In
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In AC Research contains brief introduciions to the research articles appearing in the September 1 issue of Analytical Chemistry plus a partial listing of articles tentatively scheduled for the September 15 issue. A free updated table of contents is available on the 1st and 15th of every month on the Web (http://pubs.acs.org/ac).
Accelerated Articles Microchip with a tip When doing electrospray ionization-MS from microchips, spraying from the edges of chips can lead to stability and sensitivity problems, and sample delivery can be cumbersome when using hydraulic pumping. To address these problems, J. Michael Ramsey and colleagues at Oak Ridge National Laboratory and Caliper Technologies instead attach a nanoelectrospray tip to the microchip. When a vollage is applled to a fluid reservoir on the chip, the tip draws the fluid through the microchip channel. With time-of-flight MS analysis, the device can produce a spectrum from 340 zeptomoles of a 100-nM solution of gramacidin S in only 10 ms. Additional channels for injection of multiple samples and separation also can be included. ("Subattomole-Sensitivity Microchip Nanoelectrospray Source with Time-of-Flight Mass Spectrometry Detection"; 10.1021/ac990373m; p 3627) Multichannel QCM Tetsu Tatsuma and co-workers at the Tokyo University of Agriculture and Technology and Meidensha Corp. (both in Japan) describe arrays of resonators fabricated on a single quartz wafer, which are being used as a multichannel quartz crystal microbalance (MQCM). Three types of four-channel arrays are tested. Because the mechanical oscillation of each channel is almost completely trapped in the channel, the interference between the channels is negligible. The MQCM could be used as a sensor array for multicomponent analysis or for mass mapping. ("Multichannel Quartz Crystal Microbalance"; 10.1021/ac9904260; p 3632)
LC/MS for nucleic acids Detection and characterization of nucleic acids using MS are plagued by difficulties arising from the acids' polyanionic nature and ability to form stable adducts with cations. Christian G. Huber and Alexander Krajete of Leopold-FranzensUniversity (Austria) tackle this problem with a new nucleic acid detection method based on ion-pair reversed-phase HPLC/negative-ion electrospray ionization MS, with capillary columns packed with micropellicular, octadecylated poly(styrene/divinylbenzene) particles. High-quality, fullscan mass spectra, which show little cation adduction, are acquired and used to calculate the molecular masses of separated oligonucleotides with an accuracy of 0.011%. At full scan, the
Determining end groups of synthetic polymers Polymer synthesis is becoming more sophisticated, and attempts are being made to design macromolecules for specific applications. Peter J. Derrick and co-workers at the University of Warwick (U.K.) describe collision-induced dissociation (CID) experiments using poly(ethylene glycol)s with butanoyl, benzoyl, and acetyl end groups performed with a hybrid magnetic-sector/time-of-flight instrument. High-energy (>8 keV) CID allows unambiguous end group determination and provides information about repeat units. ("Determination of End Groups of Synthetic Polymers by Matrix-Assisted Laser Desorption/Ionization: High-Energy Collision-Induced Dissociation"; 10.1021/ ac990523t; p 3637) Polishing marks on silica • Peak tailing in reversed-phase separations of organic cations is extremely difficult to solve because it often varies from one batch of silica gel to the next, even when the same procedure is used to manufacture the gel. Mary J. Wirth and co-workers at the University of Delaware use fluorescence microscopy and atomic force microscopy to investigate potential sources of peak tailing. They examine the overall patterns of strong adsorption of a cationic fluorescent dye at the interface between fused silica and water or acetonitrile,findingstrong adsorption sites at particular lines and spots rather than homogeneously distributed lines and spots. ("Spectroscopic Observation of Adsorption to Active Silanols"; 10.1021/ac990382V)
detection limits for a oligodeoxythymidine 16-mer are 104 fmol. ("Analysis of Nucleic Acids by Capiilary Ion-Pair ReversedPhase HPLC Coupled to Negative-Ion Electrospray Ionization Mass Spectrometry"; 10.1021/ac990378j; p 3730) Oligosaccharide library The lack of a rapid method for elucidating the structure of oligosaccharides is a major barrier to understanding the structurefunction relationships for these compounds. Carlito B. Lebrilla and co-workers at the University of California-Davis propose an approach to structural elucidation based on the construction of a catalog of substructural motifs, identified and characterized by collision-induced dissociation MS, which can be used to build the total structure of an unknown compound. This approach allows the elucidation of sequence, linkage, and even
ACS and other publishers have adopted the Digital Object Identifier (DO!) as a unique identifier for articles in print and on the Web. For Analytical Chemistry, the DOI consists of 10.1021/ followed by the manuscript number. DOIs can be found on the first page of publlshed articles and with In AC Research citations. More information on the DOI is available at http://www.doi.org. Please use the DOI when orderrng documents. • Denotes articles tentatively scheduled for the September 15 issue
Analytical Chemistry News & Features, September 1, 1999 577 A
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stereochemistry for picomolar levels of oligosaccharides. ("Catalog-Library Approach for the Rapid and Sensitive Structural Elucidation of Oligosaccharides"; 10.1021/ac990095r; p 3747)
in aortic and pulmonary artery perfusates from a working mouse heart. ("In Situ Fiber-Optic Oxygen Consumption Measurements from a Working Mouse Heart"; 10.1021/ ac9903003; p 3887)
Human milk sugars by MALDI MS Although the biological function of human milk oligosaccharides is not yet known, there is some evidence that the oligosaccharides may protect breast-fed infants by preventing the interaction of pathogens with epithelial cells. Knowledge of the structure of these oligosaccharides is crucial to understanding their function. Berndt Finke and co-workers at Milupa, Universitat Frankfurt, and Universitat Giessen (all in Germany) describe a strategy for the separation of acidic and neutral highmolecular-weight oligosaccharides from pooled human milk samples using gel filtration. Analysis by MALDI MS reveals acidic oligosaccharides containing up to 20 monomers in the mass range 2094-3626 Da. Neutral structures containing up to 35 monosaccharides are also identified. ("Analysis of High-Molecular-Weight Oligosaccharides from Human Milk by Liquid Chromatography and MALDI-MS"; 10.1021/ac990094z; p 3755)
Profiling induced proteins David M. Lubman and colleagues at the University of Michigan and Michigan State University describe a method for rapid profiling of water-soluble proteins from whole cell lysates of E. coll using MALDI-TOF and reversed-phase HPLC. Two columns in series at different temperatures are used to provide high loadability without losing separation efficiency. Eluting fractions are collected and analyzed to determine the molecular weights and peptide maps of the proteins. ("Rapid Profiling of Induced Proteins in Bacteria Using MALDI-TOF Mass Spectrometric Detection of Nonporous RP HPLC-Separated Whole Cell Lysates"; 10.1021/ac990120t;p3894)
HSA binding sites Human serum albumin (HSA) is an important protein for the binding and transport of many low-molecular-weight compounds in blood. Compounds are believed to bind to HSA at two well-defined sites; however, minor sites may also take part in the binding of certain drugs. David S. Hage and Arundhati Sengupta of the University of Nebraska look for these other binding regions using immobilized HSA columns and highperformance affinity chromatography. ("Characterization of Minor Site Probes for Human Serum Albumin by High-Performance Affinity Chromatography"; 10.1021/ac9903499; p 3821) Array biosensor Immunosensors are designed as portable instruments that can be used quickly, easily, and sensitively by untrained personnel. Frances S. Ligler and co-workers at the Naval Research Laboratory, Geo-Centers, and Georgetown University describe a biosensor in which antigen-specific "capture" antibodies are immobilized in an array on the surface of a planar waveguide, and the bound analyte is detected using fluorescence tracer antibodies. The array sensor is used to analyze 126 blind samples for 3 classes of analytes; it could detect viral, bacterial, and protein analytes using a 14-min assay, with sensitivity approaching that of standard ELISA methods. ("Array Biosensor for Simultaneous Identification of Bacterial, Viral, and Protein Analytes"; 10.1021/ac981425v; p 3846) In situ oxygen sensor Arterial blood oxygen content analysis is the only reliable way to confirm the delivery of proper oxygen supply to tissue. Paul Pantano and co-workers at the University of Texas-Dallas and the University of Texas Southwestern Medical Center introduce a new approach using luminescence-based imaging-fiber oxygen sensors for in situ measurement of oxygen consumption. The imaging fibers are fabricated using a technically expedient, photoinitiated polymerization, which precisely immobilizes an oxygen-sensitive polymer matrix on the fiber's distal face. The system successfully measured oxygen concentrations 578 A
Analytical Chemistry News & Features, September 1, 1999
Anabolic steroids by LC/MS • Although the use of anabolic steroids as growth promoters is prohibited, they may still be used illegally. Therefore, a suitable detection technique is required. P. E. Joos and M. Van Rycheghem of SGS Depauw & Stokoe (Belgium) describe a method for determining 36 anabolic steroids in kidney fat using atmospheric pressure chemical ionization LC/MS/MS, with preparative HPLC as a precleaning step. Detection limits are 200 ° C are often desired for digesting organic materials with nitric acid, but the Teflon tubes used in microwave-assistedflowdigestion systems cannot withstand the resulting pressure, which can get as high as 35 bar. Gtinther Knapp and colleagues at the Technical University Graz (Austria) and Joanneum Research (Austria) describe a novel pressure equilibration system for a high-pressure flow digestion device that handles these high temperatures. The system is demonstrated with the digestion of increasingly difficult oxidizable substances and standard reference materials, yielding results in good agreement with certified values. ("Microwave-Enhanced Flow System for High-Temperature Digestion of Resistant Organic Materials"; 10.1021/ac9903048) IR hollow waveguide sensor Using attenuated total reflection in combination with solid-phase microextraction, FT-IR is being used more often to detect organic compounds in aqueous solutions. Jyisy Yang and co-workers at Chung-Yuan Christian University (Taiwan) combine the two effects in a single device by coattng the inner surface of a hollow waveguide with a hydrophobic polymer. Organic species can be adsorbed into the SPME layer from aqueous samples flowing through the tube end detected db yT-IR By co-adding 100 scans with 4 cm-1 resolution, the typical detection limit can be
