Separation and detection of oxidation products of fluorodeoxyglucose and glucose by high-performance liquid chromatography-electrospray ionisation mass spectrometry

2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.     

Use of thenoyltrifluoroacetone for the determination of manganese by activation analysis

A new procedure for the substoichiometric extraction of bivalent manganese by thenoyltrifluoroacetone into ethyl acetate has been developed and used in activation analysis. The value of the extraction constant has been found to be 3.1 x 10(-6); the pH range in which the extraction can be performed is 7.8-9.2. The influence of oxalate, citrate, tartrate, fluoride and cyanide ions has been studied. A selective substoichiometric extraction of manganese in the presence of Zr, Hf, Nb, Th, Fe and Sc is possible at pH 8-8.5, tartrate and fluoride being used as masking agents. Copper and cobalt can be screened by ammonia and cyanide respectively. The method has been used for the determination of manganese in biological materials, potassium fluoride and zirconium.     

Complexation of aluminium, yttrium, lanthanum and lanthanides with 4-(2-pyridylazo)resorcinol (par)

The sensitive reactions between 4-(2-pyridylazo)resorcinol (PAR) and yttrium, lanthanum and the lanthanides can be used for the spectrophotometric determination of these elements. The method has no advantage over other methods for the determination of aluminium and lanthanum. Only M(PAR)H and M(PAR) complexes are formed in solutions where the molarity of the metal ion is greater than or nearly equal to the molarity of the ligand at pH < 7-5. If there is molar excess of PAR, 1:2 complexes may be formed but this is certain only for the yttrium-PAR system. Errors in analysis may result from the simultaneous occurrence of optically different complexes; close control of pH and reagent concentration is essential. Optical and equilibrium data are given for the systems investigated.     

Determination of some trace elements in human tooth enamel

Determination of seven elements (Cu, Fe, Mg, Mn, Pb, Sr and Zn) in whole enamel and surface layers of extracted non-carious human teeth by FAAS, ETA AAS, ICP-AES and ICP-MS (Pb) is demonstrated. Techniques are described for obtaining whole enamel and its acid dissolution. Fifty microm width enamel layers from outer enamel surface to a 200 microm depth were successively etched in 1 mL of 3 M HClO4 for 3 min dissolution periods. Enamel samples were analyzed for populations under and over 20 years of age and enamel from Bronze Age teeth. Concentrations of microelements in the whole enamel and in the first surface layer (50 microm depth) were compared. With exception of Sr and Mg, all elements show significantly higher concentrations in the first layer than in whole enamel and higher concentration in teeth of individuals over 20 years, which demonstrate the cumulative effect of these elements. The Cu, Fe, Mn, Pb and Zn concentrations in four layers of erupted and non-erupted teeth decreased while Mg and Sr concentrations increased toward enamel-dentine junction. The concentrations of most elements were almost constant as they approached the 150 microm layer. This concentration gradient may result from interaction between saliva and teeth and supports the hypothesis that the surface de- and re-mineralization process is effective at most to 150 microm from the enamel surface.     

Effects of non-ionic surfactants on isotachophoretic separations of 2-arylpropionic acids

Non-ionic surfactant (Brij 35, Tween 20, Tween 80 and Tergitol NPX) modified capillary isotachophoresis was investigated for the separation of 2-arylpropionic acids (fenoprofen, flurbiprofen, ibuprofen, ketoprofen and naproxen) and benzoic acid and its derivatives (salicylic, acetylsalicylic and gallic acids). The relative step height (RSH) values of analytes were found to be dependent on the type and concentration of the surfactant. The strength of the affinity of the 2-arylpropionic acids to the non-ionic micelles was found to be as follows: flurbiprofen > fenoprofen > ibuprofen > naproxen > ketoprofen. In general, the RSH values of 2-arylpropionic acids increase with an increase in the concentration of surfactants. However, the RSHs of benzoic, salicylic and gallic acids are not considerably affected. Separation of all acids was obtained with the Tween 20 (1.5%, w/v) in the leading electrolyte 10 mmol L(-1) hydrochloric acid/L-histidine (pH 6.0). Changes in the fluorescence intensity of fenoprofen, flurbiprofen and naproxen were also investigated in micellar media (Tween 20, Tween 80 and Brij 35). The strength of the affinity of the 2-arylpropionic acids to the Tweens micelles was found to be as follows: flurbiprofen > fenoprofen > naproxen, which is consistent with the isotachophoretic results. On the contrary, the strength of the affinity to the Brij micelles was found to be as follows: fenoprofen > naproxen > flurbiprofen.     

Minipol, a desk-computer program for refinement of protonation constants from differential-pulse polarographic data

The program MINIPOL, designed to run on a desk-computer with 32 kbytes of memory, can calculate the optimum values of overall protonation constants and molar intensities of up to 8 species with composition H_XXXL_ρ, from differential-pulse polarographic data.     

Substoichiometric determination of heavy rare earths by isotopic dilution analysis

A substoichiometric method for the determination of heavy rare earths (holmium, thulium) has been developed. After the addition of a substoichiometric amount of EDTA to the test sample of rare earth labelled with its radioactive isotopes, the negatively charged complex formed was separated by passage through a column of Dowex 50 x 8. Interfering metals can be removed by preliminary cupferron and diethylammonium diethyldithiocarbamate extraction. Concentrations of rare earth down to 4 x 10(-7)g 5 ml have been determined.     

Polarographic indication of the end-point in chelometric titrations with triethylenetetraminehexa-acetic acid

The application of d.c. and square-wave polarographic measurements for the indication of the end-point in titrations with triethylenetetraminehexa-acetic acid (TTHA) has been studied. TTHA has ten co-ordinating groups and forms complexes with metal to ligand ratios of either 1:1 or 2:1, depending on the metal and experimental conditions. The shape of the titration curves, determined by the dependence of the limiting current (peak current of the square-wave polarographic curve) or of the half-wave potential (peak potential) on the amount of TTHA added indicates the composition of the complex formed in the titration. The composition of this complex as determined from the studied titration curves agrees with that predicted by theory. Titrations with polarographic indication of the end-point were also applied for direct titrations of binary mixtures of metal ions. The resulting titration curves indicated the existence of mixed dinuclear complexes and also the kinetic factors involved in the reactions between two different metal ions and TTHA.