Roderic Cole - Academia.edu (original) (raw)
Papers by Roderic Cole
Journal of Chromatography B: Biomedical Sciences and Applications, Dec 1, 1995
Hrc-journal of High Resolution Chromatography, Aug 1, 1990
Analytical Chemistry, Mar 3, 2000
Direct on-column surface-enhanced Raman spectroscopy (SERS) detection is demonstrated in capillar... more Direct on-column surface-enhanced Raman spectroscopy (SERS) detection is demonstrated in capillary electrophoresis (CE). Distinctive SERS spectra of two test compounds, riboflavin and Rhodamine 6G, are obtained in 100 µm i.d. fused-silica capillaries under CE conditions using running buffers that contain silver colloidal solutions. Detection is performed using an unmodified commercial Raman spectrometer in a confocal microscope mode of operation. The effects of laser power, wavelength, spectra acquisition time, silver colloidal concentration, and applied voltage (i.e., flow rate) on the quality of SERS spectra are evaluated. Using laser powers of 17 mW (at the sample) at 515 nm and employing 1 s spectral acquisition times, spectra with bands exhibiting signalto-noise ratios greater than 10 could be obtained for 1.0 × 10-6 M riboflavin and very low nanomolar concentrations of Rhodamine 6G. This was accomplished without optimization of silver colloidal solution compositions and by using a low-throughput spectrometer. Incorporation of the colloidal solutions into running buffers is shown to have little effect on the separation of the test compounds as monitored using a laser-induced fluorescence instrumental scheme. However, SERS spectra degrade if the capillary is not rinsed between experiments. Riboflavin and Rhodamine 6G spectra are obtained on-the-fly for actual CE separations. In the case of the latter solute, the injected quantity was approximately 90 amol.
Talanta, 1992
Micellar electrokinetic capillary chromatography (MECC) is applied to the high-speed analysis of ... more Micellar electrokinetic capillary chromatography (MECC) is applied to the high-speed analysis of aflatoxins. Baseline separation of the four common aflatoxins G(1), G(2), B(1) and B(2), is accomplished in less than 30 sec. Small (25 mum) internal diameter capillaries are found to be critical in maintaining high efficiency under rapid MECC separation conditions. Van Deemter-like plots are generated in order to study the effects of capillary diameter and organic solvent on efficiency under high electric field conditions. Other experimental parameters affecting efficiency are investigated, including buffer concentration, surfactant concentration, and detector time constant. Simple on-column laser-based fluorescence detection, employing helium-cadmium laser radiation at 325 nm for excitation, allows for limits of detection in the range of 0.05-0.9 femtomoles injected for underivatized aflatoxins. Considerations important in the analysis of aflatoxins in real matrices are presented.
Journal of Mass Spectrometry, 2012
The rapid and direct analysis of the amount and spatial distribution of exogenous chloroquine (CH... more The rapid and direct analysis of the amount and spatial distribution of exogenous chloroquine (CHQ) and CHQ metabolites from tissue sections by liquid extraction surface sampling analysis coupled with tandem mass spectrometry (LESA-MS/MS) was demonstrated. LESA-MS/MS results compared well with previously published CHQ quantification data collected by organ excision, extraction and fluorescent detection. The ability to directly sample and analyze spatially resolved exogenous molecules from tissue sections with minimal sample preparation and analytical method development has the potential to facilitate the assessment of target tissue penetration of pharmaceutical compounds, to establish pharmacokinetic/pharmacodynamic relationships, and to complement established pharmacokinetic methods used in the drug discovery process during tissue distribution assessment.
Xenobiotica; the fate of foreign compounds in biological systems, 2011
Tissue distribution studies of drug molecules play an essential role in the pharmaceutical indust... more Tissue distribution studies of drug molecules play an essential role in the pharmaceutical industry and are commonly undertaken using quantitative whole body autoradiography (QWBA) methods. The growing need for complementary methods to address some scientific gaps around radiography methods has led to increased use of mass spectrometric imaging (MSI) technology over the last 5 to 10 years. More recently, the development of novel mass spectrometric techniques for ambient surface sampling has redefined what can be regarded as "fit-for-purpose" for MSI in a drug metabolism and disposition arena. Together with a review of these novel alternatives, this paper details the use of two liquid microjunction (LMJ)-based mass spectrometric surface sampling technologies. These approaches are used to provide qualitative determination of parent drug in rat liver tissue slices using liquid extraction surface analysis (LESA) and to assess the performance of a LMJ surface sampling probe (LM...
There continues to be strong demand for improvements in sensitivity, selectivity, throughput, qua... more There continues to be strong demand for improvements in sensitivity, selectivity, throughput, qualitative content and many other performance characteristics of high performance liquid chromatography (HPLC). A major need is for methods that provide both universal detection and quantitative analysis. It is widely recognized that no single HPLC detector is capable of distinguishing all possible analytes from a given chromatographic eluent and the term "universal" is often used to describe detection of a diverse range of analytes. A primary goal for most analyses that seek universal detection is to obtain a consistent relationship between the magnitude of response and quantity injected for a range of analytes. This "consistency of response factors" allows the use of global mathematical relationships to estimate quantity (for example, use of parent drug response factor to quantify metabolites and degradants). This characteristic is useful in many applications, where it is impractical or impossible to use individual standards to calibrate the response for each analyte such as drug library QC, pharmaceutical impurity testing, complex lipid analyses and many applications requiring mass balance assessment. Currently, performing such an analysis is difficult with available technologies.
Capillary Electrophoresis, 1992
Journal of Medicinal Chemistry
Rapid Communications in Mass Spectrometry, 1997
Rapid Communications in Mass Spectrometry, 1998
ABSTRACT Extensive automation of both random and rational drug discovery strategies greatly incre... more ABSTRACT Extensive automation of both random and rational drug discovery strategies greatly increases the number of compounds entering biological screens. Although parallel synthesis (one compound per well) strategies eliminate the deconvolution step necessary when pooled libraries are screened, parallel synthesis products are usually screened as crude mixtures, because purification slows the process of lead discovery. Screening crude products is sometimes complicated by synergies and interferences between compounds. Screening pure compounds is the only sure route to immediate, reliable structure–activity relationships.Automated purification strategies are designed to limit or remove the purification bottleneck between synthesis and screening. In this paper, a workstation is described which uses a combination of UV absorbance and mass spectrometric data to make real-time decisions for HPLC fraction collection, allowing selection of compounds based on mass or substructure. This methodology has demonstrated success with parallel synthesis products in drug discovery applications. © 1998 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry, 2002
Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to p... more Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to preparative or semi-preparative high-performance liquid chromatography (HPLC) purification of combinatorial libraries, drug metabolites, and characterizable impurities. The sensitive mass spectrometer consumes only a small fraction of the analyte while providing online structure-specific detection, and its output can thus be used to trigger collection of the desired fraction. Coupling mass spectrometry to preparative HPLC is difficult due to the susceptibility of the detector to fouling under conditions of high analyte concentration or solute amount, or to changes in solvent composition. We report here on a device, the mass rate attenuator (MRA), which automatically produces split ratios over a range of 100:1 to 100 000:1 under programmable user control. The MRA is a flow-control device that periodically gates a small aliquot from one liquid stream into another. The design allows the user to set the frequency of the gating without interruption of the HPLC flow stream. The MRA also allows control of the volume of the aliquot that is transferred between the flow streams. This additional control, compared to passive splitting devices, facilitates optimization of the tubing connecting the separation, detection and collection events. We demonstrate that such optimization can reduce the volume of the collected fraction without compromising recovery, thus reducing the time spent in evaporating solvents to reclaim purified products. Copyright © 2002 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry, 2002
Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to p... more Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to preparative or semi-preparative high-performance liquid chromatography (HPLC) purification of combinatorial libraries, drug metabolites, and characterizable impurities. The sensitive mass spectrometer consumes only a small fraction of the analyte while providing online structure-specific detection, and its output can thus be used to trigger collection of the desired fraction. Coupling mass spectrometry to preparative HPLC is difficult due to the susceptibility of the detector to fouling under conditions of high analyte concentration or solute amount, or to changes in solvent composition. We report here on a device, the mass rate attenuator (MRA), which automatically produces split ratios over a range of 100:1 to 100 000:1 under programmable user control. The MRA is a flow-control device that periodically gates a small aliquot from one liquid stream into another. The design allows the user to set the frequency of the gating without interruption of the HPLC flow stream. The MRA also allows control of the volume of the aliquot that is transferred between the flow streams. This additional control, compared to passive splitting devices, facilitates optimization of the tubing connecting the separation, detection and collection events. We demonstrate that such optimization can reduce the volume of the collected fraction without compromising recovery, thus reducing the time spent in evaporating solvents to reclaim purified products. Copyright © 2002 John Wiley & Sons, Ltd.
Journal of Chromatography B: Biomedical Sciences and Applications, 1995
A simple and highly sensitive reversed-phase fluorimetric HPLC method for the quantitation of dro... more A simple and highly sensitive reversed-phase fluorimetric HPLC method for the quantitation of droloxifene from rat, monkey, and human plasma as well as human serum is described. This assay employs solid-phase extraction and has a dynamic range of 25 to 10 000 pg/ml. Sample extraction (efficiencies >86%) was accomplished using a benzenesulfonic acid (SCX) column with water and methanol rinses. Droloxifene and internal standard were eluted with 1 ml of 3.5% (v/v) ammonium hydroxide (30%) in methanol. Samples were quantitated using post-column UV-photochemical cyclization coupled with fluorimetric detection with excitation and emission wavelengths of 260 nm and 375 nm, respectively. Relative ease of sample extraction and short run times allow for the analysis of approximately 100 samples per day.
Journal of Chromatography B: Biomedical Sciences and Applications, 2000
A method for the analysis of the substance P antagonist ezlopitant and two active metabolites in ... more A method for the analysis of the substance P antagonist ezlopitant and two active metabolites in serum using solid-phase extraction followed by GC-MS analysis is described. The linear dynamic range was 1.0 to 100 ng / ml and precision and accuracy over this range were within 15%. Upon injection of reconstituted sample extracts into the hot injector port of the gas chromatograph, the benzyl alcohol metabolite undergoes a small amount of spontaneous dehydration to the alkene metabolite. We have incorporated an additional hexadeuterated internal standard of the benzyl alcohol into the assay to permit measurement of the extent of dehydration in each sample. This novel approach should be generally applicable to the simultaneous determination of benzyl alcohols and corresponding alkenes by GC-MS when the possibility exists that the alcohol can undergo spontaneous dehydration to the alkene in the injector port of GC instrumentation.
Journal of Chromatography B: Biomedical Sciences and Applications, 1995
An analytical method has been developed and validated for the quantitation of CP-88,059 in human ... more An analytical method has been developed and validated for the quantitation of CP-88,059 in human serum. The compound and internal standard were extracted from serum by solid-phase extraction with a weak cation-exchange phase. The analytes were resolved from endogenous interferences using narrow-bore (2.1 mm I.D.) C18 reversed-phase HPLC. Column effluent was monitored by UV absorbance detection at 215 nm. The standard curve range was 1 to 250 ng/ml. The accuracy and precision values for the method were within +/- 10% and +/- 15%, respectively. A four-fold detectability enhancement was achieved using a 2.1 mm I.D. HPLC column relative to the more common 4.6 mm I.D. column. A performance comparison was made between the 2.1 mm I.D. column used for validation and a 4.6 mm I.D. column with the same stationary phase.
Hrc-journal of High Resolution Chromatography, 1990
Journal of Chromatography B: Biomedical Sciences and Applications, Dec 1, 1995
Hrc-journal of High Resolution Chromatography, Aug 1, 1990
Analytical Chemistry, Mar 3, 2000
Direct on-column surface-enhanced Raman spectroscopy (SERS) detection is demonstrated in capillar... more Direct on-column surface-enhanced Raman spectroscopy (SERS) detection is demonstrated in capillary electrophoresis (CE). Distinctive SERS spectra of two test compounds, riboflavin and Rhodamine 6G, are obtained in 100 µm i.d. fused-silica capillaries under CE conditions using running buffers that contain silver colloidal solutions. Detection is performed using an unmodified commercial Raman spectrometer in a confocal microscope mode of operation. The effects of laser power, wavelength, spectra acquisition time, silver colloidal concentration, and applied voltage (i.e., flow rate) on the quality of SERS spectra are evaluated. Using laser powers of 17 mW (at the sample) at 515 nm and employing 1 s spectral acquisition times, spectra with bands exhibiting signalto-noise ratios greater than 10 could be obtained for 1.0 × 10-6 M riboflavin and very low nanomolar concentrations of Rhodamine 6G. This was accomplished without optimization of silver colloidal solution compositions and by using a low-throughput spectrometer. Incorporation of the colloidal solutions into running buffers is shown to have little effect on the separation of the test compounds as monitored using a laser-induced fluorescence instrumental scheme. However, SERS spectra degrade if the capillary is not rinsed between experiments. Riboflavin and Rhodamine 6G spectra are obtained on-the-fly for actual CE separations. In the case of the latter solute, the injected quantity was approximately 90 amol.
Talanta, 1992
Micellar electrokinetic capillary chromatography (MECC) is applied to the high-speed analysis of ... more Micellar electrokinetic capillary chromatography (MECC) is applied to the high-speed analysis of aflatoxins. Baseline separation of the four common aflatoxins G(1), G(2), B(1) and B(2), is accomplished in less than 30 sec. Small (25 mum) internal diameter capillaries are found to be critical in maintaining high efficiency under rapid MECC separation conditions. Van Deemter-like plots are generated in order to study the effects of capillary diameter and organic solvent on efficiency under high electric field conditions. Other experimental parameters affecting efficiency are investigated, including buffer concentration, surfactant concentration, and detector time constant. Simple on-column laser-based fluorescence detection, employing helium-cadmium laser radiation at 325 nm for excitation, allows for limits of detection in the range of 0.05-0.9 femtomoles injected for underivatized aflatoxins. Considerations important in the analysis of aflatoxins in real matrices are presented.
Journal of Mass Spectrometry, 2012
The rapid and direct analysis of the amount and spatial distribution of exogenous chloroquine (CH... more The rapid and direct analysis of the amount and spatial distribution of exogenous chloroquine (CHQ) and CHQ metabolites from tissue sections by liquid extraction surface sampling analysis coupled with tandem mass spectrometry (LESA-MS/MS) was demonstrated. LESA-MS/MS results compared well with previously published CHQ quantification data collected by organ excision, extraction and fluorescent detection. The ability to directly sample and analyze spatially resolved exogenous molecules from tissue sections with minimal sample preparation and analytical method development has the potential to facilitate the assessment of target tissue penetration of pharmaceutical compounds, to establish pharmacokinetic/pharmacodynamic relationships, and to complement established pharmacokinetic methods used in the drug discovery process during tissue distribution assessment.
Xenobiotica; the fate of foreign compounds in biological systems, 2011
Tissue distribution studies of drug molecules play an essential role in the pharmaceutical indust... more Tissue distribution studies of drug molecules play an essential role in the pharmaceutical industry and are commonly undertaken using quantitative whole body autoradiography (QWBA) methods. The growing need for complementary methods to address some scientific gaps around radiography methods has led to increased use of mass spectrometric imaging (MSI) technology over the last 5 to 10 years. More recently, the development of novel mass spectrometric techniques for ambient surface sampling has redefined what can be regarded as "fit-for-purpose" for MSI in a drug metabolism and disposition arena. Together with a review of these novel alternatives, this paper details the use of two liquid microjunction (LMJ)-based mass spectrometric surface sampling technologies. These approaches are used to provide qualitative determination of parent drug in rat liver tissue slices using liquid extraction surface analysis (LESA) and to assess the performance of a LMJ surface sampling probe (LM...
There continues to be strong demand for improvements in sensitivity, selectivity, throughput, qua... more There continues to be strong demand for improvements in sensitivity, selectivity, throughput, qualitative content and many other performance characteristics of high performance liquid chromatography (HPLC). A major need is for methods that provide both universal detection and quantitative analysis. It is widely recognized that no single HPLC detector is capable of distinguishing all possible analytes from a given chromatographic eluent and the term "universal" is often used to describe detection of a diverse range of analytes. A primary goal for most analyses that seek universal detection is to obtain a consistent relationship between the magnitude of response and quantity injected for a range of analytes. This "consistency of response factors" allows the use of global mathematical relationships to estimate quantity (for example, use of parent drug response factor to quantify metabolites and degradants). This characteristic is useful in many applications, where it is impractical or impossible to use individual standards to calibrate the response for each analyte such as drug library QC, pharmaceutical impurity testing, complex lipid analyses and many applications requiring mass balance assessment. Currently, performing such an analysis is difficult with available technologies.
Capillary Electrophoresis, 1992
Journal of Medicinal Chemistry
Rapid Communications in Mass Spectrometry, 1997
Rapid Communications in Mass Spectrometry, 1998
ABSTRACT Extensive automation of both random and rational drug discovery strategies greatly incre... more ABSTRACT Extensive automation of both random and rational drug discovery strategies greatly increases the number of compounds entering biological screens. Although parallel synthesis (one compound per well) strategies eliminate the deconvolution step necessary when pooled libraries are screened, parallel synthesis products are usually screened as crude mixtures, because purification slows the process of lead discovery. Screening crude products is sometimes complicated by synergies and interferences between compounds. Screening pure compounds is the only sure route to immediate, reliable structure–activity relationships.Automated purification strategies are designed to limit or remove the purification bottleneck between synthesis and screening. In this paper, a workstation is described which uses a combination of UV absorbance and mass spectrometric data to make real-time decisions for HPLC fraction collection, allowing selection of compounds based on mass or substructure. This methodology has demonstrated success with parallel synthesis products in drug discovery applications. © 1998 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry, 2002
Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to p... more Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to preparative or semi-preparative high-performance liquid chromatography (HPLC) purification of combinatorial libraries, drug metabolites, and characterizable impurities. The sensitive mass spectrometer consumes only a small fraction of the analyte while providing online structure-specific detection, and its output can thus be used to trigger collection of the desired fraction. Coupling mass spectrometry to preparative HPLC is difficult due to the susceptibility of the detector to fouling under conditions of high analyte concentration or solute amount, or to changes in solvent composition. We report here on a device, the mass rate attenuator (MRA), which automatically produces split ratios over a range of 100:1 to 100 000:1 under programmable user control. The MRA is a flow-control device that periodically gates a small aliquot from one liquid stream into another. The design allows the user to set the frequency of the gating without interruption of the HPLC flow stream. The MRA also allows control of the volume of the aliquot that is transferred between the flow streams. This additional control, compared to passive splitting devices, facilitates optimization of the tubing connecting the separation, detection and collection events. We demonstrate that such optimization can reduce the volume of the collected fraction without compromising recovery, thus reducing the time spent in evaporating solvents to reclaim purified products. Copyright © 2002 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry, 2002
Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to p... more Flow splitting to a mass spectrometer is a common way of coupling a highly specific detector to preparative or semi-preparative high-performance liquid chromatography (HPLC) purification of combinatorial libraries, drug metabolites, and characterizable impurities. The sensitive mass spectrometer consumes only a small fraction of the analyte while providing online structure-specific detection, and its output can thus be used to trigger collection of the desired fraction. Coupling mass spectrometry to preparative HPLC is difficult due to the susceptibility of the detector to fouling under conditions of high analyte concentration or solute amount, or to changes in solvent composition. We report here on a device, the mass rate attenuator (MRA), which automatically produces split ratios over a range of 100:1 to 100 000:1 under programmable user control. The MRA is a flow-control device that periodically gates a small aliquot from one liquid stream into another. The design allows the user to set the frequency of the gating without interruption of the HPLC flow stream. The MRA also allows control of the volume of the aliquot that is transferred between the flow streams. This additional control, compared to passive splitting devices, facilitates optimization of the tubing connecting the separation, detection and collection events. We demonstrate that such optimization can reduce the volume of the collected fraction without compromising recovery, thus reducing the time spent in evaporating solvents to reclaim purified products. Copyright © 2002 John Wiley & Sons, Ltd.
Journal of Chromatography B: Biomedical Sciences and Applications, 1995
A simple and highly sensitive reversed-phase fluorimetric HPLC method for the quantitation of dro... more A simple and highly sensitive reversed-phase fluorimetric HPLC method for the quantitation of droloxifene from rat, monkey, and human plasma as well as human serum is described. This assay employs solid-phase extraction and has a dynamic range of 25 to 10 000 pg/ml. Sample extraction (efficiencies >86%) was accomplished using a benzenesulfonic acid (SCX) column with water and methanol rinses. Droloxifene and internal standard were eluted with 1 ml of 3.5% (v/v) ammonium hydroxide (30%) in methanol. Samples were quantitated using post-column UV-photochemical cyclization coupled with fluorimetric detection with excitation and emission wavelengths of 260 nm and 375 nm, respectively. Relative ease of sample extraction and short run times allow for the analysis of approximately 100 samples per day.
Journal of Chromatography B: Biomedical Sciences and Applications, 2000
A method for the analysis of the substance P antagonist ezlopitant and two active metabolites in ... more A method for the analysis of the substance P antagonist ezlopitant and two active metabolites in serum using solid-phase extraction followed by GC-MS analysis is described. The linear dynamic range was 1.0 to 100 ng / ml and precision and accuracy over this range were within 15%. Upon injection of reconstituted sample extracts into the hot injector port of the gas chromatograph, the benzyl alcohol metabolite undergoes a small amount of spontaneous dehydration to the alkene metabolite. We have incorporated an additional hexadeuterated internal standard of the benzyl alcohol into the assay to permit measurement of the extent of dehydration in each sample. This novel approach should be generally applicable to the simultaneous determination of benzyl alcohols and corresponding alkenes by GC-MS when the possibility exists that the alcohol can undergo spontaneous dehydration to the alkene in the injector port of GC instrumentation.
Journal of Chromatography B: Biomedical Sciences and Applications, 1995
An analytical method has been developed and validated for the quantitation of CP-88,059 in human ... more An analytical method has been developed and validated for the quantitation of CP-88,059 in human serum. The compound and internal standard were extracted from serum by solid-phase extraction with a weak cation-exchange phase. The analytes were resolved from endogenous interferences using narrow-bore (2.1 mm I.D.) C18 reversed-phase HPLC. Column effluent was monitored by UV absorbance detection at 215 nm. The standard curve range was 1 to 250 ng/ml. The accuracy and precision values for the method were within +/- 10% and +/- 15%, respectively. A four-fold detectability enhancement was achieved using a 2.1 mm I.D. HPLC column relative to the more common 4.6 mm I.D. column. A performance comparison was made between the 2.1 mm I.D. column used for validation and a 4.6 mm I.D. column with the same stationary phase.
Hrc-journal of High Resolution Chromatography, 1990