Amperometric biosensor based on D-aminoacid oxidase for the R-perindopril assay

A new amperometric biosensor based on D-aminoacid oxidase is described for the assay of R-perindopril. R-perindopril can be determined in the 400–¶20 nmol/L concentration range; the detection limit is ¶10 nmol/L. The selectivity was checked with S-perindopril, D- and L-proline, and polyvinylpyrrolidone. The main interfering species was D-proline. An automated system for the assay of R-perindopril based on the concept of flow injection with an amperometric biosensor (based on D-aminoacid oxidase) as detector is also described. The system is suitable for the on-line monitoring of R-perindopril at a sampling rate of 72 samples/h, in the linear range: 100 nmol/L –20 nmol/L with an RSD better than 0.09% (n = 10).     

ETAAS method for the determination of Cd, Cr, Cu, Mn and Se in blood fractions and whole blood

An electrothermal atomic absorption method (ETAAS) for the direct determination of trace elements (Cd, Cr, Cu, Mn, Se) both in blood fractions (erythrocytes, plasma and lymphocytes) and whole blood was developed. Zeeman background correction and graphite tubes with L’vov platforms were used. Samples were ¶diluted with HNO₃/Triton X-100 and pipetted directly ¶into the graphite tube. Ashing, pretreatment and atomization steps were optimized carefully for the different fractions and elements applying different matrix modifiers ¶for each element. For the lymphocyte fraction a multi-fold injection technique was applied. Low detection limits ¶of the ETAAS method (Cd 0.13 μg/L, Cr 0.11 μg/L, ¶Cu 0.52 μg/L, Mn 0.13 μg/L, Se 0.7 μg/L of whole blood) combined with small quantities of sample necessary for analysis allow determination of trace elements in this matrix. Verification of possible differences in the trace element status of humans was performed with statistical significance (P < 0.05). In addition, a contribution to the determination of normal values of essential elements was achieved. The method was applied for determination of trace elements in human blood and blood fractions of two groups (n = 50) different in health status.     

Online monitoring of aerosols with an energy-dispersive X-ray spectrometer

A continuously working sampling and analyzing device was developed and tested. It is suitable for monitoring of metals bound to particulate matter in emissions of stack gases. The samples were precipitated on a pure quartz fiber filter tape and analyzed shortly afterwards non-destructively by an energy dispersive X-ray spectrometer (EDXRS). By using this method a wide range of elements with atomic numbers from 19 (K) to 82 (Pb) can be analyzed. New experiments have shown that the novel combined particle sampling and analysis system (X-DUST) could also successfully be used for the monitoring of toxic elements in ambient air.     

Application of a hexapole collision and reaction cell in ICP-MS Part II: Analytical figures of merit and first applications

The application of an ion-guiding gas-filled hexapole collision/reaction cell in ICP-MS has been studied to characterize the analytical figures of merit that can be achieved with this approach. For the elements investigated, application of a buffer and a reaction gas resulted in improved sensitivities which are lowest for Be with about 7 · 10⁷ cps per μg mL^–1 and highest for Ba with about ¶6 · 10⁸ cps per μg mL^–1. Relative standard deviations (RSD) < 0.1% were obtained. Application of the reaction gas H₂ was used to suppress polyatomic ions caused by argon. The reduction amounted up to four orders of magnitude so that elements such as Ca, K, Cr, Fe, As and Se could be analyzed in nitric and hydrochloric acid or in methanol. Detection limits of 6 pg mL^–1 for Cr in 2% methanol, 23 pg mL^–1 for As and 9 pg mL^–1 for Se in 0.28 M HCl were achieved. For other elements detection limits ¶< 1 pg mL^–1 were realized in the medium and high mass range. Accuracy was proved using the NIST 1643d standard reference material.     

Inductively coupled plasma mass spectrometry: a versatile tool for a variety of different tasks

In a laboratory that is working in many different fields, a systematic approach is needed to decide ¶efficiently how a given analytical task should be handled. Four typical examples are presented to show how ICP-MS may be used to solve client’s problems. The examples are: the identification of lead projectiles, the determination of total and leachable fractions of impurities in a polymer (PVDF), used for manufacturing components of ultra-pure water distribution systems, the authentication of ¶antique silver alloys, and the determination of rare earth elements in geological materials. These examples demonstrate not only typical challenges for the instruments and the analysts handling them, but also ways to reach ¶a satisfactory solution within a reasonable amount of time.     

Simultaneous spectrophotometric determination of La, Ho, Mn 5-Br-PADAP complexes using multivariate calibration with partial least-squares (PLS) data evaluation

A simple and fast analytical pocedure is proposed for the simultaneous spectrophotometric determination of lanthanum, holmium and manganese in synthetic ceramics, (La_(0.8–x) Ho_x Sr_0.2 MnO₃), by using the partial least-squares (PLS) method. As chromogenic agent 5-Br-PADAP [2-(5-bromo-2-pyridylazo)-5-diethylaminophenol] was used, which form colored complexes with the three elements studied. To avoid metal hydrolysis, a mixture ¶of ethanol and Triton X-100 at pH 9.5 was used for all ¶experiments. A set of 17 calibration solutions measured throughout the 400–700 nm wavelength range was used in the calibration step. The concentration range for Mn(II) was 1–12 × 10^–6 mol L^–1, while the range for the rare earth elements La(III) and Ho(III) was 2–8 × 10^–6 mol L^–1. In order to demonstrate the applicability of the proposed method, a set of artificial samples containing the three analytes in variable proportions was prepared and analyzed. The analytical results obtained were quite acceptable with relative errors not greater than 7% in most cases.     

Monitoring of total Hg in the river Elbe: FIA-device for on-line digestion

The development of an apparatus for the on-line sampling, digestion and quantification of total mercury in surface water is described. Detection and quantification is done by flow injection cold vapor atomic absorption spectroscopy (FI-CVAAS). Three digestion methods were tested, chemical, microwave and UV. The influence of the digestion parameters (digestion method, digestion time, microwave power, concentration of oxidation solution) on the recovery of mercury in water of the river Elbe have been investigated. Mercury can be determined almost quantitatively (recovery rate > 85%) with some digestion procedures described. The best results were reached by UV digestion. The technique is fast, simple ¶to handle and robust. Each complete analysis only take four minutes. The working range is 10 to 1000 ng/L. The measuring arrangement has been applied successfully in a governmental monitoring station at Schnackenburg/Elbe, Germany.     

Spectrophotometric and direct-reading methods for the analysis of gas phase peroxyacetic acid

A new method for the determination of peroxyacetic acid (PAA) in gas phase samples is described. It is based on the oxidation of ABTS (2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate) by PAA with formation of a radical cation which is characterized by four strong absorption maxima between 405 nm and 810 nm. These allow for sensitive spectrophotometric determination of the peracid. The selectivity of the method towards hydrogen peroxide is strongly dependent on the sampling method used. Impinger sampling and sampling based on the use of coated solid sorbents (test tubes) was performed. Limits of detection are 10^–8 mol, limits of quantification are ¶5 × 10^–8 mol, the linear range consists of 1.5 concentration decades in both cases. Using ABTS-coated test tubes above 1 × 10^–7 mol, direct reading of the results is possible and may be used as rapid screening method for the PAA concentration.     

Characterization of sampling behavior for multielements in NIST SRM 2703

Sampling behavior of multielements for NIST SRM 2703, a marine sediment, was studied with sample sizes from 1 mg down to ng level by a combination of INAA, PIXE and SRXRF. On 1 mg sample size level, sampling behavior for multielements in NIST SRM 2703 and its parent SRM 2702 were comparatively characterized by using INAA combining with Ingamells model. Results showed that sampling uncertainties for 12 elements of both materials were found to be better than 1%, and those of four other elements in SRM 2703 better than in SRM 2702. At sample sizes not able to be accurately weighed (<1 mg), PIXE and SRXRF were used and the effective sample sizes estimated. Sampling uncertainties for nine elements were found to be better than 1% at sample sizes of tenth mg level, and those for six elements better than 10% on ng levels.     

Cationic cyanine as a near-infrared fluorescent probe for the determination of nucleic acids

A new method with a cationic near-IR cyanine as fluorescent probe was developed for the determination of nucleic acids. The near-IR cyanine shows maximum excitation and emission wavelengths at 765 and 790 nm, respectively, in aqueous solution. The method is based on the fluorescence decrease of near-IR cyanine in the presence of nucleic acids. Under optimal conditions, the ratio of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of ¶nucleic acids over the range 0.10–1.2 μg/mL for CT (calf thymus) DNA or SM (salmon sperm) DNA, and 0.10–¶1.6 μg/mL for yeast RNA. The detection limits were ¶30 ng/mL for CT DNA, 25 ng/mL for SM DNA and ¶70 ng/mL for yeast RNA. The relative standard deviation (n = 6) was 2.1% for 500 ng/mL CT DNA, 2.4% for ¶500 ng/mL SM DNA and 2.7% for 500 ng/mL yeast RNA, respectively.     

Application of magdala red as a fluorescence probe in the determination of nucleic acids

A fluorescence quenching method was developed for the rapid determination of DNA and RNA using magdala red as fluorescence probe. In weakly acidic ¶medium, the fluorescence of magdala red (λex>lem = 54055 nm) can be largely quenched by DNA or RNA. The calibration graphs are linear over the range 0.01–¶1.2 μg/mL for both calf thymus DNA (CT DNA) and salmon DNA (SM DNA), and 0.015–1.0 μg/mL for yeast RNA, respectively. The corresponding detection limits are ¶6.0 ng/mL for CT DNA, 7.0 ng/mL for SM DNA and ¶15.0 ng/mL for yeast RNA, respectively. CT DNA could be determined in the presence of 20% (w/w) yeast RNA, and the relative standard deviation of six replicate measurements is 3.18% for 400 ng/mL of CT DNA. Interference from coexisting substances in the determination of DNA was also examined. Real samples were determined with satisfactory results.     

Implementation of the EU Water Framework Directive in monitoring of small water bodies in Hungary, I. Establishment of surveillance monitoring system for physical and chemical characteristics for small mountain watercourses

The EU Water Framework Directives (WFD) prescribes to achieve a good status of surface waters by 2015. To keep this deadline of a new three level (surveillance, operational and investigative) monitoring system is required, including hydro-morphological, biological and chemical elements. The status of a water body should be related to the reference conditions, depending on surface water types. In Hungary, the standard monitoring network for surface water quality has been operated for rivers and large lakes; however no satisfactory information is available for small water bodies. Therefore, there is an urgent need to design a methodology to develop a monitoring network for small watercourses. For this purpose a slightly impacted mountain stream (Nagy Stream in Mátra Mountains), was selected and intensively monitored during three years (May 2002 → May 2005). Hydrological, biological and chemical parameters required by WFD were monitored in this program. Variability of parameters vs. time and space was also investigated. The minimum frequency of sampling was determined for chosen physico-chemical components to meet the WFD standards for confidence. It was found that the minimum frequency of sampling suggested by WFD in space and time may not be adequate for precise and accurate characterization of water quality.     

Multiscale and megavariate monitoring of the process networked structure: M2NET

We present a process monitoring scheme aimed at detecting changes in the networked structure of process data that is able to handle, simultaneously, three pervasive aspects of industrial systems: (i) their multivariate nature, with strong cross‐correlations linking the variables; (ii) the dynamic behavior of processes, as a consequence of the presence of inertial elements coupled with the high sampling rates of industrial acquisition systems; and (iii) the multiscale nature of systems, resulting from the superposition of multiple phenomena spanning different regions of the time‐frequency domain. Contrary to current approaches, the multivariate structure will be described through a local measure of association, the partial correlation, in order to improve the diagnosis features without compromising detection speed. It will also be used to infer the relevant causal structure active at each scale, providing a fine map for the complex behavior of the system. The scale‐dependent causal networks will be incorporated in multiscale monitoring through data‐driven sensitivity enhancing transformations (SETs). The results obtained demonstrate that the use of SET is a major factor in detecting process upsets. In fact, it was observed that even single‐scale monitoring methodologies can achieve comparable detection capabilities as their multiscale counterparts as long as a proper SET is employed. However, the multiscale approach still proved to be useful because it led to good results using a much simpler SET model of the system. Therefore, the application of wavelet transforms is advantageous for systems that are difficult to model, providing a good compromise between modeling complexity and monitoring performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of urban dust (PM<Subscript>2</Subscript>/PM<Subscript>10-2</Subscript>) in Daejeon city by instrumental neutron activation analysis

Summary As part of an air pollution monitoring study, airborne particulate matter (PM₂/PM_10-2) samples were collected from 2000 to 2003 at two sampling sites in an urban region, Daejeon, the middle of Korea. Mass concentrations of both fine and coarse fractions and that of the black carbon in the fine particles were measured using the Gent stacked filter unit sampler and the smoke stain reflectometer, respectively. In the collected samples the concentrations of 24 elements were analyzed using instrumental neutron activation analysis. Monitored data were investigated for their temporal trends under different environmental conditions and their seasonal correlation patterns. Crustal enrichment factors were also estimated to establish the contribution between anthropogenic and crustal origin. Patterns for airborne particle matter (APM) and elemental concentrations, seasonal variation of some marker elements were investigated. The results can be applied for the investigation of further air pollution sources and for the evaluation of air quality.     

Online tracking of the thermal reduction of graphene oxide by two-dimensional correlation infrared spectroscopy

Thermal reduction of graphene oxide (GO) via rapid heating is an environment-friendly and cost-effective method. However, the detailed reduction mechanism remains unclear because of lack of methods for online monitoring of GO thermal reduction. In this study, the thermal reduction of GO (from 20 °C up to 400 °C in argon atmosphere) was successfully monitored online and investigated through temperature-dependent FTIR spectroscopy combined with scaling-MW2D FTIR spectroscopy and generalized 2D correlation analyses. Raman spectroscopy, XPS, and XRD studies were also conducted to characterize the structural changes before and after reduction. SEM and AFM analyses were performed to directly observe the formation of defects in GO after thermal reduction. According to scaling-MW2D results, the thermal reduction of GO was divided into two processes, namely, 35 °C–182 °C (process I) and 182 °C–385 °C (process II). Process I rapidly eliminates oxygen functional groups, and process II gradual removes them. The 2D correlation analysis for each process indicated the sequential order of movements of the oxygen-containing functional groups during thermal reduction. Process I comprised six steps, and process II contained four sequential steps. This work elucidated the complex deoxygenation steps and the mechanism of GO thermal reduction.     

Estimation of unsaturated hydrocarbon pollutants in air based on selective gas chromatography with ozone

Regular monitoring of toxic organic pollutants in air is a very important issue in environmental pollution control. Among these, unsaturated hydrocarbon pollutants (UHP) such as ethylene and β-propylene and another ¶18 olefins are of prime importance. A very fast method for the individual identification of UHPs in air is proposed. This method is based on gas-chromatographic separation with selective detection of unsaturated organic compounds (UOC) and on the chemical reaction of UOC with ozone in the gas phase. In view of the mathematical model derived for this ozonation process, a comparison of FID-chromatogram and ozonogram can be carried out for identification of the contaminants. This identification can be performed without preliminary separation in the presence of the main components. The method provides a high sensitivity (< 0.005 to 0.72 mass %) and selectivity.     

Soil sampling uncertainty on arable fields estimated from reference sampling and a collaborative trial

On three fields of arable land of (3–6)×10⁴ m², simple reference sampling was performed by taking up to 195 soil increments from each field applying a systematic sampling strategy. From the analytical data reference values for 15 elements were established, which should represent the average analyte mass fraction of the areas. A “point selection standard deviation” was estimated, from which a prediction of the sampling uncertainty was calculated for the application of a standard sampling protocol (X-path across the field, totally 20 increments for a composite sample). Predicted mass fractions and associated uncertainties are compared with the results of a collaborative trial of 18 experienced samplers, who had applied the standard sampling protocol on these fields. In some cases, bias between reference and collaborative values is found. Most of these biases can be explained by analyte heterogeneity across the area, in particular on one field, which was found to be highly heterogeneous for most nutrient elements. The sampling uncertainties estimated from the reference sampling were often somewhat smaller compared to those from the collaborative trial. It is suspected that the influence of sample preparation and the variation due to sampler were responsible for these differences. For the applied sampling protocol, the uncertainty contribution from sampling generally is in the same range as the uncertainty contribution from analysis. From these findings, some conclusions were drawn, especially about the consequences for a sampling protocol, if in routine sampling a demanded “certainty of trueness” for the measurement result should be met.     

Real‐time reaction monitoring by probe electrospray ionization mass spectrometry

Probe electrospray ionization (PESI) is a modified version of the electrospray ionization (ESI), where the capillary for sampling and spraying is replaced by a solid needle. High tolerance to salts and direct ambient sampling are major advantages of PESI compared with conventional ESI. In this study, PESI‐MS was used to monitor some biological and chemical reactions in real‐time, such as acid‐induced protein denaturation, hydrogen/deuterium exchange (HDX) of peptides, and Schiff base formation. By using PESI‐MS, time‐resolved mass spectra and ion chromatograms can be obtained reproducibly. Real‐time PESI‐MS monitoring can give direct and detailed information on each chemical species taking part in reactions, and this is valuable for a better understanding of the whole reaction process and for the optimization of reaction parameters. PESI‐MS can be considered as a potential tool for real‐time reaction monitoring due to its simplicity in instrumental setup, direct sampling with minimum sample preparation and low sample consumption. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of trace-metal concentrations in size-classified atmospheric particles by ETV-ICP-MS

Atmospheric particles were sampled and fractionated according to their size by a cascade impactor in Berlin, capital city of Germany, on the Brocken, peak of the Harz mountains and on the Szrenica peak in the Giant mountains, Republic Poland. The fractionated particles were collected on small graphite targets and subsequently analyzed by ETV-ICP-MS. Distribution curves were measured showing trace-metal contents in air versus the aerodynamic particle diameter for the elements Pb, Ag, Cd and Tl. Despite good element correlation, the distribution curves differ significantly for the three sampling locations. The limits of detection for the elements of concern were in the pg/m³ range at a sampling time of 4 h. An attempt was made to determine single particles: in urban aerosols a content was found of 1 · 10^–13 g Tl and 9 · 10^–13 g Ag in single particles of the size fraction < 7.5 μm and > 3.45 μm.     

A Novel Way of Sampling Particles Containing Platinum Group Elements from Automobile Catalysts

A new sampling system was developed in order to be applied directly at the exhaust pipe of vehicles combined with an exhaust gas analyzer during the standard New European Driving Cycle (NEDC). In that way a quantitative sampling of Pt, Pd, and Rh (Platinum Group Elements, PGEs) in particle form on filters and gas monitoring could be achieved simultaneously, applying the sampling system on a variety of vehicles of different age and engine capacity. The samples were examined by SEM-EDX for morphological and qualitative analysis of the particles. By using an appropriate digestion procedure and the analytical techniques of ICP-MS and GFAAS, concentrations were found in the range of 0.35–87 ng/km for Pt, 3.3–437 ng/km for Pd, and 0.9–72 ng/km for Rh. Furthermore the investigation showed that fresh catalysts as well as engines with larger capacity emitted higher amounts of PGEs in comparison to older catalysts and smaller capacity engines. According to the results of this research the palladium emissions were dominant in comparison to the platinum ones. This way of sampling might prove advantageous in testing new technology catalysts through their PGEs emission.