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A simple technique has been developed for preconcentration of gaseous trace organic compounds on solid sorbents, followed by gas chromatography. The sorbent is packed in a cartridge prepared from a syringe needle placed in the gas chromatographic injector and the analytes previously adsorbed are thermally desorbed at the injector temperature and then directly swept by the carrier gas into the column...
This paper presents a method whereby trace elements are adsorbed in NH 4 Cl-NH 3 medium on activated carbon and then determined by microwave plasma torch atomic emission spectrometry (MPT-AES). The working conditions (including microwave forward power, gas flow rate, NH 3 -NH 4 Cl concentration in the sample solution, HCl concentration in the eluant, sample introduction...
A HPLC-DAD method is described for the analysis of the rodenticides warfarin, diphenadione and chlorophacinone, together with the phenylurea herbicides isoproturon and diuron, in soil samples. The HPLC parameters have been optimised to provide baseline separation with symmetrical peakshapes in short analysis times. The sample preparation consists of Soxhlet extraction followed by SPE clean-up on...
A literature search on the speciation of arsenic in environmental and biological samples shows an increasing interest of many researchers in the subject. Because of the low level of arsenic species in real samples, many problems related with its speciation remain unresolved: species instability during sampling, storage and sample treatment, incomplete recovery of all species, matrix interferences,...
5-methylphenazonium methylsulphate, (commonly named phenazine methosulphate, PMS) mediated electroxidation of β-nicotinamide adenine dinucleotide (phosphate), reduced form, (NAD(P)H), on platinum, gold and carbon electrodes has been studied by electropolymerization of 1,2-, 1,3-, 1,4-diaminobenzene (DAB), pyrrole-2-carboxylic acid (PY-2-COOH) and 4,4 -dihydroxybenzophenone (DHB) in presence of PMS...
An electrothermal vaporization (ETV) sample introduction device tantalum filament was combined with microwave plasma torch atomic emission spectrometry (MPT-AES) for determination of several trace elements. Some operating parameters of the system were optimized. The effects of easily ionized elements (EIEs) on the emission intensities of the tested elements were studied in detail. It was revealed...
The spectrophotometric determination of Cr(VI) and Cr(III) via sequential injection was used to demonstrate the sensitivity enhancement provided by a newly developed wetting film extraction system. The reaction product of Cr(VI) with 1,5-diphenylcarbazide was ion-paired with perchlorate and extracted into an organic wetting film consisting of octanol and 4-methyl-2-pentanone on the inner wall of...
A calibration procedure for solid phase microextraction--gas chromatographic (SPME-GC) analysis of organic vapours in air was described in which GC detector (MS in this case) signal is directly related to concentration of analytes of interest sampled by SPME. Gaseous standard mixtures used for the calibration were generated by means of a home-made permeation-type apparatus described elsewhere, W...
We have developed a low cost pH sensor based on an optical reflective device (ORD) coupled to a toughened, lightly crosslinked aminated polystyrene membrane. Protonation of the amine group causes the polymer to swell. This is accompanied by a decrease in the turbidity of the membrane. As a result, reflected intensity measured by the ORD is a function of pH. The resulting pH sensor is inexpensive...
An amperometric diamine sensor is developed for clinical applications in diagnosis of bacterial vaginosis (BV). The sensor is based on crosslinked putrescine oxidase (PUO) which catalyzes the conversion of diamines (mainly putrescine and cadaverine) to products including hydrogen peroxide. The hydrogen peroxide is detected anodically at platinum electrode polarized at 0.5 V versus Ag/AgCl. Platinum-plated...
Fabrication and characterization of miniature, flexible, planar biosensors for monitoring l-lactate accumulation in an ischemic myocardium are described. Three configurations of Au-based electrodes were fabricated by a photolithographic technique on flexible polyimide Kapton foil. All sensors are based on an immobilized lactate oxidase with amperometric detection of the enzymatically produced...
An overview of major combinations and recent applications of the solids/flow systems/atomic spectroscopy trinomial is presented. Several representative examples, classified according to the role played by the solids (sample or active component of a chemical reaction or separation) are described.
The utilization of a multicomponent gaseous standard mixture, containing CO and CO 2 and obtained by thermal decomposition of a so-called immobilized compound, for a single point calibration of a GC/FID system are described. The generation of such a mixture takes place as a result of thermal decomposition of a sample of chemically modified silica gel placed in a heated chamber of thermal desorber...
The development of a glucose sensor suitable for use with whole blood is described. It is based on anodic oxidation at + 700 mV of hydrogen peroxide with a platinum electrode covered with a gas permeable membrane. Glucose reacts with glucose oxidase immobilised on the external side of the membrane, and forms hydrogen peroxide which is able to cross the gas permeable membrane due to its high vapour...
The present study breaks with the earlier mechanism of electrode potential on basis of experimental investigations and theoretical considerations. It rejects that the transport through the membrane produces the electrode potential and definitely proves that the electrode potential is created via surface chemisorption; i.e., the electrode potential is produced by a surface reaction. The reaction...
A general scheme is set up for the estimation of the impurity profile of bulk drug substances by the complex use of chromatographic, spectroscopic and hyphenated techniques. Several examples are presented as illustrations to the scheme from the authors' laboratory involving the use of chromatographic methods such as thin-layer-(TLC), gas-(GC), analytical and preparative high-performance liquid chromatography...
Ultrafiltration has been used to examine the size fractionation of lead, copper, iron, aluminium, calcium, potassium and sodium in white and red wines. Fractionation patterns demonstrated that the behaviour of lead is significantly different to the other metals considered. In red wine, there was a sudden decrease for lead between 100 000 and 30 000 nominal molecular weight cut off (NMWCO) and in...
Properties of six derivatives of 1-trifluoroacetylbenzene: [4-(n-butyl)- (1), 4-(n-hexadecyl)- (2), 4-dodecyloxy- (3), 4-(n-dodecylsulfonyl)- (4), N,N-dioctyl-4-trifluoroacetylbenzamide (5), octyl-p-trifluoroacetylbenzoate (6)] as neutral carriers for carbonate ion were examined and compared. The sensitivity towards carbonate ion was for (3) pH dependent. This eliminates (3) from practical applications...
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