Complex Environmental Matrix Research Articles

Potential analytical applications of interfacing a GC to an FT-ICR MS: fingerprinting complex sample matrixes.

Details of interfacing a high-pressure gas chromatograph to the internal ion source of a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) are described. We present our preliminary results and potential analytical applications of GC/FT-ICR for analyzing complex biological and environmental sample matrixes, such as petroleum mixtures. Based on GC/FT-ICR data, rapid characterization of various automobile gasoline samples is possible. Comparison between acquired data from the GC/FT-ICR MS (in broadband mode) and a commercial GC quadrupole mass spectrometer (QMS) (over a wide mass range) indicates that sensitivity of the GC/FT-ICR MS is an order of magnitude lower. High mass resolution and mass measurement accuracy of FT-ICR MS can be utilized for unambiguous molecular formula identification of unknown analytes.

Group-specific 16S rRNA targeted probes for the detection of type I and type II methanotrophs by fluorescence in situ hybridisation.

The study of methane-oxidising bacteria (methanotrophs) is of special interest, because of their role in the natural reduction of methane emissions from many different sources. Therefore new probes were developed to detect specifically either type I (Methylococcaceae) or type II methanotrophs (Methylocystaceae). The probes have shown high specificity in fluorescence in situ hybridisations (FISH), as demonstrated by parallel hybridisation of target and reference strains as well as sequence data analysis. With these probes, methanotrophs were detected in soil and root samples from rice microcosms, demonstrating their applicability even in a complex environmental matrix.

Group-specific 16S rRNA targeted probes for the detection of type I and type II methanotrophs by fluorescence in situ hybridisation

The study of methane-oxidising bacteria (methanotrophs) is of special interest, because of their role in the natural reduction of methane emissions from many different sources. Therefore new probes were developed to detect specifically either type I (Methylococcaceae) or type II methanotrophs (Methylocystaceae). The probes have shown high specificity in fluorescence in situ hybridisations (FISH), as demonstrated by parallel hybridisation of target and reference strains as well as sequence data analysis. With these probes, methanotrophs were detected in soil and root samples from rice microcosms, demonstrating their applicability even in a complex environmental matrix.

LC-MS/MS signal suppression effects in the analysis of pesticides in complex environmental matrices.

The application of LC separation and mobile phase additives in addressing LC-MS/MS matrix signal suppression effects for the analysis of pesticides in a complex environmental matrix was investigated. It was shown that signal suppression is most significant for analytes eluting early in the LC-MS analysis. Introduction of different buffers (e.g. ammonium formate, ammonium hydroxide, formic acid) into the LC mobile phase was effective in improving signal correlation between the matrix and standard samples. The signal improvement is dependent on buffer concentration as well as LC separation of the matrix components. The application of LC separation alone was not effective in addressing suppression effects when characterizing complex matrix samples. Overloading of the LC column by matrix components was found to significantly contribute to analyte-matrix co-elution and suppression of signal. This signal suppression effect can be efficiently compensated by 2D LC (LC-LC) separation techniques. The effectiveness of buffers and LC separation in improving signal correlation between standard and matrix samples is discussed.

Quantitative LC-ESI-MS Analysis for Pesticides in a Complex Environmental Matrix Using External and Internal Standards

Quantitative liquid chromatography electrospray mass spectrometry (LC-MS) analysis for pesticides in a complex environmental matrix using external and internal standard calibration was investigated. Various approaches to introducing different internal standard compounds to address quantitative errors associated with signal suppression were also examined. The study involved the analysis of pesticides in wheat hay matrix samples using three kinds of internal standard compounds: deuterium labeled (D3), carbon-13 (singly labeled), and structural analogs (derivatives) of the target analytes. Introduction of the internal standard by volumetric addition and direct post-column infusion were also studied and compared. Isotopically labeled internal standards (i.e. D3- 13C-) were found to be effective in correcting quantitative errors associated with signal suppression. The application of singly labeled 13C compounds may result in nonlinear calibration due to mass interference with the target analyte species. The interference may be compensated by using quadratic curve-fitting or subtraction of the interfering component. Although ineffective as volumetric internal standards, structural analogs can be effective in compensating for signal suppression when introduced into the LC effluent by continuous post-column infusion. Furthermore, the post-column introduction method allows the application of a single internal standard compound for the quantification of each analyte in a multi-component mixture. The use of internal standards can be effectively incorporated into residue analysis development methods for pesticides in environmental matrices. High accuracy and reproducibility can be achieved while improving method efficiency by reducing the need for comprehensive sample clean-up.

Comparison among different extraction methods (PFE, SFE, Sonication, Soxhlet) for the isolation of organic compounds from coal

This work presents the results of a study involving modern methodologies, such as the ultrasonic extraction, pressurized fluid extraction (PFE) also termed accelerated solvent extraction (ASE), and the extraction with supercritical fluids (SFE) for the isolation of organic compounds from a complex environmental matrix coal. The validation of the results obtained through these techniques was carried out by means of comparison with the results obtained by classical standard extraction method based on Soxhlet. The obtained results demonstrated that SFE present superior performance in the extraction of organic compounds from coal samples than all other investigated techniques (PFE or ASE, Ultrasonic, and Soxhlet). On the other hand, SFE presents the worst selectivity for the extraction of some selected classes such as aromatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs). © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 292–301, 2000

Leaf construction cost, nutrient concentration, and net CO2 assimilation of native and invasive species in Hawaii.

The effects of biological invasions are most evident in isolated oceanic islands such as the Hawaiian Archipelago, where invasive plant species are rapidly changing the composition and function of plant communities. In this study, we compared the specific leaf area (SLA), leaf tissue construction cost (CC), leaf nutrient concentration, and net CO2 assimilation (A) of 83 populations of 34 native and 30 invasive species spanning elevation and substrate age gradients on Mauna Loa volcano in the island of Hawaii. In this complex environmental matrix, where annual precipitation is higher than 1500 mm, we predicted that invasive species, as a group, will have leaf traits, such as higher SLA and A and lower leaf CC, which may result in more efficient capture of limiting resources (use more resources at a lower carbon cost) than native species. Overall, invasive species had higher SLA and A, and lower CC than native species, consistent with our prediction. SLA and foliar N and P were 22.5%, 30.5%, and 37.5% higher, respectively, in invasive species compared to native ones. Light-saturated photosynthesis was higher for invasive species (9.59 μmol m-2 s-1) than for native species (7.31 μmol m-2 s-1), and the difference was larger when A was expressed on a mass basis. Leaf construction costs, on the other hand, were lower for the invasive species (1.33 equivalents of glucose g-1) than for native species (1.37). This difference was larger when CC was expressed on an area basis. The trends in the above traits were maintained when groups of ecologically equivalent native and invasive species (i.e., sharing similar life history traits and growing in the same habitat) were compared. Foliar N and P were significantly higher in invasive species across all growth forms. Higher N may partially explain the higher A of invasive species. Despite relatively high N, the photosynthetic nitrogen use efficiency of invasive species was 15% higher than that of native species. These results suggest that invasive species may not only use resources more efficiently than native species, but may potentially demonstrate higher growth rates, consistent with their rapid spread in isolated oceanic islands.

Determination of N-Nitrosodimethylamine in Complex Environmental Matrixes by Quadrupole Ion Storage Tandem Mass Spectrometry Enhanced by Unidirectional Ion Ejection

A gas chromatography (GC)/tandem mass spectrometry method using a quadrupole ion storage mass spectrometer (QISMS, trademark of Varian Associates Inc.) operated in chemical ionization (CI) mode has been developped for the determination of N-nitrosodimethylamine (NDMA) in complex environmental matrices. Using a customized scan function, the method allows for the simulateneous storage of [M+H] + ions of both NMDA and NDMA-d 6 . Collisionally activated dissociation of both native and deuterated [M+H] + ions, carried out by consecutive resonant excitation of each isolated ion species, permits daughter ion quantitation based on an internal standard

Distinguishing diphenylamine and N-nitrosodiphenylamine in hazardous waste samples by using high-performance liquid chromatography/thermospray/mass spectrometry

N-Nitrosodiphenylamine and diphenylamine in environmental samples cannot be easily distinguished and determined by conventional gas chromatography/mass spectrometry. By using a high-performance liquid chromatography/thermospray/mass spectrometry technique, the authors were able to directly distinguish these two compounds in a complex environmental matrix. Analytical results showed two distinct chromatographic peaks and distinct mass spectra of these two compounds. The unequivocal identification and measurement of one of the compounds in a contaminated soil sample from a hazardous waste site is demonstrated.