Mass spectrometric identification of polychlorinated dibenzothiophenes (PCDBTs) in surface sediments of the River Elbe

HRGC/MS was applied to six sediment samples from River Elbe for the determination of polychlorinated dibenzothiophenes (PCDBTs). Among the studied tri-, tetra- and octa-chlorinated isomers, trichlorinated species were found to be the dominating ones. The estimated concentration levels of the compounds were in the range of approximately 0.02–2 μg/kg dry weight for trichlorinated and 0.1–0.3 μg/kg for octachlorinated species. Tetrachlorinated dibenzothiophenes could not be detected. Received: 7 October 1997 / Revised: 4 February 1998 / Accepted: 9 February 1998     

A routine method for the determination of retronecine

A method for the routine determination of the necine base retronecine from biological matrices is described, using gas chromatography for quantification. The biological matrices studied included blended sheep whole rumen fluid and bacterial growth media. The structurally similar compound 2,6-dimethoxypyridine was utilized as an internal standard. Prior to gas chromatography, the bis(heptafluorobutyrate) derivatives of both compounds were formed. The relative percent recoveries of retronecine and the internal standard were 73% and 82%, respectively. The detection limit of retronecine in blended whole rumen fluid was found to be 0.09 μg/mL, and 0.02 μg/mL in bacterial growth media. The precision of the peak area ratio (retronecine to internal standard) was 10% from blended whole rumen fluid, and 14% from bacterial growth media. This method was used to analyze samples from viable cultures incubated with retronecine. Received: 6 May 1997 / Revised: 29 September 1997 / Accepted: 2 October 1997     

Disruption of DNA repair processes by carcinogenic metal compounds

Based on pronounced enhancing effects in combination with other DNA-damaging agents the potentials of Ni(II), Cd(II) and As(III) to interfere with DNA repair processes in HeLa cells was investigated. With respect to oxidative DNA damage, Ni(II) and Cd(II) induced DNA strand breaks starting at concentrations of 250 μM and 5 μM, respectively. The induction of oxidative DNA base modifications like 8-hydroxyguanine was restricted to the cytotoxic concentration of 750 μM Ni(II) and not observed after treatment with Cd(II). In contrast, the removal of oxidative DNA base modifications was inhibited at concentrations as low as 50 μM Ni(II) and 0.5 μM Cd(II). Regarding nucleotide excision repair, Ni(II) and Cd(II) disturbed the DNA-protein interactions involved in the damage recognition step when applying HeLa nuclear protein extracts and a UV-damaged oligonucleotide, while As(III) inhibited the actual incision event. In the case of Ni(II) and Cd(II), this effect was reversible by the addition of Mg(II) and Zn(II), respectively. Furthermore, Cd(II) inactivated the isolated bacterial Fpg protein, most likely by the displacement of Zn(II) from its zinc finger structure. Since DNA is continuously damaged by exogenous and endogenous sources, an impaired repair capacity might well account for the carcinogenic action of the metal compounds. Received: 30 July 1997 / Revised: 6 October 1997 / Accepted: 10 October 1997     

Speciation of arsenic(V) and arsenic(III) by cathodic stripping voltammetry in fresh water samples

A voltammetric stripping procedure is described for the determination of arsenic(V) in a mannitol-sulphuric acid medium. The arsenic is coprecipitated with copper and selenium and reduced to arsine at the hanging mercury drop electrode. Using an accumulation time of 240 s, the detection limit is 0.52 μg L^–1, the determination limit is 0.9 μg L^–1. The method has been applied to the determination of arsenic in water samples. By varying the composition of the supporting electrolyte it is possible to differentiate between arsenic(III) and arsenic(V). As both oxidation states have different toxicological characteristics, the ability to discriminate between both is an distinct advantage of the proposed method. Received: 25 October 1996 / Revised: 7 February 1997 / Accepted: 12 February 1997     

Cr(III)/Cr(VI) determination in waste water by ICP/AES with on-line HPLC (HHPN) sample introduction

Using hydraulic high-pressure nebulization (HHPN) for sample introduction, an on-line high-pressure flow system (HPLC system) becomes a functional component of the ICP spectrometer. By placing additionally an HPLC column between the sample valve and the high-pressure injection/nebulization nozzle, an improved species analysis is attained. An example is given by on-line separation and determination of Cr(III)/Cr(VI) in real waste water samples with ICP/AES. The detection limit of each Cr oxidation state is 4 μg L^–1 with an analysis cycle time of 5 min. In comparison to conventional coupling of HPLC and ICP spectrometry a considerably higher sensitivity is achieved. Using spiked samples the recovery of HHPN-ICP/AES was on an average better than 98% in contrast to only 79% for Cr(VI) determination with a UV photometric reference method. Due to chromatographic separation of Cr(VI) from matrix components and Cr (III), the technique no longer shows the typical spectral interferences caused by Ca (267.716 nm Cr line) and Fe (283.563 nm Cr line). Received: 2 August 1997 / Revised: 11 October 1997 / Accepted: 21 October 1997     

Simultaneous determination of Co(II), Cr(VI), Ni(II) and Pb(II) in water by solvent extraction and high-field 1H NMR Spectrometry

A novel analytical approach is described that combines the preconcentration power of solvent extraction with the resolution and sensitivity of a 500 MHz ¹H NMR spectroscopic detection method for the quantitative determination of metals. Co(II), Cr(VI), Ni(II) and Pb(II) in water are extracted into chloroform as dithiocarbamate complexes. By decoupling the protons and employing a solvent-induced shift method, the ¹H NMR spectrum containing the dithiocarbamate complexes of Co(II), Cr(VI), Ni(II) and Pb(II) is fully resolved at CDCl₃/ C₆D₆ below 40%/60%. The detection limits for Co(II), Cr(VI), Ni(II) and Pb(II) are estimated to be 0.12, 0.073, 0.11 and 0.27 μg/mL, respectively, in the sample solution. Received: 31 July 1997 / Revised: 24 October 1997 / Accepted: 31 October 1997     

Determination of carbaryl in foods by solid-phase room-temperature phosphorimetry

A phosphorimetric solid phase assay is proposed for the determination of the pesticide carbaryl (CBL) at room temperature. CBL was spotted on filter paper together with Tl(I) as heavy metal, and dried for 3 min, after which the diffuse transmitted phosphorescence was measured using two quartz plates to avoid the quenching effect produced by atmospheric oxygen. The linear dynamic range was 0.5–4.0 μg/mL and the detection and quantification limits were 0.09 and 0.31 μg/mL, respectively. The precision of the method, expressed as relative standard deviation, was 2.3% for a sample containing 2.0 μg/mL of CBL. The method was applied to the determination of CBL residues in cereals, potatoes and waters, obtaining recoveries ranging between 92 and 105%. Received: 10 October 1997 / Revised: 2 February 1998 / Accepted: 7 February 1998     

Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS

A simple, rapid and reproducible method for the determination of some pesticide residues in water was developed using micro liquid-liquid extraction and gas chromatography - mass spectrometry with selected ion monitoring (GC/MS-SIM). The chlorinated insecticides α- and β-endosulfan and endosulfan-sulfate as well as the synthetic pyrethroids bifenthrin, permethrin, cypermethrin, fenvalerate and deltamethrin can be separated from a 500 mL sample water extracted with 0.5 mL of n-hexane containing anthracene-d₁₀ as internal standard without clean-up in only 13 min. The recovery efficiencies of the tested compounds yielded more than 93.0% at a fortification level of 5 ng mL^–1 and their relative standard deviations were between 1.9 and 11.7%. Detection limit of each compound ranged between 3 and 35 pg mL^–1. The method was applied to ground, sea and tap waters from Almería (Spain). The solubilities in water at 20° C were determined. Received: 21 March 1997 / Revised: 28 July 1997 / Accepted: 18 August 1997     

Low-blank digestion of geological samples for platinum-group element analysis using a modified Carius Tube design

We have developed a modified Carius Tube design that permits the low-blank digestion of geological samples prior to platinum-group element analysis. The new Carius Tubes incorporate a liner of high-purity quartz glass that retains the sample and acids during the digestion procedure. This dramatically reduces the comparatively high Pt blank associated with dissolutions in conventional Carius Tubes. Using the new Carius Tube design we are able to achieve total procedural blanks for the determination of the PGE in geological samples that are at the 1–15 pg/g level for Ru, Pd, Ir and Pt. This constitutes a reduction of blank values by a factor of ∼10–100 compared to standard NiS fire assay sample preparation techniques. Received: 23 September 1997 / Revised: 24 October 1997 / Accepted: 31 October 1997     

Supercritical fluid extraction of t-resveratrol and other phenolics from a spiked solid

Supercritical fluid extraction of spiked phenolics including gallic acid, (+)-catechin, (–)-epicatechin, caffeic acid, p-coumaric acid, myricetin, t-resveratrol, quercetin and salicylic acid from an inert support using pure CO₂ and methanol-carbon dioxide mixtures was studied. Extraction and collection variables including modifier percentage, extraction temperature, flow rate, extraction time, trap packing and rinse solvent were optimized. The study revealed that the use of methanol as modifier was mandatory. Only the less hydroxylated compounds such as p-coumaric acid, t-resveratrol and salicylic acid could be quantitatively recovered (mean recovery ≥ 95%) from spiked diatomaceous earth. Mean recoveries of more polar phenolic acids and flavonoids such as gallic acid, caffeic acid, catechins and quercetin were between 30% and 70%. Myricetin was not recovered at all. Received: 19 June 1997 / Revised: 20 October 1997 / Accepted: 26 October 1997     

Supercritical fluid extraction of t-resveratrol and other phenolics from a spiked solid

Supercritical fluid extraction of spiked phenolics including gallic acid, (+)-catechin, (–)-epicatechin, caffeic acid, p-coumaric acid, myricetin, t-resveratrol, quercetin and salicylic acid from an inert support using pure CO₂ and methanol-carbon dioxide mixtures was studied. Extraction and collection variables including modifier percentage, extraction temperature, flow rate, extraction time, trap packing and rinse solvent were optimized. The study revealed that the use of methanol as modifier was mandatory. Only the less hydroxylated compounds such as p-coumaric acid, t-resveratrol and salicylic acid could be quantitatively recovered (mean recovery ≥ 95%) from spiked diatomaceous earth. Mean recoveries of more polar phenolic acids and flavonoids such as gallic acid, caffeic acid, catechins and quercetin were between 30% and 70%. Myricetin was not recovered at all. Received: 19 June 1997 / Revised: 20 October 1997 / Accepted: 26 October 1997     

Sensitive synchronous spectrofluorimetric methods for the determination of naproxen and diflunisal in serum

The interaction of diflunisal and naproxen with several surfactants was studied. Spectrofluorimetric methods were developed for the determination of both drugs in sodium dodecylsulfate micellar medium. The mixture of these drugs was resolved by synchronous fluorescence spectrometry using two scans. At Δλ = 20 nm, only naproxen yields a detectable signal that is unaffected by the presence of diflunisal. At Δλ = 110 nm the signal of diflunisal is not influenced by the presence of an up to 3-fold excess of naproxen. Mixtures containing naproxen/ diflunisal in ratios from 50:1 to 1:50 were analyzed with good results. The linear calibration ranges of both drugs were ca 0.02–2.0 μg mL^–1. The method has satisfactorily been applied to a mixture of both drugs in serum. Received: 7 October 1997 / Revised: 3 December 1997 / Accepted: 7 December 1997     

Determination of trace amounts of methylmercury in sediment and biological tissue by using water vapor distillation in combination with RP C18 preconcentration and HPLC-HPF/HHPN-ICP-MS

A novel technique has been developed for the determination of trace amounts of methylmercury in sediment and biological tissues. The well known water vapor distillation technique for the isolation of methylmercury from different matrices was coupled with an RP C18 preconcentration using dithiocarbamate complexation. A newly developed HPLC-method allowed the separation of five different mercury species at different mercury masses with HPF/HHPN (High-Performance-Flow/Hydraulic-High-Pressure-Nebulizing) and detection by ICP-MS. The method takes advantage of the ability to measure individual isotopes. Recoveries of the water vapor distillation procedure samples for different mercury compounds from sediment were tested. For methylmercury, the detection limit for a 0.5 g sample was calculated to be 0.025 μg/kg. The new technique was assured using different reference materials. Received: 23 October 1996 / Revised: 14 February 1997 / Accepted: 16 February 1997     

Conductometric determination of quaternary ammonium salts by sodium perchlorate and vice versa

A conductometric method is proposed for the determination of quaternary ammonium salts (chloride or bromide), based on the poor solubility of the relative perchlorates. A comparison between expected and found values shows that the method is suitable, rapid, and easy for quantities in the range from 0.2 to 5 g. The error depends on the solubility of the relative perchlorate. The apparent and tentative solubility product of the studied compounds were calculated. The obtained values allowed to propose benzyltributyl ammonium chloride (BTBA Cl) as precipitant for the conductometric titration of perchlorate. This easy, rapid and accurate determination can be used to analyze the perchlorate ion even in concentrated solutions and to determine stability constants for complex formation in aqueous solutions. Received: 11 June 1997 / Revised: 8 October 1997 / Accepted: 11 October 1997     

Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine

A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 10⁴ L mol^–1 cm^–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained. Received: 18 April 1997 / Revised: 20 June 1997 / Accepted: 25 June 1997     

Flow injection on-line sorption preconcentration of platinum in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed. The pyrrolidine dithiocarbamate complexes of either Pt⁴⁺ or Pt²⁺, formed in 0.7 mol L^–1 HNO₃, are on-line adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol. An enhancement factor of 112 and a detection limit (3 σ) of 10 ng L^–1 along with a sampling frequency of 21 h^–1 are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mL min^–1. The relative standard deviation is 2.5% for 0.4 μg L^–1 Pt. The method has been applied to the determination of platinum in blood samples. Received: 6 October 1997 / Revised: 26 November 1997 / Accepted: 3 December 1997     

Immuno-affinity columns versus conventional clean-up: a method-comparison study for the determination of zearalenone in corn

The efficiency of a modern analytical method employing immuno-affinity columns (IACs) is compared to a well established traditional technique with respect to the determination of zearalenone (ZON) in corn in the μg/kg range. Despite of a constant error of about 4 μg/kg in the examined working range of 10–200 μg/kg, analytical data obtained from the analysis of spiked and naturally contaminated samples showed good correspondence for the compared methods. The performance characteristics of immuno-affinity-chromatography as a new clean-up technique for the determination of ZON in corn is reported for the first time and compared to a conventional clean-up procedure Received: 25 March 1997 / Revised: 5 May 1997 / Accepted: 12 May 1997     

Optimization of the reduction of Se(VI) to Se(IV) in a microwave oven

 Parameters for the reduction of Se(VI) to Se(IV) in HCl medium by heating in a microwave oven have been optimized. The reduction resulted to be quantitative applying 100% power, corresponding to 600 W heating for 2 min in 6 mol/L or for 3 min in 4 mol/L HCl. The behavior of selenomethionine and selenocystine under the optimized reduction conditions was studied in order to evaluate a possible interference of these selenium species in the determination of Se(VI). The final determination of Se(IV), and Se(VI) were done by hydride generation-atomic absorption spectrometry. The analytical merits of the method are reported. The method was applied to the selective determination of Se(IV), and Se(VI) in spiked river and lake water. Received: 6 December 1996/Revised: 1 April 1997/Accepted: 3 April 1997     

Determination of trace amounts of Galaxolide? (HHCB) by HPLC

An analytical method for the determination of trace amounts of Galaxolide^? (HHCB) by HPLC is presented. It is based on the separation of HHCB in different samples by a C18-column and a gradient elution by water and acetonitrile, both containing some acetic acid. The detection is carried out with a combination of a fast scanning UV detector and a fast scanning fluorescence detector. The fluorescence detection limit is 5 μg/L HHCB without sample pretreatment. HHCB adsorbed on solids or suspended solids can be extracted by ethanol. Received: 17 October 1997 / Revised: 24 November 1997 / Accepted: 24 November 1997     

Synthesis and application of 4-(N,N-dimethylaminosulfonyl)-7-N-methylhydrazino-2,1,3-benzoxadiazole (MDBDH) as a new derivatizing agent for aldehydes

In a five step synthesis, 4-(N,N-dimethylaminosulfonyl)-7-N-methylhydrazino-2,1,3-benzoxadiazole (MDBDH) was prepared in high yields as a stable new derivatizing agent for carbonyl compounds. Reagent and derivatives have not been described in literature before. Major advantage of this substance compared with similar reagents is its improved solubility in polar solvents, e.g. methanol and ethanol. MDBDH reacts with aldehydes in the presence of an acidic catalyst under formation of the corresponding hydrazones. These are separated by means of reversed-phase liquid chromatography and detected UV/vis spectroscopically at wavelengths around 450 nm, depending on the individual hydrazone. MDBDH reacts with oxidizers as nitrogen dioxide and nitrite to only one product, 4-(N,N-dimethylaminosulfonyl)-7-methylamino-2,1,3-benzoxadiazole (MDBDA), which can easily be separated from the hydrazones of lower aldehydes. Due to large molar absorptivities and absorption maxima at wavelengths > 430 nm, limits of detection range from 4 × 10^–8 to 6 × 10^–8 mol · L^–1, and limits of quantification range from 1 × 10^–7 to 2 × 10^–7 mol · L^–1 for the individual hydrazones. The method was applied to the determination of aldehydes in automobile exhaust. Received: 31 July 2000 / Revised: 9 October 2000 / Accepted: 18 October 2000