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PubMed1980

Turbidimetry of inorganic sulfate, ester sulfate, and total sulfur in urine.

We describe simple and precise methods for the determination of inorganic sulfate, ester sulfate, and total sulfur in urine. The methods are based on turbidimetry of sulfate as barium sulfate in the presence of a small amount of preformed barium sulfate and with polyethylene glycol as a stabilizing agent. Inorganic sulfate is directly determined, whereas ester sulfate is measured after removal of inorganic sulfate, followed by acid hydrolysis. Total sulfur is determined after wet oxidation of the sample with nitric acid and perchloric acid in the presence of vanadate as a catalyst. We also report excretion values for healthy persons on a self-selected diet. Men excrete significantly higher amounts of inorganic sulfate and total sulfur than women, but this sex-related difference becomes insignificant if excretion values are expressed relative to creatinine.

Chromatography, Ion Exchange↗
PubMed2004

The role of oxytocin and the paraventricular nucleus in the sexual behaviour of male mammals.

The paraventricular nucleus of the hypothalamus contains the cell bodies of a group of oxytocinergic neurons projecting to extrahypothalamic brain areas and to the spinal cord, which are involved in the control of erectile function and copulation. In male rats, these neurons can be activated by dopamine, excitatory amino acids, nitric oxide (NO), hexarelin analogue peptides and oxytocin itself to induce penile erection and facilitate copulation, while their inhibition by gamma-aminobutyric acid (GABA) and GABA agonists and by opioid peptides and opiate-like drugs inhibits sexual responses. The activation of paraventricular oxytocinergic neurons by dopamine, oxytocin, excitatory amino acids and hexarelin analogue peptides is apparently mediated by the activation of nitric oxide (NO) synthase. NO in turn activates, by a mechanism that is as yet unidentified, the release of oxytocin from oxytocinergic neurons in extrahypothalamic brain areas. Paraventricular oxytocinergic neurons and mechanisms similar to those reported above are also involved in the expression of penile erection in physiological contexts, namely, when penile erection is induced in the male by the presence of an inaccessible receptive female, which is considered a model for psychogenic impotence in man, as well as during copulation. These findings show that paraventricular oxytocinergic neurons projecting to extrahypothalamic brain areas and to the spinal cord and the paraventricular nucleus play an important role in the control of erectile function and male sexual behaviour in mammals.

Animals↗
PubMed1975

Collaborative study of the determination of boric acid in caviar by emission spectroscopy.

Caviar samples were spiked at the 0.1 and 0.2% levels and digested with nitric acid in a closed Teflon-lined digestion vessel to prevent volatility losses. The boron was complexed with 2-ethyl-1,3-hexanediol and extracted into methylisobulty ketone. The emission of the boron oxide band was measured in a nitrous oxidehydrogen flame. The mean recoveries at the 0.1 and 0.2% levels for 6 collaborators were 95.7 and 97.1%, respectively.

Boric Acids↗
PubMed2004

Oxidation of titanium, RGD peptide attachment, and matrix mineralization rat bone marrow stromal cells.

The aim of this study was to compare the efficacy of attachment of arginine-glycine-aspartic acid (RGD) peptide to titanium surfaces oxidized by different methods. Titanium surfaces were treated as follows: (1) treatment A: passivation in nitric acid, (2) treatment B: heated in air at 400 degrees C for 1 hour, (3) treatment C: immersed in 8.8 M H2O2/0.1 M HCl at 80 degrees C for 30 minutes, and (4) treatment D: treated as in treatment C and then heated at 400 degrees C for 1 hour. RGD was attached to titanium samples treated as in treatments A through D. The quantity of attached RGD was determined by an enzyme-linked immunoabsorbent assay. Mineralization of a rat bone marrow stromal cell (RMSC) culture on the titanium surfaces after 21 days was determined y atomic absorption spectroscopy. The treatments were ranked according to quantity of RGD attached as C, A, B, and D. Twenty-one days after RMSC culture, the degree of mineralization was significantly higher for treatment C than for treatments A, B, and D and for controls. The efficacy of RGD attachment varies with the oxidation treatment given to titanium. Oxidation in H2O2/0.1 M HCl at 80 degrees C provided the best overall surface for RGD attachment as well as calcified matrix formation of RMSCs.

Amino Acid Sequence↗
PubMed2003

Preconcentration of selenium compounds on a porous graphitic carbon column in view of HPLC-ICP-AES speciation analysis.

The retention of organic selenium compounds on a porous graphitic carbon stationary phase was investigated. Different acids were studied as mobile phases to elute selenocystamine, selenoethionine, selenomethionine and selenocystine. Detection was achieved using inductively coupled plasma-atomic emission spectrometry to provide selenium-specific and sensitive detection. The separation of the four species was carried out using methanoic acid. An important on-column preconcentration was obtained when solutes were injected in nitric acid or trifluoroacetic acid (TFA) media. The large injection volume employed (2,500 micro L) allowed us to reach low relative detection limits (2-6 micro g/L). The method, employing TFA as injection solvent and methanoic acid as the eluent was found to be robust with respect to different matrices spiked with selenocompounds.

Buffers↗
PubMed2004

Determination of bisphosphonates by ion chromatography-inductively coupled plasma mass spectrometry.

An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) was introduced in the analysis of bisphosphonates. Two compounds (alendronic acid and etidronic acid) were separated on a Dionex AS-7 anion-exchange column with dilute nitric acid employed as the mobile phase. The analytes were detected at m/z 31, as they contain phosphorus. The detection limits achieved were 0.20 mg l(-1) for alendronic acid and 0.05 mg l(-1) for etidronic acid. Since the determination of phosphorus by ICP-MS is difficult due to polyatomic interferences at m/z 31 (15N16O+, 14N16O1H+, and 12C1H(3)16O+), a detailed study of the influence of plasma parameters on phosphorus and background signal was performed.

Chromatography, Liquid↗
PubMed1999

Optimizing the removal of carbon phases in soils and sediments for sequential chemical extractions by coulometry.

We have developed a coulometric technique to optimize the removal of the carbonate and organic fractions for sequential chemical extractions of soils and sediments. The coulometric system facilitates optimizing these two fractions by direct real-time measurement of carbon dioxide (CO2) evolved during the removal of these two fractions. Further analyses by ICP-MS and alpha-spectrometry aided in interpreting the results of coulometry experiments. The effects of time, temperature, ionic strength and pH were investigated. The sensitivity of the coulometric reaction vessel/detection system was sufficient even at very low total carbon content (< 0.1 mol kg-1). The efficiency of the system is estimated to be 96% with a standard deviation of 8%. Experiments were carried out using NIST Standard Reference Materials 4357 Ocean Sediment (OS), 2704 Buffalo River Sediment (BRS), and pure calcium carbonate. Carbonate minerals were dissolved selectively using an ammonium acetate-acetic acid buffer. Organic matter was then oxidized to CO2 using hydrogen peroxide (H2O2) in nitric acid. The carbonate fraction was completely dissolved within 120 min under all conditions examined (literature suggests up to 8 h). For the OS standard, the oxidation of organic matter self-perpetuates between 45 and 50 degrees C, a factor of two less than commonly suggested, while organic carbon in the BRS standard required 80 degrees C for the reaction to proceed to completion. For complete oxidation of organic matter, we find that at least three additions of H2O2 are required (popular methods suggest one or two).

Carbon↗
PubMed2003

Major-to-ultratrace elements in bone-marrow fluid as determined by ICP-AES and ICP-MS.

The major-to-ultratrace elements in human bone-marrow fluid were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry), and ICP-MS (inductively coupled plasma mass spectrometry). The bone-marrow fluid sample was centrifuged prior to acid digestion to exclude the bone piece from bone marrow, and then digested with nitric acid. As a result, 20 elements could be determined over the concentration range from 1610 microg g(-1) for Na to 0.00043 microg g(-1) for W. It was found that Fe, Zn and Sb were enriched by ca. 264-, 7- and 15-fold, respectively, in bone-marrow fluid, compared to those in human blood serum. Alkali metals (K, Rb, Cs), except for Na, were also significantly enriched in bone-marrow fluid. Furthermore, the concentrations of various elements, such as Fe, P, Al, Zn, Cu, Se, Zr, Sn, Ag and W, were significantly higher than those in open seawater.

Bone Marrow↗
PubMed1979

[The digestibility in vitro of some lignocellulose materials].

In our experiments we tested 11 kinds of different lignocellulose materials by means of the method in vitro according to Mellenberger et al. (1970) for a determination of their digestiblity. In experiments carried out with beech sawdust treated with 0.1 M of sulphuric acid a digestibility of 3.7% was found, in sawdust treated with 0.47 M of nitric acid a digestibility of 61.6% was found and after a neutralization with ammonia it amounted to 72.2%. Wood fibre (WF-1) treated enzymatically showed a digestibility of 28.6% and in the WF-2 complemented with newsprint paper it amounted to 33.4%. Untreated beech waste -- forest billets -- showed a low digestibility (5.6%) and that of zero fibre was somewhat higher (12.6%). Difibered beech sawdust showed a digestibility of 44.0% and the digestibility of the biomass prepared from lye waste obtained during the production of cellulose fibres amounted to 74.1%. Waste fibre also showed a high digestibility of 76.0%. Straw enriched with yeast proteins (SL-1) showed a digestibility of 58.0%. Cellulose used as a standard in the course of the testing of lignocellulose materials showed the highest digestibility -- 82.3%.

Cellulose↗
PubMed1978

Atomic absorption spectroscopic determination of lead extracted from acid-solubilized tissues.

A method is presented for determining lead in a variety of tissues. Lyophilized samples are solubilized with nitric acid at room temperature in glass screw-cap culture tubes. Following neutralization with sodium hydroxide and sodium bicarbonate, the lead is extracted into methyl isobutyl ketone as the pyrrolidine dithiocarbamate complex and analyzed by flame atomic absorption spectrophotometry. Brain, heart, liver, lung, and spleen gave recoveries ranging from 92 to 102% with standard deviations of less than 8%. Aorta, kidney, and rib were unsuitable for analysis by this method. A large number of samples can be analyzed without specialized equipment or intricate experimental steps. The detection limit is 35 ng/g tissue (wet weight) and sensitivity is approximately 140 ng/g tissue (wet weight).

Brain Chemistry↗
PubMed1986

Dietary citric acid enhances absorption of aluminum in antacids.

Ten healthy men ingested, twice daily between meals, during each of the seven-day experimental periods: (a) citric acid (as lemon juice), (b) Al(OH)3, or (c) Al(OH)3 + citric acid. Whole blood sampled after each dietary period was analyzed electrothermally after digestion with nitric acid. Moderate, but significant, increases in mean Al concentrations as compared with pretreatment values [5 (SD 3) micrograms of Al per liter] were seen after ingestion of either citric acid or Al(OH)3: 9 (SD 4) and 12 (SD 3) micrograms/L, respectively. Ingestion of both Al(OH)3 and citric acid resulted in a more pronounced, highly significant (p less than 0.001) increase in Al concentrations, to 23 (SD 2) micrograms Al/L, probably owing to formation and absorption of Al-citrate complexes.

Adult↗
PubMed2002

[3-nitrobenzylidene-2,3(3H,5H)-furandione in the Hantzsch pyridine synthesis. 1. A new approach to furo(3,4-b)pyridines].

The nitrobenzylidenefurandiones 7 react with acetoacetic ester (8) and ammonium acetate or 3-aminocrotonic esters (9a, b) and 2-amino-pent-2-en-4-on (9c), respectively heating in acetic acid to yield the tetrahydrofuro[3,4-b]pyridines 10. The dehydrogenation of 10 using nitric acid or activated manganese dioxide leads to the dihydrofuro[3,4-b]pyridines 12. When the reaction is carried out with the tetronic acid derivatives 7 and the enaminocarbonyl compounds 9 at 30 degrees C in tert-butanol the hexahydro-7a-hydroxyfuro[3,4-b]pyridines 11 are obtained. Treating the N,O-acetales 11 with acetic anhydride in pyridine affords the annulated lactones 10.

Furans↗
PubMed2003

Nitric oxide and portal hypertension: a nitric oxide-releasing derivative of ursodeoxycholic acid that selectively releases nitric oxide in the liver.

Portal hypertension, a common consequence of chronic liver diseases, is directly responsible for most complications of cirrhosis. In liver microcirculation, nitric oxide is considered a major fine tuner of vascular tone by counterbalancing vasoconstrictors (sympathetic nervous activity, the renin-angiotensin system, and endothelin-1) in normal and cirrhotic livers. The deficiency of endothelial nitric oxide release is a key factor in the hemodynamic abnormalities associated with the dynamic component of portal hypertension. Conventional nitric oxide donors release nitric oxide into the blood stream, causing systemic hypotension and progression of vasodilatory syndrome in cirrhotic patients. NCX1000 is a nitric oxide-releasing derivative of ursodeoxycholic acid-derived compounds, being capable of selectively releasing nitric oxide into the liver circulation. Administration of NCX1000 to portal hypertensive rats decreases intrahepatic resistance providing a novel therapy for the treatment of portal hypertension.

Adipocytes↗
PubMed2005

Effect of counterions on lanthanum biosorption by Sargassum polycystum.

The effect of the presence of different anions on the biosorption of La(3+) (Lanthanum) using Sargassum polycystum Ca-loaded biomass was studied in this work. Different types of metal salts were used, such as nitrate, sulphate and chloride. The presence of the anion sulphate decreased the metal uptake for tested pH values of 3--5 when compared to the nitrate and chloride systems. The presence of chloride ions did not seem to interfere with the lanthanum removal. The speciation of lanthanum in solution could explain the differences obtained for the different systems and the Mineql+ program was used for the calculations. A monovalent complex with sulphate and lanthanum was formed that had lower apparent affinity towards the biomass compared to the free trivalent metal ion. The La uptake varied from 0.6 to 1.0 mmol g(-1). The Langmuir model was used to describe quantitatively the sorption isotherms. The addition of sulphuric acid for pH adjustment decreased the metal uptake from lanthanum sulphate solutions when compared to the nitric acid addition. The effect was more pronounced with sulphuric acid due to the formation of complexes.

Anions↗
PubMed2001

Speciation and preconcentration of vanadium(V) and vanadium(IV) in water samples by flow injection-inductively coupled plasma optical emission spectrometry and ultrasonic nebulization.

An on-line separation, preconcentration and determination system for vanadium(IV) and vanadium(V) comprising inductively coupled plasma optical emission spectrometry (ICP-OES) coupled to a flow injection (FI) method with an ultrasonic nebulization (USN) system was studied. The vanadium species were retained on an Amberlite XAD-7 resin as a vanadium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (V-5-Br-PADAP) complex at pH 3.7. Enhanced selectivity was obtained with the combined use of the formation on-line of the complexes and 1,2-cyclohexanediaminetetraacetic acid (CDTA) as masking agent. The vanadium complexes were removed from the microcolumn with 25% v/v nitric acid. A sensitivity enhancement factor of 225 was obtained with respect to ICP-OES using pneumatic nebulization (15-fold for USN and 15-fold for the microcolumn). The detection limit for the preconcentration of 10 mL of aqueous solution was 19 ng L-1. The precision for 10 replicate determinations at the 5 micrograms L-1 V level was 2.3% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the separation and preconcentration system for vanadium species was linear with a correlation coefficient of 0.9992 at levels from near the detection limits up to at least 100 micrograms L-1. The method was successfully applied to the speciation of vanadium in river water samples.

Flow Injection Analysis↗
PubMed2002

The behaviour of 134Cs, 60Co, and 85Sr radionuclides in marine environmental sediment.

This work describes experimental investigations and modelling studies on the sorption of radionuclides 134Cs, 60Co, and 85Sr by certain marine sediments within Egypt. The chemical composition of the marine sediments was determined. The soluble salts were measured for the sediments and the concentrations of the released cations, Al3+, Fe3+, and Si4+, were measured for the sediment materials in 0.1 M NaClO4 aqueous solution at different hydrogen ion concentrations. The two main factors that control the uptake of the radionuclides onto the sediment are the pH and the exchangeable capacities of the sediment materials. Surface complex model was used to estimate the surface charge densities and the electric surface potential of the marine sediment materials. These two parameters were calculated at the surface capacity sites of the sediment materials. The desorption of the adsorbed cations was determined by means of selective consecutive extraction tests using different chemical reagents including (1) 1 M MgCl2 (pH 7), (2) 1 M ammonium oxalate (pH 3-5), (3) 0.04 M NH2OH,HCl in 25% acetic acid (pH 3-4), (4) H2O2 in 5% HNO3(pH 2-3), and (5) digestion with nitric acid followed by hydrofluoric and perchloric acids (pH 2).

Absorption↗
PubMed1997

N-phenyliminodiacetic acid as an etchant/primer for dentin bonding.

Effective composite-to-dentin bonding has been achieved by the sequential use of dilute aqueous nitric acid (HNO3) and acetone solutions of N-phenylglycine and a carboxylic acid monomer, e.g., p-PMDM. Both the HNO3 pre-treatment and the surface-initiated polymerization that results from reaction of infused N-phenylglycine and PMDM have been identified as key elements of this bonding system. In this study, N-phenyliminodiacetic acid, a unique imino acid derivative with acidic and chelating potential, was evaluated as a dual etchant/primer for dentin bonding. A randomized, 2(3) factorial design was used to study the effects of 3 factors on tensile bond strength (TBS): conditioner (HNO3 vs. no HNO3), primer (N-phenylglycine vs. N-phenyliminodiacetic acid), and primer solvent (acetone vs. acetone:H2O). The three-step protocol consisting of HNO3, N-phenylglycine in acetone, and PMDM in acetone served as the control. The hypothesis tested was that N-phenyliminodiacetic acid could act as both an effective conditioner (i.e., etchant) and as a primer. Two-step protocols that included only N-phenyliminodiacetic acid and PMDM were compared with the control. TBS (n = 10 per group) were determined after 24-hour storage in H2O and analyzed by ANOVA and Duncan's Multiple Range test. Primer solvent was critical for obtaining significant bonding to dentin when HNO3 was omitted. N-phenyliminodiacetic acid in acetone without prior HNO3 etching gave the lowest ranking mean TBS (95% CI, 3.8 +/- 1.9 MPa). In contrast, the mean TBS obtained from samples treated with N-phenyliminodiacetic acid in acetone:H2O without prior HNO3 etching was not statistically different (p > 0.05) from the mean TBS for the control (95% CI, 9.3 +/- 1.8 and 9.8 +/- 1.9 MPa, respectively). Due to its dual function as etchant and primer, N-phenyliminodiacetic acid in acetone:H2O provides for a simplified bonding technique that yields strong, PMDM-mediated adhesion to dentin.

Acid Etching, Dental↗