Analytical, toxicological and kinetic investigation of decomposition of the drug diclofenac in waters and wastes using gamma radiation.

The radiolytic decomposition of the drug diclofenac (DCF), and in limited extent, also two other widely used drugs, ibuprofen and carbamazepine, was examined using liquid chromatography (LC) methods. The efficiency of DCF decomposition was examined in function of the absorbed dose of gamma radiation, and also in the presence of selected scavengers of radicals, which are commonly present in natural waters and wastes. Three different tests were employed for the monitoring of toxicity changes in the irradiated DCF solutions. The LC/mass spectrometry (MS) was used for the determination of products of DCF radiolysis. Using pulse-radiolysis method with the spectrophotometric detection, the rate constant values were determined for reactions of DCF with the main products of water radiolysis: hydroxyl radicals (1.24 ± 0.02) × 10(10) M(-1) s(-1) and hydrated electrons (3.1 ± 0.2) × 10(9) M(-1) s(-1). Their values indicate that both oxidative and reductive processes in radiolytic decomposition of DCF can take place in irradiated diluted aqueous solutions of DCF. The possibility of decomposition of all examined analytes was investigated in samples of river water and hospital waste. Compared to the previous studies, the conducted measurements in real samples were carried out at the concentration levels, which are close to those reported earlier in environmental samples. Graphical abstract ᅟ.

High performance liquid chromatography of slightly soluble brominated indigoids from Tyrian purple.

Attempts at identification of mollusc species producing Tyrian purple from archaeological material are usually done with high performance liquid chromatography in the reversed-phase system, but the peaks obtained are often wide and asymmetric. This is due to the low solubility of the indigoids and their brominated derivatives in the mobile phase, especially 6,6'-dibromoindigotin, which is soluble in only few, particular solvents. Our study focused on improving both symmetry and peak height for more precise quantification. The influence of various factors was evaluated: stationary phase characteristics, mobile phase composition, elution gradient parameters and temperature on the peak shape of the main components of Tyrian purple. The best results were obtained using highly retentive, but moderately bonded ODS stationary phases (about 2.8 µmol m(-2)), percolated with gradient of acetonitrile with acidified aqueous mobile phases (0.1% strong acid) at elevated temperatures (70°C). The upper quantification limit for 6,6'-dibromoindigotin was improved by over 350%, between standard and optimised systems. Using them, the detection and quantification of trace Tyrian purple components (less than 0.15%) aside from major indigoids becomes possible. Consequently, for the first time, the new analogues of brominated and unbrominated indirubins were found in the shellfish purple from Hexaplex trunculus.

Radiolytic decomposition of pesticide carbendazim in waters and wastes for environmental protection.

The radiolytic degradation of widely used fungicide, carbendazim, in synthetic aqueous solutions and industrial wastewater was investigated employing γ-irradiation. The effect of the absorbed dose, initial concentration and pH of irradiated solution on the effectiveness of carbendazim decomposition were investigated. Decomposition of carbendazim in 100 µM concentration in synthetic aqueous solutions required irradiation with 600 Gy dose. The aqueous solutions of carbendazim have been irradiated in different conditions, where particular active radical species from water radiolysis predominate. The obtained data have been compared with the kinetic modeling. The reversed-phase high-performance liquid chromatography was used for the determination of carbendazim and its radiolytic decomposition products in irradiated solutions. The changes of toxicity of irradiated solutions were examined with different test organisms and human leukemia cells.

Radiolytic degradation of the herbicide dicamba for environmental protection.

The radiolytic degradation of the widely used herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid), employing gamma irradiation in laboratory batch conditions and with a beam of accelerated electrons in flow-through installation, was investigated. The effects of dose magnitude, ozone or hydrogen peroxide in irradiated solution, and scavengers such as nitrate and hydrogen carbonate on the effectiveness of dicamba decomposition and the products formed were investigated. Changes in the toxicity of irradiated solutions were measured with the Microtox and Spirotox toxicity tests. The application of radiolytic degradation was also examined for decomposition of herbicides in commercial agrochemical preparations.

Chromatographic separation of chlorophenoxy acid herbicides and their radiolytic degradation products in water samples.

HPLC procedure for simultaneous determination of chlorophenoxy acid herbicides and their radiolytic degradation products in waters is described with the use of octadecylsilica column and spectrophotometric detection at 280 nm. The satisfactory separation was achieved with a mobile phase of pH 2.5 consisting of 43.7 mM acetic acid with 40% (v/v) acetonitrile. Limit of detection values for herbicides and phenol derivatives were in the range of 19-41 microg/l and 10-60 microg/l, respectively. The developed method was applied for monitoring the effectiveness of radiolytic degradation of herbicides. Studies of products of gamma-radiolysis of 2,4-dichlorophenol have shown that the efficiency of this process is affected by the presence of naturally occurring scavengers of gamma-radiation such as carbonates or nitrates.

Flow-injection amperometric determination of pesticides on the basis of their inhibition of immobilized acetylcholinesterases of different origin.

Determination of the organophosphorus pesticides paraoxon, chlorpyrifos oxon, and malaoxon has been performed by a method based on inhibition of acetylcholinesterase (AChE) and amperometric detection in a flow-injection system with enzymes obtained from the electric eel (eeAChE) and Drosophila melanogaster (dmAChE) and immobilized on the surface of platinum electrode within a layer of poly(vinyl alcohol) bearing styrylpyridinium groups. dmAChE is more sensitive than eeAChE to inhibition by chlorpyrifos oxon and paraoxon. The sensitivity difference was largest for chlorpyrifos oxon (detection limit approx. 17 times lower), and practically none for malaoxon. Determination of the analytes in spiked river water samples by use of the dmAChE biosensor resulted in recoveries from 50 to 90 % for chlorpyrifos oxon at levels of 20 to 40 nmol L(-1), 50 to 100 % for paraoxon at 0.6 to 0.8 micro mol L(-1), and 140 to 190 % for malaoxon at 0.6 to 1.2 micro mol L(-1).

Miniaturized biochemical sensing devices based on planar bilayer lipid membranes.

Methods of in-vitro artificial formation of bilayer lipid membranes (BLM) and their analytical applications are reviewed, on the basis of 122 literature references. Different techniques for preparation of free-suspended planar BLMs, and gel-, filter-, and solid-supported systems are presented. The analytical applications developed are based on direct interaction of analytes with chemically unmodified BLMs, and with systems modified by use of redox mediators, ionophores, ion-channel forming species, enzymes, antibodies, or DNA.

Application of carboxymethyl-beta-cyclodextrin as a chiral selector in capillary electrophoresis for enantiomer separation of selected neurotransmitters.

The aim of this work was to optimize conditions for capillary electrophoresis separation of different neurotransmitters (serotonin, phenylalanine, dopamine, adrenaline, ephedrine, propranolol and DOPA) in a single run, including separation of existing enantiomers. As chiral selectors added to the borate background, electrolyte unsubstituted alpha-, beta- and -gamma-cyclodextrins (CDs), methyl-, dimethyl-, and trimethyl-substituted beta-CDs, and hydroxypropyl-substituted alpha-, beta- and gamma-CDs were examined. Also carboxymethyl-beta-CD and succinyl-beta-CD were used for this purpose. In addition to the kind and concentration of chiral selector, some other experimental factors also have been optimized, such as concentration of borate buffer, content of methanol, pH of electrolyte, method of sample introduction into the capillary and washing procedure between consecutive runs. The best results were obtained using 20 mM carboxymethyl-beta-CD in borate buffer of pH 7.5 as running electrolyte and hydrostatic injection. The obtained sensitivity of response (peak height) varied from 0.4 for adrenalines to 2.3 mAU mM(-1) for propranolols. The concentration detection limits (S/N=3) were in the range from 0.04 mM for propranolols to 0.2 mM for adrenalines. The resolution obtained in optimized conditions in a single run was from 0.75 for adrenalins and 1.0 for propranolols up to 2.0 for ephedrines. The developed method was employed for determination of these analytes in brain tissue extracts.

Inhibitive determination of mercury and other metal ions by potentiometric urea biosensor.

The biosensor with urease entrapped in PVC layer at the surface of pH-sensitive iridium oxide electrode was applied for testing of mercury and other metal ions inhibition on enzymatic reaction. The calculation of inhibition effect was based on the measurement of initial rate of decrease of biosensor potential (proportional to the initial rate of enzymatic reaction) after addition of substrate after inhibition step. Some differences of inhibition extent were observed for various mercury forms (Hg(NO3)2, HgCl2, PhHgCl and Hg2(NO3)2) as well as for other heavy metal ions investigated as potential interferents. Because the method was not specific, it was applied for the determination of total inhibition effect caused by heavy metal ions in water samples. In the case of most cations tested the total recovery of enzyme activity was possible using Tris buffer solution with EDTA and thioacetamide after less than 10 min regeneration time.

Porphyrins in analytical chemistry. A review.

The porphyrins, naturally occurring macrocyclic compounds, have, in the last 10 years, gained increasing interest in analytical chemistry. This review based on 123 original literature references, mostly published in the 1990s, presents catalytic applications of metalloporphyrins in electroanalysis as electroactive agents in ion selective membranes, as unique reagents in spectrophotometry and as new stationary phases offering unusual resolution in HPLC. The collected data are also presented in four tables.

Chemical speciation by flow-injection analysis. A review.

Speciation of elements in natural matrices, especially of trace metals, is one of the predominant development trends of modern inorganic analysis. The main part of the conventional speciation procedures is a suitable combination of separation and chemical conversion steps, for which the most appropriate methodology seems to be the use of flow-injection. A shorter time of performance of these operations in flow-injection manifolds is advantageous in terms of avoiding the shift of chemical equilibria during the speciation measurement. Numerous other advantages are also pointed out in this review based on 58 references. Among flow-injection analysis methods published so far for speciation the determination of different oxidation states predominates, while a much smaller number of papers have been published on the determination of the degree of complexation or the determination of organometallic compounds.

Lactate solid-state biosensor with multilayer of electrodeposited polymers for flow-injection clinical analysis.

In the lactate biosensor, electrodeposited poly(o-phenylenediamine) serves as a convenient matrix for the immobilization of lactate oxidase, but does not provide sufficient discrimination from several interfering species present in physiological fluids. Their effect, however, can be eliminated by additional modification of the working Pt electrode with a bilayer of electrodeposited polypyrrole/polyphenol. Despite continued decrease in biosensor sensitivity, the newly developed three-layer solid-state biosensor was successfully applied in flow-injection determination of lactate in both undiluted and diluted human blood serum samples over a 10 day period. For the lactate concentration range 0.2-5.0 mM in several series of measurements the correlation coefficient values for comparison with photometric determination using a DuPont dimension clinical analyzer were between 0.96 and 0.99. The reproducibility measured for 1:10 diluted serum was 0.6%. The detection limit was estimated as 2 microM.

Flame AAS determination of lead in water with flow-injection preconcentration and speciation using functionalized cellulose sorbent.

The on-line solid phase extraction of trace amount of lead in flow-injection system with flame AAS detection was investigated using cellulose sorbents with phosphonic acid and carboxymethyl groups, C(18) sorbent non-modified and modified with Pyrocatechol Violet or 8-quinolinol, commercial chelating sorbents Chelex 100 and Spheron Oxin 1000, non-polar sorbent Amberlite XAD-2 modified with Pyrocatechol Violet and several cation-exchange resins. The best dynamic characteristics of retention were observed for functionalized cellulose sorbents. For Cellex P assumed as optimum sorbent, elution with a separate fractions of nitric acid and ethanol allows the differentiation between tetraalkyllead and sum of inorganic lead and organolead species of smaller number of alkyl groups. The detection limit for the determination of inorganic Pb(II) was estimated as 0.17 microg/l. at preconcentration from 50 ml sample at a flow rate of 7 ml/min.

Enzymatic flow-injection determination of urea in blood serum using potentiometric gas sensor with internal nonactin based ISE.

Ion-selective electrode with cellulose triacetate membrane containing nonactin is employed for the potentiometric detection of ammonia produced in biocatalytic reaction in flow-injection system with enzyme reactor. The elimination of interferences occurring in the presence of alkali metal ions was achieved by covering a nonactin membrane with outer hydrophobic gas permeable membrane. The obtained flow-injection response to ammonia indicates a possibility of ammonia determination down to 10 microM ammonia. In the flow-injection system for urea determination 200 microl of 10-fold diluted blood serum sample was injected into carrier stream of distilled water merged with TRIS buffer, passed through the urease flow-through reactor and then after merging with NaOH stream delivered to the detector. It was found in several series of natural blood serum samples, that the correction for endogenous ammonia in such a determination is not indispensable.

Simultaneous determination of ammonia nitrogen and L-glutamine in bioreactor media using flow injection.

A novel split stream flow injection (FI) system suitable for the simultaneous determination of L-glutamine and ammonia nitrogen (ammonia-N) in cell culture media is described. Potentiometric detection of ammonia-N in one portion of the manifold is achieved using a commercial ammonia gas-sensing electrode fitted with a wall-jet cap. L-Glutamine is quantified in the other part of the split sample by potentiometric detection of ammonium ions (by an ammonium-selective polymer membrane electrode), liberated from the hydrolysis of glutamine after the sample flows through a glass bead reactor containing immobilized glutaminase. Endogenous ammonia-N and potassium ions that would normally interfere with the glutamine measurement are removed upstream using a unique tubular cation-exchange unit. Using 50 microliters sample volumes and mixed solutions of ammonium chloride and L-glutamine in Iscove's Modified Dulbecco's Medium to calibrate the FI measuring system, values for ammonia-N and L-glutamine determined for 22 media samples obtained from a bioreactor growing retroviral producer cells correlate well with those measured with commercial, manual enzymic-spectrophotometric assay kits.

Simultaneous enzymatic/electrochemical determination of glucose and L-glutamine in hybridoma media by flow-injection analysis.

A split-stream flow-injection analysis system is described for simultaneous determination of glucose and L-glutamine in serum-free hybridoma bioprocesses media. Amperometric measurement of glucose is based on anodic oxidation of hydrogen peroxide produced by immobilized glucose oxidase within a triple layer membrane of an integrated flow-through glucose-selective biosensor. Determination of L-glutamine is based on quantitating ammonium ions produced in a flow-through enzymes reactor containing immobilized glutaminase enzyme, and subsequent downstream potentiometric detection of these ions by a nonacting-based ion-selective polymer membrane electrode. Endogenous potassium and ammonium ion interference in the L-glutamine determination are eliminated by using a novel in-line tubular cation-exchange membrane unit to exchange these interferent species for cations undetectable by the membrane electrode. The first generation split-steam flow-injections system can assay 12 samples/h using direct injections of 50 microL of media samples, with linear responses to glucose in the range of 0.03 to 30 mM, and log-linear response to L-glutamine from 0.1 to 10 mM.

Modification of nonionic adsorbent with eriochrome blue-black R for selective nickel(II) preconcentration in conventional and flow-injection atomic-absorption spectrometry.

Chemical modification of nonionic sorbent Amberlite XAD-2 or anion exchanger Amberlyst A-26 with Eriochrome Blue-Black R (EBBR) produces a chelating resin of satisfactory chemical stability and resistance towards mineral acids. Retention of 10 metal ions has been examined for both resins. EBBR loaded XAD-2 was utilized for nickel(II) preconcentration in atomic-absorption spectrometry. In optimal conditions at a preconcentration time not exceeding 1 hr, nickel(II) can be determined at the 0.1 mug/l. level in flow measurements. Retention of metal ions on chelating resin is a convenient method of preconcentration and elimination of matrix interferences.

Use of ionomer membranes to enhance the selectivity of electrode-based biosensors in flow-injection analysis.

The use of ionomer membranes to enhance the selectivity of potentiometric enzyme electrodes in flow-injection measurement arrangements is examined. The ionomer membranes employed are permeable to analyte substrates but relatively impermeable to detectable ions that would normally interfere with the measurement of the substrates if the enzyme electrodes were in direct contact with the sample. As a model system, the selectivity of enzyme electrodes prepared with nonactin-based ammonium-sensitive polymeric membranes is evaluated. In the preferred configuration, a thin hydrophilic anion-exchange membrane is incorporated within a flow-through dialysis unit upstream from the enzyme-electrode detector. As the sample passes through the dialysis unit, neutral or anionic analyte molecules (urea or glutamine) move through the membrane while the permeation of endogenous ammonium ions and other cations in the sample is retarded. A flowing recipient buffer on the other side of the membrane carries the analyte substrate to the enzyme-electrode detector. Enhancements in selectivity for analyte substrates over endogenous ammonium and potassium ions are greater than or equal to 9-fold when compared to enzyme-electrode flow-injection analysis (FIA) systems assembled without the ionomer membrane unit. The analytical utility of the proposed system is demonstrated by the accurate measurements of urea in blood serum and L-glutamine in hybridoma bioreactor media.

Enzyme entrapped polypyrrole modified electrode for flow-injection determination of glucose.

Immobilization of glucose oxidase in electropolymerized polypyrrole film on the surface of a platinum wire electrode, provides a convenient sensor for flow-injection glucose determination. An upper limit of linear response for 100 microliters injected sample volume was estimated as 20 mM, whereas a 500 microliters injected sample volume gave an estimated detection limit of 0.5 mM. A simple electrode preparation procedure allows quick electrode renewal before each series of measurements.