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PubMed2006

Gene transfer to the gastrointestinal tract after peroral administration of recombinant adeno-associated virus type 2 vectors.

OBJECTIVES: The transfer of exogenous genetic material to cells within the gastrointestinal (GI) tract has many potential therapeutic applications. An attractive feature of the GI tract for gene transfer is its accessibility through the orogastric route. In this study, we evaluated the stability of recombinant adeno-associated virus type 2 (rAAV2) vectors within the GI tract and whether rAAV2-mediated gene transfer could be increased through manipulation of the intraluminal environment. METHODS: The stability of rAAV2 vectors carrying beta-galactosidase and enhanced green fluorescence protein transgenes was determined in the presence of hydrochloric acid, pepsin, trypsin, chymotrypsin gastric fluid and intestinal fluid and after in vivo administration. For in vivo experiments, the rAAV2 vector carrying the beta-galactosidase transgene was administered perorally to FVB/NJ mice. Groups of mice received the vector alone or in combination with sodium bicarbonate and aprotinin. Gene transfer to the stomach and small intestine was evaluated by polymerase chain reaction and histochemical assays. RESULTS: The stability of rAAV2 was reduced by hydrochloric acid, trypsin, chymotrypsin, gastric fluid and intestinal fluid. The vector was not stable within the lumen of the GI tract. Gastric acid neutralization with sodium bicarbonate and protease inhibition with aprotinin increased the in vivo stability of the vector and the level of gene transfer to the stomach and all regions of the small bowel. In both groups of mice (vector alone and vector plus sodium bicarbonate and aprotinin), transgene-derived protein expression (beta-galactosidase) was below the level of detection of the histochemical assay. CONCLUSIONS: Recombinant AAV2 are adversely affected by physiological conditions within the proximal GI tract. Gastric acid neutralization and inhibition of intestinal protease activity improved rAAV2 stability and increased the level of gene transfer within the GI tract. Despite these changes, transduction of the GI tract after peroral rAAV2 administration remained low.

Animals↗
PubMed1980

Release of vasoactive intestinal peptide by distention of the proximal stomach in dogs.

The effect of transient proximal gastric distention was studied in six conscious dogs previously submitted to antrectomy and Billroth I anastomosis (and in which the intragastric pH was not altered), and in five anaesthetised dogs prepared with an innervated acute fundic pouch in which the pouch lumen was acidified with 0.15 M hydrochloric acid. Levels of vasoactive intestinal peptide (VIP) in portal and peripheral plasma were measured by radioimmunoassay. In conscious antrectomised dogs, distention of the proximal stomach to volumes of 250 and 500 ml evoked a significant rise of portal VIP concentration, with a maximal variation of 32.7 +/- 4.4 to 67.7 +/- 14.8 pg ml-1, which was hardly reflected in systemic blood. In the anaesthetised dogs, transient distention of the acute fundic pouch with 0.15 M hydrochloric acid under a pressure of 40 cm of water elicited a significant rise of portal VIP from 36.2 +/- 8.9 to 59.8 +/- 12.4 pg ml-1 (P < 0.05) without any significant variation of the peptide concentration in peripheral plasma. These results indicate that vasoactive intestinal peptide is released under transient proximal gastric distention in dogs, and that this response is not solely dependent upon the acid secretory effect of distention in this species.

Animals↗
PubMed1980

Quantitation of M antigen in Lancefield extracts of group A streptococci type 12 using electro-immuno assay.

Anti-type 12 serum incorporated in agarose-polyethylene glycol gel in a concentration of 1.5% (vol/vol) was found to enable a distinct "rocket" precipitate in electro-immuno assay using hot hydrochloric acid extract of type 12 group A streptococci. This precipitate was removed by trypsin treatment of the extract and on addition of anti-M12 typing serum but not of five other typing sera to the extract. The streptococcal component responsible for this precipitate was eluted from a CM-cellulose ion exchange column at pH 6.5. These findings demonstrated that the precipitate was caused by the M12 antigen. Crossed immuno-electrophoresis of hot hydrochloric acid extracts of three different type 12 group A streptococci showed that the electrophoretic mobility of the M12 antigens was similar in the three extracts. A linear correlation was obtained between the concentration of the M12-antigen and the height of the precipitate obtained in the electro-immuno assay using different dilutions of a standard type 12 extract. M12 antigen could thus be quantitated by the electro-immuno assay. In quantitation experiments, uniformly prepared extracts of five randomly selected, freshly-isolated type 12 strains were found to contain from 130 to 1850% of M12 antigen, respectively (expressed in % of the content of the standard type 12 extract).

Antigens, Bacterial↗
PubMed2005

Mixing behavior of 10-(perfluorohexyl)-decanol and DPPC.

Fluorocarbon alcohol such as 10-(perfluorohexyl)-decanol are of interest for novel pulmonary drug delivery approaches. The purpose of this study was to investigate the mixing behavior of 10-(perfluorohexyl)-decanol with dipalmitoylphosphatidylcholine (DPPC), the major component of lung surfactant as an aid in assessing usefulness for this and other biomedical applications. The impact of 10-(perfluorohexyl)-decanol on the phase transitions of DPPC bilayers fully hydrated with a 0.15 M sodium chloride solution were studied using differential scanning calorimetry (DSC). No peak corresponding to excess alcohol was observed. The fluorinated alcohol caused DPPC peak broadening, especially below X(DPPC) < 0.95, and elimination of the pretransition of DPPC at X(DPPC) approximately 0.91. The onset of the main phase transition remains constant down to X(DPPC) approximately 0.91, suggesting limited miscibility in the gel phase. Hydration of the 10-(perfluorohexyl)-decanol-DPPC mixtures with calcium chloride (2 mM) in place of sodium chloride did not alter the macroscopic phase behavior. In addition to the thermal properties, the miscibility of 10-(perfluorohexyl)-decanol in DPPC in monolayers at the air water interface was investigated on water, sodium chloride (0.15 M), calcium chloride (2 mM) or hydrochloric acid (pH 1.9) subphases. The concentration dependence of the onset pressure of the liquid-expanded to liquid condensed phase transition of DPPC showed a slight change with increasing mole fraction on all four subphases. The surface area-mole fraction diagrams of 10-(perfluorohexyl)-decanol and DPPC on water, sodium chloride and calcium chloride showed near ideal behavior with slight negative deviations at higher surface pressure. A more significant negative deviation was observed for the hydrochloric acid subphase. Overall, both the DSC and the monolayer studies suggest that 10-(perfluorohexyl)-decanol and DPPC are partially miscible in biological mono- and bilayers. The macroscopic phase behavior 10-(perfluorohexyl)-decanol-DPPC system is significantly different from the analogous hydrocarbon system, which is attributed to a less favorable packing of the partially fluorinated hydrophobic tails in the mono- and bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Solubilities and intrinsic dissolution rates of sulphamethoxazole and trimethoprim.

The influence of pH on the dissolution rates and solubilities of sulphamethoxazole and trimethoprim have been examined. Sulphamethoxazole was evaluated in buffers of ionic strength 0.5 mol dm-3 over the pH range 0.45-7.8 and at 25, 32 and 37 degrees C. The minimum solubility of sulphamethoxazole was 28.1 mg/100 mL at pH 3.22 and 25 degrees C. Solubilities increased significantly with both increased and decreased pH. Intrinsic dissolution rates demonstrated a linear relationship with the solubility data. Trimethoprim solubility was both buffer- and pH-dependent. In both water and hydrochloric acid solution at 32 degrees C the solubility of trimethoprim increased from 50 mg/100 mL in water at pH 8.54 to a maximum of 1550 mg/100 mL at pH 5.5. This maximum solubility was in excess of that predicted theoretically and may be due to supersaturation. Below pH 2 the solubility of protonated trimethoprim diminished from 1125 mg/100 mL with decreasing pH. This was due to the common ion effect. Intrinsic dissolution rates increased as pH was decreased with hydrochloric acid from 6.00 to 1.78, but decreased at pH 1.48 due to the common ion effect. Dissolution profiles of trimethoprim showed complex patterns dependent upon pH. The profile was zero-order at pH 6.00 and became distinctly stepwise at pH 5.5, this effect becoming less pronounced at lower pH values. This was reconciled in terms of the rate of formation of trimethoprim hydrochloride on the surface of the disc and the differing dissolution rates of this species and trimethoprim. A simple relationship between solubility and dissolution rate was not observed.

Hydrogen-Ion Concentration↗
PubMed1985

Acid corrosive gastritis. A case report.

A patient who ingested concentrated hydrochloric acid and in whom early stricture of the gastric antrum formed is presented. Attention is drawn to the fact that the stomach usually bears the brunt of the injury following the ingestion of exogenous acid. Aspects of management are discussed, including the place of endoscopy and surgery.

Adult↗
PubMed2006

Effect of artificial gastrointestinal fluids on the excystation and metacystic development of Entamoeba invadens.

The effect of artificial gastric fluid (AGF), containing 0.5% pepsin and 0.6% hydrochloric acid, pH 1.8, in distilled water, on the excystation and metacystic development of Entamoeba invadens was examined. Excystation, which was assessed by counting the number of metacystic amoebae after inducing excystation, was enhanced by pretreatment of cysts with AGF for 30 to 60 min at 37 degrees C but not 26 degrees C. Longer exposure of cysts to AGF significantly reduced their viability. Significant enhancement of excystation was observed by pretreatment of cysts with distilled water only at 37 degrees C. In addition, 0.6% hydrochloric acid had a comparable enhancing effect on excystation to AGF. Metacystic development, when determined by the number of nuclei in amoeba, was slightly enhanced by pretreatment with AGF. An artificial intestinal fluid (AIF), containing 1% pancreatin, 1% sodium bicarbonate, and 5% ox bile, pH 8.0, in distilled water, had a significant toxic effect on cysts, where 1% pancreatin had neither an enhancing effect on excystation nor a toxic effect on cysts, whereas 5% ox bile had a toxic effect on cysts. Pretreatment of cysts with AGF followed by AIF had a similar toxic effect on cysts to that by AIF only. These results suggest that gastric fluid but not intestinal fluid at 37 degrees C contributes to enhancing excystation for Entamoeba infection.

Animals↗
PubMedDate not supplied

[The ultrastructure of the parietal exocrinocytes of the glandulae propriae in the gastric mucosa in A avitaminosis].

Electron microscopic and morphometric methods were used to study the state of the parietal exocrinocytes of the proper glands of gastric mucosa in dynamics of A avitaminosis. The experiment was performed in 80 albino rats taken from mother's feeding with the initial body mass 40-50 g, divided into 2 groups. In animals of the first group A-avitaminosis was induced by feeding the animals with semisynthetic diet devoid of vitamin A. The 2nd control group was given the same semisynthetic diet but with retinol acetate (45 units a day for each animal). Ultrastructural findings showing the elevated production of hydrochloric acid at early stages of the development of A avitaminosis were obtained: hyperplasia of the internal mitochondrial membrane, dilatation of the intracrystal space and considerable enlargement of the area of secretory membranes of tubulovesicles and microvilli of the intracellular tubules. Deep deficiency of vitamin A disturbs the stability of intracellular membranes and leads to irreversible destructive alterations in the proper gastric glands by the end of the experiment. The facts obtained are of importance for both the understanding of specific nature of secretion of hydrochloric acid and for mechanisms of development of erosion and ulcers of gastric mucosa in A avitaminosis.

Animals↗
PubMed1994

Dissolution test method for rifampicin-isoniazid fixed dose formulations.

A dissolution procedure for a rifampicin-isoniazid combination formulation was evaluated using 0.1 N hydrochloric acid solution and 0.4% (w/v) sodium lauryl sulphate solution as dissolution media. Rifampicin and isoniazid along with degradation components were chromatographed using reversed-phase liquid chromatography on a 10 microns octadecylsilica column using methanol-0.01 M disodium hydrogen phosphate (70:30, v/v; pH 4.6 +/- 0.1) as mobile phase. The detection was carried out at 254 nm. The data obtained indicate that the dissolution medium consisting of 0.4% (w/v) sodium lauryl sulphate solution is suitable for such a combination. The degradation observed in dissolution medium consisting of 0.1 N hydrochloric acid was 10-23%.

Capsules↗
PubMed1990

Magnesium bioavailability from magnesium citrate and magnesium oxide.

This study compared magnesium oxide and magnesium citrate with respect to in vitro solubility and in vivo gastrointestinal absorbability. The solubility of 25 mmol magnesium citrate and magnesium oxide was examined in vitro in solutions containing varying amounts of hydrochloric acid (0-24.2 mEq) in 300 ml distilled water intended to mimic achlorhydric to peak acid secretory states. Magnesium oxide was virtually insoluble in water and only 43% soluble in simulated peak acid secretion (24.2 mEq hydrochloric acid/300 ml). Magnesium citrate had high solubility even in water (55%) and was substantially more soluble than magnesium oxide in all states of acid secretion. Reprecipitation of magnesium citrate and magnesium oxide did not occur when the filtrates from the solubility studies were titrated to pH 6 and 7 to stimulate pancreatic bicarbonate secretion. Approximately 65% of magnesium citrate was complexed as soluble magnesium citrate, whereas magnesium complexation was not present in the magnesium oxide system. Magnesium absorption from the two magnesium salts was measured in vivo in normal volunteers by assessing the rise in urinary magnesium following oral magnesium load. The increment in urinary magnesium following magnesium citrate load (25 mmol) was significantly higher than that obtained from magnesium oxide load (during 4 hours post-load, 0.22 vs 0.006 mg/mg creatinine, p less than 0.05; during second 2 hours post-load, 0.035 vs 0.008 mg/mg creatinine, p less than 0.05). Thus, magnesium citrate was more soluble and bioavailable than magnesium oxide.

Adult↗
PubMed2004

Gastrointestinal absorption enhancement of insulin by administration of enteric microspheres and SNAC to rats.

The preparation and characteristics of insulin enteric microspheres (EMS) were studied and the gastrointestinal absorption enhancement of insulin by co-administering EMS with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC) was determined. The w/o/w and o(1)/o(2) emulsion solvent evaporation methods were used to prepare insulin-hydroxypropyl methylcellulose phthalate (HPMCP) EMS. High-performance liquid chormatography determined the drug loading, entrapment efficiency, stability to pepsin, and drug dissolution rate in hydrochloric acid solution (pH 1.2) and phosphate buffer solution (pH 6.8). The hypoglycaemic effect was studied by orally administrating the insulin EMS and SNAC to rats. The particle size of EMS (o(1)/o(2)) and EMS (w/o/w) was about 500 and 30 micro m respectively, and drug loading was 7 and 3% respectively. After being incubated with 18 micro g/mL pepsin solution (pH 1) at 37 degrees C, only 20% of insulin in EMS (o(1)/o(2)) was digested within 4 h, while 60% of the insulin in EMS (w/o/w) was digested within 1 h. In hydrochloric acid solution (pH 1.2), EMS (o(1)/o(2)) had less drug dissolution than EMS (w/o/w). In phosphate buffer solution (pH 6.8), the entire drug release time of EMS (o(1)/o(2)) and EMS (w/o/w) was 75 and 10 min, respectively. After orally administering with SNAC, EMS (o(1)/o(2)) could decrease the blood glucose level of rats remarkably and maintain the hypoglycaemic effect for 4 h, while EMS (w/o/w) had just a weakly hypoglycaemic effect. The results showed that the characteristics-optimized EMS, i.e. EMS (o(1)/o(2)) incorporating SNAC, could enhance insulin absorption significantly in the gastrointestional tract by taking advantage of both protection from enzyme degradation and improvement of drug permeability.

Administration, Oral↗
PubMed2006

Lipoxin A(4) regulates bronchial epithelial cell responses to acid injury.

Aspiration of gastric acid commonly injures airway epithelium and, if severe, can lead to respiratory failure from acute respiratory distress syndrome. Recently, we identified cyclooxygenase-2 (COX-2)-derived prostaglandin E(2) (PGE(2)) and lipoxin A(4) (LXA(4)) as pivotal mediators in vivo for resolution of acid-initiated acute lung injury. To examine protective mechanisms for these mediators in the airway, we developed an in vitro model of acid injury by transiently exposing well-differentiated normal human bronchial epithelial cells to hydrochloric acid. Transmission electron microscopy revealed selective injury to superficial epithelial cells with disruption of cell attachments and cell shedding. The morphological features of injury were substantially resolved within 6 hours. Acid triggered and early marked increases in COX-2 expression and PGE(2) production, and acid-induced PGE(2) significantly increased epithelial LXA(4) receptor (ALX) expression. LXA(4) is generated in vivo during acute lung injury, and we observed that nanomolar quantities increased basal epithelial cell proliferation and potently blocked acid-triggered interleukin-6 release and neutrophil transmigration across well-differentiated normal human bronchial epithelial cells. Expression of recombinant human ALX in A549 airway epithelial cells uncovered ALX-dependent inhibition of cytokine release by LXA(4). Together, these findings indicate that injured bronchial epithelial cells up-regulate ALX in a COX-2-dependent manner to promote LXA(4)-mediated resolution of airway inflammation.

Bronchi↗
PubMed1979

Gas exchange, pulmonary mechanics and haemodynamics in adult respiratory distress syndrome: experimental results in Lewe miniature pigs.

Adult respiratory distress syndrome (ARDS) is a common medical emergency in respiratory care complicating a great variety of traumas and diseases. An animal model from Lewe miniature pigs has been developed to study the ARDS under standardized conditions; it is based on aspiration pneumonitis, a disorder often observed in ARDS, injuring the lung alveolar surfactant system. The experimental study was conducted under neuroleptanalgesia. ARDS was produced by intratracheal application of hydrochloric acid (0.2 mol/l) in an amount of 1.0 ml/kg body wt. The animals were ventilated automatically by a standardized ventilatory pattern in IPP mode. In all animals the time course of oxygenation ratio (Pa,O2/F1O2), arterial CO2 tension (Pa,CO2), ratio of alveolo--arterial oxygen tension difference to inspired oxygen fraction (Aa,DO2/F1O2), oxygen exchange ratio ((AaDO2/Pa,O2), lung compliance (CL), inspiratory airway resistance (RrsI), dead space ratio VD/VT), pulmonary artery pressure (PAP) and systemic blood pressure were studied. Changes in quasi-static volume--pressure curves, percentage change in lung water content and gross pathological finding were used to integrate the findings into a system of pathophysiological changes in ARDS. The animal group to which hydrochloric acid was administered shows severe pulmonary distress leading to death within 3.5--7.5 h. No significant changes in the measured parameters could be observed in the control group over a 14 h period. The results suggest that aspiration pneumonitis in Lewe miniature pigs is very suitable to investigate various problems in pathogenesis of ARDS. The model provides reproducible results which correlate very well with findings in different ARDS states. The models serves both to compare clinical states and to search for newer therapeutic manoeuvres.

Animals↗
PubMed1996

X-ray structural studies of lomeridine dihydrochloride polymorphs.

Two polymorphs (forms I and II) of lomeridine dihydrochloride (1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride) were prepared and characterized by means of X-ray powder diffractometry, infrared spectroscopy (IR), thermal analysis, and moisture absorption equilibrium. The molecular structures and/or molecular conformations of the two polymorphs were determined by three-dimensional X-ray analysis. Each polymorph formed two hydrogen bonds between the two hydrochloric acids and the two nitrogen atoms of piperazine (N1, N4). In form I, the N1-chloride ion distance (2.98 A) was almost same as the N4-chloride ion distance (2.99 A). In form II, the N1-chloride ion distance (2.95 A) was shorter than the N4-chloride ion distance (3.06 A). The IR spectra showed an absorption band assigned to the NH stretching vibration of form I centered at 2361 and that of form II split into two peaks at 2186 cm-1 and 2560 cm-1. The differential thermal analysis (DTA) profiles showed that both form I and form II have an endothermic peak which would relate to the release of hydrochloric acid. The temperature of the peak in form I was higher than that in form II. The differences in the two hydrogen bond lengths of form II appear to be reflected in these IR and DTA profiles. The hygroscopic behavior of forms I and II was investigated at various relative humidities at 25 degrees C. Form II has a constant molecular composition only between 20 and 51% relative humidity (RH). On the other hand, form I has an anhydrate form between 0 and 64% RH. Accordingly, form II is not appropriate for pharmaceutical preparations, in contrast to form I.

Calcium Channel Blockers↗
PubMed2004

[Study on the reconstitution in vitro and photochemical activities of phytochrome from the Synechocystis sp. PCC6803].

Genomic DNA sequence analysis of phytochrome like photoreceptors in a number of bacteria revealed several open reading frames (ORFs) encoding proteins with amino acid sequences homologous to plant phytochromes. The phytochrome like photoreceptors, collectively called bacteriophytochromes, contain an N-terminal domain homologous to the chromophore-binding domain (CBD) of higher plants and a C-terminal domain of histidine kinase domain( HKD). Due to their simple structure, bacteriophytochromes broaden the view of phytochrome evolution and provide us with a simple model to investigate phytochrome-mediated light signal in higher plants. In this report, the bacteriophytochromes from Synechocystis sp. PCC6803 were investigated. The gene cph1 and its fragment cph1 (C-435) were isolated from the Synechocystis sp. PCC6803 genomic DNA by polymerase chain reaction(PCR) using specific primers. Then, the genes were cloned with the vector pBluescript, yielding plasmids pBlu-cphl and pBlu-cph1 ( C-435), before they are subcloned with the vector pET30, using the EcoRV and Xho I restriction sites. pBlu-cph1, pBlu-cph1 (N-435) were cleaved with Sma I and Xho I, and the released genes were ligated to the pET30a fragment. The E. coli [strain BL21 (DE3)] cells containing recombinant pET30a were grown in medium RB at 20 degrees C, and harvested 6 h later after induction with isopropyl thio-beta-D-galactoside (IPTG). Then, reconstitution systems were employed to study the characteristics of the genes. In the reconstitution system, autoassembly of aprotein of phytochrome with PCB was investigated. The chromophore addition was an autocatalytic process. Reconstitution products were red/infrared (R/FR) photochromic, which was similar to that of the phytoehrome in higher plants. How ever, the spectral change ratios (deltaAmax/deltaAmin) of the two fragments differed from each other. It was also shown that PCB was covalently bound to apo-protein via Zn2+ fluoresc ence SDS-PAGE. After irradiation by light of 700 nm, the maximum absorption spectrum o f holo-Cphl was 650nm. The absorption of it after denaturatior in the dark with ur ea in the presence of hydrochloric acid (pH = 2) was 660nm, which was similar with th at of cis-PCB. In addition, after irradiation by light of 650nm, the maximum absorption spectrum of holo-Cph1 was 700nm. The absorption of it after denaturation in the dark with urea in the presence of hydrochloric acid (pH = 2) was 600nm, which was similar with that of trans-PCB. The result showed that the photochromism of phytochrome resulted from the isomerizaation of chromophore (PCB in this report). The reconstitution of Cph1 (C-435) under the same condition supported the conclusion. Fluorescence emission spectrum of the products suggested that bacteriophytochrom e structure with cis-PCB was more stable than that with trans-PCB. The new reconstitution system in this report sets a base for the application of phytochrome as photochromic biomaterials in biosensors. In addition, phytochrome shows great potential in food, cosmetic and biological engineering, etc.

Bacterial Proteins↗
PubMed2003

Magnetic resonance imaging study of the transport phenomena of solvent into the gel layer of hypromellose matrices containing tetracycline hydrochloride.

Magnetic resonance imaging was used to study the diffusion of a water solution of hydrochloric acid into hypromellose (hydroxypropylmethylcellulose) matrices. Spatially resolved information was obtained about the self-diffusion coefficient and spin-spin relaxation time of solvent protons in the gel layer of hypromellose matrices loaded with different amounts of tetracycline hydrochloride. The data showed the influence of the drug concentration on the diffusion and spin-spin relaxation. Higher drug concentrations in the hypromellose matrix led to greater swelling of the matrix and faster diffusion of the water molecules inside the gel layer of the polymer. The observed differences between the radial and axial diffusion were interpreted in terms of the stresses imposed in the axial direction during the compression of the samples. The spin-spin and diffusion profiles indicated that the diffusion of a water solution of hydrochloric acid into hypromellose, pure and loaded with different amounts of tetracycline hydrochloride, was characterized as a Case II mechanism.

Cellulose↗
PubMed2001

Extraction and separation of cationic surfactants from river sediments: application to a spectrophotometric determination of cationic surfactant in an aquatic environment using membrane filters.

The quantitative extraction of cationic surfactant (CS+) in river sediments was studied. Further, the developed method was applied to the spectrophotometric determination of CS+ in urban river sediment samples by solid-phase extraction with membranes. A mixture of methanol and hydrochloric acid was proposed as an eluent. Dried sediment was digested in the eluent under ultrasonic irradiation. After elution, the eluent was evaporated to almost dryness. The residue was dissolved in a small volume of methanol and diluted to a certain volume with water. The pH of the solution was adjusted to 4-5 to separate iron and some other metals as precipitates of hydroxides. The solution was passed through two-piled membranes: first glass-fiber and then polytetrafluoroethylene (PTFE) membranes. A small volume of methanol was passed through the membranes to elute any CS+ retaining on the membranes. After passing the methanol solution through a cationic exchange resin column, the retained CS+ was eluted with methanol containing a high concentration of sodium chloride. Water, Bromophenol Blue (BPB) and hydrochloric acid were added to the solution. The solution was passed through a mixed cellulose ester membrane filter to retain an ion associate of CS+.BPB-. The retained ion associate was dissolved in a small volume of N,N-dimethylformamide together with the membrane filter, followed by the addition of triethanolamine to make the solution alkaline. The absorbance due to BPB2- was measured at 603 nm against a reagent blank. This method was applied to the determination of CS+ in river water and sediment. A cationic surfactant in sediments at 10(-5) mol kg-1 levels was detected with satisfactory precision. It was found that CS+ was about 500-fold enriched in the sediment from water at the place where domestic wastewater was discharged.

Benzalkonium Compounds↗
PubMed2001

Metal distribution and binding in balneological peats and their aqueous extracts.

Binding of metals in typical bath peat samples ("Grosses Gifhomer Moor", Sassenburg/North Germany) and their aqueous extracts was characterized by means of a multi-method approach. For that purpose a sequential extraction procedure based on peat-filled chromatography columns was developed. Water-soluble metal and DOM (dissolved organic matter) fractions were subdivided by use of a stepwise increased pH gradient (pH 3.8-5), finally by the chelator EDTA and 0.1 mol L(-1) hydrochloric acid. Metal fractions very strongly bound to peat were assessed by an aqua regia extraction. Metal determinations required were performed by atomic spectrometry methods (AAS, ICP-OES, and TXRF). The metal and DOM concentrations in the peat extracts varied significantly, depending on the natural variety of the peat matter under study (e.g., Al: 25-674, Cd: 0.05-0.2, Cu: 5-15.4, Fe: 77-1785, Mn: 21-505, Ni: 2-33, Pb: < 1, Zn: 9-715 (microg L(-1)); Na: 8-45, K: 1.3-14.9, Ca: 2-51, Mg: 1.1-7.9 (mg L(-1)); 26-73 mg L(-1) DOC). An increase of the pH increased the DOC (dissolved organic carbon) of the peat extracts, but hardly the concentration of heavy metals. The latter could only be re-mobilized by EDTA and dilute hydrochloric acid. Additional investigations of the peat extracts using tangential-flow ultrafiltration revealed that the heavy metals extracted at pH < 4 were predominantly dissociated. At higher pH (pH > 4.5) they were preferentially bound to macromolecular DOM. Moreover, using multistage ultrafiltration the size distribution of the DOM and their metal species was assessed.

Algorithms↗