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Analytical and Bioanalytical Chemistry (v.367, #5)
Today’s analytical instrument business: new company name, new management but any new equipment?
by J. M. Mermet (pp. 399-400).
Determination of non-ortho polychlorinated biphenyls in environmental Standard Reference Materials by W. W. Brubaker, Jr.; M. M. Schantz; S. A. Wise (pp. 401-406).
The concentrations of three non-ortho (“coplanar”) polychlorinated biphenyls, 3,3′,4,4′-tetrachlorobiphenyl (IUPAC PCB 77), 3,3′,4,4′,5-pentachlorobiphenyl (IUPAC PCB 126), and 3,3′,4,4′,5,5′-hexachlorobiphenyl (IUPAC PCB 169), were determined in five NIST Standard Reference Materials (SRMs) of environmental and biological interest. The measured levels were approximately between (0.2 to 1.3) ng/g in SRM 1588 a (Organics in Cod Liver Oil), (0.3 to 9) ng/g in SRM 1944 (New York/New Jersey Waterway Sediment), (0.2 to 0.4) ng/g in SRM 1945 (Organics in Whale Blubber), ¶(1 to 18) ng/g in SRM 2974 (Organics in Freeze-dried Mussel Tissue [Mytilus edulis]), and (0.1 to 0.4) ng/g ¶in candidate SRM 1946 (Lake Superior Fish Tissue). PCB 169 was present at < 0.1 ng/g in SRMs 1944 and 2974.
Multielemental analysis in small amounts of environmental reference materials with inductively coupled plasma mass spectrometry by J. Dombovári; J. S. Becker; H.-J. Dietze (pp. 407-413).
The lowest possible sample weight for performing multielemental trace element analysis on environmental and biological samples by ICP-MS has been investigated. The certified reference materials Bovine Liver NIST SRM 1577b, Human Hair NCS DC 73347 and Oriental Tobacco Leaves CTA-OTL-1 were applied at sample weights (1, 5, 20 and 50 mg aliquots, n = 10) which were significantly lower than those recommended with most recoveries in the range of 95–110%. Samples were digested in a mixture of nitric acid, hydrogen peroxide and hydrogen fluoride by closed-vessel microwave digestion. Multielemental analysis was performed with an optimized ICP-QMS method. Aqueous standard solutions were applied for external calibration with rhodium as the internal standard element. The detection limits varied between 0.02–¶0.38 μg/g for Li, Na, Cr, Mn, Ni, Cu, Zn, Sr, Cd, Ba and Pb, and up to 1.92 μg/g for Mg, Al, Ca, Fe and Ni. Digested human plasma samples were spiked with multielemental solution (0.5–10 μg/L) to test the analytical method and the recoveries were 95–105% for most analytes. Our results show that in the case of homogeneous SRMs it is possible to use them in very low amounts (1–5 mg) for method development and quality control.
Wavelength table of chromium emission lines in argon glow discharge optical emission spectrometry by K. Wagatsuma (pp. 414-415).
A wavelength table of chromium lines emitted from an argon glow discharge plasma, which comprises 2049 atomic and ionic emission lines in the wavelength range of 200–440 nm, is presented. The relative intensities are rather different from the data of published wavelength tables based on arc-excited and spark-excited spectra. Emission lines of Ar, Ti, V, Fe, Ni, and Cu in the neighborhood of the prominent Cr emission lines are also compiled as a table. These tables could be employed for the analytical applications in glow discharge optical emission spectrometry. All of the data are presented as Supplementary Electronic Material.
Automated chloride analysis in catalytic science: a low-cost hardware and software implementation by C. Dossi; S. Recchia; A. Fusi (pp. 416-421).
A simple computerized potentiometric titrator is described for performing automated analyses of chloride ions on solid materials as well as the continuous determination of HCl in effluent gas streams. This versatility has been obtained by a dedicated instrumental design, which offers easy interfacing to catalytic reactors and flexibility in software programs, including Gran’s plot determination of end-points. The validation of the analytical methodology for quantitative determination of chloride ions in solid matrices required the definition and the preparation of suitable reference materials of known chloride content.
Dot-immunobinding assay using indirect photoacoustic measurement by Ping Zhou; Yanzhuo Deng; Yun’e Zeng (pp. 422-425).
Dot-immunobinding assay of hepatitis B surface antigen (HBsAg) was performed by a conventionally dot-ELISA technique with 4-chloro-1-naphthol staining, and the quantitative results were measured by an indirect photoacoustic method. In this method, a 2-mW helium-neon laser was applied to provide the excitation beam, the blue spots on the membrane were detected in a piezoelectric transducer-based photoacoustic cell. The operational conditions of measurement were optimized. A significant difference from the negative human serum was obtained for 50 pg in HBsAg detection. The method proposed provides a sensitive quantitative technique for dot-immunobinding assay.
Hydrophilic sensor membrane based on cation-selective protic chromoionophore by Ch. Krause; T. Werner; Ch. Huber; O. S. Wolfbeis (pp. 426-428).
The first potassium optode based on a protic chromoionophore immobilized in a hydrogel matrix is presented. The highly selective protic chromoionophore consists of a cryptohemispherand moiety and a trinitroanilino chromophore part. The acidifying power of potassium ions over sodium ions is 0.6 pH units. This correlates with the findings in solution. In contrast to several crown and aza-crown based chromophores the highly pre-organized moiety allows ion detection even in aqueous environment. The detection limit for potassium ions at ¶pH 7.7 is 5 μM.
A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin by RH. Yang; KM. Wang; D. Xiao; XH. Yang (pp. 429-435).
A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10–6 to 8.0 × 10–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery.
Cu-Ni alloys in electrochemical oxygen analysis by L. Nei (pp. 436-439).
Cu-rich Cu-Ni alloys (containing 70–90% Cu) are shown to be excellent indicator electrode materials for voltammetric measurements at cathodic potentials. These electrodes have been characterised using a variety of methods: rotating disk voltammetry, amperometric measurements and sono-ring-disk voltammetry. The mechanism of electrochemical oxygen reduction at the Ni-30Cu alloy has been established. The results are compared with the surface study results.
Improved detection of transition and rare earth elements in marine samples with the CETAC DSX-100 preconcentration/matrix elimination system and ICP-MS by M. Kühn; M. Kriews (pp. 440-444).
A new method for detection of trace metals in saline samples is described using batch preconcentration with subsequent ICP-MS analyses after direct sample insertion of the analyte loaded chelating resin. The samples were prepared using a CETAC DSX-100 system, which preconcentrates analytes and removes matrix components by a suspended particulate reagent (SPR). The SPR is consisting of polymeric beads of 0.2 μm size that selectively binds the trace metals by iminodiacetic chelating groups. The beads with bound analytes are then nebulized directly into the ICP-MS. The enrichment factors lay between 40 and 48 due to the enrichment of 120 mL suspension to 2.5–3.0 mL eluate. The method was applied and validated to the successful determination of traces of the transition metals Mn, Fe, Ni, Co, Cu, Zn, Cd, and Pb in the Open Ocean Seawater certified reference material NASS-4 and the Coastal Seawater certified reference material CASS-3. In addition to the certified constituents the rare earth elements La, Ce, Eu, Gd, Yb, and Lu were determined.
Automated multiple solid phase micro extraction. An approach to enhance the limit of detection for the determination of pesticides in water by J. Lipinski (pp. 445-449).
A method was developed to decrease the limit of detection (LOD) for pesticide residue analysis in water using multiple SPME. To enhance the absolute amount transferred to the GC column an enrichment step is integrated in the SPME/GC-analysis. A series of several extraction and desorption steps are performed and the analytes are trapped at the front of the cold GC column before the GC analysis is started. The parameters mainly influencing this enrichment are the equilibrium time, the slope of the adsorption time/peak area profile at its start, the number and the duration of the extraction steps. The role of these parameters was investigated.
Determination of palladium in airborne particulate matter in a German city by J. Tilch; M. Schuster; M. Schwarzer (pp. 450-453).
The part of palladium in ambient urban air that is bound to particles and soluble in aqua regia was determined by means of sorbent extraction, coupled with graphite furnace atomic absorption spectrometry (GFAAS) and laser absorption fluorescence spectrometry (LAFS). Samples of about 200 m3 air were taken in a suburb of Berlin, Germany. The coupling of the selective and automated pre-concentration procedure for Pd as N,N-diethyl-N’-benzoylthiourea complex with the respective detection methods proved to be sufficiently sensitive. Severe interference with other matrix constituents, occurring mainly by direct LAFS detection, could be overcome and the detection limit was improved tremendously. The concentration of Pd in ambient air was determined to be in the range from 0.2 to 14.6 pg/m3.
Oil-in-water emulsions as suitable working media for the direct polarographic determination of aziprotryne and desmetryne from its organic extracts in water samples by R. Gálvez; M. Pedrero; F. Buyo; F. J. Manuel de Villena; J. M. Pingarrón (pp. 454-460).
The electroanalytical behavior of the reduction of the herbicides aziprotryne (2-azido-4-isopropylamino-6-methylthio-1,3,5-triazine) and desmetryne (4-isopropylamino-6-methylamino-2-methylthio-1,3,5-triazine) in oil-in-water emulsions is reported. This medium allows the differential pulse polarographic determination of these s-triazines directly from their sample extracts in an appropriate organic solvent. Sodium pentanesulfonate was chosen as the most suitable surfactant to be used as emulsifying agent, whereas ethyl acetate was selected as the organic solvent to form the emulsions. The peak current was maximum in a 0.3 mol L–1 HClO4 medium of the continuous aqueous phase for aziprotryne, and at pH 3.0 for desmetryne, and the potential became more negative as the pH increased for both herbicides. The limiting current is diffusion controlled and the electrode process is irreversible. Four electrons are involved in the overall electrochemical reduction process as determined by controlled potential coulometry, whereas the αna values suggested that two electrons are involved in the rate-determining step. Using differential pulse polarography, aziprotryne and desmetryne can be determined in the emulsified medium over the concentration ranges 1.0 · 10–7–1.0 · 10–4 mol L–1, with limits of detection of 4.5 · 10–8 mol L–1 and 6.6 · 10–8 mol L–1, respectively. The method was applied to the determination of aziprotryne and desmetryne in spiked irrigation water. At concentration levels of 6.0 · 10–7 mol L–1 aziprotryne and 4.0 · 10–7 mol L–1 desmetryne, recoveries of 94 ± 3% and 94 ± 4%, respectively, were obtained after preconcentration on Sep-Pack C18 cartridges. Finally, partial least-squares regression (PLSR) has been used for treatment of the polarographic data obtained from mixtures of aziprotryne, desmetryne and simazine in oil-in-water emulsions. The size of the calibration set was of 29 samples by ninety two current measurements at different potentials. Prediction of the herbicides concentration within the range 1.0 · 10–6 –1.0 · 10–5 mol L–1 was possible.
Determination of s-triazines with copper and glassy carbon electrodes. Flow injection analysis of aziprotryne in water samples by A. Zapardiel; E. Bermejo; J. A. Pérez; M. Chicharro (pp. 461-466).
The detection and determination of s-triazines, atrazine-desethyl and aziprotryne by cyclic voltammetry and an amperometric method using a metallic copper electrode and a glassy carbon electrode are described. The concentrations of atrazine-desethyl and aziprotryne in 0.1 M NaOH solutions were determined using the oxidation signal corresponding to the Cu(0)/Cu(I) redox process. The detection level calculated for these s-triazines were 0.3 and 0.5 μg/mL of analyte, respectively. The glassy carbon electrode was shown to give sensitive reduction response to aziprotryne in flow injection mode. No special activation was required for the glassy carbon electrode. A detection limit of 0.2 μg/mL (20 ng aziprotryne) was obtained for a sample loop of 0.1 mL at a fixed potential of –1.0 V (vs. Ag/AgCl) in 0.1 M HCl and a flow rate of ¶3.5 mL/min. Furthermore, the glassy carbon electrode showed stable response in such a system, and the relative standard deviation was only 2.7% using the same surface, and 6.3% using different surfaces. The method developed was applied to the determination of aziprotryne in environmental and tap water samples; using a prior solid-phase extraction step, aziprotryne concentrations lower than 1.0 ng/mL could be measured.
Efficiency of solvent extraction methods for the determination of methyl mercury in forest soils by J. Qian; U. Skyllberg; Q. Tu; W.F. Bleam; W. Frech (pp. 467-473).
Methyl mercury was determined by gas chromatography, microwave induced plasma, atomic emission spectrometry (GC-MIP-AES) using two different methods. One was based on extraction of mercury species into toluene, pre-concentration by evaporation and butylation of methyl mercury with a Grignard reagent followed by determination. With the other, methyl mercury was extracted into dichloromethane and back extracted into water followed by in situ ethylation, collection of ethylated mercury species on Tenax and determination. The accuracy of the entire procedure based on butylation was validated for the individual steps involved in the method. Methyl mercury added to various types of soil samples showed an overall average recovery of 87.5%. Reduced recovery was only caused by losses of methyl mercury during extraction into toluene and during pre-concentration by evaporation. The extraction of methyl mercury added to the soil was therefore quantitative. Since it is not possible to directly determine the extraction efficiency of incipient methyl mercury, the extraction efficiency of total mercury with an acidified solution containing CuSO4 and KBr was compared with high-pressure microwave acid digestion. The solvent extraction efficiency was 93%. For the IAEA 356 sediment certified reference material, mercury was less efficiently extracted and determined methyl mercury concentrations were below the certified value. Incomplete extraction could be explained by the presence of a large part of inorganic sulfides, as determined by ¶x-ray absorption near-edge structure spectroscopy (XANES). Analyses of sediment reference material CRM 580 gave results in agreement with the certified value. The butylation method gave a detection limit for methyl mercury of 0.1 ng g–1, calculated as three times the standard deviation for repeated analysis of soil samples. Lower values were obtained with the ethylation method. The precision, expressed as RSD for concentrations 20 times above the detection limit, was typically 5%.
Determination of carbendazim in soil samples by anodic stripping voltammetry using a carbon fiber ultramicroelectrode by M. J. González de la Huebra; P. Hernández; O. Nieto; Y. Ballesteros; L. Hernández (pp. 474-478).
A method for the determination of carbendazim (MBC) by anodic stripping voltammetry using a carbon fiber ultramicroelectrode was developed. The ultramicroelectrode was made in our laboratory and its electrochemical behavior was characterized by measuring the electrochemical response with a solution of potassium ferricyanide. The optimum parameters used for the determination of MBC are the following: 0.05 M phosphate buffer at pH 2.0 as supporting electrolyte; a scan rate of v = 10.00 V s–1 and an accumulation potential of Eac = 0.00 V. The MBC was determined in a soil sample with the method proposed and the results found were comparable to those obtained by HPLC.
Determination of Ca, Mg, Fe, Cu, and Zn in blood fractions and whole blood of humans by ICP-OES by C. Prohaska; K. Pomazal; I. Steffan (pp. 479-484).
Inductively coupled plasma – optical emission spectrometry (ICP-OES) was applied to the determination of the elements Ca, Mg, Fe, Cu, and Zn in blood plasma, erythrocytes, lymphocytes, and whole blood to obtain reliable data on their distribution in blood fractions. The samples were carefully collected to avoid contamination. Two different nebulizers (Babington and Meinhard) were tested and optimized for this analytical problem. Line selections for all elements of interest were performed (LODs were 0.8 μg/L for Ca, 1.7 μg/L for Cu, 3.0 μg/L for Fe, 1.1 μg/L for Mg, and 4.2 μg/L for Zn). Recoveries were determined as approx. 100%, and standard reference material was analyzed to obtain reliable data on element distribution. The optimized method was applied to the determination of Ca, Mg, Fe, Cu, and Zn in the course of a clinical study on blood and blood fractions of two groups of humans of differing health. The concentrations measured in blood fractions were verified by balancing with the values found in whole blood.
Application of ACC method to synchronous luminiscence: determination of α-tocopherol and α-tocopheryl acetate in beverages by O. Pastor-Ferrer; A. R. Maurí-Aucejo; M. Llobat-Estellés (pp. 485-490).
A new method based on the Q parameter, that permits the determination of the Ccompound A /Ccompound B ratio without preparing calibration graphs of the two compounds, is proposed. This method has been applied to signals obtained by synchronous luminiscence. Simultaneous determination of α-tocopherol and α-tocopheryl acetate in beverages using synchronous fluorescence has been carried out. To isolate the compounds from samples, liquid extraction with n-hexane as the organic phase was employed. The presence of interferences was tested using the apparent content curves (ACC) method and the Cα-tocopherol/¶Cα-tocopheryl acetate ratio was calculated using the Q parameter. The reproducibility and detection limit for the determination of α-tocopherol and α-tocopheryl acetate were 6.6% and 0.016 mg/L and 1.8% and 0.017 mg/L, respectively.
Determination of marker constituents in radix Glycyrrhizae and radix Notoginseng by near infrared spectroscopy by Y. Chen; L. K. Sørensen (pp. 491-496).
High-performance liquid chromatographic (HPLC) methods were developed for the determination of glycyrrhizin in radix Glycyrrhizae and ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf and Rg1 in radix Notoginseng. These methods were used as reference methods for near-infrared (NIR) spectroscopy. Spectroscopic calibrations were developed for the determination of glycyrrhizin, the total content of ginsenosides and the individual major ginsenosides Rb1, Rd, Re and Rg1. Standard errors of cross validation (SECV) were 1.22 mg g–1 for glycyrrhizin (concentration range 21.3–34.1 mg g–1) and 0.99 mg g–1 for the sum of ginsenosides (concentration range 55.3–¶71.1 mg g–1). The corresponding coefficients of determination (R2) were 0.94 and 0.98, respectively. The SECVs were generally less than a factor of 2.5 of the repeatability standard deviation of the HPLC methods.
Relation between prediction errors of inverse and classical calibration by D. Grientschnig (pp. 497-498).
The formulae for prediction errors of inverse and classical calibration derived by Centner, Massart and de Jong in the Fresenius’ Journal of Analytical Chemistry (1998) 361 : 2–9 are reconsidered. All calculations assume univariate calibration by ordinary least squares regression applied to an infinite number of data pairs. Inverse calibration gives rise to an error variance which is smaller by a certain factor than that of classical calibration. This factor amounts to unity plus the ratio of the variances of the measurement errors and of the responses used for the calibration. The root mean squared error of prediction is also smaller for inverse than for classical calibration, namely by the square root of this factor. A prediction error calculated in that way agrees well with a result obtained by Monte Carlo simulations.
Fluorimetric determination of methylmercury as an ion-association complex with rhodamine B in the presence of iodide by Hua-Bin Li; Feng Chen; Xiang-Rong Xu (pp. 499-501).
A fluorimetric method for the determination of methylmercury was established. The method was based on the formation of an ionic pair between iodide-methylmercury-rhodamine B in hydrochloric acid, which can be extracted with benzene. The fluorescence emission was measured at λex/λem 575/590 nm, and the experimental variables and possible interference were studied. The linear calibration range was 4 × 10–8 mol/L ∼ 5 × 10–7 mol/L with a correlation coefficient of 0.9992. The detection limit was 1 × 10–8 mol/L. The method was used to determine methylmercury in human hair. The recovery was in the range of 91% to 105% and the relative standard deviation was 2.8%. The results agreed with those obtained by gas chromatography with electron capture detection.
High-performance liquid chromatographic determination of the oxidation products of 2-isopropylnaphthalene and 2,6-diisopropylnaphthalene by J. Zawadiak; B. Orlińska; Z. Stec (pp. 502-506).
The oxidation products of 2-isopropylnaphthalene and 2,6-diisopropylnaphthalene containing hydroperoxides, alcohols and ketones can be determined by high-performance liquid chromatography on a Nova-Pak Silica column with isocratic and gradient elution using hexane and isopropanol.