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Analytical and Bioanalytical Chemistry (v.360, #7-8)
Laser desorption mass spectrometry on thin liquid jets by Frank Sobott; Andreas Wattenberg; Wolfgang Kleinekofort; Anja Pfenninger; Bernhard Brutschy (pp. 745-749).
A recently developed soft desorption method for mass spectrometry is presented, which is called Laser Induced Liquid Beam Ionization/Desorption (LILBID). Analyte ions are desorbed from a thin jet of analyte solution directly into vacuum by means of an IR laser pulse, which has been tuned to a vibrational resonance of the solvent. A comparative experiment with ammonium chloride and aniline hydrochloride shows that ion formation via proton transfer takes place in the solution. Thermally unstable compounds, as well as supra- and biomolecular complexes, can be detected intact and mass analyzed in a reflectron time-of-flight (Re-TOF) mass spectrometer. During the desorption process, noncovalent interactions and some solvation characteristics are preserved. Three examples for the capacity of LILBID are given in this short overview: (a) ion-solvent interactions with the formation of a clathrate structure Cs+(H2O)20, (b) host-guest interactions with the K+ selectivity of valinomycin, and (c) noncovalent interactions with the dimerization of gramicidin.
Surface enhanced FTIR spectroscopy on membranes by C. Kuhne; G. Steiner; W. B. Fischer; R. Salzer (pp. 750-754).
The infrared absorption of molecules in the vicinity of small metal clusters is enhanced due to an electric field around the clusters. This phenomenon is known as surface enhanced IR absorption (SEIRA). The potential of SEIRA consists in the investigation of thin layers and of membranes. SEIRA was used to detect small and specific changes in the structure of biomembranes applying two configurations: underlayer and overlayer. In the underlayer configuraiton, IR transparent Ge crystals were coated with Ag clusters before vesicles were adsorbed. In the overlayer configuration, the vesicles were first absorbed on neat Ge crystals before a layer of Ag clusters was condensed on top. An intensity increase in the SEIRA spectra was observed for both configurations compared to FTIR spectra without Ag clusters.
Sample preparation system for ion-selective electrodes by A. Trost; M. Borchardt; K. Cammann; C. Dumschat (pp. 755-758).
The sample preparation of real world water samples for potentiometric determinations is often time and labor consuming. Therefore sample preparation systems were developed for the determination of water hardness and nitrate concentrations in drinking water and well water. The systems allow the adjustment of the ionic strength and removal of interfering ions. The sample preparation agents required are fixed by using a disposable sample preparation disk. The system was tested by analyzing real water samples and the results were compared to those obtained by using reference methods.
Molecular imprinting in chemical sensing – Detection of aromatic and halogenated hydrocarbons as well as polar solvent vapors by F. L. Dickert; Peter Forth; Peter Lieberzeit; Matthias Tortschanoff (pp. 759-762).
The technique of molecular imprinting – a novel tool of sensor material synthesis – can be successfully combined with mass-sensitive transducers. Imprinted polymers are prepared in presence of inert analytes acting as molecular templates. The remaining imprint allows the molecular recognition of an analyte due to host-guest-interactions. The sensor properties of devices coated with imprint polymers can be tuned to the analyte by variation of the polymerization solvent and the amount of cross-linker added. A further sensitivity enhancement can be achieved by rising the resonant frequencies of QMBs and SAW resonators, since the signal to noise-ratio increases in an approximately linear manner with the oscillation frequency.
New stationary phases for normal-phase high-performance liquid chromatography (NP-HPLC) by Ralf L. Deisenhofer; K. Ballschmiter (pp. 763-768).
3-(2,3-Dihydroxy-propoxy)-propyl-silica (diolsilica) was modified to bonded stationary phases for normal-phase high-performance liquid chromatography (NPLC) carrying phosphorous ester, boronic ester, and nitric acid ester groups. The NPLC phases were investigated with respect to their properties towards separations of polyaromatic hydrocarbons, and chlorinated and nitrated environmental pollutants. Aminopropyl-silica and nitrooxy-propyl-silica (the latter synthesized in our working group) are presented for comparison. Depending on the functionality used for the modification the retention behavior can significantly be changed towards the three analyte classes. Especially 2,2,2-tribromoethyl-phosphoromorpholino-chloridate modified diol-silica, 2,2,2-tribromoethyl-dichlorophosphate modified diol-silica and nitrated diol-silica (nitrooxy-propoxypropyl-silica) show specific properties for the separation of polyaromatic hydrocarbons, chlorinated analytes and nitrated analytes. Preparation and packing of the adsorbents are described. Principal Component Analysis (PCA) is used as a chemometric tool for effective data reduction and visualization of the results in terms of retention behavior of the stationary phases.
Prediction of the environmental distribution of alkyl dinitrates – Chromatographic determination of vapor pressure p0, water solubility SH2O, gas-water partition coefficient KGW (Henry’s law constant) and octanol-water partition coefficient KOW by Ralf G. Fischer; K. Ballschmiter (pp. 769-776).
Alkyl nitrates are complex mixtures of homologues and isomers and are part of the large NOy pool of important atmospheric trace compounds. The knowledge of their physico-chemical parameters allows to forecast their partitioning into the environment. Water solubility, octanol-water partition coefficient, vapor pressure, and gas-water partition coefficient have been determined for 26 alkyl dinitrates by RP-HPLC and HRGC, respectively. Octanol-water partition coefficient (KOW) and water solubility (SH 2 O) were determined by C18 reversed-phase liquid chromatography using phenylalkanes as reference standards. Retention data obtained with methanol-water mixtures as eluents were extrapolated to 100% water. The vapor pressures were determined by capillary gas chromatography on a non polar stationary phase (CP-Sil 2, Chrompack). The octanol-water partition coefficients ranges from log KOW = 1.4 for 1,2-ethyl dinitrate up to log KOW = 5.9 for 1,2-decyl dinitrate, respectively. The experimental results are within ± 0.15 log units in agreement with calculations of log KOW by the increment method according to Hansch and Leo. Water solubilities are in the range of 154 mol/m3 (23.1 g/L) for 1,2-ethyl dinitrate and 0.002 mol/m3 (0.5 mg/L) for 1,2-decyl dinitrate, respectively. The vapor pressures p0 L ranges from 196 Pa for 1,2-ethyl dinitrate to 0.01 Pa for 1,10-decyl dinitrate (sub-cooled liquid value). The gas-water partition constants (dimensionless) or Henry’s law constants ranges from KGW = 0.0005 (H = 1.28 Pa m3/mol) for 1,2-ethyl dinitrate to KGW = 0.020 (H = 51.1 Pa m3/mol) for 1,2-decyl dinitrate.
Trace analysis of bromate in drinking waters by means of on-line coupling IC-ICP-MS by A. Seubert; Michael Nowak (pp. 777-780).
The on-line-coupling of ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for the determination of bromate in drinking waters. The use of a high-capacity and high-performance anion-exchanger combined with an NH4NO3-based elution system allows the determination of bromate in almost every water sample without any sample pretreatment. The method detection limits in the water samples investigated are 50 to 65 ng/L or 44 to 58 pg bromate, respectively. Considering sensivity as well as imprecision (5% at 500 ng/L bromate) and short analysis times (8 to 15 min per sample including sample uptake), the described IC-ICP-MS coupling is well suited for precise routine analyses of bromate in drinking waters at the sub μg/L level.
Detection of bound nitroaromatic residues in soil by immunoassay by Peter Pfortner; M. G. Weller; Reinhard Niessner (pp. 781-783).
Bound nitroaromatic residues have been detected in three highly polluted soils of two former TNT production plants in Germany. Selectivity of the assay signal was proven by inhibition with TNT. The concentration of extractable TNT was 1.3 g/kg, 1.1 g/kg and 0.37 g/kg, determined by HPLC. After optimization of the immunoassay only the contaminated samples showed a distinct signal. High signal intensities correlated with high amounts of extractable TNT. It could be shown that the used monoclonal anti-TNT-antibody has no significant cross-reactivity to bound nitroaromatic structures of the 4-amino-2,6-dinitrotoluene type. Therefore one can assume that the signal is probably caused by other covalently bound nitroaromatic compounds.
Use of solid-phase microextraction-capillary-gas chromatography (SPME-CGC) for the varietal characterization of wines by means of chemometrical methods by Demetrio De Calle García; M. Reichenbächer; Klaus Danzer; Christian Hurlbeck; Christine Bartzsch; Karl-Heinz Feller (pp. 784-787).
The extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspace-SPME (HS/SPME) and multiple-headspace-extraction-SPME (MHE/SPME). The aromagrams obtained by HS/SPME-CGC were evaluated with chemometrical methods for the varietal classification of wines.
Studies of copper patina by photothermal beam deflection by S. Janssen; G. R. Hofmann; W. Faubel; H. J. Ache (pp. 788-791).
Photothermal beam deflection (PBD) is a suitable method for three-dimensional, non-contact and non-destructive surface analysis. This method has been applied to the characterization of the thermal properties of natural and artificial patina and to the measurement of the thickness of the patina layers. The thickness of the outdoor and indoor patina of the roof of the Vienna Hofburg was measured to be about 22 μm and 10 μm, respectively. The thermal diffusivities of antlerite and chalcanthite were determined to 0.13 cm2/s and 0.04 cm2/s, respectively.
Contamination caused by ion-exchange resin!? Consequences for ultra-trace analysis by S. Straßburg; Dirk Wollenweber; Gerold Wünsch (pp. 792-794).
Well known sources of contamination are the laboratory environment, vessels, reagents and handling of the sample. Attention is drawn to the importance of cationic impurities included in the ion-exchangers used for trace-matrix separations (TMS) at the sub-ng/g-level. The usual rinsing and conditioning of the resins does not remove all adhering metals and thus leads to contaminated eluates in analytical work. High and badly reproducible blanks are observed, in particular for Na, Mg, Al, K, Cr, Fe, Zn and Ba. They are introduced during the polymerization process and are not ionically bound but obviously included in the polymer matrix. Any time when another “nest” of inclusion is opened in the resin column by mechanical stress, the next irreproducible event of contamination occurs.
Determination of iron in real samples by high performance capillary electrophoresis in combination with thermal lensing by B. S. Seidel; W. Faubel (pp. 795-797).
Natural iron concentrations in real water samples have been determined by thermal lensing as a high performance capillary electrophoresis detector. 1,10-Phenanthroline was used as a chromogenic reagent, which forms a stable complex with Fe(II) but not with Fe (III). The interferences by other cations can be neglected by a combination of this photometric technique with high performance capillary electrophoresis. Laser induced thermal lens spectroscopy is demonstrated as a new technique for the measurement of small absorbances in the picoliter detection volume of a capillary. A limit of detection of 36 nmol/L with a signal to noise ratio of 7 : 1 was achieved using a 75 μm fused silica capillary.
Study of ion chromatographic behavior of inorganic and organic antimony species by using inductively coupled plasma mass spectrometric (ICP-MS) detection by Nina Ulrich (pp. 797-800).
An on-line method for the analysis of Sb(III), Sb(V) and trimethylstiboxide (TMSbO) is presented. The separation is performed using ion chromatography (IC) on a strong anion-exchange column with phthalic acid plus 2% acteone at pH 5 as mobile phase. The chromatographic system is coupled to an ICP-MS as detector. The influence of different complexing agents on the chromatographic behavior of the antimony species is studied. Rather stable complexes of Sb(III) seem to be formed with citrate and tartrate under the experimental conditions. TMSbO forms a dianionic species with citrate in contrast to the otherwise monoanionic complex.
Application of high resolution-ICP-MS (sector field-ICP-MS) to the fast and sensitive quality control of process chemicals in semiconductor manufacturing by H. Wildner; Ruth Hearn (pp. 800-803).
For fast routine analysis of process chemicals used in semiconductor technology such as tetramethylammonium hydroxide (TMAH), ammonium fluoride/hydrofluoric acid mixtures, phosphoric, sulphuric or peroxodisulphuric acid (PDSA) low blanks are the paramount requirement for reliable sector field ICP-MS ultratrace analysis. When solutions containing a high amount of dissolved solids e.g. seawater samples have been analysed before, a thorough cleaning procedure and an adapted element menu is essential to lower the instrument blanks where possible or to achieve sufficient limits of detection (LoD) even at high blank levels. Due to its improved transmission and its ability to resolve spectral interferences inductively coupled plasma-sector field mass spectrometry is capable of detecting 1 ng/g of all metal impurities even K, Ca, and Fe in every matrix used for semiconductor production. LoDs range from < 1 to 30 pg/mL in diluted chemicals corresponding to 5 to 800 pg/mL in the original. This work describes the experiences with instrument cleaning and maintenance, sample preparation and introduction. The interface region between torch and lenses was seen to be the main source of blanks for elements such as Na. All sample manipulation has to be carried out under clean room conditions. The use of an inert sample introduction system (ISIS), platinum cones and at least medium resolution for elements between 24 and 80 amu creates a very robust method. High efficiency sample introduction systems such as USN and MCN have been studied alternatively.
Analysis of heterocyclic aromatic amines (HAA) by E. Richling; M. Herderich; D. Häring; P. Schreier (pp. 804-804).
A new method was developed for the analysis of heterocyclic aromatic amines (HAA) using HPLC-ESI-MS/MS with selected reaction monitoring (SRM). Detection limits between 0.1 and 50 ng/mL were achieved.
Solid-phase extraction of aminobenzoic acids and aminotoluenesulfonic acids with graphitized carbon black by C. Böhme; T. C. Schmidt; E. von Löw; G. Stork (pp. 805-807).
The extraction of amphoteric aromatic amines from water samples is difficult because of their high polarity. For the enrichment of aminobenzoic acids and aminotoluenesulfonic acids with solid-phase extraction, graphitized carbon black (GCB) was investigated. With few exceptions, the 12 analytes studied were extracted with recoveries > 60% at neutral or basic pH, whereas at pH 3 low recoveries were obtained. Addition of salt caused a decrease of about 50% in recoveries, addition of standard humic acid a decrease of about 20%. The capacity of GCB cartridges was determined with the breakthrough volume for 4-aminobenzoic acid at different concentrations to be 0.5–1% (w/w).
New HPLC methods for analysing α-and β-emitters as part of destructive testing of low- and intermediate-level waste by S. Seekamp; H.-J. Steinmetz; R. Odoj; A. Seubert (pp. 808-812).
Low- and intermediate-level waste is frequently supercompacted or solidified in cement for final disposal. In waste characterisation matrix problems arise in analysing the drum content by chromatographic methods. The cations from the cement occupy the capacity of the column and no separation of the analytes takes place. By a selective complexation the analytes get separated from the matrix. The analytes Pb, Ni, Co and Se are bound by sodiumdiethyldithiocarbamate (NaDDTC) as complexes on a precolumn and subsequently separated on a reversed-phase column. Detection is performed by a UV/VIS spectral range detector and a liquid scintillation detector (Pb-210, Ni-63, Co-60) in series.
Bifunctional alkyl nitrates – trace constituents of the atmosphere by Jürgen Kastler; K. Ballschmiter (pp. 812-816).
Mono- and multifunctional esters of nitric acid (alkyl nitrates or organonitrates) form very complex mixtures of organic trace constituents in air. An analytical method was developed which combines selectivity in separation and detection in order to simplify this complexity in analytical terms. Mononitrates, dinitrates, keto nitrates, hydroxy nitrates of alkanes and alkenes, respecitvely, and bifunctional terpene nitrates were synthesized as reference substances. A specially developed new HPLC stationary phase (organonitrate phase) allows a group separation of mono-, di-, and hydroxy nitrates. After the HPLC preseparation the single components were finally separated by capillary HRGC-ECD and HRGC-MSD on polar and non-polar stationary phases. Mass spectrometric detection in the selected-ion-mode using the highly selective NO2 + fragment (m/z = 46 amu) led to very good selectivities for the nitric acid ester moiety. The analysis of a 100 m3 ambient air sample using this new analytical protocol allowed the identification of seven hydroxy nitrates and 24 dinitrates ranging from C2 to C7, 22 of them for the first time ever.
Biomagnification of polychlorinated biphenyls (PCBs) in freshwater fish by Ralf Looser; Karlheinz Ballschmiter (pp. 816-819).
A total of 19 PCB congeners were determined in muscle of 2 European roach (Rutilus rutilus) and in muscle and liver of 3 pike (Esox lucius) of a small rural lake in the southern Black Forest (Germany) to examine the biomagnification in freshwater fish. The lake is known for a relatively high PCB contamination of its sediments due to past local emissions. The presence of a structure dependent biomagnification in these freshwater fish of two different trophical levels is confirmed. The relative contents of PCB congeners with vicinal H-atoms in m,p- and to a lesser extent, o,m-positions become smaller from roach to pike indicating a stronger induction of PCB metabolizing isoenzymes in the predatory fish. This could also be shown by application of the metabolic slope concept.
Application of headspace GC/MS screening and general parameters for the analysis of polycyclic aromatic hydrocarbons in groundwater samples by C. Zwiener; F. H. Frimmel (pp. 820-823).
Groundwater samples from a former gas plant site were investigated by headspace GC/MS and general parameters with regard to organic pollution. The contamination plume was distinguished from background with GC/MS headspace and dissolved organic carbon analyses. Headspace GC/MS analyses of these samples revealed the presence of several aromatic and heterocyclic compounds typical to coal tar leachates. Selected ion monitoring GC/MS was used to establish the relative contamination level of seven selected polycyclic aromatic hydrocarbons (PAH) from 9 sampling wells. Three wells showed a high contamination level and therefore, they could be attributed to the vicinity of contamination sources. Well samples downgradient from the pollution source showed decreasing contamination levels for all compounds except acenaphthene.
Characterization of a covalent triazine-humic acid conjugate by gas chromatography by Elfriede Simon; M. G. Weller; Reinhard Niessner (pp. 824-826).
The aim of the described method was the characterization of a “atrazine-mercaptopropionic acid” humic acid conjugate, which was required for the calibration of immunoassays to determine bound residues. In order to estimate the amount of bound triazine, an oxidative nucleophilic substitution reaction of the covalently linked “atrazine-mercaptopropionic acid” to a new triazine derivative “atrazine-methoxyethanol” was performed. This cleavage product was quantified by gas chromatography. The conditions for this cleavage procedure were optimized and applied to the “atrazine-mercaptopropionic acid” humic acid conjugate and to a humic acid blank. The amount of bound “atrazine-mercaptopropionic acid” was calculated to 16.6 ± 2.5 μmol triazine per gram humic acid, which is equivalent to 0.39 ± 0.07% atrazine.
HPAE-PAD – a sensitive method for the determination of carbohydrates by J. B. Jahnel; P. Ilieva; F. H. Frimmel (pp. 827-829).
High performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) was used for the determination of eleven monosaccharides. Three analytical columns with different selectivities were tested, and the resulting separations were compared calculating precision and detection limits. The monosaccharides could be separated on CarboPAC PA10 in one analysis run with the lowest detection limits and a high precision. For the determination of polysaccharides and humic bound carbohydrates in natural organic matter, an hydrolysis step had to be carried out. With the exception of fructose, the recoveries varied between 56% and 83%. The described methods were applied for the determination of bound carbohydrates in a bog lake water and a soil extract without preconcentrating the samples.
Different detection systems for the HPLC analysis of oxylipins, by-products of the enzymatic generation of 2E-hexenal by Bettina Rehbock; Dietmar Ganßer; R. G. Berger (pp. 830-832).
The incubation of 13-hydroperoxy-9Z,11E,15Z-octadecatrienoic acid (13-HPOT) with a hydroperoxide lyase containing extract of mung bean seedlings (Phaseolus radiatus L.) led not only to the formation of 2E-hexenal, but also to the generation of several non-volatile by-products (oxylipins). These oxylipins, generated by the catalysis of other 13-HPOT metabolizing enzymes, were analyzed by high performance liquid chromatography (HPLC) without time-comsuming derivatization procedures, which would be necessary for their volatilization and stabilization during gaschromatography (GC). Different detection systems such as an evaporative light-scattering detector (ELSD), diode-array detector (DAD), and particle beam-mass spectrometry (PB-MS) were applied. The utilization of an ELSD represented an improvement of sensitivity compared to a DAD, especially in the case of substances with low UV-activity.
NIR-spectrometric analysis of food. Methodical development and achievable performance values by H. Büning-Pfaue; R. Hartmann; J. Harder; S. Kehraus; C. Urban (pp. 832-835).
The application of near infrared spectrometry (NIRS) to estimate the distribution of macro nutrients in food provides a rapid method for predicting food quality. Three methods have been developed for quantitative determination of the constituents of foods containing high levels of moisture (meat products, “consumable meals” and potatoes) using reflectance spectrometry in the near infrared region within 1100–2500 nm. Experience concerning these NIRS method developments is reported in order to predict e.g. the fat, crude protein and carbohydrate content. Generally, the performance values achieved so far indicate that the methods may be used as a replacement for conventional expensive and time-consuming wet chemical analysis.
HPLC-MS/MS identification of tryptophan-derived tetrahydro-β-carboline derivatives in food by B. Gutsche; M. Herderich (pp. 836-839).
Based on electrospray ionization – tandem mass spectrometry coupled to liquid chromatography (HPLC-ESI-MS/MS) a method for separation and selective detection of 1,2,3,4-tetrahydro-β-carboline derivatives (THC) was developed. Retro-Diels Alder (RDA) fragmentation of the tetrahydropyrido moiety resulted in the characteristic neutral loss of 73 amu for tryptophan-derived THC-3-carboxylates. Accordingly, Pictet-Spengler condensation products of tryptamin exhibited product ions formed by loss of 29 amu. However, THC-1-carboxylates as obtained by reaction of tryptamin with α-oxo acids also yielded product ions [M+H-73]+, apparently originating from the combination of RDA-cleavage plus subsequent decarboxylation. As result, one had to consider the possibility of false-positive identification of THC-3-carboxylates in presence of isomeric THC-1-carboxylates. In order to overcome these analytical pitfalls, the unequivocal identification of trace amounts of THC-3-carboxylates by HPLC-MS/MS required the chromatographic separation of isomeric THC prior to selected reaction monitoring (SRM). Utilizing SRM, limits of detection for various THC were established in the 10 ng mL–1 range. Subsequent analysis of food samples like seasoning sauce and yeast extract by HPLC-ESI-MS/MS revealed the presence of tryptamin-derived 1,2,3,4-tetrahydro-β-carboline-1-carboxylic acid, 1-methyl-tetrahydro-β-carboline-1-carboxylic acid, 1-carboxyethyl-tetrahydro-β-carboline and 1-carboxyethyl-tetrahydro-β-carboline-1-carboxylic acid beside established THC-3-carboxylates and -1,3-dicarboxylates.
Sample preparation steps for standardization of calcium ion determination in aerobically-treated sera accounting for influences of temperature and pH by J. P. Heidrich; T. O. Kleine (pp. 839-841).
A 5 min equilibration of 0.250 mL serum sample with room air containing 5.6% CO2, by placing the gas tube < 1 cm above the sample-surface, enables a standardized determination of calcium ion concentration (cCa2+), referred to pH 7.40 and 37 °C, in aerobically handled specimens. Using this method, standardized measurement of calcium ions in serum is possible with a bias less than 2%, even in samples with pH-changes acquired during extended storage.