Analytical and Bioanalytical Chemistry (v.371, #6)

Micellar electrokinetic chromatography (MEKC) is an alternative to liquid chromatographic separations. It is a highly efficient separation technique that is performed with the same experimental set-up as is used for capillary electrophoresis (CE), thus extending the applicability of CE to neutral solutes.MEKC can be regarded as a separation technique with a similar scope to that of reversed-phase high-performance liquid chromatography (RP-HPLC), having advantages over HPLC with regard to the efficiency of the separation system, separation speed, cost, and tolerance to matrix constituents. This paper discusses the applicability of MEKC to real samples and also addresses developments widening the scope of this emerging technique: on-line concentration by stacking or sweeping and sensitive detection schemes.

The implementation of quality elements in research and development is a hot issue, still under discussion and development. In recent years much progress has been made in the development of effective proposals. However there are still problems and misunderstandings on how to apply quality assurance in research and development. This work clarifies these issues, mainly caused by the application of formal standards for quality assurance in R&D. It lists reasons for, and demonstrates benefits of, implementing quality elements in R&D and then offers detailed suggestions for addressing the most important issues without hampering the flexibility and creativity of R&D.

The new laboratory accreditation standard, ISO/IEC 17025, reflects current thinking on good measurement practice by requiring more explicit and more demanding attention to a number of activities. These include client interactions, method validation, traceability, and measurement uncertainty. Since the publication of the standard in 1999 there has been extensive debate about its interpretation. It is the author’s view that if good quality practices are already in place and if the new requirements are introduced in a manner that is fit for purpose, the additional work required to comply with the new requirements can be expected to be modest. The paper argues that the rigour required in addressing the issues should be driven by customer requirements and the factors that need to be considered in this regard are discussed. The issues addressed include the benefits, interim arrangements, specifying the analytical requirement, establishing traceability, evaluating the uncertainty and reporting the information.

Certification of the chlorine content of the isotopic reference materials IRMM-641 and IRMM-642 by Markus Ostermann; Michael Berglund; P. Taylor; M. Máriássy (721-725).
The Slovak Institute of Metrology and the Institute for Reference Materials and Measurements have collaborated in the certification of the two chlorine reference materials IRMM-641 and IRMM-642. Until now no isotopically enriched chlorine isotopic reference material certified for isotopic composition and content has been available commercially. The isotopic reference materials IRMM-641 and IRMM-642 described herein are certified for isotopic composition and for chlorine content.The chlorine content of the reference material IRMM-641 was certified by use of high-precision argentometric coulometric titration at the Slovak Institute of Metrology. The base material used for IRMM-641 is NIST Standard Reference Material 975. The chlorine content of the reference material IRMM-642 was measured by isotope dilution, using negative thermal ionization mass spectrometry at the Institute for Reference Materials and Measurements. Both standard reference materials were prepared by dissolving NaCl in water. The reference material IRMM-641 contains 0.025022±0.00011 mol kg–1 chlorine of natural isotopic composition with an n(37Cl)/n(35Cl) ratio of 0.31977±0.00082. The reference material IRMM-642 contains 0.004458±0.000028 mol kg–1 chlorine with an n(37Cl)/n(35Cl) ratio of 0.01914±0.00088.

Phase transfer and freezing processes investigated on acoustically levitated aqueous droplets by P. Jacob; A. Stockhaus; R. Hergenröder; D. Klockow (726-733).
An acoustic trap was designed and constructed to investigate, on a microscale, physicochemical processes relevant to the troposphere, mainly focusing on the temperature range below 0 °C. Droplets ranging from 0.5 nL to 4 µL (0.1 to 2 mm in diameter) were introduced into the cooled reaction chamber by means of a piezo-driven micro pump with a reproducibility better than 5%. Uptake of H2O2 from the gas phase by the levitated droplet was measured and calibrated by in-situ chemiluminescence. Freezing of stably positioned droplets was observed and documented by means of a microscope and a video camera; this demonstrated the usefulness of the technique for simulation and investigation of cloud processes. Ex-situ microanalysis of sub-microliter droplets by use of a fiber optic luminometer was also shown to be a suitable means of investigating relevant physicochemical processes on a micro scale.

A new calcium-sensor based on ion-selective conductometric microsensors – membranes and features by U. Trebbe; M. Niggemann; K. Cammann; G. Fiaccabrino; M. Koudelka-Hep; S. Dzyadevich; O. Shulga (734-739).
Based on the concept of ion-selective conductometric microsensors (ISCOM) a new calcium sensor was developed and characterized. ISCOM have a single probe, all-solid-state construction and do not need a reference electrode. These sensors are amenable to miniaturization and integration in the true sense of integrated circuit and microsystem technologies. The detection is accomplished by measurement of the bulk conductance Gm of a thin polymeric membrane containing an ion-complexing agent, where the magnitude of Gm can be related to the content of the primary ion in the analyzed solution. Thin-film platinum electrodes forming an interdigitated electrode are used as the transducer to detect the conductivity of the polymeric membrane. Optimization of the membrane composition was carried out by testing different types of calcium-ionophores, polymers, and plasticizers. The sensor characteristics have been investigated. The limit of detection is about 10–7 mol L–1. The dynamic range is 10–6–10–1 mol L–1 with a response time of less than 5 s. These parameters are comparable to those of corresponding potentiometric calcium selective electrodes (ISE). The Ca2+-ISCOM demonstrates good practical relevant selectivities against typical interfering ions for biomedical and environmental applications.

The optimization of a continuous flow system for electrochemical hydride generation coupled to microwave-induced plasma atomic emission spectrometry (MIP–AES) for the determination of Se is presented. A small electrolytic cell with a porous glassy carbon working electrode was used for hydride generation. When using an Ar MIP operated in a TE101 cavity a detection limit of 0.6 ng mL–1 (3σ) could be achieved. The calibration curve was linear up to 1 µg mL–1. A standard deviation of less than 2% (10 replicate analyses) could be achieved. It was shown that interferences of transition metals are of the same order of magnitude as with a larger electrolysis cell described earlier, and light elements hardly caused any signal depression as tested. It was possible to distinguish between Se(IV) and Se(VI) species and seleno-DL-methionine, because under optimized conditions of an electrolysis current of 10 mA, a microwave power of 210 W, an Ar flow rate of 15 L h–1 and a sample flow rate of 2.5 mL min–1 only Se(IV) was transformed to H2Se and transferred into the plasma. Finally, the possibility of an electrochemical pre-enrichment was shown to enable it to further decrease the detection limit.

Hollow-cathode (HC) radiofrequency glow-discharge (rf-GD) optical-emission spectrometry (OES) has been used as detector for the determination of inorganic mercury by cold-vapour (CV) generation in a flow-injection (FI) system. Both NaBH4 and SnCl2 were evaluated as reducing reagents for production of mercury CV. The conditions governing the discharge (pressure, He flow rate, and delivered power) and Hg CV generation (NaBH4 or SnCl2 concentration and reagent flow rate) were optimized using both reducing agents. The analytical performance characteristics of FI–CV–rf-GD–OES for mercury detection were evaluated at the 253.6 nm emission mercury line. Detection limits (DL) of 0.2 ng mL–1 using SnCl2 and 1.8 ng mL–1 using NaBH4 were obtained (100 µL sample injections were used).When the optimized experimental conditions using SnCl2 had been determined, the analytical potential of this CV–rf-GD–OES method was investigated as on-line detector for high-performance liquid chromatographic (HPLC) speciation of mercury (Hg(II) and methylmercury). The HPLC–CV–rf-GD–OES detection limits for 100 µL sample injections were found to be 1.2 and 1.8 ng mL–1 (as mercury) of inorganic mercury and methylmercury, respectively. The reproducibility observed was below ±8% for both species. Finally, the HPLC–CV–rf-GD–OES system developed was successfully applied to the determination of methylmercury (speciation) in two certified reference materials, Dorm-2 and Dolt-2.

The potential of mid-infrared attenuated total-reflection spectroscopy for dermatology studies has been increased by the development of a flexible fiber-optic probe from silver halide material. Such a tool significantly eases epidermal surface characterization. Spectra of human forearm skin and of bovine udder skin (BUS-model), which is used as a substitute for in-vivo tests on man, were compared, and as an example low concentrations of vitamin E acetate (α-tocopherol acetate) in the stratum corneum were measured after topical skin application. Depth profiling was enabled by repeated steps of tape stripping and subsequent skin measurement. The infrared methodology is rapid and can be applied to small areas of skin. It is also sufficiently sensitive for analysis of a large variety of cosmetic formulations and dermatopharmaca. Discrimination of vehicle formulations is possible because of the large information content of mid-infrared spectra.

An inductively coupled plasma–high resolution isotope dilution mass spectrometric (ICP–HRIDMS) method in combination with a microwave-assisted decomposition technique has been developed for the determination of traces of silicon in biological and clinical samples. A 30Si-enriched spike solution was used for the isotope dilution step. Decomposition of the samples was achieved by use either of HNO3 or a mixture of HNO3 and HF. By application of both methods of digestion to the same sample it was possible to differentiate between a poorly soluble silicate fraction and an HNO3-soluble silicon species. Traces of silicon were determined in different reference materials, which are not certified for this element, and in other biological and clinical samples. A concentration range of 1–600 µg g–1 was covered by the different samples. For homogeneous samples relative standard deviations of 2–4% were obtained. The detection limit was strongly affected by the blank. In this connection purification of water, used in the analytical procedure, was especially critical. The blank contribution of the ICP–MS instrument could be minimized by applying a nebulizer and a spray chamber made of PFA, a sapphire injection tube, and a silicon nitride torch. Under these conditions detection limits of 0.15 µg g–1 and 0.2 µg g–1 were obtained for the HNO3 and HNO3–HF digestion methods, respectively, when a sample weight of 0.5 g was used. With regard to expected silicon content this enables determination in almost all biological and clinical samples. The ICP–HRIDMS results were compared with those recently obtained in an interlaboratory study. This isotope-dilution method is an potential option for certification of silicon in reference materials, a method for which is still required.

A new approach for the speciation of metallothioneins (MT) in human brain cytosols is described. The analysis is performed by application of a newly developed coupling of capillary electrophoresis (CE) with inductively coupled plasma–sector field mass spectrometry (ICP–SFMS). Isoforms of metallothioneins are separated from 30–100 µL sample volumes by CE and the elements Cu, Zn, Cd, and S are detected by use of ICP–SFMS.The extraction of cytosols is the first step in the analytical procedure. Tissue samples from human brain are homogenized in a buffer solution and submitted to ultra-centrifugation. The supernatant is defatted and the cytosol pre-treatment is optimized for CE separation by matrix reduction. The buffer concentration and pH used for capillary electrophoretic separation of metallothionein from rabbit liver were optimized. CE with ICP–MS detection is compared to UV detection. In the electropherograms obtained from the cytosols three peaks can be assigned to MT-1, MT-2, and MT-3. As an additional method, size-exclusion chromatography (SEC) is applied. Fractions from an SEC separation of the cytosol are collected, concentrated, and then injected into the CE.The detection of sulfur by ICP–SFMS (medium resolution mode) and quantification by isotope dilution have also been investigated as a new method for the quantification of MT isoforms.The analytical procedure developed has been used for the first time in comparative studies of the distributions of MT-1, MT-2, and MT-3 in brain samples taken from patients with Alzheimer’s disease and from a control group.

Two-dimensional high-resolution gel electrophoresis (2DE) has been applied to the fractionation of 75Se-containing proteins in yeast, grown in 75Se-containing medium, and autoradiography was used for detection of the 75Se-containing proteins. Gel filtration and ultrafiltration were used to check whether the selenium side-chains were stable in the presence of the chemicals used for lysis and 2DE. The mass distribution of the selenium-containing proteins was estimated by use of gel filtration and the results were compared with the distribution obtained by 2DE. A 2DE map of selenium-containing proteins in yeast is presented, and compared with a total protein map of yeast.

Endocrine-disrupting nonylphenols – ultra-trace analysis and time-dependent trend in mussels from the German bight by K. Günther; H.-W. Dürbeck; E. Kleist; B. Thiele; H. Prast; M. Schwuger (782-786).
A very sensitive and efficient analytical procedure is presented for the determination of 4-nonylphenols (NP) in blue mussels by use of off-line coupling of high-performance liquid chromatography (HPLC) and gas chromatography with mass spectrometric detection (GC–MS). Combined steam distillation and solvent extraction were used to extract the analytes from the mussel samples. Before quantification by GC–MS the raw extracts were purified by normal-phase HPLC. 4-n-Nonylphenol was used as internal standard. The detection limit was 15 ng NP absolute, calculated from the blank value. The method was applied to the determination of NP in blue mussel samples from the German North Sea sampled over a period of 10 years. Collection, homogenization, and storage of the mussels were performed according to the Standard Operating Procedures of the German Environmental Specimen Bank since 1985. The total NP concentrations in the mussels decreased significantly from 1985 (4 µg kg–1) to 1995 (1.1 µg kg–1).

Pyrethroid insecticides are widely used in agriculture and private households. Analysis of urine for pyrethroid metabolites is one way to detect human exposure to these insecticides and is carried out regularly as part of the Occupational and Environmental Medicine Monitoring Program recommended by the Deutsche Forschungsgemeinschaft (DFG). Samples are analyzed using GC-MS (selected ion monitoring) following acid hydrolysis, solid phase extraction, esterification with methanol/sulfuric acid, and liquid-liquid extraction. The metabolite, 3-phenoxybenzoic acid (3-PBA), can be derived from several pyrethroids and is, therefore, a useful diagnostic analyte; however, the presence of the over-the-counter drug, ibuprofen ((R,S)-2-(4-isobutylphenyl)propionic acid), interferes with this determination, even after the ingestion of only one 200-mg tablet. The interfering analyte is carboxy-ibuprofen which is not removed by the cleanup step. Experimental work shows that it takes two days for most of the ibuprofen to clear the body before 3-PBA can reliably be determined in urine.

Several greenhouse gases, which are in part or entirely produced by human activities, have accumulated in the atmosphere since approximately the middle of the 19th century. They are assumed to have an additional greenhouse effect causing a further increase of atmospheric temperatures near the ground and a decrease in the layers above approximately 15 km altitude. The currently observed near-surface warming over nearly the entire globe is already considered by a large fraction of our society to be result of this additional greenhouse effect. Complete justification of this assumption is, however, not yet possible, because there are still too many unknowns in our knowledge of participating processes and in our modeling capabilities.

The development and operational evaluation of a calibration gas generator for the analysis of volatile organic compounds (VOC) in air is described. Details of the construction, as well as of the evaluation of the apparatus are presented here. The performance of the test gas generator is validated both by on-line GC analysis of the calibration gas produced and by off-line analysis of adsorptive samples taken from the generated calibration gas. Both, active and passive sampling have been used, and the results demonstrate the excellent accuracy and precision of the generated test gas atmosphere: For the 11 investigated organic compounds (aromatic and halogenated compounds), the found values were in most cases within 5% of the target value with a reproducibility of better than 3% RSD (as determined by the analysis of the sampled adsorbent tubes). Custom made adsorbent tubes were used for active and passive sampling and in both cases were analysed by thermal-desorption GC. Particularly the combination of passive sampling and thermodesorption-GC analysis offers significant advantages over the commonly used active sampling on activated charcoal, followed by CS2 desorption in terms of avoidance of hazardous solvents, potential for automation and improved detection limits. Both sampling techniques are capable for monitoring VOCs at concentrations and under conditions relevant for workplace monitoring.

In the past five years automated high time-resolution measurements of mercury species in ambient air have promoted remarkable progress in the understanding of the spatial distribution, short-term variability, and fate of this priority pollutant in the lower troposphere. Examples show the wide range of possible applications of these techniques in environmental research and monitoring. Presented applications of measurement methods for total gaseous mercury (TGM) include long-term monitoring of atmospheric mercury at a coastal station, simultaneous measurements during a south-to-north transect measurement campaign covering a distance of approximately 800 km, the operation on board of a research aircraft, and the quantification of mercury emissions from naturally enriched surface soils. First results obtained with a new method for the determination of reactive gaseous mercury (RGM) are presented.Typical background concentrations of TGM are between 1.5 and 2 ng m–3 in the lower troposphere. Concentrations of RGM have been determined at a rural site in Germany between 2 and 35 pg m–3. Flux measurements over naturally enriched surface soils in the Western U.S.A. have revealed emission fluxes of up to 200 ng Hg m–1 h–1 under dry conditions.

Partitioning of polycyclic aromatic hydrocarbons in the polyethylene/water system by Jochen F. Müller; K. Manomanii; Munro R. Mortimer; Michael S. McLachlan (816-822).
The suitability of polyethylene sheets as passive samplers of lipophilic contaminants in water bodies was tested. High-density polyethylene (HDPE) and low-density polyethylene (LDPE) sheets were contaminated with PAH. Uncontaminated and pre-contaminated sheets were deployed simultaneously and collected at intervals over 32 days. The exposed sheets and water samples were analyzed for PAH. The initial PAH concentrations in the contaminated and uncontaminated sheets differed by two to three orders of magnitude, but approached a common equilibrium concentration during exposure. The two- to four-ring PAH achieved quasi-equilibrium within the 32-day exposure period, whereas the five- and six-ring PAH did not. The estimated PE/water partition coefficients were approximately three times higher for HDPE than for LDPE, and they were similar in magnitude to the KOW values (the partition coefficients between n-octanol and water). The uptake rate constants were approximately four times higher for HDPE than LDPE, which was attributed to the four times higher specific surface area. The uptake and elimination in HDPE followed linear first-order kinetics, whereas for LDPE very slow elimination rates were observed that could not be explained. The results show that PE is a simple, effective, and inexpensive material for sampling trace organic contaminants in water.

The chemical processes that occur during sequential extraction of a highly Pb-contaminated soil sample were investigated using XAFS spectroscopy for the identification of the Pb species in the solid residues after each step. The sequential extraction was performed following the procedure described by Salomons and Förstner [1]. It was found that during the sequential extraction serious alteration of the chemical binding forms of the Pb occurs. The most important processes underlying the chemical changes are the re-adsorption of solubilized Pb ions by soil matrix components and the precipitation of insoluble Pb species with anions from the extractant.

In respect of complete digestion of organic waste materials, a relevant potent digestion technique was developed, and a prototype of a high pressure ashing device with infrared heating (IR-HP-asher) was built. The apparatus consists of six quartz digestion vessels inside a steel autoclave. The performance of the IR-HP-asher was tested for pure organic substances, for representative wastes from the recycling industry, and for several biological samples. In all cases, complete digestion could be attained within 90 min as well as complete recovery of metal(loid)s present in the sample. Concerning the completeness of digestion and absence of analyte loss, the IR-HP-asher was found to be superior to two conventional microwave digesters also tested.

A five-stage sequential leaching procedure was optimized for the analysis of the fly ash sample, CW6, as a candidate reference material. The distribution of particulate elements was achieved for Cd, Cr, Cu, Pb, Zn, and V into different fractions: (1) exchangeable, (2) bound to carbonate, (3) bound to Fe/Mn oxides, (4) bound to sulfide compounds, and (5) acid soluble, residual fraction. The leachability of the metals proved to be different, so various distribution patterns have been achieved. The results of the total elemental analysis and the sequential leaching method were compared and a good agreement was found. The uncertainty of the leaching method is reasonable, even when experimental parameters are strictly fixed and the analysis is quite tedious. The ratio of environmentally mobile fractions was compared to that from the conventional test method and a reasonable conformity has been found. This characterization method can be used to interpret the leaching behavior of element species and mode of binding to the matrix. Using the optimized sequential procedure, a new aspect can be interpreted to understand the behavior of toxic elements released from fly ashes into nature.

Comparison of three different leaching tests, each characterized by different conditions, e.g. liquid/solid ratio, pH, leachant, stirring conditions, duration time, has been performed within the activities of Analeach, financed by the European Union in the "Cooperation with third Countries" programme (INCO), . The comparison was performed on four highly homogenized fly ash reference materials, of different origin, provided by the Joint Research Centre of Ispra. Seven different elements (Cd, Cr, Cu, Ni, Pb, V, and Zn) were considered in this study. The influence of the main experimental conditions and of the matrix on metal release was studied. Basic characterization of the materials was also performed.

The capability of sewer slime to accumulate heavy metals from municipal wastewater can be exploited to identify the sources of sewage sludge pollution. Former investigations of sewer slime looked for a few elements only and could, therefore, not account for deviations of the enrichment efficiency of the slime or for irregularities from sampling. Results of ICP–MS multi element determinations were analyzed by multivariate statistical methods. A new dimensionless characteristic "sewer slime impact" is proposed, which is zero for unloaded samples. Patterns expressed in this data format specifically extract the information required to identify the type of pollution and polluter quicker and with less effort and cost than hitherto.

On-line flash thermodesorption–GC–MS determination of PCB in sewage sludge by A. Davies; R. Fobbe; R Kuckuk; J. Nolte (855-858).
A flash thermodesorption–gas chromatography–mass spectrometry technique has been developed for the determination of polychlorobiphenyls (PCB), especially the highly toxic planar species, in sewage sludge. A modified Curie-point pyrolyzer was used; in this the flash-desorption temperature was controlled by selecting specific metal alloys for the pyrolysis wire. Samples (3 mg) were loaded into a quartz tube with the special heating wire wound around the outer wall. By this means rapid thermal desorption (TDS) was achieved whereas uncontrolled catalytic breakdown of the analytes was avoided. The thermodesorption unit was connected via a custom-built interface to the GC–MS detection system. The average limit of detection was 15 µg kg–1 sludge – more than one order of magnitude better than the legal requirement.

Solid sampling electrothermal atomic absorption spectrometry using the boat technique and a transversely heated graphite tube was applied to direct analysis of graphite and silicon carbide powders for 14 and 12 impurity elements, respectively. With graphite, for all analytes under investigation, a very effective in-situ analyte/matrix separation was achieved. That was the case also for analytes in silicon carbide requiring atomization temperatures below 2400 °C. At higher atomization temperatures, the decomposition products of silicon carbide give rise to significant background, which can still be corrected.Sample amounts of up to 4 mg graphite and 8 mg silicon carbide per analysis cycle were applied. For all analytes in both materials, limits of detection at the lower ng g–1 and sub-ng g–1 level were achieved, excluding arsenic for which they were 50 ng g–1 and 23 ng g–1 for graphite and silicon carbide, respectively. Quantification was performed using calibration curves measured with aqueous standard solutions. The accuracy was checked by comparison of the results with those obtained by instrumental neutron activation analysis and by other independent methods.

Contribution of ICP-IDMS to the certification of antimony implanted in a silicon wafer – comparison with RBS and INAA results by W. Pritzkow; J. Vogl; A. Berger; K. Ecker; R. Grötzschel; P. Klingbeil; L. Persson; G. Riebe; U. Wätjen (867-873).
A thin-layer reference material for surface and near-surface analytical methods was produced and certified. The surface density of the implanted Sb layer was determined by Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA), and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) equipped with a multi-collector. The isotopic abundances of Sb (121Sb and 123Sb) were determined by multi-collector ICP-MS and INAA. ICP-IDMS measurements are discussed in detail in this paper. All methods produced values traceable to the SI and are accompanied by a complete uncertainty budget. The homogeneity of the material was measured with RBS. From these measurements the standard uncertainty due to possible inhomogeneities was estimated to be less than 0.78% for fractions of the area increments down to 0.75 mm2 in size. Excellent agreement between the results of the three different methods was found. For the surface density of implanted Sb atoms the unweighted mean value of the means of four data sets is 4.81×1016 cm–2 with an expanded uncertainty (coverage factor k=2) of 0.09×1016 cm–2. For the isotope amount ratio R (121Sb/123Sb) the unweighted mean value of the means of two data sets is 1.435 with an expanded uncertainty (coverage factor k=2) of 0.006.

Quantification of corrosion phenomena in plastic processing machines by B. Kemmler; P. Hoffmann; M. Cremer; H. Ortner; G. Mennig (874-881).
In a model platelet system the corrosion of metallic materials was studied by processing polyethylene, polyphenylene sulfide, and glass-fibre-reinforced polyphenylene sulfide. The measurement methods used were scanning electron microscopy (images), electron-probe microanalysis (lateral element maps), secondary-ion mass spectrometry (depth profiles), X-ray photoelectron spectroscopy (chemical bonding), and grazing-incidence X-ray diffraction (structures of crystalline compounds). As non-destructive measure of corrosive attack, grazing-incidence X-ray diffraction, using the intensity ratio (IFe-O/IFe), was found to be the method of choice. The reproducibility for the total procedure was found to range between 6 and 13% (rel.). The intensity ratio was examined as function of depth, of the time of stress, of material composition, and of the surrounding atmosphere. Oxides were identified as main corrosion products. The extent of oxide formation is proportional to the time elapsed after processing.

The main components of five technical mixtures of brominated flame retardants were identified by mass spectroscopy, H-NMR, IR spectroscopy, elementary analysis, and HRGC-MS, respectively. The mixtures have been identified as: phosphoric acid bromopropylates: Bromcal P 67–6 HP; C18-alkylated bromophenols: Bromcal P 40–3; dibromopropyl-2,4,6-tribromophenyl ether: Bromcal 73–5 PE; brominated diphenyl ethers (PBrDE): Bromcal 70–5 DE; decabromodiphenyl ether: Bromcal 82–0. Gas chromatographic retention data of the various constituents were measured on standard GC columns. The data prove the interference of some of the brominated compounds with PCBs and other halogenated pesticides in HRGC using the electron capture detector.

Automated flow-injection spectrophotometric determination of nitrosamines in solid food samples by Encarnación Luque-Pérez; Angel Ríos; Miguel Valcárcel (891-895).
A spectrophotometric method using a flow-injection system is proposed for the determination of nitrosamines in foods (cured-meats). The method is based on the photochemical cleavage of the N–NO bond of the nitrosamine to yield the corresponding amine and nitrite. The nitrite is then detected spectrophotometrically, at 542 nm, by use of its reaction with a modified Griess reagent. Different linear ranges between 0.8 and 2000 ng mL–1 are obtained for the method, depending on the time of exposure of the sample to the UV radiation. The relative standard deviation varies between 2.0 and 3.9% and the sample throughput is between three and seven samples per hour, depending on the experimental conditions. The proposed method was successfully applied to the analysis of N-nitrosodimethylamine in cured ham and loin, bacon, and sausages.