Direct Plasma Injection Research Articles

High current carbon beam production with direct plasma injection scheme

We have been studying a new heavy-ion production technique called “direct plasma injection scheme,” DPIS, since 2000. A new radio frequency quadrupole (RFQ) designed especially for the DPIS was commissioned in 2004 and very intense carbon beam was successfully obtained, reaching more than 60mA accelerated current from the RFQ. Most of the contents of the accelerated beam was carbon 4+ as verified by beam analysis.

Analysis of laser-produced heavy ions for direct plasma injection scheme

To accelerate highly charged intense ion beam, we have developed the direct plasma injection scheme (DPIS) with laser ion source. In this scheme an ion beam from a laser ion source is injected directly to a radio frequency quadrupole (RFQ) linac without a low energy beam transport (LEBT) line and then beam losses in the LEBT can be avoided. We achieved high current acceleration of carbon ions (60mA) by DPIS with the RFQ specially designed for high current heavy ions. As the next step we will use heavier elements such as Al, Fe, and Ta as targets in laser ion source (using high power laser, for example, glass laser) for DPIS and will examine properties of laser-produced plasma for highly charged ion production.

Experimental results of DPIS with a new RFQ

We have developed a new heavy ion production system which uses a combination of an RFQ and a laser ion source. Induced plasma by a laser shot is delivered to the RFQ without an extraction electrode. We named this new idea ‘direct plasma injection scheme (DPIS)’. In 2004, a new RFQ was built for demonstrating the capability of the DPIS. After a few months of commissioning period, we could obtain more than 60 mA of carbon beam from the RFQ. This new scheme could be applied to cancer therapy facilities and high energy nuclear physics accelerator complexes.

On-Line Solid Phase Extraction Using the Prospekt-2 Coupled with a Liquid Chromatography/Tandem Mass Spectrometer for the Determination of Dextromethorphan, Dextrorphan and Guaifenesin in Human Plasma

An on-line liquid chromatography/tandem mass spectrometry (LC-MS/MS) procedure, using the Prospekt- 2 system, was developed and used for the determination of the levels of the active ingredients of cough/cold medications in human plasma matrix. The experimental configuration allows direct plasma injection by performing on- line solid phase extraction (SPE) on small cartridge columns prior to elution of the analyte(s) onto the analytical column and subsequent MS/MS detection. The quantitative analysis of three analytes with differing polarities, dextromethorphan (DEX), dextrorphan (DET) and guaifenesin (GG) in human plasma presented a significant challenge. Using stable-isotope-labeled internal standards for each analyte, the Prospekt-2 on-line methodology was evaluated for sensitivity, suppression, accuracy, precision, linearity, analyst time, analysis time, cost, carryover and ease of use. The lower limit of quantitation for the on-line SPE procedure for DEX, DET and GG was 0.05, 0.05 and 5.0 ng mL(-1), respectively, using a 0.1 mL sample volume. The linear range for DEX and DET was 0.05-50 ng mL(-1) and was 5-5,000 ng mL(-1) for GG. Accuracy and precision data for five different levels of QC samples were collected over three separate days. Accuracy ranged from 90% to 112% for all three analytes, while the precision, as measured by the %RSD, ranged from 1.5% to 16.0%

Quantitative bioanalysis: an integrated approach for drug discovery and development

An integrated approach to quantitative bioanalysis, incorporating turbulent flow chromatography (TFC) with mass spectrometric detection, was developed to support in-house drug discovery and development efforts. Activities such as metabolic stability screening and pharmacokinetic characterization support are carried out on a single unified platform. Two different TFC column-switching configurations, parallel and serial, are presented. The first, a parallel TFC column configuration, is capable of high-throughput analysis but carryover can reach as high as 0.24%. The characteristics of the instrument operating in the parallel configuration are provided for analysis of samples generated during in vitro metabolic stability assessments, a key screen during the lead optimization phase of drug discovery. Operating in this configuration, the system has the capability of performing on-line solid phase extraction and analysis of approximately 400 samples containing phosphate-buffered saline in approximately 14 h. The second, a serial TFC column configuration, was used to perform direct plasma injection analysis. The advantage of the serial configuration is the relatively low carryover (<0.040%) observed due to increased number of valve washes; however these extra washes lead to increased injection cycle times. A method developed using the serial TFC column configuration for the determination of dihydropyridines in plasma samples is given as an example. Analytical performance criteria examined during method development and validation included linearity, accuracy, precision, and recovery. The robustness of the technique was demonstrated by applying the method in the analysis of over 2500 plasma samples generated during preclinical drug development studies. Further, combined analysis of plasma and brain tissue was performed using acetonitrile precipitation as sample pretreatment for both matrices.

Direct injection HPLC micro method for the determination of voriconazole in plasma using an internal surface reversed-phase column.

A direct plasma injection liquid chromatographic method has been developed for the determination of a new triazole antifungal agent, voriconazole, using an internal surface reversed phase column. Therapeutic drug monitoring of voriconazole is relevant for patient management, especially in the case of drug-drug interaction. The method is easy to perform and requires 10 microL of a plasma sample. The chromatographic run time is less than 9 min using a mobile phase of 17:83 v/v acetonitrile-potassium dihydrogen phosphate buffer, 100 mM, pH 6.0 and UV detection at 255 nm. The fl ow rate was 1 microL/min. A linear response was observed over the concentration range 0.5-10 microg/mL (r2 = 0.977). A good accuracy (bias < or = 7.5%) was achieved for all quality controls, with intra-day and inter-day variation coefficients inferior to 6.7%. The lower limit of quantitation was 0.2 microg/mL, without interference of endogenous components. The stability of voriconazole in plasma stored at different temperatures was checked. Finally, the possibility of direct injection of plasma samples into the column permits a reduction in reagent consumption and in analytical steps, and hence in analytical error.

Enantiomeric determination of the plasma levels of omeprazole by direct plasma injection using high-performance liquid chromatography with achiral–chiral column-switching

A direct injection high-performance liquid chromatographic (HPLC) method, with column-switching, for the determination of omeprazole enantiomers in human plasma is described. A restricted access media (RAM) of bovine serum albumin (BSA) octyl column has been used in the first dimension for separation of the analyte from the biological matrix. The omeprazole enantiomers were eluted from the RAM column onto an amylose tris(3,5-dimethylphenylcarbamate) chiral column by the use of a column-switching valve and the enantioseparation was performed using acetonitrile–water (60:40 v/v) as eluent. The analytes were detected by their UV absorbance at 302 nm. The validated method was applied to the analysis of the plasma samples obtained from 10 Brazilian volunteers who received a 40 mg oral dose of racemic omeprazole and was able to quantify the enantiomers of omeprazole in the clinical samples analyzed. The assay was able to determine the cytochrome P450 2C19 phenotype of the subjects participating in this study.

Direct injection HPLC method for the determination of selected benzodiazepines in plasma using a Hisep column

A direct plasma injection HPLC method has been developed for the determination of selected benzodiazepines (nitrazepam, clobazam, oxazepam, lorazepam). The method uses an analytical hydrophobic shielded phase (Hisep) column equipped with a Hisep guard column, are easy to perform and requires 20 ul of a filtered plasma sample. The chromatographic run time is less than 15 min using a mobile phase of 15:85 v/v acetonitrile–0.18 M ammonium acetate pH 2.5. The method is good for 175 injections before replacement of the guard column. The method was linear in the range 0.5–18 ug ml −1 (r>0.99, n=6) for the analytes with R.S.D. less than 10.82%. Interday and intraday variability were found to be less than 14%. The limits of detection and quantitation were 0.16 (s/n>3) and 0.5 ug ml −1 (s/n>10), respectively, for each of the four benzodiazepines.

Direct injection HPLC method for the determination of selected phenothiazines in plasma using a Hisep column.

A direct plasma injection HPLC method has been developed for the determination of selected phenothiazines (promethazine, promazine, chlorpromazine) using a Hisep column. The method is easy to perform and requires 20 microL of a filtered plasma sample. The chromatographic run time is less than 11 min using a mobile phase of 15:85 v/v acetonitrile-0.18 m ammonium acetate pH 5.0 and UV detection at 254 nm. The method is linear in the concentration range 0.1-25 microg mL(-1) (r > 0.99, n = 6) for each analyte with RSD less than 6%. Interday and intraday variability were found to be < or =14%. The limits of detection and quantitation were 0.1 (S/N > 3) and 0.25 microg mL(-1) (S/N > 10), respectively, for each of the three phenothiazines. We can also apply this method to separate three other phenothiazines (ethopromazine, trifluoroperazine, prochlorperazine), although it lacks the selectivity to determine the concentration of all six drugs concurrently. The separation is feasible using these drugs in certain combinations.

Direct plasma analysis of drug compounds using monolithic column liquid chromatography and tandem mass spectrometry.

A monolithic silica column high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed for the high-speed direct simultaneous determination of a drug discovery compound and its major circulating metabolite (M-72) in rat plasma. This methodology makes use of flow programming and an alkyl-bonded silica rod column for fast macromolecule removal and chromatographic separation without the need for significant sample preparation. The matrix ionization suppression effect on the monolithic column HPLC-MS/MS system was investigated using the postcolumn infusion technique. After 200 plasma injections on a 50 x 4.6 mm monolithic silica column, consistent column efficiency of close to 39,000 theoretical plates/m and reproducible retention times for the analytes were observed. The apparent on-column recoveries of 12 test compounds in rat plasma samples were greater than 90%. The proposed fast direct plasma injection method was tested over a 3-day period with the interday coefficient of variation less than 15% for both analytes.

Development and validation of a direct plasma injection LC-MS method for YM087 and YM440 and metabolites in human plasma

A fully automated, direct plasma-injection technique using an LC coupled to a quadrupole mass spectrometric detector with an on-line, sample clean-up procedure for two new pharmaceutical products, YM087 and YM440, has been developed.

Column-switching high-performance liquid chromatographic analysis of carbamazepine and its principal metabolite in human plasma with direct sample injection using an alkyl-diol silica (ADS) precolumn

In this paper, the on-line coupling of solid-phase extraction, based on a restricted-access support with high-performance reverse phase chromatography for the analysis of carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-E) in human plasma samples is described. A precolumn packed with 25 μm C 18 alkyl-diol support is used for direct plasma injection. Using column-switching techniques, the analytes were enriched on the precolumn by a 5 mM phosphate buffer (pH 7) with 2% of methanol solution at a flow-rate of 0.8 ml min −1, while proteins and endogenous hydrophilic substances in plasma were washed off to waste. The enriched analytes were then back-flushed onto the analytical C 18 column, separated by a mixture of 10 mM phosphate buffer (pH 7) acetonitrile (70:30 v/v) solution at a flow-rate of 1.0 ml min −1 and detected by the ultraviolet absorbance set at 212 and 285 nm and without transfer loss. Linear calibration graphs were obtained for sample injection volumes of 50 (0.2–4.0 of μg of CBZ ml −1 and 0.1–5.0 μg of CBZ-E ml −1, respectively), and 20 μl (5.0–20.0 μg of CBZ ml −1); in either case the r-value was >0.9963. Recoveries from spiked plasma samples were quantitative for both analytes and the coefficients of variation were below 3.83%. The lowest samples concentrations that can be quantified with acceptable accuracy and precision was 0.2 μg CBZ ml −1 and 0.1 μg CBZ-E ml −1 when a sample volume of 50 μl was injected. Concentrations of 0.08 and 0.05 μg ml −1 of CBZ and CBZ-E were considered the limit of detection for a signal-to-noise ratio of 3. Furthermore, the developed column-switching method was successfully applied to the determination of CBZ and CBZ-E in plasma samples of patients submitted to CBZ therapy.

Semi-automated determination of plasma stability of drug discovery compounds using liquid chromatography–tandem mass spectrometry

A simple procedure for the measurement of stability of drug candidates in plasma was developed to eliminate the traditional labor-intensive and time-consuming sample preparation procedures that are typically used for these studies. The procedure makes use of a thermostatic autosampler as an incubator combined with the direct plasma injection method based on high-performance liquid chromatography (HPLC) coupled to tandem mass spectrometry (MS–MS). Untreated human, monkey, mouse and rat plasma containing the test compound was directly injected into a mixed-function column for on-line protein removal and chromatography. The test compound and its biotransformation product were separated via HPLC and monitored using the tandem mass spectrometer. The need for adequate chromatographic separation of the test compound (M) from its carboxylic acid metabolite (M+1) is demonstrated. Plasma samples from four different species at specified incubation temperatures were sequentially assayed in one analytical procedure. The injection-to-injection time was about 6 min. The peak responses of the test compound in individual plasma samples were repeatedly determined every 24 min. The retention times and peak shape of all analytes were found to be consistent throughout the experiments. The stability of the test compound in plasma was found to be a function of animal species, incubation time and temperature. The test compound was rapidly degraded in rat plasma at 37 °C, but it could be stabilized by adding sodium thiosulfate.

Scheme for direct plasma injection into an RFQ linac

A new efficient injection method from a laser ion source to a Radio Frequency Quadropole (RFQ) was proposed and is being tested in RIKEN, Japan. A laser plasma is induced just before the entrance of the RFQ and is injected directly into the RFQ channel. Using an existing RFQ, first verification tests have been completed successfully. Finally, the preliminary specifications for the first RFQ dedicated to the new injection scheme are presented.

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.

Measurement of the laser plasma properties of the direct plasma injection method to the RFQ LINAC on the RIKEN laser ion source

The laser plasma properties of the RIKEN laser ion source on the direct plasma injection system (DPIS) were measured for analysis of the DPIS beam dynamics. From the installed electrostatic analyzer and the measured calibration value from Ceratron to Faraday Cup, the current values and pulse time structure for each carbon charge state in the laser plasma were obtained.

Direct cocktail analysis of drug discovery compounds in pooled plasma samples using liquid chromatography–tandem mass spectrometry

Direct plasma injection technology coupled with a LC–MS/MS assay provides fast and straightforward method development and greatly reduces the time for the tedious sample preparation procedures. In this work, a simple and sensitive bioanalytical method based on direct plasma injection using a single column high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) was developed for direct cocktail analysis of double-pooled mouse plasma samples for the quantitative determination of small molecules. The overall goal was to improve the throughput of the rapid pharmacokinetic (PK) screening process for early drug discovery candidates. Each pooled plasma sample was diluted with working solution containing internal standard and then directly injected into a polymer-coated mixed-function column for sample clean-up, enrichment and chromatographic separation. The apparent on-column recovery of six drug candidates in mouse plasma samples was greater than 90%. The single HPLC column was linked to either an atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI) source as a part of MS/MS system. The total run cycle time using single column direct injection methods can be achieved within 4 min per sample. The analytical results obtained by the described direct injection methods were comparable with those obtained by semi-automated protein precipitation methods within ±15%. The advantages and challenges of using direct single column LC–MS/MS methods with two ionization sources in combination of sample pooling technique are discussed.

Acceleration of heavy ion beams by means of direct injection into RFQ Linac

A heavy ion source based on a new principle of direct plasma injection system was developed at Tokyo Institute of Technology. This heavy ion source combines directly a laser ion source and a radio frequency quadrupole (RFQ) LINAC. We carried out an acceleration test of carbon ions on this source and proved this principle. An observed total carbon beam current of 8 mA at 214 keV/u was observed. Beam analysis using a bending magnet downstream of the RFQ LINAC showed that accelerated beam includes 4.0 and 0.8 mA C4+ and C3+, respectively.

Determination of the plasma levels of metyrapone and its enantiomeric metyrapol metabolites by direct plasma injection and multidimensional achiral-chiral chromatography.

The development and validation of a direct injection high-performance liquid chromatographic (HPLC) method, with column switching, for the determination of metyrapol enantiomers and metyrapone in human plasma is described. The system used in this work was composed of a restricted access media (RAM) bovine serum albumin (BSA) octyl column coupled to an amylose tris(3,5-dimethoxyphenylcarbamate) chiral column. Water was used as eluent for the first 5 min at a flow rate of 1.0 ml/min for the elution of the plasma proteins and then acetonitrile-water (30:70 v/v) for the transfer and analysis of metyrapol enantiomers and metyrapone, which were detected by UV at lambda = 260 nm. The total analysis time was about 32 min. The calibration curves for each enantiomer and for the metyrapone were linear in the ranges 0.075-0.75 microg/ml and 0.150-1.50 microg/ml, respectively. Recoveries, intra- and interday precision and accuracy were determined using three quality controls, one low (0.18 microg/ml), one medium (0.75 microg/ml), and one high (1.35 microg/ml) plasma concentration. Quantitative recoveries and good precision and accuracy were obtained. The limit of quantitation were 0.045 microg/ml for both enantiomers and for the metyrapone.

A direct plasma injection system into an RFQ for clean and safe ion implantation

A new injection system, direct plasma injection system, was tested and its principle was proved successfully. We found that one of advantages of this injection system was efficient consumption of source materials. Large portions of induced ions can be injected into a first stage accelerator. This feature is quite useful for ion implantation applications, because toxic exhaust gas can be eliminated. In order to utilize this system for industrial application, the feasibility of a boron injection scheme using a Nd:YAG laser system was investigated.