On-line Extraction Method Research Articles

Adaptive Online Extraction Method of Slot Harmonics for Multiphase Induction Motor

The accurate extraction and analysis of slot harmonics caused by slotting in an induction motor are important for the motor’s performance evaluation and state monitoring. However, the frequency distribution of rotor slot harmonics (RSHs) varies along with the operating states of the motor, such as motor speed and slip ratio, and the voltage and current signals of the motor only contain small-amplitude RSHs compared with other harmonics; both make it difficult to extract and analyze the RSHs accurately online. While offline extraction and filters with constant parameters are mainly utilized in available works, a novel adaptive extraction method for RSHs in a multiphase induction motor is proposed here to realize online RSH extraction under different speed and load conditions. In this paper, the RSHs in the multiphase induction motors are firstly modeled by using the magnetic potential permeability method, and the influence of a skewed rotor on RSHs is analyzed through a multisection method. Then, an adaptive extraction method of RSHs is proposed, which can effectively realize the online processing of RSHs of stator current. Finally, the experimental platform of a nine-phase induction motor has been used to verify the effectiveness of the proposed method under different speeds and load conditions, with a relative error of less than 1% in identifying the RSH frequency distribution.

Junction Temperature Online Extraction Method for Power MOSFET by Current Fall Time

Temperature-sensitive electrical parameter (TSEP) approaches are widely used in junction temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}_{j}$ </tex-math></inline-formula> ) prediction of insulated gate bipolar transistor (IGBT). Due to different physical characteristics, TSEPs in IGBT may not suitable for power MOSFET. In this article, a novel junction temperature extraction for power MOSFET based on current fall time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{fi}$ </tex-math></inline-formula> ) during turn-off process is proposed. The voltage rise time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{rv}$ </tex-math></inline-formula> ) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{fi}$ </tex-math></inline-formula> during turn-off process as power MOSFET’s TSEPs are evaluated, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{rv}$ </tex-math></inline-formula> is often used for junction temperature prediction of IGBT. In addition, a method of using parasitic inductance induced voltage in the circuit to extract <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{fi}$ </tex-math></inline-formula> is proposed, and the feasibility of this method has been analyzed. Then, the boost experimental platform is established, and three different types of power MOSFETs were tested. It is established that the model based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{fi}$ </tex-math></inline-formula> is a viable model with good linearity and sensitivity, and through induced voltage on parasitic inductance, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{fi}$ </tex-math></inline-formula> can be well-reflected. Finally, online extraction of power MOSFET junction temperature in the boost circuit is implemented in this article.

A Novel Method for Online Extraction of Small-Angle Scattering Pulse Signals from Particles Based on Variable Forgetting Factor RLS Algorithm.

The small-angle optical particle counter (OPC) can detect particles with strong light absorption. At the same time, it can ignore the properties of the detected particles and detect the particle size singly and more accurately. Reasonably improving the resolution of the low pulse signal of fine particles is key to improving the detection accuracy of the small-angle OPC. In this paper, a new adaptive filtering method for the small-angle scattering signals of particles is proposed based on the recursive least squares (RLS) algorithm. By analyzing the characteristics of the small-angle scattering signals, a variable forgetting factor (VFF) strategy is introduced to optimize the forgetting factor in the traditional RLS algorithm. It can distinguish the scattering signal from the stray light signal and dynamically adapt to the change in pulse amplitude according to different light absorptions and different particle sizes. To verify the filtering effect, small-angle scattering pulse extraction experiments were carried out in a simulated smoke box with different particle properties. The experiments show that the proposed VFF-RLS algorithm can effectively suppress system stray light and background noise. When the particle detection signal appears, the algorithm has fast convergence and tracking speed and highlights the particle pulse signal well. Compared with that of the traditional scattering pulse extraction method, the resolution of the processed scattering pulse signal of particles is greatly improved, and the extraction of weak particle scattering pulses at a small angle has a greater advantage. Finally, the effect of filter order in the algorithm on the results of extracting scattering pulses is discussed.

Method for extracting motor impedance characteristics online

Due to increases in switching frequency, the electromagnetic interference of motor drive systems has been receiving more attention. In a motor drive system, the devices in the inverter produce serious electromagnetic interference during high-frequency switching. It is necessary to model the motor drive system to predict the electromagnetic interference level. Extraction of the motor impedance characteristic is necessary for the modeling of a motor drive system. At present, most research only studies the measurement method of a motor in the static state. However, motor impedance characteristics in the static state cannot represent motor impedance characteristics in operation. In this paper, an online measurement method of motor impedance characteristics is proposed. For the three-phase asymmetric circuit caused by modulation, the motor impedance characteristics in operation are calculated by establishing Kirchhoff voltage equations. A precision power scope PX8000 is used to measure the harmonic components of single-phase voltage, single-phase current, and common-mode current. The time-delay difference of the precision power scope PX8000 between different probes is also considered. Experiments prove that the time-delay difference does not affect the measurement results. Through comparing the motor impedance characteristics measured by different filters, the method of extracting the motor impedance characteristics online is validated. Finally, the motor impedance characteristics in the static state and the motor impedance characteristics of online extraction are experimentally compared. The motor impedance characteristics of the online extraction method proposed in this paper have more advantages than traditional methods.

Extraction of Common-Mode Impedance of an Induction Motor by Using All-Phase FFT With Intermediate-Frequency Filtering

This letter proposes an online extraction method of common-mode (CM) impedance of induction motor based on all-phase spectrum calculation. All-phase fast Fourier transform with intermediate-frequency filtering (ApFFTIF) is proposed based on infinite impulse response filter, zero-phase filtering technique, and all-phase fast Fourier transform. By using ApFFTIF, the accurate amplitude spectrum together with accurate phase spectrum of CM impedance of induction motor are extracted. Then genetic algorithm is used to establish the model of CM impedance of inductor motor. Finally, through comparing CM impedances extracted by using different spectrum calculation methods, and through comparing measured and calculated CM currents, the accuracy of the proposed method is validated.

A simplified method for online extraction of skin conductance features: A pilot study on an immersive virtual-reality-based motor task.

There is a growing body of literature that recognizes the importance of Skin Conductance (SC) for assessing changes in emotional states, such as engagement to learning tasks, and its importance to estimate possible drawbacks affecting overall performance. To date, most of the commonly used methods for SC signal analysis, i.e. detecting its phasic and tonic components and thus extracting informative features, are either too simple and unreliable or too complex and thus inaccessible and inflexible, as well as unable to perform online analyses. The current work proposes a simplified but clear and effective algorithm based on a Machine State to search for expected behaviors in the well-defined morphology of the signal. Eleven (11) features were correctly extracted from 79 healthy subjects during an experimental setup for immersive virtual rehabilitation (balance study case). The method was also successfully applied as a tool to identify significant changes in the subjective psychophysiological response to different experimental conditions. These results point toward a potential role in virtual rehabilitation applications by getting real-time feedback in human-in-the-loop approaches.

Simultaneous Determination of Six Alkaloids in Rat Plasma with On-line SPE–HPLC Using a Homemade Four-Hydrogen Furfuryl-Based Polymer Monolithic Sorbent

A four-hydrogen furfuryl-based polymer monolithic column for solid-phase extraction was prepared via in situ radical polymerization, using tetrahydrofurfuryl methacrylate as the monomer. The monolith was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and nitrogen adsorption–desorption method, showing relatively uniform porous structure with micro-, meso- and macro-pores and a relatively high surface area of 54.99 m2 g−1. Online solid-phase extraction–high-performance liquid chromatography was carried out to quantitatively analyze six alkaloids, including caffeine, hydroxy-α-sanshool, hydroxy-β-sanshool, hydroxy-γ-sanshool, hydroxy-γ-isosanshool and γ-sanshool in rat plasma. The results show that the prepared polymer monolithic sorbent exhibits good clean-up ability for bio-matrix, as well as good extractive ability for the six concerning alkaloids in rat plasma. Method validation shows that the correlation coefficients of the linear regressions are higher than 0.998 and the accuracy represented by spiked recovery ranges in 94.37–100.7%, 99.52–101.1%, 98.93–100.8%, 98.36–101.6%, 99.22–101.2% and 99.86–101.4% for the six alkaloids, respectively, as well as the LOD ranges in 2.10–3.90 ng mL−1 and the LOQ in 6.35–10.14 ng mL−1. Compared to the reference works, the present work is a simple and effective method for online extraction and simultaneous determination of six alkaloids in plasma with high accuracy and low cost.

An on-Line Extraction Method for the Parasitic Capacitance of the Photovoltaic Panel

An on-Line Extraction Method for the Parasitic Capacitance of the Photovoltaic Panel

Online eluent-switching technique coupled anion-exchange liquid chromatography–ion trap tandem mass spectrometry for analysis of non-steroidal anti-inflammatory drugs in pig serum

A novel method for online extraction, pH-gradient separation, and analysis of nine non-steroidal anti-inflammatory drugs (NSAIDs) was developed by coupling online eluent-switching technique to single anion-exchange chromatographic column/ion trap mass spectrometer (MS) and used for monitoring NSAIDs residues in pig serum. A neutral eluent and a pH-gradient eluent were used for extraction and separation of NSAIDs, respectively. Each of nine NSAIDs has an MS precursor ion of either [M−H]− or [M−Na]−. The extracted ion chromatogram for a specific product ion of each NSAID was used for its quantitative analysis. The dynamic linear ranges of calibration curves were all 0–200ngmL−1 (R2>0.9950). The analysis accuracies estimated by spiking standard concentrations at 20, 100, and 200ngmL−1 were 80.5–99.9%. The corresponding intra-day and inter-day precisions (RSD%) were 2.5–14.5% and 2.9–15.2%, respectively. The limit of detection/limit of quantitation of NSAIDs were 1.3/4.3, 0.5/1.6, 0.2/0.5, 2.5/8.2, 1.5/4.9, 0.6/2.1, 0.6/2.0, 0.5/1.7, and 0.6/2.1ngmL−1 for carprofen, diclofenac, flunixin, ibuprofen, ketoprofen, meclofenamic acid sodium, mefenamic acid, niflumic acid, and tolfenamic acid, respectively. After 1h injection of a dose containing 2mgkg−1 weight pig of flunixin and tolfenamic acid to the pigs, a residue amount of 3480±36ngmL−1 and 431±13ngmL−1, respectively, was reached for the incurred pig serum specimens and both residues were reduced to about 20ngmL−1 at the time of 24h.

Online Feature Parameter Extraction for Pulsed Magnets

For pulsed magnets, knowing the real-time performance of the resistance and inductance is significant for both science and engineering. Investigation on the resistance and inductance performance with experimental results will deepen the understanding of electromagnetic physics in pulsed magnets. More importantly, the resistance and inductance values can be used as the thermal stability or the structure stability criterions for pulsed magnets. In this paper, an online extraction method is presented to obtain the inductance and resistance.

Direct determination of chlorophenols in water samples through ultrasound-assisted hollow fiber liquid–liquid–liquid microextraction on-line coupled with high-performance liquid chromatography

In this study we on-line coupled hollow fiber liquid–liquid–liquid microextraction (HF-LLLME), assisted by an ultrasonic probe, with high-performance liquid chromatography (HPLC). In this approach, the target analytes – 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 2,6-dichlorophenol (2,6-DCP), and 3,4-dichlorophenol (3,4-DCP) – were extracted into a hollow fiber (HF) supported liquid membrane (SLM) and then back-extracted into the acceptor solution in the lumen of the HF. Next, the acceptor solution was withdrawn on-line into the HPLC sample loop connected to the HF and then injected directly into the HPLC system for analysis. We found that the chlorophenols (CPs) could diffuse quickly through two sequential extraction interfaces – the donor phase – SLM and the SLM – acceptor phase – under the assistance of an ultrasonic probe. Ultrasonication provided effective mixing of the extracted boundary layers with the bulk of the sample and it increased the driving forces for mass transfer, thereby enhancing the extraction kinetics and leading to rapid enrichment of the target analytes. We studied the effects of various parameters on the extraction efficiency, viz. the nature of the SLM and acceptor phase, the compositions of the donor and acceptor phases, the fiber length, the stirring rate, the ion strength, the sample temperature, the sonication conditions, and the perfusion flow rate. This on-line extraction method exhibited linearity (r2≥0.998), sensitivity (limits of detection: 0.03–0.05μgL−1), and precision (RSD%≤4.8), allowing the sensitive, simple, and rapid determination of CPs in aqueous solutions and water samples with a sampling time of just 2min.

Automatic online testing methods of soil CO2 concentration

An online extraction method for monitoring CO2 concentration during soil respiration is described based on the assay of gas pump and gas extraction with a dynamic air chamber. Also, a study is done on the relationship between data collected from online CO2 measurement and time, as well as the curve fitting. This method uses the optimization algorithm to extract the CO2 concentration in the soil respiration chamber, and sets up a mathematical model for online soil CO2 concentration extraction. It is verified that the extraction method is feasible with the automatic site detection. This method, which can reduce the volume of data redundancy and improve data reliability, has a high reference value for the similar characteristics of online data extraction, compared with the traditional CO2 detection methods during soil respiration.

Post 17th-Century Changes of European PAH Emissions Recorded in High-Altitude Alpine Snow and Ice

The occurrence of organic pollutants in European Alpine snow/ice has been reconstructed over the past three centuries using a new online extraction method for polycyclic aromatic hydrocarbons (PAH) followed by liquid chromatographic determination. The meltwater flow from a continuous ice core melting system was split into two aliquots, with one aliquot directed to an inductively coupled plasma quadrupole mass spectrometer for continuous trace elements determinations and the second introduced into a solid phase C18 (SPE) cartridge for semicontinuous PAH extraction. The depth resolution for PAH extractions ranged from 40 to 70 cm, and corresponds to 0.7-5 years per sample. The concentrations of 11 PAH were determined in dated snow/ice samples to reconstruct the atmospheric concentration of these compounds in Europe for the last 300 years. The PAH pattern is dominated by phenanthrene (Phe), fluoranthene (Fla), and pyrene (Pyr), which represent 60-80% of the total PAH mass. Before 1875 the sum of PAH concentration (SigmaPAH) was very low with total mean concentrations less than 2 ng/kg and 0.08 ng/kg for the heavier compounds (SigmaPAH*, more than four aromatic rings). During the first phase of the industrial revolution (1770-1830) the PAH deposition showed a weak increase which became much greater from the start of the second phase of the industrial revolution at the end of 19th Century. In the 1920s, economic recession in Europe decreased PAH emissions until the 1930s when they increased again and reached a maximum concentration of 32 ng/kg from 1945 to 1955. From 1955 to 1975 the PAH concentrations decreased significantly, reflecting improvements in emission controls especially from major point sources, while from 1975 to 2003 they rose to levels equivalent to those in 1910. The Fla/(Fla+Pyr) ratio is often used for source assignment and here indicates an increase in the relative contribution of gasoline and diesel combustion with respect to coal and wood burning from 1860 to the 1980s. This trend was reversed during the last two decades.

Development and characterization of an immunoaffinity monolith for selective on-line extraction of bisphenol A from environmental water samples

Matrix interference and contamination from analytical procedures are two major issues in the detection of trace level of bisphenol A (BPA) in environmental water. In this paper, we report a highly selective and efficient method for on-line extraction of BPA from water samples followed by quantification with liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI/MS/MS). Poly(ethylene dimethacrylate-glycidyl methacrylate) monolith was synthesized in 50 mm × 4.6 mm i.d. stainless steel cartridges and the epoxy-groups on the surface of the monolith were hydrolyzed and oxidized to aldehyde functions. Antibodies against BPA were covalently immobilized onto the monolithic column via Schiff base reaction. The optimum application buffer and elution buffer were found to be pH 5.5 phosphate buffered saline (PBS) and methanol–water (70:30, v/v), respectively. The obtained immunoaffinity monolithic columns were on-line coupled to LC–MS/MS using column-switching valves and the system was applied to analyze BPA in real environmental water samples. The method achieved a detection limit of 0.3 ng L −1 using a sample volume of 100 mL. The linear calibration range was 1.0–160 ng L −1. Samples including tap water, lake water and effluent from municipal sewage treatment plant were all measured with satisfactory results.

Determination of MK‐0431 in human plasma using high turbulence liquid chromatography online extraction and tandem mass spectrometry

A robust and sensitive method using high turbulence liquid chromatography (HTLC) online extraction with tandem mass spectrometry (MS/MS) for the determination of MK-0431 in human plasma was developed and validated to support the clinical studies. This HTLC online extraction method eliminated the time-consuming offline sample extraction procedures and significantly increased productivity. A narrow bore large particle size reversed-phase column (Cyclone, 50 x 1.0 mm, 60 microm) and a BDS Hypersil C18 column (30 x 2.1 mm, 3 microm) were used as extraction and analytical columns, respectively. The linear dynamic range of the calibration curve was 0.5 to 1000 ng/mL. Intraday validation was conducted using five calibration curves prepared in five lots of human control plasma, and the intraday precision (RSD%) was from 2.4 to 9.0% and the accuracy was from 98.0 to 103% of the nominal value. The intraday precision (RSD%, n = 5) for plasma quality control (QC) samples varied from 2.0 to 5.3% and accuracy from 103 to 105% of the nominal value. The interday precision (RSD%) for 100 sets of plasma QC samples in 29 analytical runs varied from 6.3 to 9.0% and the accuracy from 98.8 to 104% of the nominal value. No significant difference was observed between the interday and intraday precision and accuracy of the QC samples.

A monolithic-phase based on-line extraction approach for determination of pharmaceutical components in human plasma by HPLC–MS/MS and a comparison with liquid–liquid extraction

An automated procedure using monolithic-phase based on-line extraction is described for pharmaceutical component analysis in plasma by LC–MS/MS. In this approach, a short monolithic C 18 4.6 mm × 10 mm cartridge is used for high flow extraction at 4 mL/min. Plasma samples were subjected to protein precipitation first with acetonitrile, and the supernatant was diluted and loaded onto a monolithic cartridge. Sample elution was accomplished with narrow-bore LC–MS/MS system. A method for determination of Amprenavir (APV) and Atazanavir (AZV) in human plasma was developed with this approach. After 0.1 mL of plasma was transferred into each well of a 96-well plate by a liquid handler, the rest of sample preparation time typically only takes about 20 min. A Phenomenex Luna C18(2) 2.0 mm × 150 mm analytical column was used for the separation at a flow rate of 0.3 mL/min. The run time for each sample was 4 min. The standard curve range was 2.77–1520 ng/mL for Atazanavir, and 4.50–2560 ng/mL for Amprenavir. The accuracy (%bias) at the lower limit of quantitation (LLOQ) for Atazanavir was 2.7% and the precision (%CV) at the LLOQ was 7.9%, while the accuracy at LLOQ for Amprenavir was −1.3% and the precision at LLOQ was 7.8%. The inter-day %bias and %CV of the quality control samples of Atazanavir were ≤4.5% and ≤6.5%, respectively. The inter-day %bias and %CV of the quality control samples of Amprenavir were ≤1.1% and ≤7.2%, respectively. Coefficients of determination, a measure of linearity, ranged from 0.993 to 0.999. Very low carry-over (0.006%) even after high standard sample was demonstrated in the monolithic-phase based method. Other characteristics of such method include high recovery and good tolerance to matrix effect, which was demonstrated by 12 lots of plasma. The back pressure of the monolithic extraction cartridge remained the same after 450 samples injected. The performance of the monolithic-phased on-line extraction method was compared with that done by an automated 96-well liquid–liquid extraction procedure, which was carried out using hexane:ethyl acetate as the extraction solvent. The results showed that similar precision and accuracy were achieved by both methods.

Evaluation of online extraction/mass spectrometry for in vivo cassette analysis

An online extraction/mass spectrometry technique was evaluated for direct analysis of plasma samples. A simple user-friendly online extraction system that consists of two pumps, an autosampler, a six-port switching valve and a mass spectrometer is described. The system was controlled by the LC–MS software (Masslynx 3.5, Waters Corporation, Beverly, MA). Various analytical conditions such as extraction column, mobile phases, run time and wash solvent were optimized to establish an analytical method that was simple, easy to set up and generic. Sample preparation effort was minimal, which included dilution of plasma with water and centrifugation conducted in 96-well plate format. The system was used to analyze in vivo plasma samples from rat n-in-one cassette dosing studies. Concentration and pharmacokinetic (PK) data obtained from the online extraction method were comparable with data obtained from the protein precipitation extraction method. Overall, the simple, robust online extraction system provides cost savings by minimizing sample preparation and method development time. The system was used to analyze compounds from different structural classes. These studies suggest that calculated lipophilicity of a compound can be used as a tool for pre-selection of extraction column, which would save method development time for early discovery studies.

A Cost-Effective Screening Method for Pesticide Residue Analysis in Fruits, Vegetables, and Cereal Grains

This paper reports the results of studies performed to investigate the potential of applying thin layer chromatography (TLC) detection in combination with selected extraction and cleanup methods, for providing an alternative cost-effective analytical procedure for screening and confirmation of pesticide residues in plant commodities. The extraction was carried out with ethyl acetate and an on-line extraction method applying an acetone-dichloromethane mixture. The extracts were cleaned up with SX-3 gel, an adsorbent mixture of active carbon, magnesia, and diatomaceous earth, and on silica micro cartridges. The Rf values of 118 pesticides were tested in eleven elution systems with UV, and eight biotest methods and chemical detection reagents. Cabbage, green peas, orange, and tomatoes were selected as representative sample matrices for fruits and vegetables, while maize, rice, and wheat represented cereal grains. As an internal quality control measure, marker compounds were applied on each plate to verify the proper elution and detection conditions. The Rf values varied in the different elution systems. The best separation (widest Rf range) was achieved with silica gel (SG)—ethyl acetate (0.05–0.7), SG—benzene, (0.02–0.7) and reverse phase RP-18 F-254S layer with acetone: methanol: water/30:30:30 (v/v) (0.1–0.8). The relative standard deviation of Rf values (CVRf) within laboratory reproducibility was generally less than 20%, except below 0.2 Rf, where the CVRf rapidly increased with decreasing Rf values. The fungi spore inhibition, chloroplast inhibition, and enzyme inhibition were found most suitable for detection of pesticides primarily for confirming their identity or screening for known substances. Their use for determination of pesticide residues in samples of unknown origin is not recommended.

The investigation and the use of high flow column-switching LC/MS/MS as a high-throughput approach for direct plasma sample analysis of single and multiple components in pharmacokinetic studies

Recently direct plasma injection LC/MS/MS technique has been increasingly used in pharmaceutical research and development due to the demand for higher throughput of sample analyses. In this work, two on-line extraction methods including high flow LC/MS/MS and high flow column switching LC/MS/MS were investigated. The evaluations were conducted and focused on their performances with respect to peak responses, separation efficiency, and signal to-noise ratio in a multiple-component LC/MS/MS assay. Two HPLC pumps were used-with one for high flow delivery and one for gradient elution. A CTC autosampler was used to inject plasma samples. High flow LC was achieved by the use of 4 ml/min flow rate on a 1×50 mm Waters Oasis column. A 2×100 mm YMC column was coupled via a column-switching valve. The extracted analytes were analyzed in multiple-reaction-monitoring (MRM) mode using a triple quadrupole MS/MS. As a rapid and simple procedure, vortex-mixing plasma and internal standard directly in sample vials completed sample preparation. The high flow column switching method (two-column system) provided sharper peak shape than the conventional high flow method. This effect increased analyte signal-to-noise ratio and sensitivity. Narrower peak width resulted in much better separation efficiency, which was required for multiple compound ( N-in-1) analysis. A 2 mm I.D. column resulted in better peak shape and resolution than using a smaller I.D. column. The selected method achieved acceptable recoveries for most of the compounds tested, and it was successfully applied to a 10-in-1 pharmacokinetic (PK) study. The results showed that the dynamic range, lower limit of quantitation, assay accuracy and precision were acceptable for all compounds. Rapid sample preparation eliminated labor intensive and time consuming processes and improved productivity. This high throughput on-line extraction high flow column switching method has been proven particularly useful for multiple component analysis in PK studies.

Direct-injection HPLC assay for the determination of a new carbapenem antibiotic in human plasma and urine

Reversed-phase high-performance liquid chromatography (RP-HPLC) assays using ultraviolet (UV) absorbance detection have been developed for the determination of a new carbapenem antibiotic I in human plasma and urine. A column-switching technique is employed in the HPLC methods to perform on-line extraction and separation for each sample. Each plasma sample is thawed, centrifuged, stabilized, and then injected onto an in-line reversed-phase extraction column using a methanol (8%)/phosphate buffer, pH 6.5. After 3 min, the analytes are back-flushed off the extraction column with a mixture of acetonitrile (5.5%) and methanol (10%)/phosphate buffer (pH 6.5) for 3 min onto a BDS Hypersil 3 μm C18 (100×4.6 mm i.d.) analytical column. The sample preparation and HPLC conditions for the urine assay are similar to the plasma assay, except that a CN extraction column is used. Both assays are specific with respect to endogenous material and the major metabolite II, and both are linear over the concentration range of 0.25–50, and 2–200 μg/ml, respectively. The assays were successfully applied to a clinical dose-ranging study. One limitation of the on-line extraction method is that the extraction column needs to be replaced regularly every 100–150 plasma samples and every 200–300 urine samples. Subsequently, the urine method was modified to an ion-pair HPLC assay for the simultaneous determination of both the antibiotic I and its metabolite II.