,mm) were modified with multiwalled carbon nanotubes (MWCNTs) and their electrochemical behavior was evaluated as detectors in CE microchip using water-soluble vitamins (pyridoxine, ascorbic acid, and folic acid) in pharmaceutical preparations as representative examples. The SPE modified with MWCNT was the best electrode for the vitamin analysis in terms of analytical performance. In addition, accurate determination of the three vitamins in four different pharmaceuticals was obtained (systematic error less than 9%) in only 400,s using a protocol that combined the sample analysis and the methodological calibration. [source] Electrical field-assisted solid-phase extraction coupled on-line to capillary electrophoresis-mass spectrometryELECTROPHORESIS, Issue 10 2008Gabriel Morales-Cid Abstract A substantial demand currently exists for analytical methods affording the determination of very low concentrations of analytes in complex matrices, such as those of environmental and biological samples, as simply as possible. However, the pretreatment of complex samples, which is unavoidable prior to CE-MS analysis, is usually complicated and time-consuming. In this work, we used voltage-assisted SPE for the first time as an alternative to conventional treatments for preconcentrating and purifying analytes. To this end, we used a simple flow system coupled on-line to CE-MS equipment. The system is quite robust and provides reproducible peak areas (the precision ranges from 2.5 to 3.8%). Also, it provides increased sensitivity affording the determination of trace amounts (nanogram per liter levels) of analytes in only a few milliliters of sample. The proposed system was applied to the determination of members of two compound families (viz. tetracyclines and amines). [source] Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flowELECTROPHORESIS, Issue 10 2008Liya Ge Abstract In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25,min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8,1.9,,M) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples. [source] Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wineELECTROPHORESIS, Issue 7 2008Sara Almeda Abstract This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20,mL volume of a standard solution at pH,1 or a wine sample at pH,8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1,mL water, pH,11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4,mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1,mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1,mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30,,g/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis. [source] On-line automatic SPE-CE coupling for the determination of biological markers in urineELECTROPHORESIS, Issue 5 2007José Ruiz-Jiménez Abstract Automatic SPE has been coupled on-line to CE by a transfer tube and the replenishment system of the CE instrument. The approach allows the target analytes (viz. creatinine, creatine, xanthine, hypoxanthine, uric acid, p -aminohippuric acid and ascorbic acid in urine samples) to be removed from the sample matrix, cleaned up, preconcentrated and injected into the capillary. The detection limits range between 0.14 and 4.50,,g/mL, the quantification limits between 0.45 and 15.0,,g/mL, and linear dynamic ranges , which include the reference healthy human values , from the quantification limits to 1332,,g/mL. The precision, expressed as RSD, ranges between 0.38 and 2.22% for repeatability and between 1.79 and 7.61% for within-laboratory reproducibility. The errors, expressed as RSD for all compounds, range between 0.20 and 6.90%. The time for automatic SPE and that necessary for the individual separation,detection of the target analytes are 13 and 12,min, respectively; the analysis frequency is 5,h,1. The accuracy of the method and potential matrix effects were studied by using spiked samples and recoveries between 96.00 and 103.07 % were obtained. The proposed method was applied to samples from healthy young students. [source] Ammonium perfluorooctanoate as a volatile surfactant for the analysis of N -methylcarbamates by MEKC-ESI-MSELECTROPHORESIS, Issue 22 2006Geert Van Biesen Abstract Ammonium perfluorooctanoate (APFOA) was investigated as an MS-friendly surfactant for the analysis of a mixture of ten N -methylcarbamates with MEKC-ESI-MS. Because of the relatively low boiling point of perfluorooctanoic acid (,190°C), APFOA can be introduced into a mass spectrometer without the adverse effects of less volatile surfactants such as SDS. With a BGE consisting of 50,mM APFOA/isopropanol (IPA) 98:2 and with 30,kV applied, a very fast separation (,6,min) was possible with only one pair of analytes comigrating. Using an experimental design with four factors (voltage, nebulizer pressure, concentration of APFOA, and concentration of IPA) we were able to resolve all analytes in just over 11,min. Sheath liquid composition and flow rate, drying gas temperature and flow rate, and fragmentor voltage were then optimized for maximum signal intensity and S/N. It was found that the faster method gave better S/N because of narrower peak widths, and detection limits in SIM mode were between 0.01 (aldicarb) and 0.08,mg/L (methomyl). Calibration curves were prepared with standards of 0.50, 1.00, and 2.00,mg/L for the analysis of samples obtained after SPE of tap water spiked with the ten N -methylcarbamates at a level of 10,µg/L. All analytes showed very good recoveries (>86%), except for the most polar analyte aldicarb sulfone (recovery of 73%), testifying for the potential use of APFOA for this kind of analyses. [source] In-capillary solid-phase extraction,capillary electrophoresis for the determination of chlorophenols in waterELECTROPHORESIS, Issue 16 2006Luo-Hong Zhang Abstract A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5,mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4,nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N,=,3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1,ng/mL and 0.07,ng/mL, respectively. For replicate analyses of 5,ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8,2.0%, 4.0,4.4% and 4.1,4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration. [source] Determination of tobacco-specific N -nitrosamines in rabbit serum by capillary zone electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry with solid-phase extractionELECTROPHORESIS, Issue 11 2006Chenchen Li Abstract In this paper, we propose a new strategy for separation and determination of tobacco-specific N -nitrosamines (TSNAs), a group of strong carcinogens found only in tobacco products, by using CZE and CE-MS associated with SPE. Six TSNAs: N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol were simultaneously separated by either of two CZE methods, one of which worked with ammonium formate buffer (pH,2.5) and another with citrate buffer (pH,2.4), as well as a CE-MS method. The CZE conditions including pH and concentration of running buffer, capillary length, applied voltage, and capillary temperature were systematically optimized. For CE-MS method, an optimized sheath liquid consisted of methanol,water was used at a flow rate of 10,,L/min. With SPE procedure, our proposed CE-MS method was successfully applied to determine TSNAs after 15,min metabolism in rabbits. A comparison study between CZE and CE-MS methods for quantitative purposes was carried out, showing that both methods provided similar separation efficiency, selectivity, repeatability, linearity, and recovery. However, CE-MS method was better suited for the analysis of TSNAs in complicated biological samples for its sensitivity and extra information on molecular structure. Having good accordance with our previous work by using LC-MS, the new CE-MS method is expected to be an alternative to the LC-MS method and applied to study the metabolism of TSNAs. [source] Sensitive chiral analysis by capillary electrophoresisELECTROPHORESIS, Issue 1 2006Carmen García-Ruiz Abstract In this review, an updated view of the different strategies used up to now to enhance the sensitivity of detection in chiral analysis by CE will be provided to the readers. With this aim, it will include a brief description of the fundamentals and most of the recent applications performed in sensitive chiral analysis by CE using offline and online sample treatment techniques (SPE, liquid,liquid extraction, microdialysis, etc.), on-column preconcentration techniques based on electrophoretic principles (ITP, stacking, and sweeping), and alternative detection systems (spectroscopic, spectrometric, and electrochemical) to the widely used UV-Vis absorption detection. [source] Determination of bupivacaine and metabolites in rat urine using capillary electrophoresis with mass spectrometric detectionELECTROPHORESIS, Issue 14 2003Ryan M. Krisko Abstract A method using capillary electrophoresis-mass spectrometry (CE-MS) was developed for the structural elucidation of bupivacaine and metabolites in rat urine. Prior to CE-MS analysis, solid-phase extraction (SPE) was used for sample cleanup and preconcentration purposes. Exact mass and tandem mass spectrometric (MS/MS) experiments were performed to obtain structural information about the unknown metabolites. Two instruments with different mass analyzers were used for mass spectrometric detection. A quadrupole time-of-flight (Q-TOF) and a magnetic sector hybrid instrument were coupled to CE and used for the analysis of urine extracts. Hydroxybupivacaine as well as five other isomerically different metabolites were detected including methoxylated bupivacaine. [source] Determination of cypermethrin in palm oil matricesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 10 2009Badrul Hisyam Zainudin Abstract In this study, a new method was developed for the determination of cypermethrin residue in both crude palm oil (CPO) and crude palm kernel oil (CPKO) using GC with electron capture detector. In this method, the oil was extracted with acetonitrile. Aliquots were cleaned-up using combined solid phase extraction (SPE), and a primary-secondary amine in combination with graphitized carbon black. The SPE cartridges were first conditioned and then eluted with acetonitrile. Cypermethrin recoveries from the fortified CPO samples were 87,98% with relative standard deviation (RSD) values of 4,8%, while those for the fortified CPKO samples were 83,100% with RSD values of 3,10%. Since good recoveries were obtained with RSD values below 10% in most cases, the proposed methodology will be useful for the analyses of palm oil samples. The method was successfully applied to the analysis of cypermethrin in real palm oil samples from various parts of Malaysia. No cypermethrin residue was found among 30 samples analyzed. [source] Capacity Fading Mechanism in All Solid-State Lithium Polymer Secondary Batteries Using PEG-Borate/Aluminate Ester as Plasticizer for Polymer ElectrolytesADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Fuminari Kaneko Abstract Solid-state lithium polymer secondary batteries (LPB) are fabricated with a two-electrode-type cell construction of Li|solid-state polymer electrolyte (SPE)|LiFePO4. Plasticizers of poly(ethylene glycol) (PEG)-borate ester (B-PEG) or PEG-aluminate ester (Al-PEG) are added into lithium-conducting SPEs in order to enhance their ionic conductivity, and lithium bis-trifluoromethansulfonimide (LiTFSI) is used as the lithium salt. An improvement of the electrochemical properties is observed upon addition of the plasticizers at an operation temperature of 60,°C. However, a decrease of discharge capacities abruptly follows after tens of stable cycles. To understand the origin of the capacity fading, electrochemical impedance techniques, ex-situ NMR and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) techniques are adopted. Alternating current (AC) impedance measurements indicate that the decrease of capacity retention in the LPB is related to a severe increase of the interfacial resistance between the SPE and cathode. In addition, the bulk resistance of the SPE film is observed to accompany the capacity decay. Ex situ NMR studies combined with AC impedance measurements reveal a decrease of Li salt concentration in the SPE film after cycling. Ex situ SEM/EDS observations show an increase of concentration of anions on the electrode surface after cycling. Accordingly, the anions may decompose on the cathode surface, which leads to a reduction of the cycle life of the LPB. The present study suggests that a choice of Li salt and an increase of transference number is crucial for the realization of lithium polymer batteries. [source] Psychometric testing of the Swedish version of the Philadelphia Geriatric Center Multilevel Assessment InstrumentINTERNATIONAL JOURNAL OF NURSING PRACTICE, Issue 3 2007Margareta Minhage OT We examined whether the Swedish adaptation of the Philadelphia Geriatric Center Multilevel Assessment Instrument (PGCMAI) developed by Lawton meets criteria for reliability and validity in an elderly Swedish population with locomotor disability. Data were collected, using the mid-length version of the instrument, from 199 elderly people with locomotor disability in two Swedish counties. Reliability was determined by Cronbach's alpha and construct validity was tested by means of exploratory factor analysis. Comparison was made with the Standardized Practical Equipment (SPE) test. Factor analysis identified eight factors, which were comparable to the original eight domains. There was a logical correlation between the PGCMAI and the SPE test. Further psychometric testing is recommended on other groups of elderly people. [source] Physical Activity and Social Physique Anxiety in Older Women: The Moderating Effects of Self-Presentation EfficacyJOURNAL OF APPLIED BIOBEHAVIORAL RESEARCH, Issue 2 2003Jennifer Woodgate Given the inconsistent relationships observed between social physique anxiety (SPA) and physical activity, it is possible that other variables moderate this relationship. This study examined self-presentation efficacy (SPE) as a potential moderator. Participants were 81 older women. Multiple regression analysis revealed that SPA, SPE, and the SPA x SPE interaction significantly predicted physical activity, with the SPA x SPE interaction explaining 6% of the variance in activity. Evaluation of this interaction indicated that SPA was negatively correlated with activity only for women with high and mean SPE and was unrelated to activity for women with low SPE. These findings suggest that, for older women, lower levels of SPA are not always related to greater activity. Rather, SPE is an important moderator of the SPA-physical activity relationship. [source] On unifying multiblock analysis with application to decentralized process monitoringJOURNAL OF CHEMOMETRICS, Issue 9 2001S. Joe Qin Abstract Westerhuis et al. (J. Chemometrics 1998; 12: 301,321) show that the scores of consensus PCA and multiblock PLS (Westerhuis and Coenegracht, J. Chemometrics 1997; 11: 379,392) can be calculated directly from the regular PCA and PLS scores respectively. In this paper we show that both the loadings and scores of consensus PCA can be calculated directly from those of regular PCA, and the multiblock PLS loadings, weights and scores can be calculated directly from those of regular PLS. The orthogonal properties of four multiblock PCA and PLS algorithms are explored. The use of multiblock PCA and PLS for decentralized monitoring and diagnosis is derived in terms of regular PCA and PLS scores and residuals. While the multiblock analysis algorithms are basically equivalent to regular PCA and PLS, blocking of process variables in a large-scale plant based on process knowledge helps to localize the root cause of the fault in a decentralized manner. New definitions of block and variable contributions to SPE and T,2 are proposed for decentralized monitoring. This decentralized monitoring method based on proper variable blocking is successfully applied to an industrial polyester film process. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of MMP inhibitor radiotracers [11C]methyl-CGS 27023A and its analogs, new potential PET breast cancer imaging agentsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 6 2002Xiangshu Fei Abstract [11C]Methyl-CGS 27023A (1a) and its analogs [11C]methyl-2-picolyl-CGS 27023A (1b), [11C]methyl-benzyl-CGS 27023A (1c), [11C]methyl-2-nitro-CGS 27023A (1d), [11C]methyl-3-nitro-CGS 27023A (1e), and [11C]methyl-4-nitro-CGS 27023A (1f), novel radiolabeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) breast cancer imaging agents. The appropriate precursors for radiolabeling were obtained in four to five steps from starting material amino acid D -valine with moderate to excellent chemical yields. Precursors were labeled by [11C]methyl triflate through 11C,O-methylation method at the aminohydroxyl position under basic conditions and isolated by solid-phase extraction (SPE) purification to produce pure target compounds in 40,60% radiochemical yields (decay corrected to end of bombardment), in 20,25 min synthesis time. Copyright © 2002 John Wiley & Sons, Ltd. [source] A combined loop-SPE method for the automated preparation of [11C]doxepinJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2002R. Iwata Abstract A simple and versatile loop-solid phase extraction (SPE) method was developed for the automated preparation of [11C]doxepin, a histamine H1 receptor antagonist, from [11C]methyl triflate ([11C]MeOTf). This labeling agent was passed through a Teflon or Tefzel loop coated internally with a film of the precursor solution. The reaction products were then flushed from the loop to a short SPE column, where they were concentrated and then injected onto a semi-preparative HPLC column simply by switching an injection valve. By applying this combined loop-SPE technique the whole procedure turned out to be easily automated. The formation of [11C]methylated doxepin ([11C]methyldoxepin) was observed and the ratio of doxepin to methyldoxepin was found to be clearly correlated with the mass ratio of nordoxepin to MeOTf. This observation highlights the importance of [11C]MeOTf specific activity in the [11C]methylation of secondary amines. Using this method, [11C]Doxepin was prepared in over 40% radiochemical yield from high specific activity [11C]MeOTf. Copyright © 2002 John Wiley & Sons, Ltd. [source] Recent advances in the assessment of the ratios of cortisol to cortisone and of some of their metabolites in urine by LC-MS-MSJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2009Alessandro Saba Abstract A previously reported method for the assessment of the ratio of tetrahydrocortisol (THF) + allo-tetrahydrocortisol (A-THF) to tetrahydrocortisone (THE) by HPLC-MS-MS has been significantly improved, in order to increase either ruggedness and reliability. That was achieved by the introduction of an on-line sample cleanup stage, which made use of a perfusion column as a solid phase microextraction (SPE) cartridge. The set of analytes was expanded, by introducing cortisol and cortisone, whose ratio supply additional diagnostic information. The response factors of both THF and A-THF has been checked, resulting almost identical, as well as the influence of the matrix on the calibration curves which, although different for water and urine, had similar effect on the ratios of interest. As a consequence, the calibration solutions can be prepared in pure water. The influence of several different storage procedures has also been tested, resulting in no substantial effect on the final result. Finally, the improved method has been used to run real samples from healthy volunteers, with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Investigating the presence of pesticide transformation products in water by using liquid chromatography-mass spectrometry with different mass analyzers,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2008Félix Hernández Abstract Many pesticide transformation products (TPs) can reach environmental waters as a consequence of their normally having a higher polarity than their parent pesticides. This makes the development of analytical methodology for reliable identification and subsequent quantification at the sub-microgram per liter levels necessary, as required under current legislation. In this paper we report the photodegradation of several pesticides frequently detected in environmental waters from the Spanish Mediterranean region using the high-resolution and exact-mass capabilities of hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) hyphenated to liquid chromatography (LC). Once the main photodegradation/hydrolysis products formed in aqueous media were identified, analytical methodology for their simultaneous quantification and reliable identification in real water samples was developed using on-line solid-phase extraction (SPE)-LC-tandem MS with a triple-quadrupole (QqQ) analyzer. The methodology was validated in both ground and surface water samples spiked at the limit of quantification (LOQ) and 10 × LOQ levels, i.e. 50 and 500 ng/l, obtaining satisfactory recoveries and precision for all compounds. Subsequent analysis of ground and surface water samples resulted in the detection of a number of TPs higher than parent pesticides. Additionally, several soil-interstitial water samples collected from the unsaturated zone were analyzed to explore the degradation/transformation of some pesticides in the field using experimental plots equipped with lisimeters. Several TPs were found in these samples, with most of them having also been detected in ground and surface water from the same area. This paper illustrates the extraordinary potential of LC-MS(/MS) with QTOF and QqQ analyzers for qualitative/structural and quantitative analysis, respectively, offering analytical chemists one of the most powerful tools available at present to investigate the presence of pesticide TPs in water. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of intracellular short organic acid-coenzyme A esters from actinomycetes using liquid chromatography-electrospray ionization-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2007Je Won Park Abstract A method employing silicone oil density centrifugation, solid-phase extraction (SPE) cleanup, and LC-ESI-MS/MS analysis was developed for the rapid, selective, sensitive, and quantitative detection of an intracellular pool of short organic acid-CoA esters in actinomycetes. The detection limit was determined to be approximately 0.8 pmol (1.2 ng/ml) for each standard CoA-ester analyzed by the present LC-ESI-MS/MS method. A selected ion chromatogram for a typical fragment ion (m/z 428) specific to CoA-esters enabled the detection of eight intracellular CoA-esters involved in both primary and secondary metabolisms. The application of this method to bacterial metabolomic study is demonstrated by the profiling of the intracellular CoA-ester pools in the wild-type Streptomyces venezuelae strain producing polyketide antibiotics (methymycin and pikromycin), a polyketide synthase (PKS)-deleted S. venezuelae mutant, and a S. venezuelae mutant expressing the heterologous PKS genes. By quantifying the individual CoA-esterlevel in three different genotypes of the S. venezuela e strain, further insight could be gained into the role of CoA-estersin polyketide biosynthesis. This analytical approach can be extended to the quantification of the size and composition of in vivo CoA-ester pools in various microbes, and can provide a detailed understanding of the relationship between the in vivo CoA-ester pool and the production of pharmaceutically important polyketides. Copyright © 2007 John Wiley & Sons, Ltd. [source] Measurement of serum salicylate levels by solid-phase extraction and desorption/ionization on silicon mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2005Shoji Okuno Abstract The applicability of the matrix-free laser desorption/ionization on silicon mass spectrometry (DIOS-MS) to measuring serum drug levels was examined by analyzing serum salicylic acid. The optimized and simple solid-phase extraction (SPE) allowed good recovery, 88.9 ± 5.8%, for 1.4 mM (200 mg/L) of salicylic acid in serum. The negative ion MS allowed measurements of deprotonated molecules without interference from other signals. Using a deuterium-labeled internal standard, good linearity was obtained in the 0.14 to 4.2 mM (20,600 mg/L) range, which was sufficient for monitoring the therapeutic anti-inflammatory dose. SPE followed by DIOS-MS is anticipated to be a method of measuring drug levels in blood and may allow high throughput analysis. 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