Electrochemical studies of berberine and jatrorubine by pulse polarography

The application of pulse polarography (PP) and differential pulse polarography (DPP) for the quantitative determination of berberine and Jatrorubine in aqueous, acidic solutions was investigated. The proposed methods could be successfully applied in the concentration range between 5·10^–7 (DPP) or 1·10^–6 (PP) and 5·10^–5 mol/dm³ of alkaloids.     

Analysis of Zoledronic Acid and Its Related Substances by Ion-Pair RP-LC

A simple high-performance liquid chromatographic method – ion-pair reversed- phase high performance liquid chromatography (RPIC) has been developed and employed for the analysis of zoledronic acid and its related substances in bulk material and commercial dosage forms. The mobile phase was a mixture of methanol (20%) and 5 mmol L^–1 phosphate buffer (80%) containing 6 mmol L^–1 tetrabutylammonium bromide, adjusted to pH 7.0 with sodium hydroxide. C₈ column was used as the stationary phase. The chromatographic conditions were optimized. The active ingredient – zoledronic acid was successfully separated from its related substances, including remained imidazol-1-yiacetic acid in the synthesis of zoledronic acid and other possible impurities of oxidation and decomposition. The excipients did not interfere with the determination of zoledronic acid in commercial dosage formulations. The method was rapid, simple, accurate and reproducible. It was not only successfully employed for the assay of zoledronic acid in bulk material and pharmaceutical dosage forms but also for the determination of its related substances.     

Volumetric properties of tetraphenylporphine,their metallo-complexes and some substituted tetraphenylporphines in benzene solution

Densities, apparent molar volumes and partial molar volumes of benzene solutions of tetraphenylporphine, H₂TPP, tetraphenylporphine metallo-complexes, MTPP (where M=Ni,Cu,Zn,Pd,Ag, and Cd), and some substituted tetraphenylporphines H₂T(i-R)PP (where i=2–4 and R=–Cl,–CH₃,–OCH₃) H₂T(i-F)PP (where i-2,3), H₂T(3-Br)PP, and H₂T(3-I)PP were determined at 25°C. It was found that the partial molar volumes of the studied compounds correlate linearly with the first ionization potential of the corresponding metal atom. The calculated values of the surface and volume accessible to the solvent, and the solvent-excluded volume for different conformations of H₂TPP, were compared with experimental data. The volume per molecule for different crystalline forms of H₂TPP and MTPP were compared with the partial molar volumes of the corresponding compounds in benzene solutions. The correlation between the partial molar volumes of H₂T(3-R)PP and their Van der Waals volumes are presented for R=–H, –F,–CH₃,–Cl,–Br,–OCH₃, and –I. The experimental data are rationalized in terms of differences in the conformational states of the molecules.     

Sampling procedure and a radio-indicator study of mercury determination in whole blood by using an AMA 254 atomic absorption spectrometer

A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a ¹⁹⁷Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised ¹⁹⁷Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na₂EDTA (0.05 mol L^–1). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period.     

Detection of 2,4,6-trichloroanisole in chlorinated water at nanogram per litre levels by SPME–GC–ECD

A method involving solid-phase micro extraction (SPME) and gas chromatography with electron capture detection (SPME–GC–ECD) has been optimised for identification and quantification of 2,4,6-trichloroanisole (TCA) at ng L^–1 concentrations in disinfected (chlorinated) water samples. A central composite design was used for factorial analysis of four factors, three factors related to the SPME (PDMS fibre) procedure (adsorption time, temperature of the sample during headspace sampling, and desorption time) and one related to the GC operation (the rate of increase of the temperature of the GC oven). Good linearity (linear correlation coefficient greater than 0.999) was observed for TCA concentrations up to 50 ng L^–1, limits of detection and quantification of 0.7 and 2.3 ng L^–1, respectively, and good precision (relative standard deviation 2.8% and 3.4% for 5 and 30 ng L^–1 of TCA, respectively). Besides TCA, this system also enables the detection and quantification of the four trihalomethanes in the g L^–1 concentration range with limits of detection and quantification of approximately 0.3 g L^–1 and 1 g L^–1, respectively.     

Continuous solid-phase extraction and preconcentration of bisphenol A in aqueous samples using molecularly imprinted columns

A bisphenol A (BPA) molecularly imprinted polymer, the composition of which was optimised using a chemometric approach, has been applied to the selective preconcentration of the template from aqueous samples. The selectivity of the polymer toward BPA and related compounds was evaluated chromatographically. The BPA-imprinted polymer was packed in a column and used for continuous on-column solid-phase extraction (MISPE) of aqueous samples followed by subsequent analysis by HPLC with fluorescence detection of the eluted fractions. The composition of the washing solvent applied in the MISPE procedure was optimised to favour the specific interactions of the MIP with BPA and to remove the non-selectively bound matrix components. The MISPE method has proven to be effective for selective preconcentration of BPA in aqueous samples (recoveries >84% obtained in the eluate for 10–100 mL sample volumes) enabling detection and quantification limits of 1.0 and 3.3 ng mL^–1, respectively (based on 25 mL sample size). Analytical recoveries were between 92 and 101% for river water samples spiked with known amounts of BPA (30, 60, and 80 ng mL^–1); relative standard deviations (RSD) were lower than 5.0%.     

Use of near-infrared reflectance spectroscopy in predicting nitrogen,phosphorus and calcium contents in heterogeneous woody plant species

Near-infrared reflectance spectroscopy was applied to determine nitrogen (N), phosphorus (P) and calcium (Ca) content in leaf samples of 18 woody species. A total of 183 samples from mountain, riparian and dry areas from the Central–Western Iberian Peninsula were collected for this purpose. The wide intervals of variation observed in nutrient concentrations (6.6–45.0 g kg^–1 for N, 0.24–2.97 g kg^–1 for P, and 1.00–20.06 g kg^–1 for Ca) were due to the great heterogeneity of the samples. To develop calibration equations, multiple linear regression, and partial least-squares regression (PLSR) were used. In both cases, three mathematical transformations of the data were applied: log1/R and first and second derivatives. The best calibration statistics were obtained using PLSR and derivative transformations (second derivative for N and first derivative for P and Ca). The following coefficients of multiple determination (R²) and standard errors of cross validation were obtained: 0.99 and 0.93 for N, 0.94 and 0.15 for P, and 0.95 and 0.88 for Ca. In the external validation the standard errors of prediction obtained were 0.76 (N), 0.11 (P) and 0.60 (Ca).     

Determination of ochratoxin A in pig tissues by liquid–liquid extraction and clean-up and high-performance liquid chromatography

A fast, simple, and sensitive HPLC–FD method is described for determination of ochratoxin A (OTA) in pig kidney and muscle; a small mass (<2.5 g) of sample and a relatively small volume (<15 mL) of a non-halogenated extraction solvent are required. Ochratoxin B, systematically absent from all the samples investigated, was used as internal standard. Liquid–liquid partition was used for sample clean-up. Recoveries at the 1 ng g^–1 level were 86±15% and 74±8% for kidney and muscle, respectively, and detection limits were 0.14 and 0.15 ng g^–1. Clean-up by solid-phase extraction (SPE) is required for pig liver. A survey of the OTA content of tissues of pigs slaughtered in southern Italy revealed that 52 out of 54 analysed samples were contaminated; the OTA concentration in kidney ranged between 0.26 and 3.05 ng g^–1. The effect of measurement precision on compliance with legal limits is also discussed.     

Anion-exchange of the chemical species of tracer concentrations of polonium(IV) in chloride solutions

An anion-exchange method is used for determining the average anionic charge of polonium species in chloride solutions. This method is based on measurements of the distribution ratio of polonium at a constant internal chloride ion concentration of the anion-exchanger phase. In 1.0 mol·dm^–1 (H, Na)CL solution in a vicinity of –log[H⁺]=1.0, tracer concentrations of polonium(IV) is found to exist in both chemical forms of [PoCl₄(OH) ₂ ^2– ] and [PoCl₃(OH) ₂ ^– ].     

Homogeneous liquid-liquid extraction combined with gas chromatography-electron capture detector for the determination of three pesticide residues in soils

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid–liquid extraction (HLLE) and gas chromatography with electron capture detector (GC–ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05–40 μg kg⁻¹ for malathion, 0.04–10 μg kg⁻¹ for lambda-cyhalothrin and 0.05–50 μg kg⁻¹ for cypermethrin, respectively. Coefficients of correlation (r²) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 μg kg⁻¹ for lambda-cyhalothrin, and 10 μg kg⁻¹ for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n = 3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 μg kg⁻¹. The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 μg kg⁻¹ were in the range of 82.20–91.60%, 88.90–110.5% and 77.10–98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples.     

Quantitative determination of carboxylate by infrared spectroscopy: application to humic acids

The carboxylate content has been determined by infrared (IR) spectroscopy in different commercial salts of carboxylic acids and also in commercial and isolated samples of soil humic acids. A linear standard curve using anhydrous sodium salicylate has been obtained from the plot of carboxylate (COO^–) concentration vs. the weight of the IR band area, using the COO^– antisymmetric stretch vibration at 1580 cm^–1. Parallel determinations of carboxy groups by the commonly used Ca(OAc)₂ method with related carboxylic acids and humic acids in the H⁺ form has been carried out for comparison. A much better sensitivity and a similar accuracy was obtained. This method is furthermore much faster, simpler and more economical, and offers in some cases a better applicability.     

Fluorimetric determination of tetracycline and anhydrotetracycline

Summary A rapid fluorimetric method employing the complexes of Al³⁺ with tetracycline (TC) and anhydrotetracycline (ATC) has been used for the measurement of the concentrations of TC and ATC in about 10^–7–10^–6 mol/l. The assay offers simplicity and rapidly compared with other methods. The recoveries in the determination of synthetic samples are in the range of 95–103% for TC and 101–120% for ATC. Several determinations of TC and ATC in serum and urine have been carried out with satisfactory results.     

Application of isotope-dilution laser ablation ICP–MS for direct determination of Pu concentrations in soils at pg g<Superscript>−1</Superscript> levels

The methods available for determination of environmental contamination by plutonium at ultra-trace levels require labor-consuming sample preparation including matrix removal and plutonium extraction in both nuclear spectroscopy and mass spectrometry. In this work, laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) was applied for direct analysis of Pu in soil and sediment samples. Application of a LINA-Spark-Atomizer system (a modified laser ablation system providing high ablation rates) coupled with a sector-field ICP–MS resulted in detection limits as low as 3×10^–13 g g^–1 for Pu isotopes in soil samples containing uranium at a concentration of a few g g^–1. The isotope dilution (ID) technique was used for quantification, which compensated for matrix effects in LA–ICP–MS. Interferences by UH⁺ and PbO₂⁺ ions and by the peak tail of ²³⁸U⁺ ions were reduced or separated by use of dry plasma conditions and a mass resolution of 4000, respectively. No other effects affecting measurement accuracy, except sample inhomogeneity, were revealed. Comparison of results obtained for three contaminated soil samples by use of -spectrometry, ICP–MS with sample decomposition, and LA–ICP–IDMS showed, in general, satisfactory agreement of the different methods. The specific activity of ^239+240Pu (9.8±3.0 mBq g^–1) calculated from LA–ICP–IDMS analysis of SRM NIST 4357 coincided well with the certified value of 10.4±0.2 mBq g^–1. However, the precision of LA–ICP–MS for determination of plutonium in inhomogeneous samples, i.e. if "hot" particles are present, is limited. As far as we are aware this paper reports the lowest detection limits and element concentrations yet measured in direct LA–ICP–MS analysis of environmental samples.Sergei F. Boulyga is on leave from The Radiation Physics and Chemistry Problems Institute, 220109 Sosny, Minsk, Belarus.     

Alternative Method for Forensic Determination of Lysergic Acid Diethylamide and Related Compounds in Body Fluids by Liquid–Liquid Extraction and HPLC with Fluorescence Detection

An alternative and practical method is described for simultaneous detection and quantification of the potent hallucinogen lysergic acid diethylamide (LSD) and related compounds in urine and serum samples. The procedure is based on liquid–liquid re-extraction with ethyl acetate and reversed-phase liquid chromatography coupled with fluorescence detection (HPLC–FLD). With detection limits in urine and serum samples of ca 0.07 ng mL^–1 for LSD, nor-LSD, and iso-LSD, respectively, the method is well suited to forensic investigations. Application of the method to clinical samples and autopsy material enable selective identification and accurate quantification of LSD and related compounds. Comparison of results with those obtained from an LSD immunoassay (EMIT II) emphasize the need for chromatographic confirmation.Revised: 1 December 2003 and 9 February 2004     

Spectrophotometric determination of cationic and anionic surfactants with anionic dyes in the presence of nonionic surfactants,part II: Development of batch and flow injection methods

On the basis of the changes in absorption spectra of azo dyes on the addition of an organic onium ion, spectrophotometric methods for the determination of organic onium salts and anionic surfactants were developed, and applied to flow injection method. Propyl orange (PO^–) was used for the determination of organic onium ions. Pairs of PO^– and Zeph⁺ (tetradecyldimethyl-benzylammonium ion) or PO^– and nC₁₈TMA⁺ (n-octadecyltrimethylammonium ion) were used for the determination of anionic surfactants. The determination range of organic onium ions were (0–3) × 10^–5 M by a batch method and were (0–2) × 10^–5 M by a flow injection method. The determination ranges of anionic surfactants were (0–2) × 10^–5 M by the batch method, and were (0–5) × 10^–5 M by the flow injection method, and the detection limit corresponding toS/N = 3 was 3 × 10^–7 M by the flow injection method. By the proposed flow injection method, anionic surfactants in water samples were determined.     

Instrumental neutron activation analysis of geochemical and cosmochemical samples: A fast and reliable method for small sample analysis

We have developed a fast and reliable procedure to routinely measure the abundances of up to about 35 elements even in small (<1 mg) samples. Depending on the type of samples, they are either irradiated for about 8 hours at a flux of about 2·10¹²n·cm^–2·s^–1, or up to 100 hours at a flux of about 6·10¹³n·cm^–2·s^–1. As standards, high-purity synthetic multielement standards and well-characterized geological reference materials are used. Synthetic standards are used as primary standards because they have several advantages over secondary (geological) standards. Three to four counts are done one each sample, starting 1–3 days after the end of the irradiation. We use high-purity germanium (HpGe) detectors with high efficiencies and very good energy resolution (1.6–1.8 keV at 1332 keV). To allow high throughput rates we use fast preamplifiers and gated integrator spectroscopy amplifiers with fast fixed conversion time ADCs. The signals are fed into an acquisition interface module (AIM) and via Ethernet into a Micro VAX. To allow better peak deconvolution, 8k spectra are taken where possible. A specially designed annular NaI(TI) guard detector allows Compton suppression spectrometry. The system uses standard software and was tested with sets of geological standards and has given reliable results for a wide variety of samples, e.g., cosmic spherules in the 30–200 g weight range.     

Instrumental neutron activation analysis of sediment reference materials using the k0-standardization method

An instrumental neutron activation analysis technique has been developed for the determination of As, Au, Ba, Co, Cr, Fe, Hf, Sb, Ta, Th, U, W and Zn in large (10–15 g) geological samples using in-pool irradiation with a SLOWPOKE-2 reactor. The technique allows for the simultaneous irradiation of multiple samples using a neutron flux of between 4·10¹³ and 8·10¹³ n·m^–2·s^–1. The detection limits obtained using the analytical methodology described in this paper are acceptable for exploration geochemistry and the technique has been used to analyze samples collected as part of a metallic minerals survey of Jamaica.     

Effect of gamma radiation on the performance of jute fabrics-reinforced polypropylene composites

Jute fabrics-reinforced polypropylene (PP) composites (50% fiber) were prepared by compression molding. Composites were fabricated with non-irradiated jute fabrics/non-irradiated PP (C-0), non-irradiated jute fabrics/irradiated PP (C-1), irradiated jute fabrics/non-irradiated PP (C-2) and irradiated jute fabrics/irradiated PP (C-3). It was found that C-3 composite performed the best mechanical properties over other composites. Total radiation dose varied from 250–1000 krad and composites made of using 500 krad showed the best results. The optimized values (C-3 composites) for tensile strength (TS), bending strength (BS) and impact strength (IS) were found to be 63 MPa, 73 MPa and 2.93 kJ/m², respectively.     

A new and sensitive resonance-scattering method for determination of trace nitrite in water with rhodamine 6G

In the medium HCl–KI–rhodamine dye, NO₂^– reacts with excess I^– to form I₃^– and the I₃^– and rhodamine dye combine to form an association particle which gives three resonance-scattering (RS) peaks at 320 nm, 400 nm, and 595 nm. In systems containing rhodamine 6G (Rh6G), rhodamine B (RhB), rhodamine S (RhS), and butyl rhodamine B (BRhB) the resonance scattering intensity at 400 nm is proportional to nitrite concentrations in the range 2.3–276 ng mL^–1, 9.2–184 ng mL^–1, 9.2–184 ng mL^–1, and 9.2–92 ng mL^–1, respectively. Because of the high sensitivity, wide linear range, and good stability of the Rh6G system, it has been used for determination of nitrite in water samples, with satisfactory results. The spectral results have been used to verify that the formation of (Rh6G·I₃)_n association particles and their interface with the system are main factors that cause the RS enhancement.     

4-(21-thiazolylazo) resacetophenone oxime. A new analytical reagent for the spectrophotometric determination of uranium (VI)

4-(2¹-Thiazolylazo) resacetophenone oxime forms a pink colored soluble complex with uranium(VI) in buffer solutions of pH 6.0. The colored complex has a maximum absorbance at the wavelength 572 nm and the color is stable for about 48 h. The system obeys Beer's law over the concentration range 0.2–6.0 g of uranium cm^–3. The molar absorptivity and the Sandell sensitivity of the complex are 6.2×10⁴ dm³.mol^–1.cm^–1 and 0.0038 g cm^–2, respectively. Effect of various diversions has been studied and the method was successfully applied for the determination of uranium in rock samples.