Raimo Ketola - Academia.edu (original) (raw)

Papers by Raimo Ketola

Drug Testing and Analysis

Analytical and bioanalytical chemistry, 2016

A novel platform is introduced for simultaneous identification and quantification of new psychoac... more A novel platform is introduced for simultaneous identification and quantification of new psychoactive substances (NPS) in blood matrix, without the necessity of using authentic reference standards. The instrumentation consisted of gas chromatography (GC) coupled to nitrogen chemiluminescence detection (NCD) and atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (APCI-QTOFMS). In this concept, the GC flow is divided in appropriate proportions between NCD for single-calibrant quantification, utilizing the detector's equimolar response to nitrogen, and QTOFMS for accurate mass-based identification. The principle was proven by analyzing five NPS, bupropion, desoxypipradrol (2-DPMP), mephedrone, methylone, and naphyrone, in sheep blood. The samples were spiked with the analytes post-extraction to avoid recovery considerations at this point. All the NPS studies produced a protonated molecule in APCI resulting in predictable fragmentation with high mas...

Analytical and bioanalytical chemistry, 2017

Gas chromatography coupled to atmospheric pressure chemical ionization quadrupole time-of-flight ... more Gas chromatography coupled to atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (GC-APCI-QTOFMS) was evaluated for the identification of new psychoactive substances (NPS). An in-house high mass resolution GC-APCI-QTOFMS test library was developed for 29 nitrogen-containing drugs belonging mostly to synthetic stimulants. The library was based on 12 intra-day measurements of each compound at three different collision energies, 10, 20 and 40 eV. The in-house library mass spectra were compared to mass spectra from a commercial library constructed by liquid chromatography-electrospray ionization (LC-ESI) QTOFMS. The reversed library search scores between the in-house GC-APCI library and the commercial LC-ESI library were compared once a week during a 5-week period by using data measured by GC-APCI-QTOFMS. The protonated molecule was found for all drugs in the full scan mode, and the drugs were successfully identified by both libraries in the targeted MS...

Analytical Chemistry, Sep 1, 2007

Effective analytical performance of native, all-SU-8 separation microdevices is addressed by comp... more Effective analytical performance of native, all-SU-8 separation microdevices is addressed by comparing their performance to commercial glass microdevices in microchip zone electrophoresis accompanied by fluorescence detection. Surface chemistry and optical properties of SU-8 microdevices are also examined. SU-8 was shown to exhibit repeatable electroosmotic properties in a wide variety of buffers, and SU-8 microchannels were successfully utilized in peptide and protein analyses without any modification of the native polymer surface. Selected, fluorescent labeled, biologically active peptides were baseline resolved with migration time repeatability of 2.3-3.6% and plate numbers of 112 900-179 800 m-1. Addition of SDS (0.1%) or SU-8 developer (1.0%) to the separation buffer also enabled protein analysis by capillary zone electrophoresis. Plate heights of 2.4-5.9 µm were obtained for fluorescent labeled bovine serum albumin. In addition, detection sensitivity through SU-8 microchannels was similar to that through BoroFloat glass, when fluorescence illumination was provided at visible wavelengths higher than 500 nm. On the whole, the analytical performance of SU-8 microchips was very good and fairly comparable to that of commercial glass chips as well as that of traditional capillary electrophoresis and chromatographic methods. Moreover, lithography-based patterning of SU-8 enables straightforward integration of multiple functions on a single chip and favors fully microfabricated lab-on-a-chip systems. Miniaturization of analytical methods has been of enormously growing interest since electrophoretic separation on a glass chip was demonstrated in 1992. 1 Owing to the ease of electrokinetic

Chromatographia, Jan 8, 1995

A new analytical technique; purge-and-membraneelectron capture detection (ECD), is described and ... more A new analytical technique; purge-and-membraneelectron capture detection (ECD), is described and applied to the screening of halogenated aliphatic hydrocarbons. A water sample is first purged by helium and the purged compounds are collected from the gas phase through a silicone membrane to the analytical system. Purge-and-membrane-ECD provides very fast, selective and sensitive screening method for halogenated aliphatic hydrocarbons. The method was compared with conventional direct membrane extraction. Results obtained show that the limits of detection (0.01-2 lag L-1) were comparable with both methods. However, significant shorter response times were measured with purge-and-trap than with direct membrane extraction.

Jpc Journal of Planar Chromatography Modern Tlc, Mar 14, 2015

Steroids, Mar 1, 2007

Synthesis of reference standards is needed to determine the presence and function of steroid gluc... more Synthesis of reference standards is needed to determine the presence and function of steroid glucuronides in the brain or other tissues, because commercial sources of steroid glucuronide standards are limited or unavailable. In the present study porcine, rat, and bovine liver microsomes were tested to evaluate their ability to glucuronidate eight neurosteroids and neuroactive steroids of various types: dehydroepiandrosterone, pregnenolone, isopregnanolone, 5␣-tetrahydrodeoxycorticosterone, corticosterone, cortisol, ␤-estradiol, and testosterone. In general, the glucuronidation efficiency of rat liver was rather poor compared with that of bovine and porcine liver microsomes. Since porcine liver apparently has a relatively large amount of dehydrogenase, its microsomes also produced dehydrogenated steroids and their glucuronides, as well as various regioisomers in which the site of glucuronidation varied. In contrast, bovine liver microsomes produced mainly a single major glucuronidation product and few dehydrogenation products and gave the best overall yield for two-third of the steroids tested. The enzymatic synthesis of five glucuronides of four steroids was carried out and the conditions, purification, and analytical methods for the glucuronidation products were optimized. The steroid glucuronides synthesized were characterized by nuclear magnetic resonance spectroscopy (NMR) and liquid chromatography-mass spectrometry (LC-MS). The stereochemically pure steroid glucuronide conjugates were recovered in milligram amounts (yield 10-78%) and good purity (>85-90%), which is sufficient for LC-MS/MS method development and analyses of steroid glucuronides in biological matrices such as brain, urine, or plasma.

In order to understand better the chemistry of soil proteinaceous material, there is a need for a... more In order to understand better the chemistry of soil proteinaceous material, there is a need for an effective extraction and purification method for different types of soil. The aim of this study was to test the effectiveness of different extractants and of phenol extraction for the extraction and purification of native soil proteinaceous material and the added protein (bovine serum albumin, BSA) from different types of soil, and to test the applicability of matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) for the analysis of soil proteinaceous material. Extraction of three types of boreal soil was carried out with water or different buffers. Purification of the extracted proteinaceous material was carried out with phenol extraction, the concentration being measured using Bradford's method, and the analysis performed with MALDI-TOF-MS. The concentration of extracted proteinaceous material was dependent on the soil and the extractant, and the amount of N in the extracted material was ca. 3-90% of soil total N, being highest for sandy soil and lowest for highly organic forest floor and fine-textured clay soil. Non-purified extracts contained high amounts of non-proteinaceous (e.g. humic) material, especially the highly organic soil; this material may cause artifacts with Bradford's method. The recovery of BSA was dependent on soil and extractant, suggesting a different sorption mechanism for different types of soil. MALDI-TOF-MS spectra suggested that the molecular weight of the extracted compounds was mainly <10 kDa, but compounds in the range ca. 15-50 kDa were also detected. However, individual compounds could not be identified.

Analytica Chimica Acta, Sep 28, 2009

Neurosteroid glucuronides were found for the first time in brain samples. The intact glucuronides... more Neurosteroid glucuronides were found for the first time in brain samples. The intact glucuronides were extracted from the cortex, hippocampus, hypothalamus, and mid-brain tissues of nicotine- and water-treated mice, and detected with capillary liquid chromatography-electrospray-tandem mass spectrometry (CapLC-ESI-MS/MS). The glucuronides of estradiol, cortisol, corticosterone, tetrahydrodeoxycorticosterone, pregnenolone, and isopregnanolone were identified by comparing retention times in selected reaction monitoring (SRM) chromatograms and the relative abundances of two SRM transitions of each neurosteroid glucuronide between the reference and authentic samples, thus providing reliable identification. In vitro experiments, carried out by using S9 fractions from mouse and rat brains, showed a formation of glucuronides with selected test compounds (corticosterone, pregnenolone, and dehydroepiandrosterone), suggesting that biosynthesis of neurosteroid glucuronides is possible in rodent brain.

Current Drug Metabolism, Sep 1, 2010

Glucuronidation is one of the main phase II metabolic reactions in humans and animals. A variety ... more Glucuronidation is one of the main phase II metabolic reactions in humans and animals. A variety of analytical techniques and methods have been used for the detection and quantification of glucuronides of both endogenous and xenobiotic compounds from different biological samples of humans and animals. Drug metabolism has been extensively studied with both in vitro and in vivo experiments under various conditions. The purpose of this review is to explore in detail the benefits and drawbacks of different liquid chromatography-mass spectrometric (LC/MS) methods and techniques in detection and identification of all forms of glucuronide conjugates from in vitro, biological, and environmental samples. The entire analytical procedure is covered, from sample treatment, separation, and ionization to qualitative and quantitative analyses. The aim of this review is not to cover every published paper where glucuronides are identified and/or quantified, but rather to focus on special cases where a new analytical approach or technical development has led to a better, more specific, or more comprehensive detection, identification, or quantitation of glucuronide conjugates.

Journal of Mass Spectrometry, Apr 1, 2005

The suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DI... more The suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) for the identification of amphetamines and fentanyls in forensic samples was studied. With both ionization techniques, the mass spectra recorded showed abundant protonated molecules, and the background did not disturb the analysis. The use of tandem mass spectrometry (MS/MS) allowed unambiguous identification of the amphetamines and fentanyls. AP-DIOS-MS/MS and AP-MALDI-MS/MS were also successfully applied to the identification of authentic compounds from drug seizures. Common diluents and tablet materials did not disturb the analysis and compounds were unequivocally identified. The limits of detection (LODs) for amphetamines and fentanyls with AP-DIOS-MS/MS were 1-3 pmol, indicating excellent sensitivity of the method. The LODs with AP-MALDI-MS/MS were about 5-10 times higher.

Industrial Engineering Chemistry Research, Oct 2, 2008

The aim of this study was to evaluate the benefits of the simultaneous use of two different analy... more The aim of this study was to evaluate the benefits of the simultaneous use of two different analytical methods, namely Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS), for online analysis of environmental and process samples. A mathematical method ( ...

Sensors and Actuators B Chemical, Jun 16, 2008

A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fab... more A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fabricated, and characterized. The chip has three parts: a liquid sample introduction spot, a flow channel, and a sharp electrospray ionization tip. A regular micropillar array is micromachined inside the whole channel. The chip has no lid, which makes the sample application and chip fabrication easier. A two photomask level fabrication process utilizes nested masks of silicon dioxide and aluminum oxide. A combination of anisotropic and isotropic plasma etching steps allows formation of a truly three-dimensional electrospray ionization tip without double-sided lithography. The filling properties of the lidless micropillar channel are studied. Because of the capillary forces facilitated by the micropillar array, the sample applied onto the sample introduction spot spontaneously fills the whole flow channel including the electrospray ionization tip, without external pumping. Besides reliable self-filling, the chip offers stable electrospraying and high sensitivity chemical analysis when coupled to a mass spectrometer (MS).

Fresenius J Anal Chem, 1994

GC-Direct deposition-FTIR spectra of 55 nerve agent homologues and dialkyl methylphosphonates wer... more GC-Direct deposition-FTIR spectra of 55 nerve agent homologues and dialkyl methylphosphonates were analysed. Spectral features of these compounds are discussed. A method is proposed for identification of the alkyl and alkoxy groups of compounds belonging to sarin, tabun or dialkyl methylphosphonates families.

VTT Publications

Membrane inlet mass spectrometry (MIMS) is an established technique for the analysis of volatile ... more Membrane inlet mass spectrometry (MIMS) is an established technique for the analysis of volatile organic compounds in aqueous solutions and in air. A thin membrane is the only interface between a liquid or gaseous sample at atmospheric pressure and the vacuum of a mass spectrometer. Since its introduction about 35 years ago MIMS has been applied mainly in biochemistry and environmental analysis.

2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, 2011

ABSTRACT This paper presents a novel multi-tip electrospray ionization (ESI) platform design, whi... more ABSTRACT This paper presents a novel multi-tip electrospray ionization (ESI) platform design, which has 60 individual ESI tips. The unique feature of the design is that the tips are located at the periphery of a circular platform. The platform is fixed in front of a mass spectrometer (MS), on a computer controlled rotating table. After each MS measurement a new tip is aligned towards the MS by rotating the table electrically. Our platform design enables high throughput analyses. Sixty MS measurements were done in less than 12 minutes. The fabrication process of silicon-made platform is described in detail. We also demonstrate that a similar microchip could be made of polycarbonate using a high-throughput, low-cost injection compression molding process.

Journal of High Resolution Chromatography, 1997

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic co... more Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in the analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethylmethyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low pgh levels with the two gas chromatographic methods and clearly below pg/l level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.

Drug Testing and Analysis

Analytical and bioanalytical chemistry, 2016

A novel platform is introduced for simultaneous identification and quantification of new psychoac... more A novel platform is introduced for simultaneous identification and quantification of new psychoactive substances (NPS) in blood matrix, without the necessity of using authentic reference standards. The instrumentation consisted of gas chromatography (GC) coupled to nitrogen chemiluminescence detection (NCD) and atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (APCI-QTOFMS). In this concept, the GC flow is divided in appropriate proportions between NCD for single-calibrant quantification, utilizing the detector's equimolar response to nitrogen, and QTOFMS for accurate mass-based identification. The principle was proven by analyzing five NPS, bupropion, desoxypipradrol (2-DPMP), mephedrone, methylone, and naphyrone, in sheep blood. The samples were spiked with the analytes post-extraction to avoid recovery considerations at this point. All the NPS studies produced a protonated molecule in APCI resulting in predictable fragmentation with high mas...

Analytical and bioanalytical chemistry, 2017

Gas chromatography coupled to atmospheric pressure chemical ionization quadrupole time-of-flight ... more Gas chromatography coupled to atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (GC-APCI-QTOFMS) was evaluated for the identification of new psychoactive substances (NPS). An in-house high mass resolution GC-APCI-QTOFMS test library was developed for 29 nitrogen-containing drugs belonging mostly to synthetic stimulants. The library was based on 12 intra-day measurements of each compound at three different collision energies, 10, 20 and 40 eV. The in-house library mass spectra were compared to mass spectra from a commercial library constructed by liquid chromatography-electrospray ionization (LC-ESI) QTOFMS. The reversed library search scores between the in-house GC-APCI library and the commercial LC-ESI library were compared once a week during a 5-week period by using data measured by GC-APCI-QTOFMS. The protonated molecule was found for all drugs in the full scan mode, and the drugs were successfully identified by both libraries in the targeted MS...

Analytical Chemistry, Sep 1, 2007

Effective analytical performance of native, all-SU-8 separation microdevices is addressed by comp... more Effective analytical performance of native, all-SU-8 separation microdevices is addressed by comparing their performance to commercial glass microdevices in microchip zone electrophoresis accompanied by fluorescence detection. Surface chemistry and optical properties of SU-8 microdevices are also examined. SU-8 was shown to exhibit repeatable electroosmotic properties in a wide variety of buffers, and SU-8 microchannels were successfully utilized in peptide and protein analyses without any modification of the native polymer surface. Selected, fluorescent labeled, biologically active peptides were baseline resolved with migration time repeatability of 2.3-3.6% and plate numbers of 112 900-179 800 m-1. Addition of SDS (0.1%) or SU-8 developer (1.0%) to the separation buffer also enabled protein analysis by capillary zone electrophoresis. Plate heights of 2.4-5.9 µm were obtained for fluorescent labeled bovine serum albumin. In addition, detection sensitivity through SU-8 microchannels was similar to that through BoroFloat glass, when fluorescence illumination was provided at visible wavelengths higher than 500 nm. On the whole, the analytical performance of SU-8 microchips was very good and fairly comparable to that of commercial glass chips as well as that of traditional capillary electrophoresis and chromatographic methods. Moreover, lithography-based patterning of SU-8 enables straightforward integration of multiple functions on a single chip and favors fully microfabricated lab-on-a-chip systems. Miniaturization of analytical methods has been of enormously growing interest since electrophoretic separation on a glass chip was demonstrated in 1992. 1 Owing to the ease of electrokinetic

Chromatographia, Jan 8, 1995

A new analytical technique; purge-and-membraneelectron capture detection (ECD), is described and ... more A new analytical technique; purge-and-membraneelectron capture detection (ECD), is described and applied to the screening of halogenated aliphatic hydrocarbons. A water sample is first purged by helium and the purged compounds are collected from the gas phase through a silicone membrane to the analytical system. Purge-and-membrane-ECD provides very fast, selective and sensitive screening method for halogenated aliphatic hydrocarbons. The method was compared with conventional direct membrane extraction. Results obtained show that the limits of detection (0.01-2 lag L-1) were comparable with both methods. However, significant shorter response times were measured with purge-and-trap than with direct membrane extraction.

Jpc Journal of Planar Chromatography Modern Tlc, Mar 14, 2015

Steroids, Mar 1, 2007

Synthesis of reference standards is needed to determine the presence and function of steroid gluc... more Synthesis of reference standards is needed to determine the presence and function of steroid glucuronides in the brain or other tissues, because commercial sources of steroid glucuronide standards are limited or unavailable. In the present study porcine, rat, and bovine liver microsomes were tested to evaluate their ability to glucuronidate eight neurosteroids and neuroactive steroids of various types: dehydroepiandrosterone, pregnenolone, isopregnanolone, 5␣-tetrahydrodeoxycorticosterone, corticosterone, cortisol, ␤-estradiol, and testosterone. In general, the glucuronidation efficiency of rat liver was rather poor compared with that of bovine and porcine liver microsomes. Since porcine liver apparently has a relatively large amount of dehydrogenase, its microsomes also produced dehydrogenated steroids and their glucuronides, as well as various regioisomers in which the site of glucuronidation varied. In contrast, bovine liver microsomes produced mainly a single major glucuronidation product and few dehydrogenation products and gave the best overall yield for two-third of the steroids tested. The enzymatic synthesis of five glucuronides of four steroids was carried out and the conditions, purification, and analytical methods for the glucuronidation products were optimized. The steroid glucuronides synthesized were characterized by nuclear magnetic resonance spectroscopy (NMR) and liquid chromatography-mass spectrometry (LC-MS). The stereochemically pure steroid glucuronide conjugates were recovered in milligram amounts (yield 10-78%) and good purity (>85-90%), which is sufficient for LC-MS/MS method development and analyses of steroid glucuronides in biological matrices such as brain, urine, or plasma.

In order to understand better the chemistry of soil proteinaceous material, there is a need for a... more In order to understand better the chemistry of soil proteinaceous material, there is a need for an effective extraction and purification method for different types of soil. The aim of this study was to test the effectiveness of different extractants and of phenol extraction for the extraction and purification of native soil proteinaceous material and the added protein (bovine serum albumin, BSA) from different types of soil, and to test the applicability of matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) for the analysis of soil proteinaceous material. Extraction of three types of boreal soil was carried out with water or different buffers. Purification of the extracted proteinaceous material was carried out with phenol extraction, the concentration being measured using Bradford's method, and the analysis performed with MALDI-TOF-MS. The concentration of extracted proteinaceous material was dependent on the soil and the extractant, and the amount of N in the extracted material was ca. 3-90% of soil total N, being highest for sandy soil and lowest for highly organic forest floor and fine-textured clay soil. Non-purified extracts contained high amounts of non-proteinaceous (e.g. humic) material, especially the highly organic soil; this material may cause artifacts with Bradford's method. The recovery of BSA was dependent on soil and extractant, suggesting a different sorption mechanism for different types of soil. MALDI-TOF-MS spectra suggested that the molecular weight of the extracted compounds was mainly <10 kDa, but compounds in the range ca. 15-50 kDa were also detected. However, individual compounds could not be identified.

Analytica Chimica Acta, Sep 28, 2009

Neurosteroid glucuronides were found for the first time in brain samples. The intact glucuronides... more Neurosteroid glucuronides were found for the first time in brain samples. The intact glucuronides were extracted from the cortex, hippocampus, hypothalamus, and mid-brain tissues of nicotine- and water-treated mice, and detected with capillary liquid chromatography-electrospray-tandem mass spectrometry (CapLC-ESI-MS/MS). The glucuronides of estradiol, cortisol, corticosterone, tetrahydrodeoxycorticosterone, pregnenolone, and isopregnanolone were identified by comparing retention times in selected reaction monitoring (SRM) chromatograms and the relative abundances of two SRM transitions of each neurosteroid glucuronide between the reference and authentic samples, thus providing reliable identification. In vitro experiments, carried out by using S9 fractions from mouse and rat brains, showed a formation of glucuronides with selected test compounds (corticosterone, pregnenolone, and dehydroepiandrosterone), suggesting that biosynthesis of neurosteroid glucuronides is possible in rodent brain.

Current Drug Metabolism, Sep 1, 2010

Glucuronidation is one of the main phase II metabolic reactions in humans and animals. A variety ... more Glucuronidation is one of the main phase II metabolic reactions in humans and animals. A variety of analytical techniques and methods have been used for the detection and quantification of glucuronides of both endogenous and xenobiotic compounds from different biological samples of humans and animals. Drug metabolism has been extensively studied with both in vitro and in vivo experiments under various conditions. The purpose of this review is to explore in detail the benefits and drawbacks of different liquid chromatography-mass spectrometric (LC/MS) methods and techniques in detection and identification of all forms of glucuronide conjugates from in vitro, biological, and environmental samples. The entire analytical procedure is covered, from sample treatment, separation, and ionization to qualitative and quantitative analyses. The aim of this review is not to cover every published paper where glucuronides are identified and/or quantified, but rather to focus on special cases where a new analytical approach or technical development has led to a better, more specific, or more comprehensive detection, identification, or quantitation of glucuronide conjugates.

Journal of Mass Spectrometry, Apr 1, 2005

The suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DI... more The suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) for the identification of amphetamines and fentanyls in forensic samples was studied. With both ionization techniques, the mass spectra recorded showed abundant protonated molecules, and the background did not disturb the analysis. The use of tandem mass spectrometry (MS/MS) allowed unambiguous identification of the amphetamines and fentanyls. AP-DIOS-MS/MS and AP-MALDI-MS/MS were also successfully applied to the identification of authentic compounds from drug seizures. Common diluents and tablet materials did not disturb the analysis and compounds were unequivocally identified. The limits of detection (LODs) for amphetamines and fentanyls with AP-DIOS-MS/MS were 1-3 pmol, indicating excellent sensitivity of the method. The LODs with AP-MALDI-MS/MS were about 5-10 times higher.

Industrial Engineering Chemistry Research, Oct 2, 2008

The aim of this study was to evaluate the benefits of the simultaneous use of two different analy... more The aim of this study was to evaluate the benefits of the simultaneous use of two different analytical methods, namely Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS), for online analysis of environmental and process samples. A mathematical method ( ...

Sensors and Actuators B Chemical, Jun 16, 2008

A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fab... more A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fabricated, and characterized. The chip has three parts: a liquid sample introduction spot, a flow channel, and a sharp electrospray ionization tip. A regular micropillar array is micromachined inside the whole channel. The chip has no lid, which makes the sample application and chip fabrication easier. A two photomask level fabrication process utilizes nested masks of silicon dioxide and aluminum oxide. A combination of anisotropic and isotropic plasma etching steps allows formation of a truly three-dimensional electrospray ionization tip without double-sided lithography. The filling properties of the lidless micropillar channel are studied. Because of the capillary forces facilitated by the micropillar array, the sample applied onto the sample introduction spot spontaneously fills the whole flow channel including the electrospray ionization tip, without external pumping. Besides reliable self-filling, the chip offers stable electrospraying and high sensitivity chemical analysis when coupled to a mass spectrometer (MS).

Fresenius J Anal Chem, 1994

GC-Direct deposition-FTIR spectra of 55 nerve agent homologues and dialkyl methylphosphonates wer... more GC-Direct deposition-FTIR spectra of 55 nerve agent homologues and dialkyl methylphosphonates were analysed. Spectral features of these compounds are discussed. A method is proposed for identification of the alkyl and alkoxy groups of compounds belonging to sarin, tabun or dialkyl methylphosphonates families.

VTT Publications

Membrane inlet mass spectrometry (MIMS) is an established technique for the analysis of volatile ... more Membrane inlet mass spectrometry (MIMS) is an established technique for the analysis of volatile organic compounds in aqueous solutions and in air. A thin membrane is the only interface between a liquid or gaseous sample at atmospheric pressure and the vacuum of a mass spectrometer. Since its introduction about 35 years ago MIMS has been applied mainly in biochemistry and environmental analysis.

2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, 2011

ABSTRACT This paper presents a novel multi-tip electrospray ionization (ESI) platform design, whi... more ABSTRACT This paper presents a novel multi-tip electrospray ionization (ESI) platform design, which has 60 individual ESI tips. The unique feature of the design is that the tips are located at the periphery of a circular platform. The platform is fixed in front of a mass spectrometer (MS), on a computer controlled rotating table. After each MS measurement a new tip is aligned towards the MS by rotating the table electrically. Our platform design enables high throughput analyses. Sixty MS measurements were done in less than 12 minutes. The fabrication process of silicon-made platform is described in detail. We also demonstrate that a similar microchip could be made of polycarbonate using a high-throughput, low-cost injection compression molding process.

Journal of High Resolution Chromatography, 1997

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic co... more Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in the analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethylmethyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low pgh levels with the two gas chromatographic methods and clearly below pg/l level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.