In AC Research: In AC Research

In AC Research contains brief introductions to the research articles appearing in the July 1 issue. A free updated ... by one-way or reciprocal flow o...
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in ac research

In AC Research contains brief introductions to the research articles appearing in the July 1 issue. A free updated table of contents is available on the Web (http://pubs.acs.org/ac).

ACCELERATED ARTICLE TOF SIMS of drug surface concentration. Joseph A. Gardella, Jr., and Joo-Woon Lee at the State University of New York report a new quantitative method of analyzing the earliest stage of degradation of a polymer and the surface concentration of an additive using TOF secondary ion MS. The static SIMS spectra of triphenylamine/poly(L-lactic acid) (Ph3N/PLLA) blend matrixes hydrolyzed in buffered conditions within a 48-h period are simultaneously analyzed in the low-mass range for the surface accumulation profile of Ph3N and in the high mass range to determine the hydrolytic degradation kinetics of PLLA. The relative PLLA surface degradation at pH 10.0 is ~2 times faster than that at pH 7.4. The relative extent of increase in Ph3N surface concentration assayed in a pH 10.0 buffer system is 9 times greater than that at pH 7.4. (“Simultaneous Time-of-Flight Secondary Ion MS Quantitative Analysis of Drug Surface Concentration and Polymer Degradation Kinetics in Biodegradable Poly(L-lactic acid) Blends”; 10.1021/ac034305i; p 2950)

BIOANALYTICAL ESI-MS and tandem MS for disaccharide composition. Julie Leary and Ola Saad at the University of California–Berkeley introduce a new method that combines ESI-MS and tandem MS for identifying and quantitating disaccharides. The method is accurate and rapid, and samples from enzymatic depolymerization of compounds such as heparin do not need purification or separation. The technique is also applied to heparins from porcine and bovine sources. (“Compositional Analysis and Quantification of Heparin and Heparan Sulfate by Electrospray Ionization Ion Trap Mass Spectrometry”; 10.1021/ac0340455; p 2985)

Sex and the snail. Ka Wan Li and colleagues at Vrije Universiteit (The Netherlands) and Applied Biosystems (U.K.) use retrograde labeling with nickel–lysine to label neurons and then perform MALDI-TOF on the individual cells to identify molecular ion species. The researchers label neuronal

circuits associated with copulation in the freshwater snail Lymnaea stagnalis. (“Retrograde Labeling of Single Neurons in Conjunction with MALDI High-Energy Collision-Induced Dissociation MS/MS Analysis for Peptide Profiling and Structural Characterization”; 10.1021/ac034057q; p 2996)

DNA probe array enhances capillary turbulent flow. Yoshinobu Kohara at Hitachi reports the reaction kinetics of a DNA probe array by means of theoretical fluid mechanical examinations and hybridization experiments. The array is made of DNA probes conjugated on 103-µm-diam beads queued in a 150-µm-diam capillary. The hybridization reaction is performed by one-way or reciprocal flow of the sample solution. The probe array demonstrates fast hybridization that captures most of the targeted molecules in 10 min. (“Hybridization Reaction Kinetics of DNA Probes on Beads Arrayed in a Capillary Enhanced by Turbulent Flow”; 10.1021/ac0341214; p 3079)

Parallel precursor ion scanning MS for DMA residue. Matthias Mann and co-workers at the University of Southern Denmark and the University of Pennsylvania School of Medicine introduce a new method that localizes dimethylarginine (DMA) residues in gel-separated proteins at a sensitivity level of >1 pmol and distinguishes between isomeric symmetric and asymmetric positions of the methyl groups. Their method uses two side-chain fragments of DMA—the dimethylcarboammonium ion (m/z 46.06) and the dimethylcarbodiimidium ion (m/z 71.06)—for positive ion mode precursor ion scanning. The researchers have discovered at least 20 DMA sites in the protein FUL/TLS. The parallel monitoring of fragments in precursor ion scans is a versatile tool to specify the nature of protein modifications in cases where a single fragment is not conclusive. (“Detection of Arginine Dimethylated Peptides by Parallel Precursor Ion Scanning Mass Spectrometry in Positive Ion Mode”; 10.1021/ac026283q; p 3107)

Detecting plant benzoxazinone derivatives. Damià Barceló and co-workers at IIQAB-CSIC and the University of Lleida (both in Spain) report a novel method for separating and quantifying benzoxazinone derivatives in plant extracts. The researchers use LC/MS/MS to characterize six naturally occurring derivatives, which can be detected down to 0.002–0.023 ng/µL. (“Development of a Liquid Chromatography-ElectrosprayTandem Mass Spectrometry Method for the Quantitative Determination of Benzoxazinone Derivatives in Plants”; 10.1021/ ac0207877; p 3128) J U LY 1 , 2 0 0 3 / A N A LY T I C A L C H E M I S T R Y

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CIEF/CRPLC gives proteomics a boost. Cheng Lee

New stationary phases for bioactive peptides.

and co-workers at the University of Maryland and Calibrant Biosystems develop an integrated proteome concentration/ separation approach involving the on-line combination of capillary isoelectric focusing (CIEF) with capillary reversed-phase LC (CRPLC). The technique provides significant analyte concentration and extremely high resolving power for protein and peptide mixtures. The method requires a protein loading of only 9.6 µg, which is 2–3 orders of magnitude lower than non-gel-based proteome methods, and allows the identification of a greater number of yeast-soluble proteins. (“Capillary Isoelectric Focusing-Based Multidimensional Concentration/Separation Platform for Proteome Analysis”; 10.1021/ac034014+; p 3145)

Teruo Okano and colleagues at Waseda University and the Tokyo Women’s Medical University (both in Japan) build on a recently introduced form of hydrophobic interaction chromatography to separate bioactive peptides in a purely aqueous mobile phase. After creating stationary phases from silica beads coated with one of two thermoresponsive hydrogel layers, which separate on the basis of hydrophobic and electrostatic partitioning interactions, the researchers test the system on a mixture of angiotensins and analyze the retention behavior. (“Cross-Linked Thermoresponsive Anionic Polymer-Grafted Surfaces To Separate Bioactive Basic Peptides”; 10.1021/ac026364m; p 3244)

Europium-based immunoassay. Piia Von Lode and colleagues at the University of Turku and Innotrac Diagnostics (both in Finland) introduce a non-adentate europium chelate with two chromophores that is highly soluble in water. The label is tested as an immunoassay for human chorionic gonadotropin. In addition to low detection limits, the label facilitates short recovery times and simple instrumentation. (“Europium Chelate for Quantitative Point-of-Care Immunoassays Using Direct Surface Measurement”; 10.1021/ac0340051; p 3193)

Manipulating single beads. In previous work, Hideyuki Noda and colleagues at Hitachi (Japan) described a new “bead array” device that results in efficient hybridizations between target DNA molecules and beads coated with DNA probes. The researchers have now developed an apparatus that automatically aligns the beads used in the bead array and also report a new method for capturing single beads with micro-vacuum tweezers. (“Automated Bead Alignment Apparatus Using a Single Bead Capturing Technique for Fabrication of a Miniaturized BeadBased DNA Probe Array”; 10.1021/ac020674n; p 3250)

Sialylated carbs. Robert J. Cotter and colleagues at Johns Hopkins University use a 2.94-µm Er:YAG laser for IR atmospheric pressure MALDI on an ion trap mass spectrometer for the structural characterization of sialylated oligosaccharides. (“Liquid Infrared Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Ion Trap Mass Spectrometry of Sialylated Carbohydrates”; 10.1021/ac0262006; p 3212)

Evaluating SOS spectra. Robert J. Linhardt and colleagues at the University of Iowa, Teikyo University School of Medicine, and Chiba University (both in Japan) describe a systematic approach for evaluating the electrospray ionization mass spectra of sucrose octasulfate, an important pharmaceutical agent that is also a model for other difficult-to-analyze sulfated carbohydrates. Quaternary ammonium and phosphonium salts yield excellent spectra, particularly in the positive ion mode. (“Evaluation of Counterions for Electrospray Ionization Mass Spectral Analysis of a Highly Sulfated Carbohydrate, Sucrose Octasulfate”; 10.1021/ac034053l; p 3226)

ELECTROANALYTICAL Shielding effects. Allen J. Bard, Cynthia G. Zoski, and Julio Aguilar at the University of Texas–Austin provide an approximate theory for the feedback mode of the scanning electrochemical microscope to interpret the effects of substrate shielding on an ultramicroelectrode tip while recording reversible and quasireversible kinetics at a substrate surface. Shielding experiments provide new insights into approach curves, which suggests possible applications for measuring heterogeneous kinetics for fast reactions and determining diffusion coefficients. (“Scanning Electrochemical Microscopy. 46. Shielding Effects on Reversible and Quasireversible Reactions”; 10.1021/ac034011x; p 2959) Oxidation–reduction on electrodes. Allen J. Bard and

Characterizing phosphopeptides by MS. To get more information on phosphopeptides analyzed by MS, Rainer Cramer and colleagues at the Ludwig Institute for Cancer Research and University College London (both in the U.K.) enrich phosphopeptides using metal ion affinity chromatography and derivatize the phosphates using -elimination with Michael addition. With this protocol, the researchers detect and sequence phosphopeptides at low femtomole levels and identify new phosphorylation sites on two proteins. (“Characterization of Protein Phosphorylation by Mass Spectrometry Using Immobilized Metal Ion Affinity Chromatography with On-Resin -Elimination and Michael Addition”; 10.1021/ac034134h; p 3232) 280 A

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José L. Fernández at the University of Texas–Austin investigate the oxidation–reduction reaction in acidic medium on different electrodes using a scanning electrochemical microscope operating in a new variation of the tip generation–substrate collection mode. The primary difference between this new mode and the classical feedback mode is that the feedback diffusion process is not required for the measurement. They discuss applying this method to the combinatorial chemical analysis of electrode materials and electrocatalysts. (“Scanning Electrochemical Microscopy. 47. Imaging Electrocatalytic Activity for Oxygen Reduction in an Acidic Medium by the Tip Generation–Substrate Collection Mode”; 10.1021/ac0340354; p 2967)

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Electrochemistry of encapsulated enzymes. Frank Caruso and Aimin Yu at the Max Planck Institute of Colloids and Interfaces (Germany) and the University of Melbourne (Australia) deposit polyelectrolyte (PE)-encapsulated catalase microcrystals onto gold electrodes to produce an enzyme thin film for sensing H2O2. Films with PE-encapsulated catalase give higher responses to a reduction in H2O2 than films in which catalase is not encapsulated. Increasing the number of PE layers decreases the electrocatalytic activity of the electrode. (“Thin Films of Polyelectrolyte-Encapsulated Catalase Microcrystals for Biosensing”; 10.1021/ac0340049; p 3031)

Plasticizer-free sensors. Eric Bakker and colleagues at Auburn University introduce a plasticizer-free process to incorporate ionophores into polymer membranes to construct ion-selective membrane electrodes for potentiometric detection of ions. Plasticizer-free polymer membranes containing ionophores for calcium are evaluated, and their binding constant and diffusion coefficients are determined. Diffusion is reduced because the ionophores are covalently bound to the polymer. (“Plasticizer-Free Polymer Containing a Covalently Immobilized Ca2+-Selective Ionophore for Potentiometric and Optical Sensors”; 10.1021/ac0263059; p 3038)

Better sensitivity to glucose. Taek Dong Chung, Hee Chan Kim, and Sejin Park at Seoul National University and Sungshin Women’s University (both in Korea) construct mesoporous structures on the surfaces of pure platinum electrodes to respond with more sensitivity to glucose than to common interfering species. Sensitivity as high as 9.6 µA cm–2 mM–1 is reproducibly observed in the presence of a high chloride ion concentration. (“Nonenzymatic Glucose Detection Using Mesoporous Platinum”; 10.1021/ac0263465; p 3046)

Better DNA detection. Adam Heller and colleagues at the University of Texas–Austin discuss an improvement on their enzyme-amplified sandwich-type amperometric assay. In the assay, a carbon electrode is electrodeposited with a redox polymer with a DNA capture sequence and, when the DNA is hybridized, an electroreduction current is generated. In the improvement, the 3.6-mm-diam carbon electrode is replaced with a 10-µm electrode, allowing a >104-fold improvement in the detection limit with as few as 3000 copies of DNA being detected. (“Enzyme-Amplified Amperometric Detection of 3000 Copies of DNA in a 10-µL Droplet at 0.5-fM Concentration”; 10.1021/ac034445s; p 3267)

Durable electrodes. Kamil Wojciechowski and colleagues at the Warsaw University of Technology (Poland) obtain a significant decrease in the rate of decomposition of uranyl salophene in the electrode membrane by the efficient buffering of phosphate and uranyl ions in the internal electrolyte solution. (“Anion Buffering in the Internal Electrolyte Resulting in Extended Durability of Phosphate-Selective Electrodes”; 10.1021/ac026384o; p 3270)

ENVIRONMENTAL LC/APCI-MS determines nitrated phenolic compounds in rain. Martin Kohler and Norbert Heeb at the Swiss Federal Laboratories for Materials Testing and Research analyze trace amounts of nitrated phenolic compounds in rain samples using a method based on liquid–liquid extraction and LC/atmospheric pressure chemical ionization MS (LC/ APCI-MS). The method is sensitive, specific, and rapid and can determine alkylated (C1– C3) and nonalkylated (C0) nitroand dinitrophenols in one step. They can confirm the presence of nitrated phenolic compounds in rain samples using tandem MS by relying on their characteristic loss of a NO2 neutral molecule upon collision-induced dissociation. (“Determination of Nitrated Phenolic Compounds in Rain by Liquid Chromatography/Atmospheric Pressure Chemical Ionization Mass Spectrometry”; 10.1021/ac0264067; p 3115)

Detecting explosives vapors. Ramón Batlle and coworkers at Stockholm University (Sweden) and the Swedish Defense Research Agency describe a new method for detecting vapors above military grade 2,4,6-trinitrotoluene. A solidphase extraction cartridge is used to collect samples. The analytes are then desorbed with supercritical fluid extraction and introduced into a GC via a loop-type injection interface. (“Enhanced Detection of Nitroaromatic Explosive Vapors Combining Solid-Phase Extraction-Air Sampling, Supercritical Fluid Extraction, and Large-Volume Injection-GC”; 10.1021/ ac0207271; p 3137) Humate interactions. Wolfram Schüssler and colleagues at the Institut für Nukleare Entsorgung (Germany) and the University of Manchester (U.K.) assess the applicability of the cation exchange resins Chelex-100, Dowex 50Wx4, and Cellphos for europium humate dissociation kinetics investigations. A systematic study of parameters affecting the dissociation rates of the europium humate complexes is performed. (“Kinetic Investigation of Eu(III)–Humate Interactions by Ion Exchange Resins”; 10.1021/ac020668r; p 3168)

Unraveling methylmercury formation in references. D. Amouroux and colleagues at the Université de Pau et des Pays de l’Adour (France) investigate the generation of monomethylmercury in certified reference sediments to localize the sources of unintentional abiotic methylmercury formation during analysis. Different spiking and derivatization procedures are tested. Using various analytical methods, they find that the amount of inorganic mercury initially present in the sample is the critical factor and should be carefully controlled. (“Using Speciated Isotope Dilution with GC/ Inductively Coupled Plasma MS to Determine and Unravel the Artificial Formation of Monomethylmercury in Certified Reference Sediments”; 10.1021/ac026411a; p 3202) J U LY 1 , 2 0 0 3 / A N A LY T I C A L C H E M I S T R Y

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MASS SPECTROMETRY Electron monochromator reflectron TOF MS. Max Deinzer and colleagues at Oregon State University, the Pacific Institute of Bioorganic Chemistry, Bashkir State Agricultural University (both in Russia), and Ionwerks describe an electron monochromator reflectron TOF mass spectrometer that can capture complete resonant electron capture (REC) mass spectra in ~1 s, rather than the several days needed with a quadrupole or magnetic sector instrument. The new mass spectrometer has several other advantages over current techniques, not the least of which is making it possible to perform GC REC MS. (“Resonant Electron Capture Time-of-Flight MS with Trochoidal Electron Monochromator”; 10.1021/ac030019v; p 3001)

Cellulase –cellulose interactions by ESI-MS. Sheng Zhang and colleagues at Advion BioSciences and Cornell University describe a fully automated chip-based nanoelectrospray ionization (ESI) MS system for determining the dissociation constants of protein–ligand complexes. They perform titration and competitive binding experiments and report the first use of ESI MS to study the noncovalent interactions between cellulase and oligosaccharide ligands. (“Quantitative Determination of Noncovalent Binding Interactions Using Automated Nanoelectrospray Mass Spectrometry”; 10.1021/ac034089d; p 3010)

Determining matrix effects in HPLC/MS/MS. Although HPLC in combination with MS/MS is assumed to be a selective method, B. K. Matuszewski and colleagues at Merck Research Laboratories say that ion suppressions by the sample matrix can result in a lack of selectivity. The researchers perform a set of validation experiments for one of their new drug candidates and develop a method to determine the “true” recovery of analytes. The matrix effect for the new drug is absent when a heated nebulizer interface is used. (“Strategies for the Assessment of Matrix Effect in Quantitative Bioanalytical Methods Based on HPLC/MS/MS”; 10.1021/ac020361s; p 3019)

Oligomers help determine MALDI discrepancies. Toby Chapman and colleagues at the University of Pittsburgh and Vanderbilt University report the first work detailing the application of synthetic, discrete mass oligomers as a quantitative model for MS analysis of macromolecular systems. To quantify discrepancies in MALDI TOF MS mass determinations of synthetic polymers, the researchers use equimolar mixtures of synthetic, discrete mass poly(butylene glutarate) oligomers of known structure having degrees of polymerization of 8, 16, 32, and 64, spanning a mass range of 760–6000 amu. Their results demonstrate that the equimolar mixture can be used as an internal standard for examining mass dependency of response in polydispersed synthetic materials, and as a calibration standard for MALDI and gel permeation chromatography. (“Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry of Dis282 A

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crete Mass Poly(butylene glutarate) Oligomers”; 10.1021/ ac030061q; p 3092)

APPI for small molecules. Yunsheng Hsieh and colleagues at the Schering-Plough Research Institute and Applied Biosystems report that atmospheric pressure photoionization (APPI) is a suitable alternative interface between HPLC and tandem MS for the study of many small molecules. Plasma levels in rats after exposure to various drug discovery compounds are studied. Matrix ionization suppression effects on the HPLC/APPI/ MS/MS method are studied using the postcolumn infusion technique. (“High-Performance Liquid Chromatography-Atmospheric Pressure Photoionization/Tandem Mass Spectrometric Analysis for Small Molecules in Plasma”; 10.1021/ac0300082; p 3122) ECD with lantibiotics. Ron M. A. Heeren and colleagues with FOM Institute for Atomic and Molecular Physics and Utrecht University (both in The Netherlands) discover that electron capture dissociation (ECD) of lantibiotics yields c and z • ions along with less common c• and z ions as a result of cleaving a backbone amine bond and the thioether bond in a lanthionine bridge. This suggests that ECD can be used to identify the Cterminal attachment site of lanthionine bridges in newly discovered lantibiotics. (“Localization of Intramolecular Monosulfide Bridges in Lantibiotics Determined with Electron Capture Induced Dissociation”; 10.1021/ac0263770; p 3219) Fragmentation methods for FTMS. IR multiphoton dissociation (IRMPD) and electron capture dissociation (ECD) are complementary fragmentation techniques. Alan Marshall and colleagues at the National High Magnetic Field Laboratory have developed a way to do both methods on a 9.4-T FT ion cyclotron MS. A dispenser cathode electron source is placed on-axis inside the magnet bore and an off-axis laser geometry is implemented, allowing simultaneous access to ECD and IRMPD. (“Combined Electron Capture and Infrared Multiphoton Dissociation for Multistage MS/MS in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer”; 10.1021/ac030015q; p 3256)

New application of ECD. Neil Kelleher and co-workers at the University of Illinois at Urbana–Champaign report the first use of electron capture dissociation (ECD) in combination with hydrogen/deuterium exchange for intact proteins prior to MS and MS/MS. By depleting 13C and 15N and using ECD, the researchers report an increased number of c and z• ions for ubiquitin over previous methods. (“Electron Capture Dissociation and 13 C, 15N Depletion for Deuterium Localization in Intact Proteins after Solution-Phase Exchange”; 10.1021/ac020690k; p 3263)

MICROSCALE Smart microfluidic array. Patrick Stayton and colleagues at the University of Washington use stimuli-responsive polymer

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beads that not only can capture and release targets but also can be reversibly immobilized in microfluidic channels. The latex beads are covered with temperature-sensitive poly(N-isopropylacrylamide), and when the temperature is lowered below a critical point, the beads swell and adhere to the channel walls. Beads are modified with biotin capture streptavidin, and by changing the temperature, the streptavidin could be eluted. (“Smart Microfluidic Affinity Chromatography Matrix Composed of Poly(N-isopropylacrylamide)-Coated Beads”; 10.1021/ac034274r; p 2943)

Microfluidic reversible immobilization of DNA. Steven Soper and colleagues at Louisiana State University use photoactivated polycarbonate in microfluidic chips for solid-phase reversible immobilization of dye-labeled DNA fragments. Exposing the polycarbonate surface to UV light generates carboxyl groups, for which DNA fragments in an immobilization buffer have a high affinity. The DNA can be released, and the readlength is 620 bases with a calling accuracy of 98.9%. (“SolidPhase Reversible Immobilization in Microfluidic Chips for the Purification of Dye-Labeled DNA Sequencing Fragments”; 10.1021/ac030031n; p 2975)

Increased detection sensitivity. Stephen Williams and colleagues from Aclara BioSciences and Northwestern University describe a microfluidic approach that improves detection of fluorescent molecules by using a buffer system that operates first in an isotachophoretic mode and then transitions to a zone electrophoretic mode. This approach offers a ~50-fold increase in detection sensitivity over equivalent separations by zone electrophoresis alone. (“Tandem Isotachophoresis-Zone Electrophoresis via Base-Mediated Destacking for Increased Detection Sensitivity in Microfluidic Systems”; 10.1021/ac0259921; p 3059)

Continuous-flow microfluidic system measures enzyme kinetics. Richard Crooks and colleagues at Texas A&M University present a microanalytical method for determining enzyme kinetics using a continuous-flow microfluidic system. They immobilize the enzyme on microbeads, pack them into a chip-based microreactor (volume ~1.0 nL), and flow the substrate over the packed bed. The continuous-flow method requires ~10 µL of substrate solution and 109 enzyme molecules. The approach provides a new means for rapid determination of enzyme kinetics in microfluidic systems, which may be useful for clinical diagnostics and drug discovery and screening. (“Measurement of Enzyme Kinetics Using a Continuous-Flow Microfluidic System”; 10.1021/ac034155b; p 3161)

can generate high-resolution coherent Raman signals suitable for rapid multichannel detection. (“Gas Chromatography/Multiplex Coherent Raman Spectroscopy”; 10.1021/ac0207123; p 3066)

Fluorescence imaging of desorption dye in chromatography. Mary Wirth and co-workers at the University of Delaware attempt to address the problems of mixed-mode retention in reversed-phase chromatography by using fluorescence imaging combined with correlation spectroscopy to probe the desorption kinetics of the cationic dye 1,1´-diodececyl-3,3,3´,3´tetramethylindocarbocyanine perchlorate. The slow desorption from silica gel is measured using fluorescence movies of silica gel particles. Their technique shows that three types of adsorption sites on fused silica are chemically the same as those on chromatographic silica gel, and the researchers examine whether those adsorption sites are unique to fused silica or common to all silica. (“Fluorescence Imaging of the Desorption of Dye from Fused Silica versus Silica Gel”; 10.1021/ac0264170; p 3073)

Cavity ring-down for HPLC. Richard Zare and Kate Snyder at Stanford University use cavity ring-down spectroscopy (CRDS) as a detector method for HPLC. CRDS has a linear range over 2 orders of magnitude of concentration for HPLC measurements. The simple pulsed CRDS device can measure microliter volumes and is comparable to high-quality UV–vis absorption detectors. (“Cavity Ring-Down Spectroscopy as a Detector for Liquid Chromatography”; 10.1021/ac0340152; p 3086)

Amine counterion effect on ODS and PBD-ZrO2 phases. Peter Carr and colleagues at the University of Minnesota show through chromatographic methods that the molecular geometry of the amine counterion has a significant effect on the retention of basic solutes on the polybutadiene-coated zirconia (PBD-ZrO2) phase. By examining reversed-phase and ion exchange interactions, the researchers report that the degree of substitution of the charge center of both the analyte and the amine counterion have a substantial effect on separations on the PBD-ZrO2 phase. However, even on the specific type B silica of the ODS-bonded silica studied, the effect of the counterion type is much smaller on the PBD-ZrO2 phase and not nearly as large as found in prior studies on type A silica-based phases. (“Effect of Amine Counterion Type on the Retention of Basic Compounds on Octadecyl Silane-Bonded Silica-Based and PolybutadieneCoated Zirconia Phases”; 10.1021/ac034107r; p 3153)

Calibrating permeation passive samplers. Perme-

SEPARATIONS GC and Raman. Peter C. Chen and colleagues at Spelman College describe a new GC detector based on nonlinear Raman spectroscopy. The system uses a windowless cell as the interface between the chromatograph and the detector. The spectrometer

ation passive samplers are attractive devices for air analysis because they are not very affected by ambient conditions; however, the samplers need to be calibrated for each target analyte. Tadeusz Górecki and co-workers from the University of Waterloo (Canada) and Gdan ´ sk University of Technology (Poland) find that the calibration strongly depends on the molecular weights, boiling points, and the number of carbon atoms among families of compounds, as well as the linear temperature-programmed retention indexes. (“Calibration of Permeation Passive J U LY 1 , 2 0 0 3 / A N A LY T I C A L C H E M I S T R Y

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Samplers with Silicone Membranes Based on Physicochemical Properties of the Analytes”; 10.1021/ac034087t; p 3182)

SPECTROSCOPY New algorithm for spectroscopic data. Frank Vogt and Boris Mizaikoff at the Georgia Institute of Technology have developed a novel algorithm called secured principal component regression (sPCR) for detecting and correcting spectroscopic data for uncalibrated features that appear after PCR calibration has been finalized. The researchers applied sPCR to three spectroscopic data sets obtained by different methods and excluded one substance from the calibration for each data set. In 109 out of 110 samples, sPCR correctly classified the data sets as disturbed or undisturbed. (“Introduction and Application of Secured Principal Component Regression for Analysis of Uncalibrated Spectral Features in Optical Spectroscopy and Chemical Sensing”; 10.1021/ac020758w; p 3050)

Analyzing alkali salts. Mahmoud Tabrizchi of Isfahan University of Technology (Iran) reports the first thermal ion-

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ization ion mobility spectrometry of inorganic compounds by studying sodium and potassium halides. This approach shows promise as a quantitative method, detecting as little as 0.01% K+ in NaBr. (“Thermal Ionization Ion Mobility Spectrometry of Alkali Salts”; 10.1021/ac0263420; p 3101)

New postionization method of sputtered actinide material. Nicole Erdmann, Maria Betti, and colleagues at the European Commission Joint Research Center (Italy and Germany), Westfälische Wilhelms-Universität Münster, Johannes Gutenberg-Universität Mainz (both in Germany), and Katholieke Universiteit Leuven (Belgium) design a new setup to analyze actinide-containing micrometer-size particles and show that information about the main components and specific isotopic information of trace elements could be obtained from the same sample. They combine nonresonant sputtered neutral MS with sputter-initiated resonance ionization spectroscopy to study uranium atoms sputtered from thin films and single microparticles. Their design is equipped with an ion gun, one laser system for resonance and another for nonresonant postionization of the sputtered neutrals, and a TOF mass spectrometer. (“Resonance and Nonresonant Laser Ionization of Sputtered Uranium Atoms from Thin Films and Single Microparticles: Evaluation of a Combined System for Particle Trace Analysis”; 10.1021/ac0264426; p 3175)