Influence of heavy metals, especially lead, on lipid metabolism, serum alpha-tocopherol level, total antioxidant status, and erythrocyte redox status of copper smelter workers

An assessment of influence of the occupational exposure to heavy metals, especially lead, on serum lipids (including lipid peroxides), total antioxidant status, erythrocyte redox status, and serum alpha-tocopherol level was performed in a group of 141 healthy male copper smelter workers. The following parameters were measured: blood lead and cadmium levels, serum manganese, copper, zinc, calcium and magnesium levels, free erythrocyte protoporphyrins (FEP), total cholesterol, HDL₂-, HDL₃-cholesterol, triglycerides and lipid peroxides in serum, erythrocyte superoxide dismutase (SOD_E), catalase (Cat_E) and glutathion peroxidase (PxGSH_E) activities, erythrocyte reduced glutathione level (GSH_E), serum alpha-tocopherol level, and serum total antioxidant status (TAS). Mean Pb_B was within the norm range (328.2 ± 141.7 μg/L), but mean Mn_S concentration slightly exceeded 10 μg/L (11.04 ± 3.79 μg/L). Mean cholesterol and triglycerides concentrations were near the highest borderline values. We found a significantly negative correlation between lead levels and HDL₃-cholesterol (r = 0.253, P < 0.05). Erythocyte catalase activity and TAS were lowered. TAS showed significant negative correlation with Pb_B. A group of workers with Pb_B≥ 400 μg/L had significantly lower Cat_E, lower TAS, and lower HDL₃-cholesterol, compared to the workers with Pb < 400 μg/L. We have also found positive correlation between alpha-tocopherol and total cholesterol (r = 0.267, P < 0.05) and between alpha-tocopherol and LDL-cholesterol (r = 0.207, P < 0.05).     

Full automation of solid-phase microextraction/on-fiber derivatization for simultaneous determination of endocrine-disrupting chemicals and steroid hormones by gas chromatography–mass spectrometry

A fully automated method using direct immersion solid-phase microextraction (DI-SPME) and headspace on-fiber silylation for simultaneous determinations of exogenous endocrine-disrupting chemicals (EDCs) and endogenous steroid hormones in environmental aqueous and biological samples by gas chromatography–mass spectrometry (GC-MS) was developed and compared to a previously reported manual method. Three EDCs and five endocrine steroid hormones were selected to evaluate this method. The extraction and derivatization time, ion strength, pH, incubation temperature, sample volume, and extraction solvent were optimized. Satisfactory results in pure water were obtained in terms of linearity of calibration curve (R ²=0.9932–1.0000), dynamic range (3 orders of magnitude), precision (4–9% RSD), as well as LOD (0.001–0.124 μg L⁻¹) and LOQ (0.004–0.413 μg L⁻¹), respectively. These results were similar to those obtained using a manual method, and moreover, the precision was improved. This new automated method has been applied to the determinations of target compounds in real samples used in our previous study on a manual SPME method. Exogenous octylphenol (OP), technical grade nonylphenol (t-NP), and diethylstilbestrol (DES) were at 0.13, 5.03, and 0.02 μg L⁻¹ in river water and 3.76, 13.25, and 0.10 μg L⁻¹ in fish serum, respectively. Natural steroid hormones estrone (E₁), 17β-estradiol (E₂), and testosterone (T) were at 0.19, 0.11, and 6.22 μg L⁻¹ in river water; and in female fish serum E₁, E₂, and pregnenolone (PREG) were at 1.37, 1.95, and 6.25 μg L⁻¹, respectively. These results were confirmed by the manual method. The developed fully automated SPME and on-fiber silylation procedures showed satisfactory applications in environmental analysis and the performances show improved precision and a reduced analysis time compared to the manual method.     

Determination of fumonisins B1 and B2 in Portuguese maize and maize-based samples by HPLC with fluorescence detection

Fumonisins B₁ (FB₁) and fumonisin B₂ (FB₂) are the main members of a family of mycotoxins produced by Fusarium verticillioides, Fusarium proliferatum, and other fungi species of the section Liseola. The present work shows the results of comparative studies using two different procedures for the analysis of fumonisins in maize and maize-based samples. The studied analytical methods involve extraction with methanol/water, dilution with PBS, and clean-up through immunoaffinity columns. Two reagents (o-phthaldialdehyde and naphthalene-2,3-dicarboxaldehyde) were studied for formation of fluorescent derivatives. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of fumonisins in maize involved extraction with methanol/water (80:20), clean-up with an immunoaffinity column, and derivatization with naphthalene-2,3-dicarboxaldehyde (NDA). The limit of detection was 20 μg kg⁻¹ for FB₁ and 15 μg kg⁻¹ for FB₂. Recoveries of FB₁ and FB₂ ranged from 79% to 99.6% for maize fortified at 150 μg kg⁻¹ and 200 μg kg⁻¹, respectively, with within-day RSDs of 3.0 and 2.7%. The proposed method was applied to 31 samples, and the presence of fumonisins was found in 14 samples at concentrations ranging from 113 to 2,026 μg kg⁻¹. The estimated daily intake of fumonisins was 0.14 μg kg⁻¹ body weight per day.     

Determination of cyanide in blood by electrospray ionization tandem mass spectrometry after direct injection of dicyanogold

An electrospray ionization tandem mass spectrometric (ESI-MS-MS) method has been developed for the determination of cyanide (CN^–) in blood. Five microliters of blood was hemolyzed with 50 μL of water, then 5 μL of 1 M tetramethylammonium hydroxide solution was added to raise the pH of the hemolysate and to liberate CN^– from methemoglobin. CN^– was then reacted with NaAuCl₄ to produce dicyanogold, Au(CN)₂^–, that was extracted with 75 μL of methyl isobutyl ketone. Ten microliters of the extract was injected directly into an ESI-MS-MS instrument and quantification of CN^– was performed by selected reaction monitoring of the product ion CN^– at m/z 26, derived from the precursor ion Au(CN)₂^– at m/z 249. CN^– could be measured in the quantification range of 2.60 to 260 μg/L with the limit of detection at 0.56 μg/L in blood. This method was applied to the analysis of clinical samples and the concentrations of CN^– in the blood were as follows: 7.13 ± 2.41 μg/L for six healthy non-smokers, 3.08 ± 1.12 μg/L for six CO gas victims, 730 ± 867 μg for 21 house fire victims, and 3,030 ± 97 μg/L for a victim who ingested NaCN. The increase of CN^– in the blood of a victim who ingested NaN₃ was confirmed using MS-MS for the first time, and the concentrations of CN^– in the blood, gastric content and urine were 78.5 ± 5.5, 11.8 ± 0.5, and 11.4 ± 0.8 μg/L, respectively.     

Investigation of the effect of berberines alkaloids in <Emphasis Type="Italic">Coptis chinensis</Emphasis> Franch on <Emphasis Type="Italic">Bacillus shigae</Emphasis> growthby microcalorimetry

The inhibitory effects of five berberines alkaloids (BAs) from rhizoma of Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Bacillus shigae (B. shigae) growth were investigated by microcalorimetry. The power-time curves of B. shigae with and without BAs were acquired; meanwhile, the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constants (k1, k2), half inhibitory ratio (IC50), maximum heat output (Pmax), and peak time (tp). The values of k1 and k2 of B. shigae in the presence of the five BAs decreased with the increasing concentrations of BAs. Moreover, Pmax was reduced, and the value of tp increased with increasing concentrations of the five drugs. The inhibitory activity varied with different drugs. IC50 of the five BAs was respectively 75 μg/mL for berberine, 90 μg/mL for coptisine, 115 μg/mL for palmatine, 220 μg/mL for epiberberine, and 400 μg/mL for jatrorrhizine. The sequence of antimicrobial activity of the five BAs berberine ＞ coptisine ＞ palmatine ＞ epiberberine ＞ jatrorrhizine. The functional groups methylenedioxy at C2 and C3 on phenyl ring improve antimicrobial activity more strongly than methoxyl at C2 and C3 on phenyl ring. However, the effect of bacteriostasis is not significant with methylenedioxy or methoxyl at C9 and C10 on phenyl ring.     

Anodic stripping voltammetric determination of total lead, copper and selenium in whole blood and blood serum

A two-step procedure including appropriate wet-digestions, separation of selenium from interfering ions such as heavy metal ions with pentyl alcohol and anodic stripping voltammetric (ASV) determination of Pb²⁺, Cu²⁺ and SeO₃ ^2– is developed. The elements in digested whole blood and serum sample solutions were determined by using a standard addition method. 1 × 10^–9 mol/L SeO^2– ₃, Cu²⁺ and Pb²⁺ were successfully determined with relative standard deviations of approximately 1–2% (n = 6–8). Received: 19 August 1996 / Revised: 24 February 1997 / Accepted: 28 February 1997     

Determination of carbon impurities in epitaxial layers from semiconductor silicon by means of charged particles

The energy-dependent range of charged particles in activation analysis according to the reaction¹²C(d,n)¹³N permits the method to be applied to carbon determination in model epitaxial layers of sufficient thickness. We investigated 100 μm epitaxial layers of the n-type and undoped 50 μ layers as to p⁻ Czochralski substrates. Deuterons were slowed down with Cu and Ta foils having a limiting energy of 13.5 MeV, to 4.2 MeV and 2.9 MeV, respectively. In the resulting activation depths of 52 and 102 μm, the sensitivity of the method, which is 3·10¹⁴ at ·cm⁻³C at E_d=10 MeV in silicon, is reduced to 25% and 10%, respectively. An optimal flux of 0.9 μA·cm⁻² was maintained. After irradiation, 20 or 10 μm were etched off. The sample was inductively fused at 1500 K in a Pb₃O₄/B₂O₃ mixture.¹³N was passed with He as carrier gas into an absorption vessel kept at 77 K, and its activity was measured in γ, γ-coincidence.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

Quantitation ofAcidothermus cellulolyticus E1 endoglucanase andThermomonospora fusca E3 exoglucanase using enzyme-linked immunosorbent assay (ELISA)

Two distinct quantitative indirect ELISAs were developed to determine the concentration of recombinant cellulase enzymes in culture filtrates. A monoclonal antibody (E1P7) was used as the primary antibody in developing an ELISA specific forAcidothermus cellulolyticus E1 endoglucanase. Likewise, a polyclonal rabbit serum (Ab684) was used to develop an ELISA specific forThermomonospora fusca E₃ exoglucanase. Dose-response curves indicated a dynamic range for both assays between 0.01 and 0.08 μg/mL (1–8 ng/assay) when purified enzymes were used as standards. These assays have been used to estimate concentrations of secreted recombinant E1 and/or E₃ in culture supernatants ofStreptomyces lividans strain TK24 in which the corresponding genes have been cloned and expressed.     

Denitrification in presence of benzene,toluene, and <Emphasis Type="Italic">m</Emphasis>-xylene

Denitrification of the electron donors toluene-C(15–100 mg/L), m-xylene-C (15–70 mg/L), benzene-C (5–25 mg/L), and acetate-C as experimental reference (50–140 mg/L) was carried out in batch culture. An initial concentration of 1.1±0.15 g of volatile suspended solids/L of denitrifying sludge without previous exposure to aromatic compounds was used as inoculum. The results showed toluene and nitrate consumption efficiency (E _T and E _N′ respectively) of 100%. Toluene was completely mineralized (oxidized) to CO₂. In all cases, the N₂ (γ_N2) and HCO ₃ ⁻ yields (γ_HCO3) were 0.97±0.01 and 0.8±0.05, respectively. The consumption efficiency (E _x ) of m-xylene (53±5.7%) was partial. The γ_N2 and γ_HCO3 were 0.96±0.01 and 0.86±0.02, respectively. Benzene was not consumed under denitrifying conditions. The specific consumption rates of toluene (q _T ) and m-xylene (q _X ) were lower than that of acetate (q _A ). The differences in specific consumption rates were probably owing to the negative effect of benzene, toluene, and isomers of xylene on the cell membrane.     

Determination of (E)-3,5,4′-Trimethoxystilbene in Rat Plasma by LC with ESI-MS

(E)-3,5,4′-trimethoxystilbene (BTM-0512) is a resveratrol analog with a variety of pharmacological action, including anti-cancer properties, anti-allergic activity, estrogenic activity, antiangiogenic activity, and vascular-targeting activity against microtubule-destabilization. There is, however, no validated analytical method for quantification of (E)-3,5,4′-trimethoxystilbene in biological matrices, so pharmacokinetic data and suitable methods for determination of the compound in plasma are currently lacking. A rapid and sensitive liquid chromatographic–mass spectrometric method for determination of (E)-3,5,4′-trimethoxystilbene in rat plasma, using carbamazepine as internal standard, has been developed and validated. Plasma samples were treated with acetonitrile to precipitate proteins. Samples were then analyzed by HPLC on a 250mm × 4.6 mm i.d., 5-μm particle, C₁₈ column with methanol–water, 80:20 (v/v), containing 10 mm ammonium acetate and 0.2% formic acid (pH 3.0), as mobile phase, delivered at 0.85 mL min⁻¹. A single-quadrupole mass spectrometer with an electrospray interface operated in selected-ion monitoring mode was used to detect [M + H]⁺ ions at m/z 271.3 for (E)-3,5,4′-trimethoxystilbene and m/z 237.5 for the internal standard. (E)-3,5,4′-trimethoxystilbene and the internal standard eluted as sharp, symmetrical peaks with retention times of 8.9 and 4 min, respectively. Calibration plots for (E)-3,5,4′-trimethoxystilbene in rat plasma at concentrations ranging from 0.01 to 5.0 μg mL⁻¹ were highly linear. Intra-day and inter-day precision, as RSD, was <12.9%, and accuracy was in the range 94.8–104.7%. The limit of detection in plasma was 0.005 μg mL⁻¹. The method was successfully used to determine the concentration of (E)-3,5,4′-trimethoxystilbene after oral administration of 86 mg kg⁻¹ of the drug to Sprague–Dawley rats and can be used to investigate the pharmacokinetics of the compound.     

Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

Summary Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L⁻¹. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were <30 ngL⁻¹ from 200-μL injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated solid-phase extraction with C₁₈ cartridges has been applied to water samples (50 mL) spiked at 0.01, 0.1 and 1 μg L⁻¹. The overall procedure was satisfactory (recoveries >80% and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ng L⁻¹. Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2 μg L⁻¹. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 μL.     

Kinetic and Stoichiometric Parameters in the Production of Carotenoids by <Emphasis Type="Italic">Sporidiobolus salmonicolor</Emphasis> (CBS 2636) in Synthetic and Agroindustrial Media

With the objective of determining the kinetic behavior (growth, substrate, pH, and carotenoid production) and obtain the stoichiometric parameters of the fermentative process by Sporidiobolus salmonicolor in synthetic and agroindustrial media, fermentations were carried out in shaken flasks at 25°C, 180 rpm, and initial pH of 4.0 for 120 h in the dark, sampling every 6 h. The maximum concentrations of total carotenoids in synthetic (913 μg/L) and agroindustrial (502 μg/L) media were attained approximately 100 h after the start of the fermentative process. Carotenoid bioproduction is associated with cell growth and the ratio between carotenoid production and cell growth (Y _P/X) is 176 and 163 μg/g in the synthetic and agroindustrial media, respectively. The pH of the agroindustrial fermentation medium varied from 4.2 to 8.5 during the fermentation. The specific growth rate (μ _X) for S. salmonicolor in synthetic and agroindustrial media was 0.07 and 0.04 h⁻¹, respectively. The synthetic medium allowed for greater productivity, obtaining maximum cell productivity (P _x) of 0.08 g L⁻¹ h⁻¹ and maximum total carotenoid productivity (P _car) of 14.2 μg L⁻¹ h⁻¹. Knowledge of the kinetics of a fermentative process is of extreme importance when transposing a laboratory experiment to an industrial scale, as well as making a quantitative comparison between different culture conditions.     

Determination of uranium and thorium in natural waters by ICP-OES after on-line solid phase extraction and preconcentration in the presence of 2,3-dihydro-9,10-dihydroxy-1,4-antracenedion

An on-line solid phase extraction method, linked to inductively coupled plasma optical emission spectrometry (ICP-OES), has been examined using octadecyl-bonded silica cartridge for determination of low levels of uranium and thorium in aqueous samples. 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedion forms a hydrophobic complex with cations and the resulted complex was retained on SPE. The retained complex was eluted using an acidic solution and introduced into ICP for determination. Various effective parameters and chemical variables such as sample pH, amount of ligand (as a complexing agent), sampling and eluting flow rates and concentration of the eluent were optimized. Under optimal conditions, calibration curves with dynamic linear ranges of 1–200 μg/L (r ₂ = 0.9999) and 1–500 μg/L (r ₂ = 0.9994) for U and Th were obtained, respectively. Detection limits based on three times of standard deviations of blank by 6 replicates were 0.69 μg/L and 0.84 μg/L for U and Th, respectively. Sample throughput was 10 samples/h. The interference effects of several metal ions on percentage of recovery of U and Th were also studied. The method was applied to the recovery and sequential determination of these actinide elements in different water samples.     

Recurrence and Differential Relations for Spherical Spinors

We present a comprehensive table of recurrence and differential relations obeyed by spin one-half spherical spinors (spinor spherical harmonics) Ω_{κ μ}(n) used in relativistic atomic, molecular, and solid state physics, as well as in relativistic quantum chemistry. First, we list finite expansions in the spherical spinor basis of the expressions A·B Ω_κμ(n) and A·(B×C) Ω_κμ(n), where A, B, and C are either of the following vectors or vector operators: n=r/r (the radial unit vector), e ₀, e _±1 (the spherical, or cyclic, versors), (the 2×2 Pauli matrix vector), (the dimensionless orbital angular momentum operator; I is the 2×2 unit matrix), (the dimensionless total angular momentum operator). Then, we list finite expansions in the spherical spinor basis of the expressions A·B F(r)Ω_κμ(n) and A·(B×C) F(r)Ω_κμ(n), where at least one of the objects A, B, C is the nabla operator , while the remaining ones are chosen from the set .     

Electrodeposition iron target for the cyclotron production of 55Co in labeling proteins

Natural iron electrodeposition on copper substrate was studied with the aim of production of cobalt-55 radionuclide. ⁵⁵Co seems well suited for PET imaging due to its high abundance of positron decay (I _β+ = 76%), its relatively long half-life (T _1/2 = 17.5 h) and its mean positron energy (E _avg = 570 keV). The electrodeposition experiments were carried out by chloride bath. Operating parameters such as pH, temperature, current density and amount of the electrolyte components are also optimized. The optimum conditions of the iron electrodeposition were follows: 8 g/L FeCl₂, 2 g/L CaCl₂, pH = 1, DC current density of 21.3 A/dm² with a bath temperature of 75 °C temperature and 20% current efficiency. SEM photomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. The electroplated iron-target was irradiated with 29.5 MeV protons at current of 100 μA for 1 h and yields of about 31.25 MBq/μAh were experimentally obtained.     

Fe(II) complex with chiral pyrazolylquinoline L and Fe(II), Co(II), and Cu(II) complexes with achiral pyrazolylquinoline L1: Synthesis and properties. The crystal structures of [ML1Cl2] (M = Fe, Co, and Cu)

The complexes FeLCl₂ (I), [FeL¹Cl₂] (II), [CoL¹Cl₂] (III), and [CuL¹Cl₂] (IV) (where L and L¹ are chiral and achiral pyrazolylquinolines, respectively) were obtained. Complexes II–IV were structurally characterized by single-crystal X-ray diffraction analysis. Crystals of complexes II and III are triclinic (space group P $ \bar 1 The complexes FeLCl₂ (I), [FeL¹Cl₂] (II), [CoL¹Cl₂] (III), and [CuL¹Cl₂] (IV) (where L and L¹ are chiral and achiral pyrazolylquinolines, respectively) were obtained. Complexes II–IV were structurally characterized by single-crystal X-ray diffraction analysis. Crystals of complexes II and III are triclinic (space group P ) and crystals of complex IV are monoclinic (space group P2₁/n). Structures II–IV are built from discrete mononuclear acentric molecules. In these complexes, the M²⁺ ion (M = Fe, Co, and Cu) coordinates two N atoms of the bidentate chelating ligand L¹ and two Cl atoms. The coordination cores MCl₂N₂ are distorted tetrahedra. For complexes I and II, μ_eff = 5.05 and 5.07 μ_B, respectively, correspond to the high-spin configuration d ⁶. For complex III, μ_eff = 4.51 μ_B (high-spin configuration d ⁷) and for complex IV, μ_eff = 1.80 μ_B (configuration d ⁹). Original Russian Text ? Z.A. Savel’eva, L.A. Glinskaya, R.F. Klevtsova, S.A. Popov, A.V. Tkachev, N.V. Semikolenova, V.A. Zakharov, S.V. Larionov, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 4, pp. 285–292.     

Accurate quantification of mercapturic acids of styrene (PHEMAs) in human urine with direct sample injection using automated column-switching high-performance liquid chromatography coupled with tandem mass spectrometry

Styrene is one of the most important industrial chemicals, with an enormously high production volume worldwide. The urinary mercapturic acids of its metabolite styrene-7,8-oxide, namely N-acetyl-S-(2-hydroxy-1-phenylethyl)-l-cysteine (PHEMA 1) and N-acetyl-S-(2-hydroxy-2-phenylethyl)-l-cysteine (PHEMA 2), are specific biomarkers for the determination of individual internal exposure to this highly reactive intermediate of styrene. We have developed and validated a fast, specific and very sensitive method for the accurate determination of the sum of phenylhydroxyethyl mercapturic acids (PHEMAs) in human urine with an automated multidimensional liquid chromatography–tandem mass spectrometry method using ¹³C₆-labelled PHEMAs as internal standards. Analytes were stripped from the urinary matrix by online extraction on a restricted access material, transferred to the analytical column and subsequently determined by tandem mass spectrometry. The limit of quantification (LOQ) for the sum of PHEMAs was 0.3 μg/L urine and allowed us to quantify the background exposure of the (smoking) general population. Precision within series and between series ranged from 1.5 to 6.8% at three concentrations ranging from 3 to 30 μg/L urine; the mean accuracy was between 104 and 110%. We applied the method to spot urine samples from 40 subjects of the general population with no known occupational exposure to styrene. The median levels (range) for the sum of PHEMAs in urine of non-smokers (n = 22) were less than 0.3 μg/L (less than 0.3 to 1.1 μg/L), whereas in urine of smokers (n = 18), the median levels were 0.46 μg/L (less than 0.3 to 2.8 μg/L). Smokers showed a significantly higher excretion of the sum of PHEMAs (p = 0.02). Owing to its automation and high sensitivity, our method is well suited for application in occupational or environmental studies.     

Growth Pattern, Electronic Structures and Magnetic Moments of Small Lutetium Clusters

The lowest-energy configurations, electronic structures and magnetic moments of small Lu _n (n = 2–20) clusters have been investigated within the framework of density functional theory. The results show that Lu _n (n = 4, 8, 13, and 18) clusters are more stable than their respective neighbors, and structural transformation reveals at n = 16. As the number of atoms increases, the magnetic moments increase in an alternating fashion until they reach a maximum of 4.00 μ_B for Lu₈ clusters, followed by even–odd oscillation between 0.00 and 1.00 μ_B over the range n = 9–20.     

Determination of hydrazine by liquid chromatography with preliminary derivatization with naphthalene-2,3-dialdehyde

A method is proposed for the quantification of hydrazine by reversed-phase chromatography after its derivatization with naphthalene-2,3-dialdehyde. The conditions of derivatization and the chromatography separation on a Zorbax Eclipse XDB-C8 column in the gradient mode are optimized. The derivatization and chromatography analysis take 1 and 16 min, respectively. If fluorimetry detection (λ_ex = 273 nm, λ_em = 500 nm) is used and the injection volume is 100 μL, the detection limit is 0.05 μg/L. The procedure is applicable to the quantification of hydrazine in natural waters and soil extracts. A simple and rapid procedure is elaborated for the determination of 0.1–50 μg/L hydrazine in natural waters, RSD = 12% (n = 3).