Determination of adsorption entropies on solid surfaces by reversed-flow gas chromatography.

The reversed-flow gas chromatography (RF-GC) method has been applied to measure the time separation of adsorption entropies and their probability density functions, when acetic and formic acid vapors, responsible for artifacts degradation inside museums, are adsorbed on various heterogeneous surfaces. The solid materials studied were Penteli marble and solid metals (lead, copper and iron), which are commonly used for the construction of the artifacts. Physicochemical measurements were performed at various temperatures in the range 353-473 K, the surface coverage theta being also calculated over time. A new mathematical model, based on well known equations was used in order to extract the above quantities.

Comparative study of pretreatment methods for the determination of metals in atmospheric aerosol by electrothermal atomic absorption spectrometry.

A comparative study of pretreatment methods for the determination of 10 elements (As, Cd, Pb, V, Ni, Mn, Cr, Cu, Fe, Al) in atmospheric aerosols by electrothermal atomic absorption spectrometry (ETAAS) was conducted. For the digestion of the particulates collected in filters, six methods were compared using a mixture of HNO(3) and HF with or without the addition of various oxidative agents (HClO(4) or H(2)O(2)) or acids (HCl). The comparative study was performed using loaded cellulose filter samples, which were digested in Parr bombs and heated in a conventional oven at 170 degrees C for 5h. The extraction efficiency and blanks were compared and it was proved that the digestion method using only HNO(3)-HF extracted most of the metals and gave the lowest blanks. The HNO(3)-HF mixture was selected for the development of an improved microwave digestion method specific for aerosol-loaded filters. The operating parameters were optimized, so that quantitative recovery of the reference materials NIST 1649a urban dust and NIST 1648 urban particulate matter was achieved. The blank of cellulose and teflon filters were also determined and compared. Teflon filters present the lowest blanks for all the elements. The obtained limits of detection for each type of filters were adequate for environmental monitoring purposes. ETAAS instrumental operation was also optimized for the compensation and the elimination of interferences. The temperature optimization was performed for each metal in every type of filter and optimized parameters are proposed for 10 elements.

Study of excretion of ecdysterone in human urine.

A study of excretion in human urine of ecdysterone, which is the active component of several over-the-counter supplements such as "Ecdysten", reportedly used by athletes, is presented. The study was performed after oral administration of 20 mg of ecdysterone. The collected urine samples were prepared using the standard screening extraction procedure for the free and conjugated fraction of anabolic steroids, and analyzed by gas chromatography (GC) coupled with quadrupole mass spectrometry (MS) and also with high-resolution mass spectrometry (HRMS). Two ecdysterone metabolites were identified and detected along with unchanged ecdysterone. Accurate mass measurements were made for diagnostic ions, including the molecular ion of the main metabolite of ecdysterone, deoxyecdysone, which, to our knowledge, has not previously been reported in the literature. These accurate mass measurements support the proposed fragmentation scheme.

Chemical characterization of PM2.5 aerosols in Athens-Greece.

Atmospheric aerosols, PM2.5 were simultaneously collected in the center of Athens and in a semi-urban area of the Athens basin, using the Harvard Impactor (HD) system, from March 1995 to March 1996. 224 24-hr samples were collected. Chemical analysis of the filter samples was performed using ion chromatography (Cl-, SO4(2-); NO3-, Na+, K+, NH4+, Mg2+, Ca2+). In addition aerosol addity was measured using a semi-micro electrode. No significant differences in chemical composition of particles were observed between the two sampling sites. At the city center the annual-average of non-sea-salt sulfate concentration was 85 nmoles m(-3). Also the annual mean values of chloride, ammonium and sodium concentrations were 48, 88 and 71 nmoles m(-3) respectively. Lower concentrations were observed for the rest of the ions. Aerosol acidity was higher at the city center, 18 nmoles m(-3), compared to that observed at the semi-urban site, 14 nmoles m(-3). Species concentrations were examined by season. The mean monthly concentrations of Cr, NO3-, Ca2+ and H+ were higher in the winter. In contrast those of Mg2+ Na+ and K+, were higher in the summer and the spring, respectively. The concentrations of SO4(-2)and NH4+ ions did not exhibit a seasonal pattern. Sulfate and ammonium ions were the predominant ionic species and their ionic ratio ranged between those of ammonium sulfate and letovicite.

Determination of ephedrines in urine by gas chromatography-mass spectrometry.

A selective gas-liquid chromatographic method with mass spectrometry (GC-MS) for the simultaneous confirmation and quantification of ephedrine, pseudo-ephedrine, nor-ephedrine, nor-pseudoephedrine, which are pairs of diastereoisomeric sympathomimetic amines, and methyl-ephedrine was developed for doping control analysis in urine samples. O-Trimethylsilylated and N-mono-trifluoroacetylated derivatives of ephedrines--one derivative was formed for each ephedrine--were prepared and analyzed by GC-MS, after alkaline extraction of urine and evaporation of the organic phase, using d3-ephedrine as internal standard. Calibration curves, with r2>0.98, ranged from 3.0 to 50 microg/ml depending on the analyte. Validation data (specificity, % RSD, accuracy, and recovery) are also presented.

Human neutral brush border endopeptidase EC 3.4.24.11 in urine, its isolation, characterisation and activity in renal diseases.

Human neutral brush border endopeptidase (NEP) was purified from the urine of patients suffering from acute toxic tubulointerstitial nephropathy. An enzyme preparation with specific activity of 102 Ug(-1) protein was obtained. The urinary activities of neutral endopeptidase and alanine aminopeptidase were measured in patients with renal disease and in 30 control patients, resulting in a reference range from 0.1 to 0.7 Ug(-1) creatinine and 1.4-14.1 Ug(-1) creatinine, respectively. Urine enzyme activities were highest in patients with acute tubulotoxic renal diseases. Neutral endopeptidase and alanine aminopeptidase activities were found to be 6.5- and 10-fold higher than the upper value of the reference range, respectively. Smaller increases in the rate of excretion of these enzymes (2.5- and 3.5-fold), respectively, were observed in patients suffering from acute tubular insufficiency and even lower increases, 2- and 1.5-fold, respectively, were observed in patients with chronic renal diseases. In diabetics and kidney transplant patients the enzyme excretion rates were within the reference range. Assay of both transmembrane metalloproteinases in urine may prove valuable in serving as markers for renal toxicity. Together with beta-NAG these enzymes could be employed as differentiation markers between acute and chronic tubular insufficiency.

Evaluation of a hypercrosslinked polystyrene, MN-200, as a sorbent for the preconcentration of volatile organic compounds in air.

Breakthrough volumes, average percentage recoveries, and storage stabilities were obtained for vapors of 8 volatile organic compounds (pentane, octane, undecane, isooctane, cyclohexane, toluene, methanol, and dichloromethane) on a new adsorbent material, Hypersol-Macronet, MN-200. Breakthrough volumes were estimated as half of the gas chromatographic specific retention volumes at 20 degrees C for the compounds. Recoveries of the adsorbates were determined by both solvent extraction and thermal desorption methods. The results obtained compare favorably with those for Tenax GR (values reported in the published literature and others obtained in our laboratory). Results of storage stability studies on MN-200 meet the criterion for acceptability (<10% loss). High adsorption capacity for very volatile and polar compounds, combined with ease of desorption of less volatile compounds, render MN-200 a highly promising adsorbent for sampling volatile organic compounds in indoor and outdoor air.

Nitro-PAH in ambient particulate matter in the atmosphere of Athens.

Nitrated polynuclear aromatic hydrocarbons (NPAH) with a molecular mass of 247 Daltons were found in soot collected in downtown Athens during a campaign performed in 1996. In particular, 2-nitrofluoranthene (2-NFa) and 2-nitropyrene (2-NPy), which are mainly related to photo-induced chemical processes occurring in the atmosphere, were more abundant than 1-nitropyrene (1-NPy) usually associated to motor vehicle exhaust.

Determination of sialic acids in biological fluids using reversed-phase ion-pair high-performance liquid chromatography.

A simple, rapid and sensitive reversed-phase ion-pair high-performance liquid chromatographic method for the determination of N-acetylneuraminic acid and 2-deoxy-2,3-dehydro-N-acetylneuraminic acid in biological fluids is described. Determination of N-acetylneuraminic acid released by acidic hydrolysis, in serum, urine and saliva, and 2-deoxy-2,3-dehydro-N-acetylneuraminic acid in urine, without hydrolysis, was accomplished by injecting the sample without derivatization, into the chromatograph. Measurements were carried out isocratically within 6 min using a C18 column and a mobile phase of aqueous solution of triisopropanolamine, as ion-pair reagent, 60 mM, pH 3.5 at room temperature with UV absorbance detection. The present method is reported for the first time for the determination of sialic acids in biological fluids. Recoveries in serum, urine and saliva ranged from 90 to 102% and the limits of detection were 60 nM and 20 nM for the two sialic acids, respectively. The method has been applied to normal and pathological sera from patients with breast, stomach, colon, ovarian and cervix cancers, to normal urine and urine from patient with sialuria and to normal saliva.

Simplified cleanup and liquid chromatographic ultraviolet determination of linuron and three metabolites in potatoes.

A simple and efficient method is presented for the extraction, cleanup, and liquid chromatographic (LC) determination of linuron and 3 of its metabolites, 3-(3,4-dichlorophenyl)-1-methyl urea (DCPMU), 3-(3,4-dichlorophenyl) urea (DCPU), and 3,4-dichloroaniline (DCA), in potatoes. Samples are extracted with acetone, partitioned into dichloromethane-hexane (1 + 1), and cleaned up using disposable silica cartridges. LC determination is performed using a LiChrosorb NH2 5 microns column, with an isopropanol-isooctane gradient mobile phase and UV detection at 248 nm. Recoveries of linuron and 2 of the metabolites from untreated samples fortified at 0.02-2 micrograms/g ranged from 80 to 102%, while recoveries for the metabolite DCA ranged from 60 to 78%. The detection limit was 0.015 micrograms/g for linuron and each metabolite; the minimum quantitation level was 0.5 micrograms/g. The developed method was applied to potato samples from a field experiment.

Determination of ursodeoxycholic acid in serum by a new fluorometric enzymatic method using 7 beta-hydroxysteroid dehydrogenase from Clostridium absonum.

A fluorometric enzymatic method for the determination of ursodeoxycholic acid (UDCA) and its glycine and taurine conjugates in human serum has been developed. A simple and fast purification and preconcentration procedure using Sep Pak C18 cartridges was employed for the UDCA extraction from human serum. UDCA and its conjugates were determined in the extracted sample by an equilibrium method based on the enzymatic conversion of the 7 alpha-hydroxy group into 7-oxo group by beta-nicotinamide adenine dinucleotide phosphate in the presence of 7 beta-hydroxysteroid dehydrogenase (7 beta-HSD) and the produced NADPH was monitored fluorometrically. The 7 beta-HSD, which is not yet commercially available, was isolated from Clostridium absonum cultures (ATCC No. 27555) and purified by affinity chromatography. The method has a limit of detection of 0.8 microM in serum and the precision varied from 6.1 to 2.0% for low and high concentrations, respectively. The recovery of UDCA from serum samples was about 99% (range 85-105%). The method was successfully applied to UDCA determination in serum samples from patients treated with UDCA for primary biliary cirrhosis.

Total selenium concentration in tap and bottled drinking water and coastal waters of Greece.

The total selenium concentration in various waters from all over Greece was determined fluorimetrically. The concentration in most of the drinking water, either from the tap or bottled, was within the range 100-200 ng l-1 and showed no great seasonal fluctuations. Most Greeks receive 0.2-0.4 micrograms selenium per day from drinking water. Coastal surface water contains 100-250 ng Se l-1, while higher concentrations are found at locations regarded as polluted.

Determination of polycyclic aromatic hydrocarbons in Athens atmosphere.

Concentrations of total suspended particulates (TSP), benzene soluble fraction (BSF) and polycyclic aromatic hydrocarbons (PAH) have been determined in ambient air from four different sites in Athens, situated in urban, semi-industrial and industrial areas. GLC analysis has been applied for the determination of PAH, while the CGC/MS technique was used in order to confirm the obtained results. The same PAH pattern was observed for all stations. The identified PAH have been fluoranthene (FLA), pyrene (PYR), benzo(a)anthracene (BaA), chrysene (CHR), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), benzo(e)pyrene (BeP) and benzo(ghi)perylene (B(ghi)P). The concentrations of individual PAH ranged from traces to 33 ng m-3 (e.g. same or lower comparing to other large cities). The higher values of PAH were found during adverse meteorological conditions.

Mutagenicity and polycyclic aromatic hydrocarbons analysis of ambient airborne particles collected in Athens, Greece.

Samples of airborne particulates from the Athens atmosphere were examined for mutagenicity and various polycyclic aromatic hydrocarbons (PAH). Extracts induced linear, dose-related increases in TA98 His+ revertants in the Ames/Salmonella assay and contained average benzo[a]pyrene (BaP) levels of 3.9 ng/m3 of air. The levels of revertants/m3 of the samples showed a linear relation to their BaP and benzo[b]-(BbF) + benzo[k]-fluoranthene (BkF) concentrations and were higher in areas with dense traffic than in industrial areas. It is suggested that the atmosphere of Athens favours the formation of secondary direct-acting mutagens due to the oxidation and nitration of PAH by ozone and nitrogen oxides, which are more abundant in the late spring months.

Fluorimetric kinetic studies and sub-muM determination of aluminium with 2-hydroxy-1-naphthaldehyde p-methoxybenzoylhydrazone.

A fluorimetric study has been made of the kinetics of the reaction of 2-hydroxy-1-naphthaldehyde p-methoxybenzoylhydrazone with aluminium, and a rate equation and a possible kinetic scheme are proposed. Experimental conditions are defined under which 0.020-10.0muM aluminium can be determined with an average error of 3.7% and a coefficient of variation of about 4.6%.

Potentiometric titration of sulphate, sulphite and dithionate mixtures, with use of a lead ion-selective electrode.

Simple methods are described for the analysis of sulphate, sulphite and dithionate mixtures by potentiometric titration with lead perchlorate (and use of a lead ion-selective electrode). The error and precision are both about 2-5% for the sulphate concentration range 3 x 10(-3) -6 x 10(-4)M. The sulphur content in fuels derived from refuse was determined by potentiometric titration after bomb-combustion and the results compared favourably with those from the standard BaSO(4) gravimetric method.

Direct enzymic fluorimetric method for the determination of individual bile acids in bile.

We describe a new, simple, fluorimetric enzymic method for the determination of individual bile acids in bile. Bile is diluted 4000-fold with water and 3 alpha- and 7 alpha-hydroxy bile acids are determined by equilibrium methods and chenodeoxycholic acid is determined by a differential kinetic method, without any prior separation and preparatory step. The equilibrium methods are based on the reaction of 3 alpha- or 7 alpha-hydroxy bile acids with beta-NAD+ in the presence of the enzyme 3 alpha- or 7 alpha-hydroxysteroid dehydrogenase (HSD). The kinetic method is based upon the reaction of chenodeoxycholic acid with beta-NAD+ in the presence of the enzyme 7 alpha-HSD. All measurements are monitored fluorimetrically. Cholic and deoxycholic acid are calculated by difference. Recovery experiments gave satisfactory results. Gallbladder bile from patients was analysed for the three major bile acids. The proposed method is suitable for clinical use.