Ultra-fast HPLC-ICP-MS analysis of oxaliplatin in patient urine

A novel method for rapid HPLC-ICP-MS analysis of oxaliplatin in human urine was developed implementing a stationary HPLC phase with a particle size of 1.8 μm. The method allowed a cycle time of <1 min at a HPLC flow rate of 0.9 mL min⁻¹. Procedural limits of detection of 0.05 μg L⁻¹ oxaliplatin (150 fg on column) were obtained. Analysis of oxaliplatin in patient urine showed that accurate quantification of the intact drug demanded for storage at −80 °C and rapid measurement after thawing.     

LC–MS–MS determination of ibuprofen, 2-hydroxyibuprofen enantiomers,and carboxyibuprofen stereoisomers for application in biotransformation studies employing endophytic fungi

The purpose of this study was the development and validation of an LC–MS–MS method for simultaneous analysis of ibuprofen (IBP), 2-hydroxyibuprofen (2-OH-IBP) enantiomers, and carboxyibuprofen (COOH-IBP) stereoisomers in fungi culture medium, to investigate the ability of some endophytic fungi to biotransform the chiral drug IBP into its metabolites. Resolution of IBP and the stereoisomers of its main metabolites was achieved by use of a Chiralpak AS-H column (150 × 4.6 mm, 5 μm particle size), column temperature 8 °C, and the mobile phase hexane–isopropanol–trifluoroacetic acid (95: 5: 0.1, v/v) at a flow rate of 1.2 mL min⁻¹. Post-column infusion with 10 mmol L⁻¹ ammonium acetate in methanol at a flow rate of 0.3 mL min⁻¹ was performed to enhance MS detection (positive electrospray ionization). Liquid–liquid extraction was used for sample preparation with hexane–ethyl acetate (1:1, v/v) as extraction solvent. Linearity was obtained in the range 0.1–20 μg mL⁻¹ for IBP, 0.05–7.5 μg mL⁻¹ for each 2-OH-IBP enantiomer, and 0.025–5.0 μg mL⁻¹ for each COOH-IBP stereoisomer (r ≥ 0.99). The coefficients of variation and relative errors obtained in precision and accuracy studies (within-day and between-day) were below 15%. The stability studies showed that the samples were stable (p > 0.05) during freeze and thaw cycles, short-term exposure to room temperature, storage at −20 °C, and biotransformation conditions. Among the six fungi studied, only the strains Nigrospora sphaerica (SS67) and Chaetomium globosum (VR10) biotransformed IBP enantioselectively, with greater formation of the metabolite (+)-(S)-2-OH-IBP. Formation of the COOH-IBP stereoisomers, which involves hydroxylation at C3 and further oxidation to form the carboxyl group, was not observed.     

Simultaneous speciation of arsenic (As(III), MMA, DMA, and As(V)) and selenium (Se(IV), Se(VI), and SeCN−) in petroleum refinery aqueous streams

High-performance liquid chromatography (HPLC) coupled to an ICP-MS with an octapole reaction system (ORS) has been used to carry out quantitative speciation of selenium (Se) and arsenic (As) in the stream waters of a refining process. The argon dimers interfering with the ⁷⁸Se and ⁸⁰Se isotopes were suppressed by pressurizing the octapole chamber with 3.1 mL min⁻¹ H₂ and 0.5 mL min⁻¹ He. Four arsenic species arsenite—As(III), arsenate (As(V)), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA)—and three inorganic Se species—selenite Se(IV), selenate Se(VI), and selenocyanate (SeCN⁻)—were separated in a single run by ion chromatography (IC) using gradient elution with 100 mmol L⁻¹ NH₄NO₃, pH 8.5, adjusted by addition of NH₃, as eluent. Repeatabilities of peak position and of peak area evaluation were better than 1% and about 3%, respectively. Detection limits (as 3σ of the baseline noise) were 81, 56, and 75 ng L⁻¹ for Se(IV), Se(VI), and SeCN⁻, respectively, and 22, 19, 25, and 16 ng L⁻¹ for As(III), As(V), MMA, and DMA, respectively. Calibration curve R ² values ranged between 0.996 and 0.999 for the arsenic and selenium species. Column recovery for ion chromatography was calculated to be 97 ± 6% for combined arsenic species and 98 ± 3% for combined selenium species. Because certified reference materials for As and Se speciation studies are still not commercially available, in order to check accuracy and precision the method was applied to certified reference materials, BCR 714, BCR 1714, and BCR 715 and to two different refinery samples—inlet and outlet wastewater. The method was successfully used to study the quantitative speciation of selenium and arsenic in petroleum refinery wastewaters.     

A cellulose-based carboxyl cotton chelator having citric acid as an anchored ligand: preparation and application as solid phase extractant for copper determination by flame atomic absorption spectrometry

Citric acid was thermochemically esterified onto defatted cotton fibre to produce a carboxyl cotton chelator (CCC), which had been used for extraction of copper prior to its determination by flame atomic absorption spectrometry. The extraction of copper has been studied under both batch and column methods. Quantitative extraction of copper was achieved in the pH range 4–7. The time needed to extract each sample was less than 30 min by the batch method. The copper extraction capacity of CCC was found to be 22.7 mg g⁻¹ at optimal pH value. The elution was quantitative with 1 mol L⁻¹ hydrochloric acid. The feasible flow rate of copper-containing solution for quantitative extraction onto the column packed with CCC was 0.5–4.0 mL min⁻¹, whereas for elution it was less than 1.5 mL min⁻¹. A 100-fold extraction factor could be achieved under the optimal column conditions. The tolerance limits for common metal ions on the extraction of copper and the time of column reuse were investigated. The proposed method has been successfully applied for extraction and determination of copper in industrial wastewater and natural water samples.     

Evaluation of polychlorotrifluoroethylene as sorbent material for on-line solid phase extraction systems: determination of copper and lead by flame atomic absorption spectrometry in water samples

Polychlorotrifluoroethylene (PCTFE) in the form of beads was applied, as packing material for flow injection on-line column preconcentration and separation systems coupled with flame atomic absorption spectrometry (FAAS). Its performance characteristics were evaluated for trace copper determination in environmental samples. The on-line formed complex of metal with diethyldithiophosphate (DDPA) was sorbed on the PCTFE surface. Isobutyl methyl ketone (IBMK) at a flow rate of 2.8 mL min⁻¹ was used to elute the analyte complex directly into the nebulizer-burner system of spectrophotometer. The proposed sorbent material reveal, excellent chemical and mechanical resistance, fast adsorption kinetics permitting the use of high sample flow rates up to 15 mL min⁻¹ without loss of retention efficiency. For copper determination, with 90 s preconcentration time the sample frequency was 30 h⁻¹, the enhancement factor was 250, which could be further improved by increasing the loading (preconcentration) time. The detection limit (3s) was c_L = 0.07 μg L⁻¹, and the precision (R.S.D.) was 1.8%, at the 2.0 μg L⁻¹ Cu(II) level. For lead determination, the detection limit was c_L = 2.7 μg L⁻¹, and the precision (R.S.D.) 2.2%, at the 40.0 μg L⁻¹ Pb(II) level. The accuracy of the developed method was evaluated by analyzing certified reference materials and by recovery measurements on spiked natural water samples.     

Flow injection on-line determination of uranium after preconcentration on XAD-4 resin impregnated with dibenzoylmethane

A flow injection on-line determination of uranium(VI) after preconcentration in a minicolumn having amberlite XAD-4 resin impregnated with dibenzoylmethane (DBM) is described. Uranium(VI) is selectively adsorbed from aqueous solution of pH 5.5 in the minicolumn (5.5 cm long with 5.0 mm i.d.) at a flow rate of 13.6 mL min⁻¹. The uranium(VI) complex was desorbed from the resin by 0.1 mol dm⁻³ HCl at a flow rate of 4.2 mL min⁻¹ and mixed with arsenazo-III solution (0.05% solution in 0.1 mol dm⁻³ HCl, 4.2 mL min⁻¹), and taken to the flow through cell of spectrophotometer where its absorbance was measured at 651 nm. Various parameters affecting the complex formation and its elution were optimized. Peak height (absorbance) was used for data analyses. The preconcentration factors of 36 and 143, detection limits of 0.9 and 0.232 μg L⁻¹, sample throughputs of 40 and 10 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV) and rare-earth elements were improved. The proposed method was applied on different water (spiked tap, well and sea water) and biological samples and good recovery was obtained. The method was also validated on mocked uranium ore sample and the results were in good agreement with the reported value.     

Multi-wall carbon nanotube aqueous dispersion monitoring by using A4F-UV-MALS

In this work, the potentiality of asymmetrical flow field-flow fractionation (A4F) hyphenated to UV detector and multi-angle light scattering (MALS) was investigated for accurately determining multi-walled carbon nanotube (MWCNT) length and its corresponding dispersion state in aqueous medium. Fractionation key parameters were studied to obtain a method robust enough for heterogeneous sample characterization. The main A4F conditions were 10⁻⁵ mL min⁻¹ NH₄NO₃, elution flow of 1 mL min⁻¹, and cross flow of 2 mL min⁻¹. The recovery was found to be (94 ± 2)%. Online MALS analysis of eluted MWCNT suspension was performed to obtain length distribution. The length measurements were performed with a 4% relative standard deviation, and the length values were shown to be in accordance with expected ones. The capabilities of A4F-UV-MALS to size characterize various MWCNT samples and differentiate them according to their manufacturing process were evaluated by monitoring ball-milled MWCNT and MWCNT dispersions. The corresponding length distributions were found to be over 150–650 and 150–1,156 nm, respectively. A4F-UV-MALS was also used to evaluate MWCNT dispersion state in aqueous medium according to the surfactant concentration and sonication energy involved in the preparation of the dispersions. More especially, the presence or absence of aggregates, number and size of different populations, as well as size distributions were determined. A sodium dodecyl sulfate concentration of 15 to 30 mmol L⁻¹ and a sonication energy ranged over 20–30 kJ allow obtaining an optimal MWCNT dispersion. It is especially valuable for studying nanomaterials and checking their manufacturing processes, size characterization being always of high importance.     

Study on an on-line molecularly imprinted solid-phase extraction coupled to high-performance liquid chromatography for separation and determination of trace estrone in environment

Estrone is one of the important potential endocrine-disrupting compounds, and the sensitive and reliable analytical methods for the determination of estrone are required for the assurance of human health. In this paper, using estrone as template molecule, 3-aminopropyltriethoxysilane as function monomer, and tetraethoxysilicane as cross-linker, a highly selective molecularly imprinted microsphere was synthesized by surface molecular imprinting technique combined with a sol–gel process. The imprinted material was characterized by the Fourier transform infrared and static adsorption experiments, and the results showed that it exhibited good recognition and selective ability for estrone. A novel method for separation and determination of trace estrone in environmental sample was developed using on-line molecularly imprinted solid-phase extraction coupled to high-performance liquid chromatography. With a sample loading flow rate of 2.6 mL min⁻¹ for a 9.6-min extraction, the enrichment factor obtained by the slopes of the linear portion in comparison with the direct injection of 10 μL standard sample solution was 1,045. The detection limit (S/N = 3) was 5.7 ng L⁻¹, and the relative standard deviations for nine replicate extractions of 5.0 μg L⁻¹ estrone was less than 10.0%. This method was evaluated for quantitative determination of estrone in well and lake water samples spiked at two levels (0.5 and 1.0 μg L⁻¹) with recoveries ranging from 86% to 95%.      

Scale up and Application of Biosurfactant from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> in Enhanced Oil Recovery

There is a lack of fundamental knowledge about the scale up of biosurfactant production. In order to develop suitable technology of commercialization, carrying out tests in shake flasks and bioreactors was essential. A reactor with integrated foam collector was designed for biosurfactant production using Bacillus subtilis isolated from agricultural soil. The yield of biosurfactant on biomass (Y _p/x), biosurfactant on sucrose (Y _p/s), and the volumetric production rate (Y) for shake flask were obtained about 0.45 g g⁻¹, 0.18 g g⁻¹, and 0.03 g l⁻¹ h⁻¹, respectively. The best condition for bioreactor was 300 rpm and 1.5 vvm, giving Y _x/s, Y _p/x, Y _p/s, and Y of 0.42 g g⁻¹, 0.595 g g⁻¹, 0.25 g g⁻¹, and 0.057 g l⁻¹ h⁻¹, respectively. The biosurfactant maximum production, 2.5 g l⁻¹, was reached in 44 h of growth, which was 28% better than the shake flask. The obtained volumetric oxygen transfer coefficient (K _L a) values at optimum conditions in the shake flask and the bioreactor were found to be around 0.01 and 0.0117 s⁻¹, respectively. Comparison of K _L a values at optimum conditions shows that biosurfactant production scaling up from shake flask to bioreactor can be done with K _L a as scale up criterion very accurately. Nearly 8% of original oil in place was recovered using this biosurfactant after water flooding in the sand pack.     

Development of a sequential injection–square wave voltammetry method for determination of paraquat in water samples employing the hanging mercury drop electrode

This work describes the development and optimization of a sequential injection method to automate the determination of paraquat by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h⁻¹. Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of 25 mV, a potential step of 2 mV, and a flow rate of 100 μL s⁻¹. For a concentration range between 0.010 and 0.25 mg L⁻¹, the current (i _p, μA) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration (mg L⁻¹): i _p = (−20.5 ± 0.3)C _paraquat − (0.02 ± 0.03). The limits of detection and quantification were 2.0 and 7.0 μg L⁻¹, respectively. The accuracy of the method was evaluated by recovery studies using spiked water samples that were also analyzed by molecular absorption spectrophotometry after reduction of paraquat with sodium dithionite in an alkaline medium. No evidence of statistically significant differences between the two methods was observed at the 95% confidence level.     

Development of a flow system for the determination of low concentrations of silver using Moringa oleifera seeds as biosorbent and flame atomic absorption spectrometry

In this study a method for the determination of low concentrations of silver in waters using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry (FAAS) was developed. Moringa oleifera seeds were used as a biosorbent material. Chemical and flow variables of the on-line preconcentration system such as sample pH and flow rate, preconcentration time, eluent concentration and sorbent mass were studied. The optimum preconcentration conditions were obtained using sample pH in the range of 6.0-8.0, preconcentration time of 4 min at a flow rate of 3.5 mL min^− 1, 0.5 mol L^− 1 HNO₃ eluent at a flow rate of 4.5 mL min^− 1 and 35 mg of sorbent mass. With the optimized conditions, the preconcentration factor, precision, detection limit and sample throughput were estimated as 35 (for preconcentration of 14 mL sample), 3.8% (5.0 μg L^− 1, n = 7), 0.22 μg L^− 1 and 12 samples per hour, respectively. The developed method was successfully applied to mineral water and tap water, and accuracy was assessed through analysis of a certified reference material for water (APS-1071 NIST) and recovery tests, with recovery ranging from 94 to 101%.     

Flow injection on-line hydrophobic sorbent extraction for flame atomic absorption spectrometric determination of cadmium in water samples

A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was formed on-line in 0.1 mol L⁻¹ HNO₃ and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized. By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h⁻¹. For 30 s preconcentration time the detection limit was 0.3 μg L⁻¹ and the relative standard deviation at 5.0 μg L⁻¹ Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 μg L⁻¹. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water). Good recoveries were obtained for spiked natural-water and waste-water samples. Correspondence: Aristidis N. Anthemidis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, GR-Thessaloniki 54124, Greece     

Application of molecularly imprinted polymer solid-phase extraction for salivary cotinine

A method constituted by molecularly imprinted solid-phase extraction (MISPE) with high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) was developed for cotinine analysis in saliva samples. For this purpose, the separation was carried out with a C18 reversed-phase column at 20 °C. The mobile phase which was composed of a mixture of 09:91 (v/v) acetonitrile/phosphate buffer, pH 6.3, was delivered with isocratic flow rate at 1.4 mL min⁻¹. Employing MISPE, the best conditions were achieved with 1.5 mL of saliva plus 1.5 mL of 0.1 mol L⁻¹ of acetate buffer, pH 5.5, which were then passed through a cartridge previously conditioned with 2 mL acetonitrile, 2 mL methanol, and 2 mL of 0.1 mol L⁻¹ sodium acetate buffer, pH 5.5. The washing was carried out with 1 mL deionized water, 1 mL of 0.1 mol L⁻¹ sodium hydroxide, and 1 mL hexane; finally; the cotinine elution was carried out with 3 mL methanol/water (97.5: 2.5, v/v). Linearity ranged from 30 to 500 ng mL⁻¹ with r > 0.99. Intra-assay, interassay precision, and accuracy ranged from 3.1% to 10.1%, 5.2% to 15.9%, and 99.22% to 111.17%, respectively. The detection and quantification limits were 10 and 30 ng mL⁻¹, respectively. This investigation has provided a reliable method for routine cotinine determination in saliva, and it is an important tool for monitoring cigarette smoke exposure in smokers. The method was applied in five smokers’ samples who consumed around five to 20 cigarettes per day and the values of cotinine in saliva were from 66.7 to 316.16 ng mL⁻¹.     

Quantitative nuclear magnetic resonance for additives determination in an electrolytic nickel bath

The use of proton nuclear magnetic resonance (¹H-NMR) for the quantitation of additives in a commercial electrolytic nickel bath (Supreme Plus Brilliant, Atotech formulation) is reported. A simple and quick method is described that needs only the separation of nickel ions by precipitation with NaOH. The four additives in the bath (A-5(2X), leveler; Supreme Plus Brightener (SPB); SA-1, leveler; NPA, wetting agent; all of them are commercial names from Atotech) can be quantified, whereas no other analytical methods have been found in the literature for SA-1 and NPA. Two calibration methods have been tried: integration of NMR signals with the use of a proper internal standard and partial least squares regression applied to the characteristic NMR peaks. The multivariate method was preferred because of accuracy and precision. Multivariate limits of detection of about 4 mL L⁻¹ A-5(2X), 0.4 mL L⁻¹ SPB, 0.2 mL L⁻¹ SA-1 and 0.6 mL L⁻¹ NPA were found. The dynamic ranges are suitable to follow the concentration of additives in the bath along electrodeposition. ¹H-NMR spectra provide evidence for SPB and SA-1 consumption (A-5(2X) and NPA keep unchanged along the process) and the growth of some products from SA-1 degradation can be followed. The method can, probably, be extended to other electrolytic nickel baths.     

Effect of organic load on the performance and methane production of an AnSBBR treating effluent from biodiesel production

Currently, there is an increasing demand for the production of biodiesel and, consequently, there will be an increasing need to treat wastewaters resulting from the production process of this biofuel. The main objective of this work was, therefore, to investigate the effect of applied volumetric organic load (AVOL) on the efficiency, stability, and methane production of an anaerobic sequencing batch biofilm reactor applied to the treatment of effluent from biodiesel production. As inert support, polyurethane foam cubes were used in the reactor and mixing was accomplished by recirculating the liquid phase. Increase in AVOL resulted in a drop in organic matter removal efficiency and increase in total volatile acids in the effluent. AVOLs of 1.5, 3.0, 4.5 and 6.0 g COD L⁻¹ day⁻¹ resulted in removal efficiencies of 92%, 81%, 67%, and 50%, for effluent filtered samples, and 91%, 80%, 63%, and 47%, for non-filtered samples, respectively, whereas total volatile acids concentrations in the effluent amounted to 42, 145, 386 and 729 mg HAc L⁻¹, respectively. Moreover, on increasing AVOL from 1.5 to 4.5 g COD L⁻¹ day⁻¹ methane production increased from 29.5 to 55.5 N mL CH₄ g COD⁻¹. However, this production dropped to 36.0 N mL CH₄ g COD⁻¹ when AVOL was increased to 6.0 g COD L⁻¹ day⁻¹, likely due to the higher concentration of volatile acids in the reactor. Despite the higher concentration of volatile acids at the highest AVOL, alkalinity supplementation to the influent, in the form of sodium bicarbonate, at a ratio of 0.5–1.3 g NaHCO₃ g COD_fed⁻¹, was sufficient to maintain the pH near neutral and guarantee process stability during reactor operation.     

Selective and sensitive molecularly imprinted sol–gel film-based electrochemical sensor combining mercaptoacetic acid-modified PbS nanoparticles with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Au–multi-walled carbon nanotubes–chitosan

A sensitive molecularly imprinted electrochemical sensor was developed for selective detection of streptomycin by combination of mercaptoacetic acid-modified PbS nanoparticles with Au-coated Fe₃O₄ magnetic nanoparticles dispersed multi-walled carbon nanotubes doped chitosan film. The imprinted sensor was fabricated onto the Au electrode via stepwise modification of nanocomposites and an electrodeposited thin film of molecularly imprinted polymers via sol–gel technology. The morphologies and electrochemical behaviors of the imprinted sensor were characterized by scanning electron microscope, cyclic voltammetry, and differential pulse voltammetry, respectively. The prepared sensor showed very high recognition ability and selectivity for streptomycin. Under optimal conditions, the imprinted sensor displayed good electrocatalytic activity to the redox of streptomycin. And the differential voltammetric anodic peak current was linear to the logarithm of streptomycin concentration in the range from 1.0 × 10⁻⁶ to 1.0 × 10⁻³ mol L⁻¹, and the detection limit obtained was 1.5 × 10⁻⁹ mol L⁻¹. This proposed imprinted sensor was used successfully for streptomycin determination in different injection solution samples.     

Organosilica composite for preconcentration of phenolic compounds from aqueous solutions

A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO₂) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol) (TX). Under static conditions phenol was quantitatively extracted onto TX-SiO₂ in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO₂ for phenol is 2.4 mg g⁻¹ with distribution coefficients up to 3.4 × 10⁴ mL g⁻¹; corresponding data for 1-naphthol are 1.5 mg g⁻¹ and 3 × 10³ mL g⁻¹. The distribution coefficient does not change significantly for solution volumes of 0.025–0.5 L and adsorbent mass less than 0.03 g; 1–90 μg analyte can be easily eluted by 1–3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A ₅₄₀) and phenol concentration (C) in water was found according to the equation A ₅₄₀ = (6 ± 1) × 10⁻² + (0.9 ± 0.1)C (μmol L⁻¹) with a detection range from 1 × 10⁻⁸ mol L⁻¹ (0.9 μL g⁻¹) to 2 × 10⁻⁷ mol L⁻¹ (19 μL g⁻¹), a limit of quantification of 1 μL g⁻¹ (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical analysis. The detection limit of 1-naphthol with this method is 6 μL g⁻¹ while the quantification limit is 20 μL g⁻¹. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08–3.2 mL g⁻¹.     

Production and analytical characterization of neopterin immunoreagents for biosensor developments

Neopterin is a valuable biomarker of cellular immunity associated with various pathological situations such as viral and bacterial infections, autoimmune, cardiovascular, neurodegenerative and malignant disorders. To produce specific antibodies against neopterin for a rapid multi-biomarker-based diagnosis, a novel hapten derivative was synthesized and attached to carrier proteins. The thoroughly characterized conjugates were used for immunization of BALB/c mice and rabbits. The produced monoclonal antibody reached in both direct and indirect enzyme-linked immunosorbent assay (ELISA) format LoD of 0.18 and 0.45 μg L⁻¹, respectively, and was a superior immunoreagent for further biosensor developments with regard to assay sensitivity and material availability. The best polyclonal antibody was somewhat more sensitive in direct ELISA with LoD of 0.05 μg L⁻¹. The optimized ELISA method was evaluated with blood samples collected from patients with renal insufficiency, patients with sepsis, patients without confirmed clinical diagnosis, and healthy volunteers. In plasma samples, neopterin concentrations ranging from 3.2 to 103 μg L⁻¹ could be determined with the monoclonal ELISA whereas twofold lower results were obtained with the polyclonal ELISA. A satisfactory correlation of results was found between the polyclonal ELISA and IBL Neopterin ELISA kit within the concentration range 0.5–16 μg L⁻¹ (R = 0.874; n = 40), and slightly lower correlation was found for monoclonal-based ELISA (R = 0.819; n = 40). These data show that the generated antibodies may be used as functional analytical reagents for the integration into multianalyte biochip detection systems.     

Simultaneous First Derivative Spectrophotometric Determination of Palladium and Nickel Using 2-(2-Thiazolylazo)-5-Dimethylaminobenzoic Acid as an Analytical Reagent

 A simple, rapid, selective, sensitive and economical method has been developed for the simultaneous determination of trace amounts of palladium and nickel in aqueous methanolic medium using 2-(2-thiazolylazo)-5-dimethylam inobenzoic acid as an analytical reagent by first derivative spectrophotometr y. Palladium is determined by measuring base to peak distance at λ=695.0 nm while nickel is estimated by zero crossing method in the mixture. The linearity is maintained between 0.12–1.75 μg mL⁻¹ for palladium and 0.07–1.60 μg mL⁻¹ for nickel in the pH range 2.8–7.2 and 3.4–8.8 respectively. Seven replicate determinations of 1.0 μ g mL⁻¹ of palladium and 0.8 μg mL⁻¹ of nickel in a mixture give a mean signal height of 0.391 for Pd and 0.541 for Ni with relative standard deviations of 0.9% and 1.2%, respectively. The sensitivity of the proposed method is 0.391 (dA/dλ)/(μg mL⁻¹) for palladium and 0.685 (dA/dλ)/(μg mL⁻¹) for nickel. Various parameters have been optimised for the simultaneous determination of palladium and nickel in various complex samples. Received March 30, 1999. Revision November 25, 1999.     

Determination of chromium(VI) and lead in water samples by on-line sorption preconcentration coupled with flame atomic absorption spectrometry using a PCTFE-beads packed column

A new time-based flow injection on-line solid phase extraction method for chromium(VI) and lead determination using flame atomic absorption spectrometry was developed. The use of hydrophobic poly-chlorotrifluoroethylene (PCTFE)-beads as absorbent in on-line preconcentration system was evaluated. Effective formation of ammonium pyrrolidine dithiocarbamate complexes and subsequently retention in PCTFE packed column, was achieved in pH range 1.0-1.6 and 1.5-3.2 for Cr(VI) and Pb(II) ions, respectively. The sorbed analyte was efficiently eluted with isobutyl-methyl-ketone for on-line FAAS determination. The proposed packing material exhibited excellent chemical and mechanical resistance, fast kinetics for adsorption of Cr(VI) and Pb(II) permitting the use of high sample flow rates at least up to 15 mL min⁻¹ without loss of retention efficiency. For a preconcentration time of 90 s, the sample frequency was 30 h⁻¹, the enhancement factor was 94 and 220, the detection limit was 0.4 and 1.2 μg L⁻¹, while the precision (R.S.D.) was 1.8% (at 5 μg L⁻¹) and 2.1% (at 30 μg L⁻¹) for chromium(VI) and lead, respectively. The applicability and the accuracy of the developed method were estimated by the analysis spiked water samples and certified reference material NIST-CRM 1643d (Trace elements in water) and NIST-SRM 2109 (chromium(VI) speciation in water).