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Analytical and Bioanalytical Chemistry (v.368, #4)
Stripping voltammetry in environmental and food analysis by Kh. Z. Brainina; N. A. Malakhova; N. Yu. Stojko (pp. 307-325).
The review covers over 230 papers published mostly in the last 5 years. The goal of the review is to attract the attention of researchers and users to stripping voltammetry in particular, its application in environmental monitoring and analysis of foodstuffs. The sensors employed are impregnated graphite, carbon paste, thick film carbon/graphite and thin film metallic electrodes modified in-situ or beforehand. Hanging mercury drop electrodes and mercury coated glassy carbon electrodes are also mentioned. Strip and long-lived sensors for portable instruments and flow through systems are discussed as devices for future development and application of stripping voltammetry.
A new method of the determination of significant factors with factor analysis in AES by R. Pieterwas; G. Ecke; R. Kosiba; H. Rößler (pp. 326-334).
An important step of the factor analysis method is the determination of the number of significant factors. Common techniques as Malinowski indicator function provide perhaps uncertain results in spectroscopic cases depending on signal to noise ratio, the overlap of spectra, sample misalignment and concentration of the factors. ¶A new method for the determination of the number of components in Auger depth profiling is established. The new method of correlation of abstract basic spectra (CABS) takes into consideration the influence of experimental error especially noise. Simulations were carried out, to prove the CABS method. The results are compared with those obtained by established methods. Auger depth profiles of SiC and Si3N4-layers on Si(111) were analyzed by means of the CABS method and Target Factor Analysis. Aspects of data pretreatment as filtering are discussed.
Plastic membrane electrode for the potentiometric determination of pethidine hydrochloride in pharmaceutical preparations by Z.-H. Liu; M.-L. Wen; Y. Yao; J. Xiong (pp. 335-337).
A novel poly(vinyl chloride) membrane electrode with dibutyl phthalate as plasticizer based on the pethidine-tetraphenylborate ion-association complex as ion-exchange site for the determination of pethidine hydrochloride in injections and tablets was developed. A linear response for 1 × 10–5 to 1 × 10–2 mol/L drug with a slope of 51.77 mV/decade was established. The optimum ¶pH range was 2–8. The lower detection limit was 2.18 × 10–6 mol/L. There were negligible interferences from a number of inorganic and organic cations and some common drug excipients. The electrode proposed had been successfully applied to determine pethidine hydrochloride in tablets and injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.
Construction and analytical application of a biosensor based on stearic acid-graphite powder modified with sweet potato tissue in organic solvents by O. Fatibello-Filho; I. Cruz Vieira (pp. 338-343).
A biosensor based on stearic acid-graphite powder modified with sweet potato (Ipomoea batatas (L.) Lam.) tissue as peroxidase source was constructed and applied in organic solvents. Several parameters were studied to evaluate the performance of this biosensor such as stearic acid-graphite powder and tissue composition, type and concentration of supporting electrolyte, organic solvents, water/organic solvent ratio (% v/v) and hydrogen peroxide concentration. After selection of the best conditions, the biosensor was applied for the determination of hydroquinone in cosmetic creams in methanol. At the peroxidase electrode hydroquinone is oxidized in the presence of hydrogen peroxide and the radical formed was reduced back electrochemically at –180 mV vs Ag/AgCl (3.0 mol L–1 KCl). The reduction current obtained was proportional to the concentration of hydroquinone from 6.2 × 10–5 to 1.5 × 10–3 mol L–1 (r = 0.9990) with a detection limit of 8.5 × 10–6 mol L–1. The recovery of hydroquinone from two samples ranged from 98.8 to 104.1% and an RSD lower than 1.0% for a solution containing ¶7.3 × 10–4 mol L–1 hydroquinone and 1.0 × 10–3 mol L–1 hydrogen peroxide in 0.10 mol L–1 tetrabutylammonium bromide methanol-phosphate buffer solution (95:5% v/v) (n = 10) was obtained.
Determination of trace amounts of gold and silver in high-purity iron and steel by electrothermal atomic absorption spectrometry after reductive coprecipitation by T. Itagaki; T. Ashino; K. Takada (pp. 344-349).
Trace amounts of gold and silver in high-purity iron or steel were preconcentrated by reductive coprecipitation with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry (ET-AAS). Both gold and silver could be simultaneously separated and sensitively determined in 10 metals (aluminum, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, vanadium and zinc). Comparable values were obtained for gold and silver in reference materials (low alloy steel) by the proposed method and a non-separation method; good agreement was found between the analytical values by both methods and the certified values. The proposed method is easy, simple and not dependent on sample composition and content. Moreover, gold and silver in metal samples could be simultaneously separated together with selenium and tellurium. The detection limits for gold and silver (3 σ) are 0.003 μg g–1 and 0.002 μg g–1, respectively.
Determination of AlN and Al2O3 in steels by electrolytic separation and wavelength dispersive X-ray fluorescence spectrometry by J. Reisel; J. Flock; J. A. C. Broekaert (pp. 350-357).
The determination of non-metallic aluminium inclusions in steel samples, mainly consisting of AlN and Al2O3, can be performed with the aid of their X-ray fluorescence Kβ-line. The enrichment of these inclusions with an electrolytic isolation is described and shown to enable the analysis of samples with even very low aluminium content. The absolute detection limit of the combined electrolysis and X-ray fluorescence spectrometric detection using the Al-Kβ line was found to be 3 μg Al in the residue that is below 0.001 mass-% in the steel sample under the given conditions. Due to low spectral resolution a deconvolution of the obtained data is required, but then a detection limit of 1.8 mass-% Al2O3 and 0.4 mass-% AlN in the binary mixture can be achieved. Sixteen samples of two low-alloyed steel qualities with a total amount of insoluble aluminium in the range of 0.003 to 0.013 mass-% have been analyzed with the procedure developed.
Determination of trace impurities in some nickel compounds by flame atomic absorption spectrometry after solid phase extraction using Amberlite XAD-16 resin by L. Elçi; M. Soylak; A. Uzun; E. Büyükpatır; M. Doğan (pp. 358-361).
A simple flame atomic absorption spectrometric (FAAS) procedure for the determination of lead, bismuth, gold, palladium and cadmium as impurities in Raney nickel and nickel oxide was developed using a preconcentration step on an Amberlite XAD-16 resin packed column. Lead, bismuth, gold, palladium and cadmium were quantitatively recovered and separated from a solution containing 1 M HCl and 0.3 M NaI by the column system. Effects of the various parameters such as reagent concentrations, sample volume, matrix effects, etc. have been investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (n = 7) is generally lower than 12%. The limit of detection (3s, n = 20) was between 10–270 ng/g. The results were used for separation and preconcentration of five trace elements from nickel matrices.
Isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS) for the certification of lead and cadmium in environmental standard reference materials by K. E. Murphy; E. S. Beary; M. S. Rearick; R. D. Vocke (pp. 362-370).
Lead (Pb) and cadmium (Cd) have been determined in six new environmental standard reference materials (SRMs) using isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The SRMs are the following: SRM 1944, New York-New Jersey Waterway Sediment, SRMs 2583 and 2584, Trace Elements in Indoor Dust, Nominal 90 mg/kg and 10,000 mg/kg Lead, respectively, SRMs 2586 and 2587, Trace Elements in Soil Containing Lead from Paint, Nominal 500 mg/kg and 3000 mg/kg Lead, respectively, and SRM 2782, Industrial Sludge. The capabilities of ID ICP-MS for the certification of Pb and Cd in these materials are assessed. Sample preparation and ratio measurement uncertainties have been evaluated. Reproducibility and accuracy of the established procedures are demonstrated by determination of gravimetrically prepared primary standard solutions and by comparison with isotope dilution thermal ionization mass spectrometry (ID TIMS). Material heterogeneity was readily demonstrated to be the dominant source of uncertainty in the certified values.
Matrix interferences in the determination of trace elements in waste waters by inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization by B. Budič (pp. 371-377).
The use of inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization (USN-ICP-AES) for determining Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Sr, V and Zn in complex matrices of Ca, Na, K and P in waste waters is described. Generally, depressions in the analyte emission intensity occur in the presence of concomitants. Matrix interferences can be minimized by increasing the operating power and lowering the carrier gas flow rate. However, the enhancement of the signal-to-background ratios (SBRs) shows an opposite trend. Therefore, routine analyses were performed at a compromise power setting of 1350 W, a carrier gas flow rate of 0.8 L min–1 and an observation height of 14 mm above the load coil and using a matrix matched calibration procedure. Limits of detection (LODs) at chosen operating conditions were at μg L–1 levels for most of the elements studied, including mercury when KBr is added to the analyte solution to enhance sensitivity. LODs were not significantly changed in the presence of matrix elements. Recoveries for the majority of added elements from spiked waste water samples are between 93 and 105% using a matrix matched calibration.
Extraction of PCDD/PCDF from soil with supercritical CO2: Optimization by a three-level factorial design approach by C. von Holst; G. Maio; B. W. Wenclawiak; R. L. Darskus (pp. 378-383).
Two factors (pressure and temperature) varied over three levels were optimized for the extraction of PCDD/F from native contaminated soil with toluene-modified supercritical carbon dioxide. Temperature had a strong positive effect on the recovery. The most efficient extraction was achieved at 120 °C. This is in contrast to the influence of the temperature on the extraction of HCH, where a higher recovery is obtained at 60 °C than at 150 °C. The optimized conditions found for this soil were applied to the analysis of a BCR (European Commission) reference material prepared from contaminated industrial soil. The results are in good agreement with those of an interlaboratory study.
Determination of Δ4-3-ketosteroids based on oxime formation by difference circular dichroism spectroscopy by A. Szentesi; A. Gergely; P. Horváth; Gy. Szász (pp. 384-388).
Δ4-3-Ketosteroids exhibit an intensive negative Cotton effect on the circular dichroism (CD) spectra in the wavelength range for the n-π* electronic transition (270–¶350 nm). With hydroxylamine hydrochloride, Δ4-3-ketosteroid compounds can be transformed into oxime derivatives. Following oxime formation, positive ellipticity with low intensity can be registered in this wavelength range. The quantitative determination of Δ4-3-ketosteroids is based on the considerable difference between the ellipticities before and after oxime formation. The difference ellipticity for the six ketosteroids examined (norethisterone, levonorgestrel, levonorgestrel acetate, methyltestosterone, testosterone phenylpropionate, nortestosterone phenylpropionate) varies linearly with the concentration in the interval 6 × 10–6–3 × 10–3 mol/L. The method can be well applied to determination of Δ4-3-ketosteroid contamination of norgestimate [(+)-13-ethyl-17-hydroxy-18,19-dinor-17α-pregn-4-en-20-yn-3-one oxime acetate]; 0.02–10% impurity can be measured.
Microscale gas generator of methane for the dead time determination of capillary columns by J. M. F. Nogueira (pp. 389-391).
Methane produced by the reduction of iodomethane by sodium borohydride in diglyme can be used to determine the dead time in capillary gas chromatography. Best results were achieved using standard non-polar capillary columns, hydrogen, helium and nitrogen carrier gases and flame ionization detection.
Enrichment method for trace amounts of rare earth elements using chemofiltration and XRF determination by I. E. De Vito; R. A. Olsina; A. N. Masi (pp. 392-396).
A preconcentration method for subsequent determination of rare earth elements (REE) by X-ray fluorescence (XRF) spectrometry was developed. The method is based on using (o-[3,6-disulfo-2-hydroxy-1-naphthylazo]-benzenearsonic acid) (Thorin) as a complexing agent which is retained on a polyamide membrane by a chemofiltration process. The pH dependence of the chemofiltration of these metal ions on the membrane and other variables, such as flow-rate, contact time, kinetic of complex formation, etc. were determined. The membrane containing the chemofiltrate formed a thin film, which eliminated the interelemental effects when measured by XRF. The detection limits were 23, 23 and 49 ng/mL for Sm(III), Eu(III) and Gd(III), respectively. High enrichment factors were obtained. The method was successfully applied to the preconcentration of Sm(III), Eu(III) and Gd(III) from different samples.
Identification and quantification of sources of variation in the analysis of steel by Renger H. Jellema; David J. Louwerse; Age K. Smilde; Mathieu J. P. Gerritsen; Daan Guldemond (pp. 397-406).
In steel industries a need exists for the reduction of variation in the element concentrations. This need is triggered by an increasing demand for high quality steel products by clients. The results of a large-scale experiment concerning the identification and quantification of sources of variation in the production, sampling and analysis of steel are presented. The results are obtained by means of a strategic approach that consists of six steps. By means of this strategic approach, insight is obtained in the build-up of the total variation. This knowledge can be used to reduce the influence of those factors that have a major impact on the total variation. Attention is focused on estimating the magnitude of sources of variation apparent in sampling of certain stages of the steel making process and in analysis of steel samples by means of spark emission spectrometry.
On the presence of PCDD/Fs and other chlorinated hydrocarbons in the second generation of the European Reference Soil Set – the EUROSOILS by B. M. Gawlik; D. Martens; K.-W. Schramm; A. Kettrup; A. Lamberty; H. Muntau (pp. 407-411).
The second generation of the European Reference Soil-Set, the so-called EUROSOILS, has been introduced recently. The presence of organic micro-pollutants in this new type of reference materials has already been studied for polycyclic aromatic hydrocarbons, triazines, phenylureas and other pesticides. The already large amount of data concerning the level of different contaminants, the elemental composition and matrix properties is completed by a survey by means of GC/MS on the polychlorinated dibenzodioxins/furans (PCDD/Fs) and other chlorinated hydrocarbons. Higher concentrations for ¶4,4′-DDT in EUROSOIL 2 (10.57 ± 0.02 ng/g), for dieldrin in EUROSOIL 3 (8.85 ± 0.87 ng/g) and for heptachlor-epoxide in EUROSOIL 4 (5.86 ± 0.16 ng/g) could be detected. Sum concentrations for PCDD/Fs were 15.02 ng/kg (EUROSOIL 1), 214.29 ng/kg (EUROSOIL 2), 873.32 ng/kg (EUROSOIL3), 54.47 ng/kg (EUROSOIL 4) and 119.61 ng/kg (EUROSOIL 5).
Sonoelectroanalytical detection of lead at a bare copper electrode by D. F. Tibbetts; J. Davis; R. G. Compton (pp. 412-414).
The sonochemically facilitated, mercury free detection of Pb2+ at a copper electrode has been investigated as a means of simplifying the quantification of this important analyte and to minimise the interference of copper ion. The procedure relies upon maximising the formation of Pb-Cu intermetallic compounds leading to the emergence of a single, easily quantifiable stripping signal. Linear responses to Pb2+ were obtained with a sensitivity comparable to that obtained at a bare glassy carbon electrode. Interference from Cu2+, Zn2+ and Cd2+ was assessed on the copper electrode with no appreciable change in the Pb2+ voltammetric profile observed. In contrast, bare glassy carbon showed a significant change in Pb2+ voltammetric profile as Cu2+ was added, due to the formation of intermetallic species.
Sono-anodic stripping voltammetric determination of cadmium in the presence of surfactant by Y. C. Tsai; J. Davis; R. G. Compton (pp. 415-417).
The effect of applying ultrasound in anodic stripping voltammetry analysis of Cd2+ in pH 4.6 buffer containing the surfactant Triton X-100 has been investigated. Manipulation of the horn intensity and the horn/electrode distance was found to reduce the deleterious influence of the surfactant on the height of the cadmium peak. The system has been optimised to take advantage of the in situ cleaning action offered by ultrasound. As a result facile detection of Cd2+ (0.05–4 μM) in solutions containing 10 μg/mL Triton X-100 can be achieved without recourse to sample pretreatments or electrode modifications.
Determination of arsenic by continuous hydride generation with direct introduction into an O2-argon microwave plasma torch atomic emission spectrometer by Peihong Liang; Anmo Li (pp. 418-420).
The determination of arsenic was studied with a simple and economic method. A continuous hydride generation system is interfaced to a microwave plasma torch atomic emission spectrometer (MPT-AES). Arsenic hydride is transferred directly and continuously by the carrier gas into the plasma torch without separation of hydrogen. When oxygen is introduced into the outer tube of the plasma torch, the plasma is more stable and has a higher tolerance to hydrogen. The detection limit (3σ) is 5.2 μg/L when the forward power is 100 W with argon as support gas. Application to the standard sample coal fly ash showed a comparable result to the certified quantity.
Flame atomic absorption spectrometric determination of trace chromium in various standard samples after preconcentration with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol by M. A. Taher (pp. 421-423).
Chromium can be quantitatively retained as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-tetraphenylborate(TPB) complex onto microcrystalline naphthalene in the pH range 4.8–5.9 from a large volume of aqueous solutions of various standard samples. After filtration, the solid mass consisting of the chromium complex and naphthalene was dissolved with 5 mL of dimethylformamide and the metal was determined by air-acetylene FAAS. A detection limit of ¶4 ng/mL for chromium was established. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of chromium in various standard alloys and biological samples.
Phenylacetylene as a new surrogate standard for the determination of BTEX by GC/FID by A. Fischer; P. Werner (pp. 424-425).
Benzene, toluene, ethylbenzene, xylene (short form: BTEX) and other monoaromatic compounds are environmental contaminants which are often analyzed by GC/FID. For the calculation of BTEX concentrations in water samples normally external quantification with defined BTEX solutions is sufficient. However, for accurate quantification of BTEX in complex matrices it is necessary to use internal standards, e.g. ¶1-chlorohexane. Isotopes of BTEX are usually the best alternative but they are only applicable to GC/MS, because their retention times are similar to the original BTEX. 1-Chlorohexane and phenylacetylene were compared with respect to their quality as internal standards. Good results were obtained with ¶the monoaromatic phenylacetylene as a surrogate standard. The physical properties of phenylacetylene are very similar to BTEX species and it normally does not occur in environmental samples. 1-Chlorohexane was more strongly adsorbed on the used soil than BTEX during sample preparation. This fact suggests that the single aromatic rings of BTEX and phenylacetylene are mainly responsible for the adsorption behavior.
Determination of nicotinamide (NA) using its polarographic catalytic wave in the presence of KIO3 by J. F. Song; Y. J. Su; W. Guo (pp. 426-428).
Nicotinamide (NA) yields a polarographic catalytic wave with a peak potential –1.38 V (vs. SCE) in 0.1 mol/L HAc-NaAc (pH 4.7)/4 × 10–3 mol/L KIO3 buffer solution. The sensitivity of the catalytic wave increased in one order of magnitude as compared to that of the responding reduction wave without KIO3. Based on this observation, a new method for the determination of NA was recommended. The second order derivative peak current was proportional to the NA concentration in the range of 5 × 10–8 – 6 × 10–7 mol/L. 0.11-fold vitamin B1, 0.13-fold B2, 0.14-fold B6 and 8-fold nicotinic acid amounts do not interfere the determination of 1 × 10–6 mol/L NA. The proposed method was used to determine the NA content in multivitamin tablets, with good agreement to the declared amount.
A flow injection chemiluminescence system for the determination of isoniazid by Y. Huang; Z. Zhang; D. Zhang; J. Lv (pp. 429-431).
A chemiluminescence (CL) flow system is described for the determination of isoniazid based on its enhancement on the chemiluminescence (CL) emission produced upon mixing a hexacyanoferrate(III) solution with an alkaline luminol solution. The system responds linearly to isoniazid concentration in the range 0–1 mg/L with a detection limit (3σ) of 0.03 μg/L, relative standard deviation (RSD) of 1.2% for 0.1 mg/L isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations.