Showing papers in "Analytical Chemistry in 1994"
TL;DR: A new approach to the identification of mass spectrometrically fragmented peptides is demonstrated and an algorithm developed here that uses the sequence tag to find the peptide in a sequence database is up to 1 million-fold more discriminating than the partial sequence information alone.
Abstract: We demonstrate a new approach to the identification of mass spectrometrically fragmented peptides. A fragmentation spectrum usually contains a short, easily identifiable series of sequence ions, which yields a partial sequence. This partial sequence divides the peptide into three parts-regions 1, 2, and 3-characterized by the added mass m1 of region 1, the partial sequence of region 2, and the added mass m3 of region 3. We call the construct, m1 partial sequence m3, a "peptide sequence tag" and show that it is a highly specific identifier of the peptide. An algorithm developed here that uses the sequence tag to find the peptide in a sequence database is up to 1 million-fold more discriminating than the partial sequence information alone. Peptides can be identified even in the presence of an unknown posttranslational modification or an amino acid substitution between an entry in the sequence database and the measured peptide. These concepts are demonstrated with model and practical examples of electrospray mass spectrometry/mass spectrometry of tryptic peptides. Just two to three amino acid residues derived by fragmentation are enough to identify these peptides. In peptide mapping applications, even less information is necessary.
1,492 citations
TL;DR: The analysis of aqueous H 2 O 2 at concentrations as low as 1 μM is conveniently done by the I 3 - method, which is based on the spectrophotometric determination of I 3, formed when H 2 o 2 is added to a concentrated solution of I -. At 351 nm, E max (I 3 - ) was measured to be 26 450 M -1 cm -1.
Abstract: The analysis of aqueous H 2 O 2 at concentrations as low as 1 μM is conveniently done by the I 3 - method, which is based on the spectrophotometric determination of I 3 - formed when H 2 O 2 is added to a concentrated solution of I - . At 351 nm, E max (I 3 - ) was measured to be 26 450 M -1 cm -1 . By contrast, an apparent value of 25 800 M -1 cm -1 was determined from a calibration of the I 3 - method against titration by permanganate. The difference could only be partially accounted for by the equilibrium between I 3 - , I 2 , and I -
802 citations
TL;DR: In this paper, a glass microchip column was fabricated for free-solution electrophoresis and two methods of sample introduction were evaluated employing a cross-type channel geometry.
Abstract: A glass microchip column was fabricated for free-solution electrophoresis. The channels were wet chemically etched on a substrate using standard photolithographic techniques and were sealed using a direct bonding technique. Two methods of sample introduction are evaluated employing a cross-type channel geometry. With the preferred sample loading method, the volume of the sample plug can be accurately controlled and is time independent, enabling a constant volume to be injected. The injection can be controlled electronically and does not induce any electrophoretic mobility based bias. Separations were performed on a compact chip with a serpentine column geometry that has a 165-mm separation channel in an area of less than 10 mm x 10 mm. Band-broadening effects in a serpentine column pattern were studied. 18 refs., 9 figs.
745 citations
TL;DR: Infrared multiphoton dissociation (IRMPD) of ionized proteins as large as carbonic anhydrase yields fragment information similar to, but with valuable additions to, that of other dissociation techniques.
Abstract: Characterization and verification of the structures of large biomolecules with high-resolution tandem Fourier transform mass spectrometry with electrospray ionization is critically dependent on the technique used to fragment the multiply charged ions produced. Infrared multiphoton dissociation (IRMPD) of ionized proteins as large as carbonic anhydrase (29 kDa) yields fragment information similar to, but with valuable additions to, that of other dissociation techniques. IRMPD yields product ions on-axis, providing efficient dissociation in further stages; MS3 of ubiquitin (8.6 kDa) yields 11 new sequence ions. Optimum irradiation times for protein ion dissociation vary by more than a factor of 6, with times for oligonucleotides far lower, possibly due to photon resonance with a P-O stretching frequency. IRMPD provides far greater selectivity than collisionally activated dissociation and also appears to yield much less mass discrimination and to dissociate much more stable ions. A technique to remove product ions on formation from the laser beam should improve the present efficiencies of 30-80%.
739 citations
TL;DR: In this paper, a membrane inlet mass spectrometer was modified to perform rapid, high-precision measurements of dissolved N 2, O 2, and Ar in water, and the instrument pumps water at <1 ML MIN -1 through semipermeable nucrobore silicone tubing positioned inside an inlet vacuum line of a quadrupole mass analyzer.
Abstract: A membrane inlet mass spectrometer was modified to perform rapid, high-precision measurements of dissolved N 2 , O 2 , and Ar in water. The instrument pumps water at <1 ML MIN -1 through semipermeable nucrobore silicone tubing positioned inside an inlet vacuum line of a quadrupole mass spectrometer. Precise pumping and temperature control of the water sample contribute to high signal stability and reproducibility. Dissolved gas concentrations are determined from intensities of the mass spectrometer signals in the multiple ion detection mode. Precision (coefficient of variation) is <0.5% for N 2 , O 2 , and Ar concentrations and <0.05% for N 2 /Ar and O 2 /Ar ratio data
709 citations
TL;DR: A simple new sample preparation procedure in which matrix and sample handling are completely decoupled is described, which could be used for protein analysis in particular.
Abstract: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF) is becoming a standard tool in mass spectrometry in general and protein analysis in particular. Its advantage include high sensitivity, tolerance to buffers, fast data acquisition, and simple and robust instrumentation. Diadvantages have been caused by factors related to sample preparation. Here we describe a simple new sample preparation procedure in which matrix and sample handling are completely decoupled
700 citations
TL;DR: In this article, three representative macrocyctic compounds were covalently linked to silica gel and evaluated by HPLC for their ability to resolve racemic mixtures as well as for their stability and loadability.
Abstract: There are a large number of antibiotic macrocycles which include several different structural types. Three representative macrocyctic compounds were covalently linked to silica gel and evaluated by HPLC for their ability to resolve racemic mixtures as well as for their stability and loadability. Over 70 compounds were resolved. In some cases separations were achieved that have not been reported on any other chiral stationary phase (CSP). These stationary phases appear to be multimodal in that they can be used in both the normal-phase and reversed-phase modes. Different compounds are resolved in each mode.
662 citations
625 citations
619 citations
TL;DR: In this paper, a glass microchip device for free solution electrophoresis was fabricated using standard photolithographic procedures and chemical wet etching, and separation was performed at several separation lengths from the injector to the detector with electric field strengths from 0.06 to 1.5 kV/cm.
Abstract: Fast, efficient separations are sought in liquid-phase analyses which incorporate a nondiscriminatory sample injection scheme and can implement a variety of detection modes. A glass microchip device for free solution electrophoresis was fabricated using standard photolithographic procedures and chemical wet etching. Separations were performed at several separation lengths from the injector to the detector with electric field strengths from 0.06 to 1.5 kV/cm. For a separation length of 0.9 mm, electrophoretic separations with baseline resolution are achieved in less than 150 ms with an electric field strength of 1.5 kV/cm and an efficiency of 1820 plates/s. For a separation length of 11.1 mm, a minimum plate height of 0.7 [mu]m and a maximum number of plates per second of 18,600 were achieved. 19 refs., 5 figs., 2 tabs.
590 citations
TL;DR: In this article, a solid phase microextraction (SPME) method based on poly(acrylate)coated fibers has been developed for the phenol regulated by U.S. EPA wastewater method 604 and 623 and Ontario MISA Group 20 regulations.
Abstract: In solid-phase microextraction (SPME), sorbent-coated silicafibers are used to extract analytes from aqueous or gaseous samples. After extraction, the fibers are directly transferred to the injector of a gas chromatograph, where the analytes are thermally desorbed and subsequently separated and quantified. This is a fast and simple analytical technique, which does not require solvents. An SPME method based on poly(acrylate)coated fibers has been developed for the phenol regulated by U.S. EPA wastewater method 604 and 623 and Ontario MISA Group 20 regulations. The method is capable of sub parts per billion detection limits of detection, and precision of 5-12 RSD, depending on the compound
TL;DR: An imprinted dispersion polymer capable of molecular recognition of pentamidine (PAM), a drug used for the treatment of AIDS-related pneumonia, was used in solid-phase extraction in order to selectively retain PAM from a dilute solution as mentioned in this paper.
Abstract: A new approach to sample enrichment and analyte determination is reported. An imprinted dispersion polymer capable of molecular recognition of pentamidine (PAM), a drug used for the treatment of AIDS-related pneumonia, was used in solid-phase extraction in order to selectively retain PAM from a dilute solution. At a physiological concentration (30 nM) this gave an enrichment factor of 54 using a PAM-selective polymer whereas the enrichment factor on a benzamidine- (BAM-) imprinted reference polymer was only 14. The high selectivity of the polymer allowed the drug to be detected directly in the desorption step, thus eliminating the need for a successive chromatographic analysis. In this way, PAM could be enriched and directly analyzed when present in low concentration in a urine sample
TL;DR: In this article, a capillary electrophoresis system with a sample injector has been integrated on a 1×2 cm planar glass chip by use of micromachining techniques.
Abstract: A capillary electrophoresis system with a sample injector has been integrated on a 1×2 cm planar glass chip by use of micromachining techniques. Separation of three amino acids was achieved in the device within 4 s. A maximum of 6800 theoretical plates was obtained with 470 V between injection and detection points. Electric fields of 2300 V/cm and power dissipation of 2.3 W/m did not result in Joule heating effects due to the thermal mass and conductivity of the glass chips. Leakage at channel intersection points was found to arise from convective as well as diffusion effects. Methods of device fabrication are presented
TL;DR: Glucose oxidase or lactate oxidase were immobilized in an osmium-based three-dimensional redox hydrogel that electrically connected the enzyme's redox centers to electrodes that correlated well with a substrate calibration in phosphate buffer.
Abstract: Glucose oxidase (GOX) or lactate oxidase (LOX) were immobilized in an osmium-based three-dimensional redox hydrogel that electrically connected the enzyme's redox centers to electrodes The enzyme "wiring" hydrogel was formed by cross-linking poly(1-vinylimidazole) (PVI) complexed with Os-(4,4'-dimethylbpy)2Cl (termed PVI15-dmeOs) with poly(ethylene glycol) diglycidyl ether (peg) Glucose and lactate sensors exhibited typical limiting current densities of 250 and 500 microA/cm2, respectively When the electrodes were poised at 200 mV (SCE), the currents resulting from electrooxidation of ascorbate, urate, acetaminophen, and L-cysteine were negligible When a Nafion film was employed, the linear range was extended from 6 to 30 mM glucose and from 4 to 7 mM lactate The redox potential of the gel-forming polymer was 95 mV (SCE) Glucose and lactate measurements performed in bovine calf serum correlated well with a substrate calibration in phosphate buffer
TL;DR: In this paper, an online method for S-isotope analysis is described, where samples are combusted in an elemental analyzer and SO 2 is separated from other combustion gases by gas chromatography, and the gases enter the ion source of the mass spectrometer through a split interface.
Abstract: An on-line method for S-isotope analysis is described. Samples are combusted in an elemental analyzer. SO 2 is separated from other combustion gases by gas chromatography, and the gases enter the ion source of the mass spectrometer through a split interface. Integrated peak areas for 32 SO 2 + and 34 O 2 + are compared to the response for a standard gas sample to determine the δ 34 S value. δ 34 S values of samples analyzed using the on-line method correspond linearly with those achieved from the same sample prepared off-line, where Kiba reduction followed by oxidation of the sulfur to SO 2 is carried out prior to S-isotope analysis against a known standard. With the described on-line method, the amount of sulfur necessary for S-isotope analysis is reduced to about 10 μg of S per analysis
TL;DR: In this paper, simple methods for using sub- and supercritical water for quantitative extraction of organics from environmental solids are presented, where the extraction temperature from 50 to 250[degree]C (subcritical water) and finally to 400[degree]-C (supercritical water if P > 221 bar) allowed class-selective extractions of polar organics (e.g., chlorinated phenols), low-polarity organics, and nonpolar organics(alkanes) to be performed.
Abstract: Low-polarity organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) typically have very low solubilities (e.g., ppb) in water at ambient conditions because of water's high polarity (dielectric constant, [epsilon] = 80). However, the dielectric constant can be drastically lowered by raising the temperature of the water under moderate pressure with dramatic increases (e.g., to percent levels) in the solubility of low-polarity organics. For example, subcritical water at 250[degree]C and 50 bar has [epsilon] = 27, which allowed quantitative extractions of PAHs in 15 min from soil and urban air particulates. Decreasing the polarity of water by sequentially raising the extraction temperature from 50 to 250[degree]C (subcritical water) and finally to 400[degree]C (supercritical water if P > 221 bar) allowed class-selective extractions of polar organics (e.g., chlorinated phenols), low-polarity organics (e.g., PAHs), and nonpolar organics (alkanes) to be performed. Simple methods for using sub- and supercritical water for quantitative extraction of organics from environmental solids are presented. 30 refs., 6 figs., 5 tabs.
TL;DR: A synthesized 20-mer DNA probe complementary to a part of an oncogene v-myc region having a mercaptohexyl group at the 5'-phosphate end was immobilized on a gold electrode by chemisorption resulting in a sequence-specific detection of the targeted DNA quantitatively ranging from 10(-7) to 10(-13) g/mL in a buffer solution.
Abstract: A synthesized 20-mer DNA probe complementary to a part of an oncogene v-myc region having a mercaptohexyl group at the 5'-phosphate end was immobilized on a gold electrode by chemisorption. The immobilized DNA was detected voltammetrically using Hoechst 33258 with a DNA minor groove binder and an electrochemically active dye. The modified electrode was immersed into a 100 mumol/L Hoechst 33258 solution and washed with a phosphate buffer (pH 7.0). The anodic peak current (ipa) of Hoechst 33258 on the modified electrode was higher than that on a bare gold electrode (128 and 75 nA, respectively). It was considered that Hoechst 33258 was concentrated on the electrode surface due to its association with DNA. When the modified electrode was hybridized in a solution of a model targeted gene (10(-7) g/mL), single-stranded pVM623 containing the PstI fragment of a 1.5-kilobase pair of oncogene v-myc, the ipa was 192 nA. On the other hand, the ipa was 128 nA when the modified electrode was reacted in a solution of single-stranded pUC119 without a region complementary to v-myc in pVM623. The ipa was related to the concentration of the targeted DNA in the hybridization reaction. The use of Hoechst 33258 resulted in a sequence-specific detection of the targeted DNA quantitatively ranging from 10(-7) to 10(-13) g/mL in a buffer solution.
TL;DR: In this paper, the influence of ionic sites on the behavior of charged carrier-based ion-selective liquid membrane electrodes is described by theory and experiments for cation- and for anionselective electrodes.
Abstract: The influence of ionic sites on the behavior of charged carrier-based ion-selective liquid membrane electrodes is described by theory and experiments for cation- and for anion-selective electrodes. The cation exchanger potassium tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate proved to be a beneficial additive for nitrite-selective electrodes. On the other hand, the anion exchanger tridodecylmethylammonium chloride improved the potentiometric properties of cation-selective electrodes. By the incorporation of a defined amount of these sites, the selectivity was enhanced, the emf functions became theoretical, the electrode resistance was lowered, and the long-term stability improved. The optimal molar ratio of additive to ionophore was in the range of 0.3-0.6 for the ionophores studied
TL;DR: DNA-modified electrodes modified by the inclusion of either octadecylamine or stearic acid were used as solid phases to which DNA was covalently bound to study hybridization with analyte poly(dA)4000, and results indicate slow (> or = 1 h) hybridization at low ionic strength and fast (< or = 10 min) hybridized at high ionicstrength.
Abstract: Carbon paste electrodes modified by the inclusion of either octadecylamine or stearic acid were used as solid phases to which DNA was covalently bound. Immobilized DNA was detected by voltammetry of solutions containing submillimolar quantities of Co(bpy)3(ClO4)3, Co(phen)3(ClO4)3, and Os(bpy)3-Cl2 (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline), all of which associate reversibly with immobilized DNA and yield increased peak currents at DNA-modified electrodes. Immobilization onto octadecylamine-modified electrodes was performed using a water-soluble carbodiimide, and at high DNA concentrations in the reaction mixture, it resulted in visible polymerization of DNA on the surface. Optimization of the deoxyguanosine- (dG-) selective immobilization reaction for stearic acid-modified electrodes, using water-soluble carbodiimide and N-hydroxysulfosuccinimide reagents to activate carboxylate groups on the surface, yielded conditions of 4.5% (w/w) stearic acid and 10 micrograms/mL DNA. Polythymidylic acid of 4000-base average length (poly(dT)4000) was immobilized at stearic acid-modified electrodes following enzymatic elongation with dG residues at the 3'-end. These DNA-modified electrodes were used to study hybridization with analyte poly(dA)4000 by in situ voltammetry of 60 microM Co(bpy)3(ClO4)3 at low ionic strength (20 mM NaCl), and by voltammetry of the same complex, following exposure of the electrode to poly(dA)4000 in a separate hybridization step conducted at high ionic strength (0.5 M NaCl). Results indicate slow (> or = 1 h) hybridization at low ionic strength and fast (< or = 10 min) hybridization at high ionic strength.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: A micromachined chemical analysis device based on capillary electrophoresis has been successfully used for very fast size separation of a synthetic mixture of fluorescent phosphorothioate oligonucleotides ranging from 10 to 25 bases in length.
Abstract: A micromachined chemical analysis device based on capillary electrophoresis has been successfully used for very fast size separation of a synthetic mixture of fluorescent phosphorothioate oligonucleotides ranging from 10 to 25 bases in length. The device consists of a channel system which has been formed in the surface of a glass plate by a standard photolithographical process. An integrated volume-defined sample injector allowed for unbiased electrokinetic introduction of sample plugs of 150-μm length (corresponding sample volume, 90 pL) into the separation channel. This well-defined injection procedure, in combination with the application of high electric fields of up to 2300 V/cm, resulted in size separation of single-stranded oligonucleotides in less than 45 s when a separation distance of 3.8 cm was used
TL;DR: In this article, a new class of composite electrodes made of sol-gel derived carbon-silica materials is introduced, which can exhibit hydrophobic or hydrophilic surface characteristics and can serve as an indicator (inert) electrode, as a potentiometric (selective or reference) electrode.
Abstract: A new class of composite electrodes made of sol-gel derived carbon-silica materials is introduced. Modifed porous composite carbon-silica electrodes can exhibit hydrophobic or hydrophilic surface characteristics and can serve as an indicator (inert) electrode, as a potentiometric (selective or reference) electrode, and in amperometric sensing and biosensing. The composite (carbon) ceramic electrodes (CCP) are rigid, porous, easily modified chemically and have a renewable external surface. The electrodes otter higher stability than carbon paste electrodes, and they are moreamenable to chemical modification than monolithic and (organic) composite carbon electrodes
TL;DR: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent "tag" for amino acids as mentioned in this paper.
Abstract: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent «tag» for amino acids. This miniaturized separation device was constructed using standard photolithographic, wet chemical etching, and bonding techniques. Effects of the reagent stream on separation efficiency were investigated. In addition, a novel gated injector was demonstrated which maintains the integrity of the analyte, buffer, and reagent streams
TL;DR: Kirchhoff's rules for resistive networks were found to predict the currents and fluid flow within the capillaries and application of potentials to the intersecting channels could fully arrest such leakage.
Abstract: Fluid flow was driven within a network of intersecting capillaries integrated on a glass chip using electroosmotic pumping. Potentials could be applied to several capillaries simultaneously to quantitatively control the amount of each reagent stream delivered to an intersection of capillaries. An example of a simple dilution of sample with buffer is shown. Kirchhoff's rules for resistive networks were found to predict the currents and fluid flow within the capillaries. Leakage of sample from one channel to another at an intersection was shown to arise from both diffusive and hydrodynamic effects. Application of potentials to the intersecting channels could fully arrest such leakage
TL;DR: In this paper, a triacontyl polymeric surface modification of a moderate pore size (approximately 20 nm), moderate surface area (approximately 200 m2/g) silica, without subsequent endcapping, was demonstrated for the separation of structurally similar carotenoid standards, an extract of a food matrix Standard Reference Material, and a beta-carotene dietary supplement under consideration as an agent for cancer intervention/prevention.
Abstract: A variety of bonded phase parameters (endcapping, phase chemistry, ligand length, and substrate parameters) were studied for their effect on column retention and selectivity toward carotenoids. Decisions were made on how each of these variables should be optimized based on the separation of carotenoid and polycyclic aromatic hydrocarbon test probes. A column was designed with the following properties: high absolute retention, enhanced shape recognition of structured solutes, and moderate silanol activity. These qualities were achieved by triacontyl (C30) polymeric surface modification of a moderate pore size (approximately 20 nm), moderate surface area (approximately 200 m2/g) silica, without subsequent endcapping. The effectiveness of this "carotenoid phase" was demonstrated for the separation of a mixture of structurally similar carotenoid standards, an extract of a food matrix Standard Reference Material, and a beta-carotene dietary supplement under consideration as an agent for cancer intervention/prevention.
TL;DR: In this article, a glass microchip having a channel with a cross section of 5.6 [m]m high and 66 [mu]m wide was fabricated using standard photolithographic and etching techniques and the surface of the channel was chemically modified with octadecylsilane to function as the stationary phase for open channel chromatography.
Abstract: A glass microchip having a channel with a cross section of 5.6 [mu]m high and 66 [mu]m wide was fabricated using standard photolithographic and etching techniques. The surface of the channel was chemically modified with octadecylsilane to function as the stationary phase for open channel chromatography. Electroosmotic flow was used to [open quotes]load[close quotes] the sample into the microchip and to [open quotes]pump[close quotes] the mobile phase during the experiments. For electric field strengths in the separation column from 27 to 163 V/cm, the linear velocity for the electroosmotic flow ranged from 0.13 to 0.78 mm/s. Detection was performed using direct fluorescence for separation monitoring and indirect fluorescence for void time measurements. Plate heights as low as 4.1 and 5.0 [mu]m were generated for unretained and retained components, respectively. 28 refs., 6 figs., 2 tabs.
TL;DR: In this article, a perturbational approach is used to relate velocity and attenuation responses to film translational and strain modes generated by the SAW, and two distinct regimes of film behavior arise, causing different SAW responses.
Abstract: The response of polymer-coated surface acoustic wave (SAW) devices to temperature changes and polymer vapor absorption is examined. A perturbational approach is used to relate velocity and attenuation responses to film translational and strain modes generated by the SAW. Two distinct regimes of film behavior arise, causing different SAW responses. For glassy films, displacement is nearly uniform across the film thickness, varying only in the direction of propagation. A model developed to predict velocity and attenuation in this regime (model 1), reduces to the familiar Tiersten (Wohltjen) equation for purely elastic films. For elastomeric (rubbery) films, inertial effects cause a phase lag to occur across the film for shear displacements. A model to account for these cross-film displacement gradients (model 2) predicts a characteristic resonant response when the film phase shift reaches n[pi]/2, where n is an odd integer. These model predictions are compared with measured responses from polyisobutylene-coated SAW devices as temperature is varied and during exposure to high vapor concentrations. 48 refs., 15 figs., 6 tabs.
TL;DR: In this paper, a glass microchip was constructed to perform chemical reactions and capillary electrophoresis sequentially, and the microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separation length.
Abstract: A glass microchip was constructed to perform chemical reactions and capillary electrophoresis sequentially. The channel manifold on the glass substrate was fabricated using standard photolithographic, etching, and deposition techniques. The microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separation length. Electrical control of the buffer, analyte, and reagent streams made possible the precise manipulation of the fluids within the channel manifold. The microchip was operated under a continuous reaction mode with gated injections to introduce the reaction product onto the separation column with high reproducibility (<1.8% rsd in peak area). The reaction and separation performances were evaluated by reacting amino acids with o-phthaldialdehyde to generate a fluorescent product which was detected by laser-induced fluorescence. Control of the reaction and separation conditions was sufficient to measure reaction kinetics and variation of detection limits with reaction time. Half-times of reaction of 5.1 and 6.2 s and detection limits of 0.55 and 0.83 fmol were measured for arginine and glycine, respectively. 18 refs., 10 figs.
TL;DR: In this paper, microwave assisted extraction of organic compounds from solid materials (or ''matrices») was evaluated as part of an ongoing evaluation of new sample preparation techniques by the U.S. Environmental Protection Agency (EPA), especially those that minimize waste solvents.
Abstract: As part of an ongoing evaluation of new sample preparation techniques by the U.S. Environmental Protection Agency (EPA), especially those that minimize waste solvents, microwave-assisted extraction (MAE) of organic compounds from solid materials (or «matrices») was evaluated. Six certified reference materials containing polynuclear aromatic hydrocarbons (PAHs) and a few base/neutral/acidic compounds, all of which are common pollutants of interest to the EPA, were subjected to MAE in a closed-vessel microwave system with hexane/acetone (1:1) at different temperatures (80, 115, and 145 o C) and for different periods of time (5, 10, and 20 min)
TL;DR: Polyvinyl alcohols (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins as mentioned in this paper.
Abstract: Poly(vinyl alcohols) (PVA) of a molecular weight of about 50 000 were applied to the modification of fused silica surfaces for the separation of large charged molecules such as proteins. Basic and acidic proteins could be separated in PVA-modified capillaries at highly optimized and analytically suitable performance with regard to efficiency, zone symmetry, and resolution. PVA can be used in the dynamic mode as an additive to the buffer medium or as a water-insoluble permanent coating on the fused silica surfaces which can be achieved by a simple procedure of thermal immobilization