Showing papers in "Analytical Chemistry in 1990"

New developments in biochemical mass spectrometry: electrospray ionization

Abstract: The principles, development, and recent application of electrospray ionization-mass spectrometry (ESI-MS) to biological compounds are reviewed. ESI-MS methods now allow determination of accurate molecular weights for proteins extending to over 50,000, and in some cases well over 100,000. Similar capabilities are being developed for oligonucleotides. The instrumentation used for ESI-MS is briefly described and it is shown that, although ionization efficiency appears to be uniformly high, detector sensitivity may be directly correlated with molecular weight. The use of tandem mass spectrometry (e.g., MS/MS) for extending collision-induced dissociation (CID) methods to the structural studies of large molecules is described. For example, effective CID of various albumin species (molecular weight approximately 66,000) can be obtained, far larger than obtainable for singly charged molecular ions. The combination of capillary electrophoresis, in both free solution zone electrophoresis and isotachophoresis formats, as well as microcolumn liquid chromatography with ESI-MS, provides the capability for on-line separation and analysis of subpicomole quantities of proteins. These and other new developments related to ESI-MS are illustrated by a range of examples. Fundamental considerations suggest even more impressive developments may be anticipated related to detection sensitivity and methods for obtaining structural information.

Cross-linked redox gels containing glucose oxidase for amperometric biosensor applications.

Abstract: Oxidoreductases, such as glucose oxidase, can be electrically wired to electrodes by electrostatic complexing or by covalent binding of redox polymers so that the electrons flow from the enzyme, through the polymer, to the electrode. We describe two materials for amperometric biosensors based on a cross-linkable poly(vinylpyridine) complex of (Os-(bpy){sub 2}Cl){sup +/2+} that communicates electrically with flavin adenine dinucleiotide redox centers of enzymes such as glucose oxidase. The uncomplexed pyridines of the poly(vinylpyridine) are quaternized with two types of groups, one promoting hydrophilicity (2-bromoethanol or 3-bromopropionic acid), the other containing an active ester (N-hydroxysuccinimide) that forms amide bonds with both lysines on the enzyme surface and with an added polyamine cross-linking agent (tri-ethylenetetraamine, trien). In the presence of glucose oxidase and trien this polymer forms rugged, cross-linked, electroactive films on the surface of electrodes, thereby eliminating the requirement for a membrane for containing the enzyme and redox couple. The glucose response time of the resulting electrodes is less than 10 s. The glucose response under N{sub 2} shows an apparent Michaelis constant, K{sub m}{prime} = 7.3 mM, and limiting current densities, j{sub max}, between 100 and 800 {mu}A/cm{sup 2}. Currents are decreased by 30-50% in air-saturated solutions because of competitionmore » between O{sub 2} and the Os(III) complex for electrons from the reduced enzyme. Rotating ring disk experiments in air-saturated solutions containing 10 mM glucose show that about 20% of the active enzyme is electrooxidized via the Os(III) complex, while the rest is oxidized by O{sub 2}. These results suggest that only part of the active enzyme is in electrical contact with the electrode.« less

Development and use of charged partial surface area structural descriptors in computer-assisted quantitative structure-property relationship studies

Abstract: Intermolecular interactions that are polar in nature contribute to observed physicochemical properties such as chromatographic retention and normal boiling point. However, these types of interactions are difficult to encode with structural parameters currentlyavailable for use in SPR studies. A new series of molecular structural parameters have been developed that combine molecular surface area and partial atomic charge information to form charged partial surface area (CPSA) descriptors

General least-squares smoothing and differentiation by the convolution (Savitzky-Golay) method

Abstract: The convolution approach to least-squares smoothing and differentiation is extended to remove the data truncation problem of the original Savitzky and Golay algorithm. A formalism based on the recursive properties of Gram polynomials provides a simple and direct means of calculating the convolution weights for all cases and thus enables a short but completely general routine to be written

Glucose fast-response amperometric sensor based on glucose oxidase immobilized in an electropolymerized poly(o-phenylenediamine) film

Abstract: o-Phenylenediamine has been used for glucose oxidase (GOx) immobilization on Pt electrodes by electrochemical polymerization at +0.65 V vs SCE. By this approach the enzyme is entrapped in a strongly adherent, highly reproducible thin membrane, whose thickness is around 10 nm. This one-step procedure produces a glucose sensor with a response time less than 1 s, an active enzyme loading higher than 3 units/cm2 of electrode surface, a high sensitivity, and a sufficiently wide linear range. The glucose response shows an apparent Michaelis-Menten constant, K'm = 14.2 mM, and a limiting current density, jmax of 181 microA/cm2. The product kD of partition and diffusion coefficients of glucose in the polymer film is on the order of 10(-13) cm2/s. Due to permselectivity characteristics of the membrane, the access of ascorbate, a common interfering species, to the electrode surface is blocked. To our knowledge, this represents the first report of a membrane capable, at the same time, of immobilizing GOx and rejecting ascorbate. The interesting electrode behavior can be rationalized by using an existing model predicting the amperometric response of an immobilized GOx system.

Ion Mobility Spectrometry

Abstract: Introduction to Ion Mobility Spectrometry Background Methods of Ion Mobility Spectrometry Emerging Patterns in the Development of Ion Mobility Methods Summary Comments History of Ion Mobility Spectrometry Introduction The Formative Years of Discovery (1895 to 1960) Ion Mobility Spectrometry for Chemical Measurements (1960 to 1990) Mobility Methods beyond Military and Security Venues (1990 to 2000) Commercial Production of Mobility-Based Analyzers (2000 to Present) The Society for Ion Mobility Spectrometry and Journal Sample Introduction Methods Introduction Vapor Samples Semi-volatile Samples Aqueous Samples Solid Samples Summary Ion Sources Introduction Radioactivity: Nickel, Americium, and Tritium Corona Discharges Photo-ionization: Discharge Lamps and Lasers Electrospray Ionization and Its Derivatives Matrix-Assisted Laser Desorption Ionization Surface Ionization Sources Flames Plasma-Based Ion Sources Glow Discharge Ion Source Other Ion Sources Summary Appendix Ion Injection and Pulsed Sources Introduction Operation and Structures of Ion Shutters Models and Modes of Operation Ion Injection to Drift Regions without Wire-Based Ion Shutters Mobility Methods with Continuous Flow of Ions into the Drift Region Summary and Conclusions Drift Tubes in Ion Mobility Spectrometry Introduction Traditional Drift Tubes with Stacked-Ring Designs High Field Asymmetric Drift Tubes Aspirator Drift Tubes Traveling Wave Drift Tubes Tandem Mobility Spectrometers Other Drift Tube Designs Selection of Materials Summary and Conclusions Ion Detectors Introduction Ambient Detection of Mobility-Separated Ions Low-Pressure Detection of Mobility-Separated Ions Summary The Ion Mobility Spectrum Introduction Mobility, Electric Field, and Pressure Ion Mobility Spectra IMS as a Separation Device Quantitative Aspects to Response Summary Ion Mobility-Mass Spectrometry Combining Mobility with Mass Low-Pressure Drift Tube Ion Mobility Spectrometry-Mass Spectrometry Atmospheric Pressure Drift Tube Ion Mobility Mass Spectrometry Differential Mobility Spectrometry-Mass Spectrometry Aspiration Ion Mobility Spectrometry-Mass Spectrometry Ion Mobility MS and the Future Ion Characterization and Separation: Mobility of Gas Phase Ions in Electric Fields Introduction Motion of Slow Ions in Gases Models for Ion-Neutral Interactions Linear Ion Mobility Spectrometers: Models and Experimental Evidence Differential Mobility Spectrometer and the Dependence of Ion Mobility on the Electric Field Strength Traveling Wave IMS Summary Control and Effects of Experimental Parameters Introduction Chemical Composition of the Support Gas Atmosphere Moisture and Temperature of the Supporting Gas Atmosphere Effects of Pressure Effects of Field Strength and Ion Residence Time Effects of Analyte Concentration Summary Detection of Explosives by IMS General Comments on Detection of Explosives The Chemistry Underlying Detection of Explosives by IMS Sampling and Pre-concentration Techniques for Detection of Explosives Measurement with Handheld Devices, Portable Instruments, and Portals Research and Operational Experience Walk-Through Portals and Systems for Luggage Screening Homemade and Alternate Explosives Standards for Calibration of Explosive Detectors Database for Explosives Chemical Weapons Introduction and General Comments on Detection of Chemical Warfare Agents The Ion Chemistry Underlying Detection of Chemical Weapons Sampling and Pre-concentration Techniques Research, Operational Experience, and Historical Perspective of Instrumentation State-of-the-Art Commercial Instruments, Standards, and Calibration Summary Drugs of Abuse Introduction and General Comments on Detection of Drugs The Ion Chemistry Underlying Detection of Drugs Sampling and Pre-concentration Techniques Research, Operational Experience, and Instrumentation Standards and Calibration Database for Drugs Pharmaceuticals Introduction Compound Identification Formulation Validation Cleaning Validation Reaction Monitoring Monitoring Biological Samples Summary and Conclusion Industrial Applications Introduction Industrial Processes Industrial Feedstock or Products Food Production Conclusions Environmental Monitoring Introduction Airborne Vapors Water Soil Conclusions Biological and Medical Applications of IMS Introduction and General Comments on Biological and Medical Applications Medical Diagnostics Using IMS Food Freshness, Molds, and Odor Detection Macromolecules: Biomolecules and Biopolymers Detection and Determination of Bacteria Other Biological Applications Conclusion Current Assessments and Future Developments in Ion Mobility Spectrometry State of the Science and Technology of IMS Next Generation in Ion Mobility Methods Directions for IMS Final Thoughts

Nuclear magnetic resonance spectroscopy.

Abstract: Fundamental Principles. L.W. Jelinsky, Experimental Methods. The Chemical Shift. Coupling of Nuclear Spins. Nuclear Relaxation and Chemical Rate Processes. P.A. Mirau and F.A. Bovey, Two-Dimensional Nuclear Magnetic Resonance Spectroscopy. Macromolecules. NMR of Solids. F.A. Bovey, L.W. Jelinsky, P.A. Mirau, Special Topics. Appendixes. Author Index. Subject Index.

Comparison of multivariate calibration methods for quantitative spectral analysis

Abstract: The quantitative prediction abilities of four multivariate calibration methods for spectral analyses are compared by using extensive Monte Carlo simulations. The calibration methods compared include inverse least-squares (ILS), classical least-squares (CLS), partial least-squares (PLS), and principal component regression (PCR) methods. ILS is a frequency-limited method while the latter three are capable of full-spectrum calibration. The simulations were performed assuming Beer's law holds and that spectral measurement errors and concentration errors associated with the reference method are normally distributed. Eight different factors that could affect the relative performance of the calibration methods were varied in a two-level, eight-factor experimental design in order to evaluate their effect on the prediction abilities of the four methods. It is found that each of the three full-spectrum methods has its range of superior performance. The frequency-limited ILS method was never the best method, although in the presence of relatively large concentration errors it sometimes yields comparable analysis precision to the full-spectrum methods for the major spectral component. The importance of each factor in the absolute and relative performances of the four methods is compared.

Nonlinear least-squares fitting of multivariate absorption data

Abstract: The introduction of fast scanning and diode-array spectrophotometers facilitates the acquisition of large series of absorption spectra as a function of reaction time (kinetics), elution time (chromatography), or added reagent (equilibrium investigations). It is important to develop appropriate programs that are able to handle the wealth of data and to extract all information. In this contribution a new application of factor analysis in a nonlinear least-squares fitting algorithm is presented

Automated instrumentation for comprehensive two-dimensional high-performance liquid chromatography of proteins

Abstract: A comprehensive two-dimensional (2-D) liquid chromatographic separation system is presented. The system uses a microbore cation exchange column, operated under gradient conditions, as the first dimension separation. Effluent from this first column alternately fills one of two loops on a computer-controlled eight-port valve. A second pump then forces loop material onto a second column, a size exclusion column. UV detection is used, and the system is applied to the separation of protein standards and serum proteins. The 2-D system has a higher resolving power and peak capacity than either of the two columns used alone. The entire first column effluent is analyzed on the second column in virtually the same time it takes to complete the first column separation, without the use of stopped flow methods. The entire system is automated and operated under computer control. Three-dimensional (3-D) data representation provides a means of viewing peak profiles in either separation dimension and contour mapping of the 3-D data provides a more reliable means of peak identification from run to run than that provided by single-column elution times.

High-accuracy molecular mass determination of proteins using matrix-assisted laser desorption mass spectrometry

Abstract: A method for obtaining protein molecular masses with an accuracy of approximately +/- 0.01% by matrix-assisted laser desorption using an internal calibrant is described. The technique allows accurate mass determinations of protein sample sizes as small as 1 pmol. High concentrations of organic and inorganic contaminants (e.g. 1 M urea) do not strongly affect either the signal intensity or the mass assignment. The ability to assign an accurate molecular mass to a protein is contingent on the observation of clearly resolved protonated molecule ions in the mass spectrum.

Electrophoretic separations of proteins in capillaries with hydrolytically stable surface structures.

Abstract: A procedure for obtaining highly stable coated capillaries for use in capillary electrophoresis (CE) is described. Reaction of surface-chlorinated fused silica capillaries with the Grignard reagent, vinyl magnesium bromide, followed by reaction of the vinyl group with acrylamide, results in an immobilized layer of polyacrylamide attached through hydrolytically stable Si-C bonds. This method is an extension of the capillary coating procedure described previously by Hjerten, differing in the means by which the polyacrylamide layer is bonded to the capillary walls. Capillaries treated in the manner described here can be used over a pH range of 2-10.5, without noticeable decomposition of the coating. In comparison to uncoated capillaries, separations of proteins using such coated capillaries are improved due to a reduction in protein adsorption to the capillary walls, although interaction is still present to some degree as evidenced by an inability to obtain plate counts as high as those predicted by theory. Electroosmotic flow is virtually eliminated in the coated capillaries, resulting in improved reproducibilities of protein migration times in comparison to uncoated capillaries. Additionally, peak skew is evaluated for model proteins and improvements are noted for the coated capillaries. Results are presented for separations of model protein mixtures, comparing the performance of the vinyl-bound polyacrylamide coated capillaries and uncoated capillaries at both high and low pH extremes.

Electrochemical behavior of reversible redox species at interdigitated array electrodes with different geometries: consideration of redox cycling and collection efficiency

Abstract: Des electrodes IDA avec differents parametres geometriques sont fabriques par lithographie et appliquees a des mesures de voltammerie cyclique et de chronoamperometrie d'especes redox

Investigations of the electrospray interface for liquid chromatography/mass spectrometry

Abstract: Factors affecting the yield of positive ions in the gas phase from electrosprayed methanol solutions of some inorganic ions and 30 organic onium ions BH + from nitrogen bases B are studied with an atmospheric pressure triple quadrupole mass spectrometer

Enzyme-linked immunosorbent assay compared with gas chromatography/mass spectrometry for the determination of triazine herbicides in water.

Abstract: An enzyme-linked immunosorbent assay (ELISA) was compared to a gas chromatography/mass spectrometry (GC/MS) procedure for the analysis of triazine herbicides and their metabolites in surface water and groundwater. Apparent recoveries from natural water and spiked water by both methods were comparable at 0.2-2 micrograms/L. Solid-phase extraction (SPE) was examined also, and recoveries were determined for a suite of triazine herbicides. A significant correlation was obtained between the ELISA and GC/MS method for natural water samples that were extracted by SPE. Because ELISA was developed with an atrazine-like compound as the hapten with conjugation at the 2-position, it was selective for triazines that contained both ethyl and isopropyl side chains. Concentrations for 50% inhibition (IC50) were as follows: atrazine, 0.4 microgram/L; ametryne, 0.45 microgram/L; prometryn and propazine, 0.5 microgram/L; prometon, 0.7 microgram/L; simazine and terbutryn, 2.5 micrograms/L; hydroxyatrazine, 28 micrograms/L; deethylatrazine and deisopropylatrazine, 30 micrograms/L; cyanazine, 40 micrograms/L; didealkylatrazine had no response. The combination of screening analysis by ELISA, which requires no sample preparation and works on 160 microL of sample, and confirmation by GC/MS was designed for rapid, inexpensive analysis of triazine herbicides in water.

High-speed separations of DNA sequencing reactions by capillary electrophoresis

Abstract: Fluorescently labeled DNA fragments generated in enzymatic sequencing reactions are rapidly separated by capillary gel electrophoresis and detected at attomole levels within the gel-filled capillary. The application of this technology to automated DNA sequence analysis may permit the development of a second generation automated sequencer capable of efficient and cost-effective sequence analysis on the genomic scale.

Applications of dioxetane chemiluminescent probes to molecular biology

Abstract: DNA probes and synthetic oligonucleotides in general present one of the key tools in modern molecular biology research and increasingly also in commercial applications. Along with the many applications that have been developed for and with DNA probes, faster and more sensitive detection methods are being developed. One of the most promising recent developments presents a method based on enzymatically triggered chemiluminescence. Details of this chemistry along with applications in molecular biology and immunology will be discussed and compared to conventional methods.

Effect of reducing disulfide-containing proteins on electrospray ionization mass spectra.

Abstract: Electrospray ionization produces multiply charged molecular ions for biomolecules with molecular weights in excess of 100,000. This allows mass spectrometers with limited mass-to-charge range to extend their molecular weight range by a factor equal to the number of charges. The maximum number of observed charges for peptides and smaller proteins correlates well with the number of basic amino acid residues (Arg, Lys, His), except for disulfide-containing molecules, such as lysozyme and bovine albumin. However, reduction of disulfide linkages with 1,4-dithiothreitol (Cleland's reagent) may allow the protein to be in an extended conformation and make "buried" basic residues available for protonation to yield higher charged molecular ions by the electrospray ionization process. For larger proteins reduction of disulfide bridges greatly increases the maximum charge state, but charging of basic amino acid residues remains less efficient than for smaller proteins.

Prediction of gas chromatography flame ionization detector response factors from molecular structures

Abstract: The prediction of flame ionization detector response factors as a function of molecular structure components is evaluated with modern capillary column gas chromatography equipment that included an on-column injector. The effect on the standard carbon content based response by electronegative atoms is analyzed for various functional groups. This study updates much earlier work that characterized the decrease in signal response by using average correction factors for each functional group. The effective carbon number concept based on naphthalene as the internal standard was used. For 56 compounds containing a single functional group, predictions based on these average responses reproduced the actual response to within 1.7% on average. This model was then extended to bifunctional groups with similar success for several molecules. The effects of changes in temperature programming and concentration were found to be minimal within the range studied.

Electrospray ionization combined with ion trap mass spectrometry

Abstract: Ions from a variety of molecules, formed via electrospray, have been injected into and analyzed with a quadrupole ion trap mass spectrometer. Examples are shown in which one or more stages of mass spectrometry (e.g., mass spectrometry/mass spectrometry) have been performed on both multiply charged anions and cations. Compounds for which data are described include the disodium salt of 2-hydroxynapthalene-3,6-disulfonic acid, Direct Red 81, bradykinin, melittin, cytochrome c, myoglobin, and bovine albumin. For some compounds, notable the sulfonates, evidence is presented for the injection of highly solvated ions that desolvate within the ion trap. The cations derived from the peptides, on the other hand, appear to be essentially desolvated prior to injection into the ion trap.

Capillary electrophoresis in 2 and 5 .mu.m diameter capillaries: application to cytoplasmic analysis

Abstract: Capillary electrophoresis with electrochemical detection in 2- and 5-micron capillaries has been developed to study ultrasmall biological environments. Sample volumes as low as 270 fL have been injected into the electrophoresis capillary with subattomole detection limits for easily oxidized species. We have applied this method to the analysis of single cell cytoplasm. Sampling of the cytoplasm is accomplished by inserting one end of the electrophoresis capillary directly into a single nerve cell. The high-voltage end of the electrophoresis capillary has been etched with hydrofluoric acid to form a microinjector. This injection scheme represents an improvement over those previously used for similar applications. The excellent selectivity of this method is demonstrated for catecholamine and indolamine neurotransmitters and their metabolites found in the invertebrate system, the pond snail Planorbis corneus.