Electrochemical treatment of iopromide under conditions of reverse osmosis concentrates--elucidation of the degradation pathway

Application of reverse osmosis for the reuse of treated wastewater on the one hand offers a way to provide high quality effluent waters. On the other hand reverse osmosis concentrates exhibiting highly concentrated contaminants are produced simultaneously. Electrochemical treatment of those concentrates is regarded as one possible answer to the problem of their disposal into surface waters. Nevertheless, due to the diversity of direct and indirect degradation processes during electrolysis, special care has to be taken about the formation of toxic transformation products (TPs). In this study the electrochemical transformation of the X-ray contrast medium iopromide was investigated as a representative of biologically persistent compounds. For this purpose, anodic oxidation at boron doped diamond as well as cathodic reduction using a platinum electrode were considered. Kinetic analyses revealed a transformation of 100 μM iopromide with first order kinetic constants between 0.6 and 1.6 × 10(-4) s(-1) at the beginning and a subsequent increase of the reaction order due to the influence of secondary oxidants formed during electrolysis. Mineralization up to 96% was achieved after about 7.5 h. At shorter treatment times several oxidatively and reductively formed transformation products were detected, whereas deiodinated iopromide represented the major fraction. Nevertheless, the latter exhibited negligible toxicological relevance according to tests on vibrio fisheri. Additional experiments utilizing a divided cell setup enabled the elucidation of the transformation pathway, whereas emerging TPs could be identified by means of high resolution mass spectrometry and MS(n)-fragmentations. During electrolysis the iodine released from Iopromide was found to 90% as iodide and to 10% as iodate even in the open cell experiments, limiting the potential formation of toxic iodo-disinfection by-products. Chlorinated TPs were not found.

Stereoisomeric profiling of pharmaceuticals ibuprofen and iopromide in wastewater and river water, China

Stereoisomeric compositions can provide insights into sources, fate, and ecological risks of contaminants in the environment. In this study, stereoisomeric profiles of ibuprofen and iopromide were investigated in wastewater and receiving surface water of the Pearl River Delta, south China. The enantiomeric fraction (EF) of ibuprofen was 0.108-0.188 and 0.480, whereas the isomer ratio (IR) of iopromide was 1.426-1.673 and 1.737-1.898 in the influent and final effluent, respectively, suggesting stereoselective degradation occurred for both pharmaceuticals during wastewater treatment. Ibuprofen showed enantioselective degradation in the anaerobic, anoxic, and aerobic conditions, whereas iopromide displayed isomer-selective degradation only under the aerobic condition. In the river waters, the EF of ibuprofen was 0.130-0.327 and the IR of iopromide was 1.500-2.531. The results suggested that pharmaceuticals in the mainstream Pearl River were mainly from discharge of treated wastewater, whereas in the tributary rivers and urban canals, direct discharge of untreated wastewater represented a significant contribution. The IR of iopromide can be an applicable and efficient tracer for wastewater discharge in the environment.

Investigating the fate of iodinated X-ray contrast media iohexol and diatrizoate during microbial degradation in an MBBR system treating urban wastewater

The capability of a moving bed biofilm reactor (MBBR) to remove the iodinated contrast media (ICM) iohexol (IOX) and diatrizoate (DTZ) from municipal wastewater was studied. A selected number of clones of microorganisms present in the biofilm were identified. Biotransformation products were tentatively identified and the toxicity of the treated effluent was assessed. Microbial samples were DNA-sequenced and subjected to phylogenetic analysis in order to confirm the identity of the microorganisms present and determine the microbial diversity. The analysis demonstrated that the wastewater was populated by a bacterial consortium related to different members of Proteobacteria, Firmicutes, and Nitrisporae. The optimum removal values of the ICM achieved were 79 % for IOX and 73 % for DTZ, whereas 13 biotransformation products for IOX and 14 for DTZ were identified. Their determination was performed using ultra-performance liquid chromatography-tandem mass spectrometry. The toxicity of the treated effluent tested to Daphnia magna showed no statistical difference compared to that without the addition of the two ICM. The MBBR was proven to be a technology able to remove a significant percentage of the two ICM from urban wastewater without the formation of toxic biodegradation products. A large number of biotransformation products was found to be formed. Even though the amount of clones sequenced in this study does not reveal the entire bacterial diversity present, it provides an indication of the predominating phylotypes inhabiting the study site.

Removal of iopromide and degradation characteristics in electron beam irradiation process

The aim of this study is to evaluate the removal efficiency of iopromide using electron beam (E-beam) irradiation technology, and its degradation characteristics with hydroxyl radical (OH) and hydrated electron (e(aq)(-)). Studies are conducted with different initial concentrations of iopromide in pure water and in the presence of hydrogen peroxide, bicarbonate ion, or sulfite ion. E-beam absorbed dose of 19.6 kGy was required to achieve 90% degradation of 100 μM iopromide and the E-beam/H(2)O(2) system increased the removal efficiency by an amount of OH· generation. In the presence of OH scavengers (10 mM sulfite ion), the required dose for 90% removal of 100 μM iopromide was only 0.9 kGy. This greatly enhanced removal was achieved in the presence of OH· scavengers, which was rather unexpected and unlike the results obtained from most advanced oxidation process (AOP) experiments. The reasons for this enhancement can be explained by a kinetic study using the bimolecular rate constants of each reaction species. To explore the reaction scheme of iopromide with OH· or e(aq)(-) and the percent of mineralization for the two reaction paths, the total organic carbon (TOC), released iodide, and intermediates were analyzed.

Doxorubicin-loaded drug-eluting beads (DC Bead®) for use in transarterial chemoembolization: a stability assessment

PURPOSE

Evaluation of doxorubicin stability over time when stored into the DC Bead embolic agent, in various containers, which are used for the delivery of the doxorubicin-loaded beads to the patients for up to 14 days under refrigerated conditions.

METHODS

The doxorubicin was loaded through the ionic exchange mechanism into the calibrated polyvinyl alcohol-based hydrogel beads (DC Bead), with the loading process carried out either in the original DC Bead glass vials or within a polypropylene plastic syringe. The loaded samples were eluted at given time points and the extracted doxorubicin was analysed by high-performance liquid chromatography for concentration and chromatographic area response purity.

RESULTS

The variance on the doxorubicin concentration of the samples stored in the syringes under refrigerated conditions was less than 10% over the 14 days period. The chromatographic purity of doxorubicin eluted from the DC Bead in their primary glass vial packaging was measured at 99.7%. The dissolution test showed that the elution rate and amount recovered from samples stored in vials were statistically similar between Day 0 and Day 14. The chromatographic purity of the doxorubicin loaded into DC Bead in presence of non-ionic contrast medium was >99.0% for 7 days under refrigerated conditions.

CONCLUSIONS

Doxorubicin-loaded DC Bead® are shown to have adequate physicochemical stability over a period of 14 days when stored in syringes or vials under refrigerated conditions for up to 14 days. The admixtures of doxorubicin-loaded beads with contrast medium are stable for up to 7 days under refrigerated conditions.

Behavior of pharmaceuticals and drugs of abuse in a drinking water treatment plant (DWTP) using combined conventional and ultrafiltration and reverse osmosis (UF/RO) treatments

The behavior along the potabilization process of 29 pharmaceuticals and 12 drugs of abuse identified from a total of 81 compounds at the intake of a drinking water treatment plant (DWTP) has been studied. The DWTP has a common treatment consisting of dioxychlorination, coagulation/flocculation and sand filtration and then water is splitted in two parallel treatment lines: conventional (ozonation and carbon filtration) and advanced (ultrafiltration and reverse osmosis) to be further blended, chlorinated and distributed. Full removals were reached for most of the compounds. Iopromide (up to 17.2 ng/L), nicotine (13.7 ng/L), benzoylecgonine (1.9 ng/L), cotinine (3.6 ng/L), acetaminophen (15.6 ng/L), erythromycin (2.0 ng/L) and caffeine (6.0 ng/L) with elimination efficiencies ≥ 94%, were the sole compounds found in the treated water. The advanced treatment process showed a slightly better efficiency than the conventional treatment to eliminate pharmaceuticals and drugs of abuse.

Dehalogenation of iodinated X-ray contrast media in a bioelectrochemical system

Iodinated X-ray contrast media (ICM) are only to a limited extent removed from conventional wastewater treatment plants, due to their high recalcitrance. This work reports on the cathodic dehalogenation of the ICM iopromide in a bioelectrochemical system (BES), fed with acetate at the anode and iopromide at the cathode. When the granular graphite cathode potential was decreased from -500 to -850 mV vs standard hydrogen electrode (SHE), the iopromide removal and the iodide release rates increased from 0 to 4.62 ± 0.01 mmol m(-3) TCC d(-1) and 0 to 13.4 ± 0.16 mmol m(-3) TCC d(-1) (Total Cathodic Compartment, TCC) respectively. Correspondingly, the power consumption increased from 0.4 ± 1 to 20.5 ± 3.3 W m(-3) TCC. The Coulombic efficiency of the iopromide dehalogenation at the cathode was less than 1%, while the Coulombic efficiency of the acetate oxidation at the anode was lower than 50% at various granular graphite cathode potentials. The results suggest that iopromide could be completely dehalogenated in BESs when the granular graphite cathode potential was controlled at -800 mV vs SHE or lower. This finding was further confirmed using mass spectrometry to identify the dehalogenated intermediates and products of iopromide in BESs. Kinetic analysis indicates that iopromide dehalogenation in batch experiments can be described by a first-order model at various cathode potentials. This work demonstrates that the BESs have a potential for efficient dehalogenation of ICM from wastewater or environmental streams.

Degradation of iopromide by combined UV irradiation and peroxydisulfate

The aqueous degradation of iopromide, an iodinated X-ray contrast media (ICM) compound, by the combination of UV(254) irradiation and potassium peroxydisulfate (K(2)S(2)O(8)) has been studied in laboratory scale experiments. The influence of various parameters on the performance of the treatment process has been considered, namely the UV irradiation light intensity, the initial concentrations of iopromide and peroxydisulfate, and the initial solution pH. Iopromide degradation increased with UV light intensity and peroxydisulfate concentration, but decreased with initial pH. Under specific conditions complete removal of iopromide was achieved within 30 min, and near-complete mineralisation (loss of solution TOC) within 80 min. Degradation was believed to be caused by a combination of direct photolysis, sulphate radical attack, and, to a minor degree, direct oxidation by peroxydisulfate. Approximate values for the reaction rate constants have been determined and found to be equal to 1-2x10(4) M(-1) s(-1) for sulfate radicals, and 1-2 M(-2) s(-1) for S(2)O(8)(2-). Overall compound degradation was observed to follow first-order kinetics where the rate constant decreased with initial solution pH. During the reaction, the solution pH decreased as a consequence of sulfate radical scavenging.

Biotransformation of selected iodinated X-ray contrast media and characterization of microbial transformation pathways

Iodinated X-ray contrast media (ICM) are commonly detected in the aquatic environment at concentrations up to the low microgram per liter range. In this study, the biotransformation of selected ICM (diatrizoate, iohexol, iomeprol, and iopamidol) in aerobic soil-water and river sediment-water batch systems was investigated. In addition, microbial transformation pathways were proposed. Diatrizoate, an ionic ICM, was not biotransformed, while three nonionic ICM were transformed into several biotransformation products (TPs) at neutral pH. Iohexol and iomeprol were biotransformed to eleven TPs and fifteen TPs, respectively, while eight TPs were detected for iopamidol. Since seven of the TPs detected during biotransformation had not been previously identified, mass fragmentation experiments were completed to elucidate the chemical structures. Oxidation of primary alcoholic moieties, cleavage of the N-C bonds (i.e., deacetylation and removal of hydroxylated propanoic acids), and decarboxylation are potential reactions that can explain the formation of the identified TPs. Iohexol and iomeprol had similar biotransformation rates, while iopamidol was biotransformed slower and to a lesser extent. A LC tandem MS method confirmed the presence of ICM TPs in aqueous environmental samples. Fifteen of the ICM TPs were even detected in drinking water with concentrations up to 120 ng/L.

Comparison of quantitative parameters in cervix cancer measured by dynamic contrast-enhanced MRI and CT

Cervical tumors of 38 cervix cancer patients were scanned by T(1)-weighted dynamic contrast enhanced (DCE) MRI and then by DCE-CT on the same day. Gadodiamide and iohexol were respectively used as the low-molecular-weight contrast agent in DCE-MRI and DCE-CT. Under an extended Tofts model, DCE-MRI data were analyzed using either individual arterial input functions estimated by a multiple reference tissue method or a population arterial input function by Parker et al., whereas DCE-CT data were analyzed using the arterial input function directly measured from the external iliac arteries. The derived quantitative parameters of cervical tumors were compared between DCE-MRI and DCE-CT. When using the individual multiple reference tissue method arterial input functions to analyze the DCE-MRI data, the correlation coefficients between DCE-MRI- and DCE-CT-derived parameters were, respectively, back-flux rate constant (r = 0.80), extravascular extracellular fractional volume (r = 0.73), contrast agent transfer rate (r = 0.62), and blood plasma volume (r = 0.32); when using the Parker population arterial input function, the correlation coefficients were back-flux rate constant (r = 0.79), extravascular extracellular fractional volume (r = 0.77), contrast agent transfer rate (r = 0.63), and blood plasma volume (r = 0.58). Tumor parametric maps derived by DCE-MRI and DCE-CT had very similar morphologies. However, the means of most derived quantitative parameters were significantly different between the two imaging methods. Close correlation of quantitative parameters derived from two independent imaging modalities suggests both are measuring similar tumor physiologic variables.

Elucidation of phototransformation reactions of the X-ray contrast medium iopromide under simulated solar radiation using UPLC-ESI-QqTOF-MS

The highly polar, nonionic X-ray contrast agent iopromide (C(18)H(24)N(3)O(8)I(3); 791 Da) is resistant to microbial degradation during the activated sludge process in wastewater treatment plants and hence is released into the aquatic environment. Against this background, the present study was conducted to evaluate the phototransformation, potentially constituting the most relevant removal mechanism in rivers and streams. The photolysis of the iodinated aromatic compound was investigated in a Suntest solar simulator using aqueous solutions. Following a 120-min irradiation period, an almost complete primary degradation of iopromide gave rise to a series of photoproducts that were chromatographed on a reversed-phase UPLC and subsequently characterized by a combination of accurate mass measurements on a ESI-QqToF-MS instrument and H/D-exchange experiments. This analytical approach facilitated confident identification of eight prominent products with the following elemental compositions and molecular weights: C(18)H(25)N(3)O(9)I(2) (681 Da); C(18)H(25)N(3)O(8)I(2) (665 Da); C(17)H(23)N(3)O(8)I(2) (651 Da); C(18)H(24)N(3)O(9)I (553 Da); C(17)H(24)N(3)O(8)I (525 Da); C(15)H(20)N(3)O(6)I (465 Da); C(14)H(18)N(3)O(6)I (451 Da); and C(18)H(25)N(3)O(9) (427 Da). Their formation was the result of four principal photoreactions: (1) gradual, and eventually complete, deiodination of the aromatic ring; (2) substitution of the halogen by a hydroxyl group; (3) N-dealkylation of the amide in the hydroxylated side chain; and (4) oxidation of a methylene group in the hydroxylated side chain to the corresponding ketone. In conclusion, the findings of the artificial sunlight irradiation experiments indicated that in real environmental settings iopromide might suffer partial or even complete deiodination.

Degradation of the endocrine disrupting chemicals (EDCs) carbamazepine, clofibric acid, and iopromide by corona discharge over water

Common wastewater treatment plants often do not eliminate endocrine disrupting chemicals (EDCs). Aqueous solutions of three EDCs were treated with an enhanced corona discharge technology. The three EDCs were clofibric acid, a blood lipid regulator, carbamazepine, an antiepileptic drug, and iopromide, a contrast media. To simulate real conditions, EDC solutions containing landfill leachate were also used. In our setup, two barrier electrodes provided an atmospheric pressure corona discharge over a thin water film, in which the counter-electrode was submerged. Clofibric acid, carbamazepine, and iopromide were effectively removed from a single solution. After a treatment of 15min, there were no traces of iopromide estrogen activity either as a single substance or as degradation products when using an E-Screen Assay. Continuous treatment was compared with pulsed treatment using carbamazepine solutions mixed with pretreated landfill leachate. Best degradation results were achieved with a 500 W continuous duty cycle treatment. Counter-electrodes from materials such as boron doped diamond (BDD), titanium iridium oxide, and iron were investigated for their influences on the process effectivity. Significant improvements were achieved by using an enclosed reactor, BDD electrodes, and circulating only a fresh air or argon/air mixture as cooling gas through the barrier electrodes.

Transformation of the X-ray contrast medium iopromide in soil and biological wastewater treatment

In water/soil systems, the iodinated contrast medium iopromide was quantitatively biotransformed into several transformation products (TPs). Twelve TPs were identified via HPLC-UV and LC tandem MS. The chemical structures of the TPs were elucidated via fragmentation in MS2 and MS3 of LC tandem MS with a linear ion trap and 1H and 13C NMR analyses. All TPs exhibited transformations at the side chains containing either carboxylic moieties and/or primary and secondary amide moieties, while the triiodoisophthalic acid structure remained unaltered. A transformation pathway was proposed based on the sequence of TP formation in aerobic batch experiments. Additionally, the occurrence of iopromide TPs was investigated in native water samples. All TPs identified were found in municipal WWTP effluents because of their formation during biological wastewater treatment with maximum concentrations of up to 3.7 +/- 0.9 microg/L (TP 819). Predominantly, those TPs were present at higher concentrations in WWTP effluents which were formed at the beginning of the transformation pathway. Furthermore, four TPs formed at the end of the transformation pathway (TP 759, 701A/B, and 643) were also found in bank filtrate up to 0.050 microg/L and in groundwater of an wastewater irrigation area up to 4.6 microg/L.

The mineralization of 5-amino-2,4,6-triiodoisophthalic acid by a two-stage fixed-bed reactor

Iodinated X-ray contrast media have been detected in hospital effluent, sewage treatment plant effluent, rivers and groundwater aquifers. No process has been developed to remove triiodinated aromatic molecules. In this paper, we present a biological sequential process using an anaerobic fixed-bed reactor coupled in series with an aerobic fixed-bed reactor for degrading 5-amino-2,4,6-triiodoisophthalic acid (ATIA), the core structure of a X-ray contrast media family. The results obtained showed that the coupled reactor eliminated up to 870+/-44 mg of carbon L(-1) day(-1), with a molar ethanol/ATIA ratio of 4 in the feeding medium. The anaerobic reactor (ANR) undertook the majority of the deiodination of the aromatic nucleus and had a maximum deiodination rate of 23.4+/-0.06 mM day(-1). The aerobic reactor (AER) mineralized ATIA and was also able to eliminate its metabolites. This study suggests that the mineralization of ATIA can be achieved efficiently in a coupled anaerobic-aerobic bioreactor.

Rapid metal-catalyzed hydrodehalogenation of Iodinated x-ray contrast media

Iodinated X-ray contrast media (ICM) are detected in natural waters at high concentrations relative to other pharmaceuticals due to extensive use in medical diagnostics and high recalcitrance during conventional wastewater treatment. This study examines, for the first time, reductive treatment of ICM in water with hydrogen gas in combination with supported palladium and porous nickel catalysts. Kinetic experiments demonstrate rapid and complete hydrodehalogenation of both ionic (diatrizoate) and neutral (iopromide) ICM. Reaction rates in batch systems (continuous mixing, P(H2) = 0.1 MPa, 25 degrees C) appear to be surface-reaction controlled and are dependent upon catalyst identity (e.g., 5 wt % versus 1 wt % Pd/ Al2O3) as well as the concentration of ICM and catalyst. Reaction rates are not markedly affected by ICM structure, pH, or by the presence of many common ions (Na+, Ca2+, Mg2+, F-, Cl-, Br-, ClO4-, SO4(2-), HCO3-, and NO3-). In contrast, elevated concentrations of iodide, (bi)sulfide, and dissolved organic matter inhibit hydrodehalogenation of ICM. However, catalyst activity can be regained by washing the catalyst (e.g., with water, NaOCl, or alkaline solution). Catalytic reduction of ICM present in treated wastewater effluent is slower than in deionized water, but similar reaction rates are observed when the effluent is pretreated to reduce the level of dissolved organic matter. The high selectivity of reductive catalytic treatment processes suggest that this is a promising strategy for targeted treatment of ICM present in mixed waste streams and natural water matrices containing much higher concentrations of nontarget constituents.

Reductive dehalogenation of iopromide by zero-valent iron

Iodinated X-ray contrast media (ICM), as derivatives of 2, 4, 6-triiodo benzoic acid, are applied in high doses to humans and are excreted unchanged via urine within 24 h. Common as well as advanced wastewater treatment is not able to remove the iodinated compounds leading to an environmental pollution. A specific treatment of contaminated urine or hospital wastewater could minimise the emission. For that reason the deiodination of iopromide, the most commonly used ICM, was investigated using zero-valent iron. Initial experiments carried out in stirred batch reactors with an initial pH of 2 using iron powder and iopromide dissolved in ultra pure water showed that iopromide can be deiodinated by zero-valent iron. Even in contaminated urine collected in a hospital a deiodination of ICM was possible. Further experiments at different constant pH values, temperatures and stirring speeds were performed. The kinetic studies at constant pH showed that the deiodination can be described by pseudo-first order for equal iopromide and iron concentrations. In general, the reaction depends strongly on the pH, the temperature and the stirring speed. The observed rate constant K(obs) has an optimum at pH 3 and rises with increasing temperature and stirring speed.

Degradation of X-ray contrast media compounds by combined ozone and ultrasound

The aqueous degradation of iodinated X-ray contrast media (ICM) by the combination of ozone and ultrasound has been studied. Experiments were conducted at a constant ultrasound frequency of 20 kHz, at five power densities up to 0.235 W/mL, and various ozone centrations. In experiments involving dissolved ozone in solution, the addition of ultrasound significantly decreased the oxidation performance of the dissolved ozone, while the combination of dissolved oxygen and ultrasound gave a greater oxidation performance than ultrasound alone. However, the combination of gaseous ozone and ultrasound was found to give a higher degree of compound degradation than either ozone or ultrasound alone. In the experiments with final effluent, the degradation of ICM compounds by gaseous ozone and ultrasound was found to depend on the ozone dose applied. The degradation of ICM compounds in final effluent was modeled, which was found to moderately overestimate the observed compound degradation.

Comparison between slope–intercept and slope-only techniques for measuring glomerular filtration rate: Use of two independent markers and an independent arbiter

PURPOSE

Exclusive use of the half-time of clearance of a filtration marker in the bolus injection, single compartment technique for measuring glomerular filtration rate (GFR) is a convenient approach that gives GFR (GFR(SO)) already scaled for extracellular fluid volume (ECV). It has been criticized as less accurate than the conventional, slope-intercept technique (GFR(SI)). The aim of the study was to compare the respective levels of agreement of GFR(SI) and GFR(SO) with GFR based on plasma creatinine (eGFR) used as an independent arbiter.

METHODS

GFR was measured with both 51Cr-EDTA and iohexol, simultaneously injected into opposite arms. Plasma obtained bilaterally 20, 40, 60, 120, 180 and 240 min after injection was assayed for marker injected contra-laterally, 51Cr-EDTA by well-counting and iohexol by X-ray fluorescence. ECV and GFR, scaled to body surface area (BSA), were formally measured from six samples and GFR(SI) (scaled to BSA) and GFR(SO) from the last three.

RESULTS

Disagreement between GFR(SO) measured with 51Cr-EDTA and eGFR was not significantly higher than the corresponding disagreement between eGFR and GFR(SI). Disagreement between GFR(SO) measured with iohexol and eGFR was significantly higher than between eGFR and GFR(SI). GFR(SI) and GFR(SO) correlated more closely when measured with 51Cr-EDTA than with iohexol. Individual differences between GFR(SI) and GFR(SO) using one marker correlated significantly with ECV measured with the other.

CONCLUSIONS

GFR(SO) is critically dependent on the accuracy of half-time measurement and, measured with iohexol, appeared less reliable than GFR(SI). GFR(SI) and GFR(SO) measured with 51Cr-EDTA, however, have similar levels of reliability.

[Preparation and quality evaluation of Iohexol liposomes]

The liposomes were prepared by reverse-phase evaporation technique. The morphology of the liposomes, the entrapment efficiency and the particle size distribution were evaluated. The CT signals of Iohexol liposomes in rabbits were compared with those of Iohexol injection in rabbits. The entrapment efficiency of Iohexol liposomes was 82.35% +/- 1.82%. The liposmes were spherical or ellipsoidal shape in shape. The mean diameter of the Iohexol liposomes was 207 7 nm. The polydispersity index was 0.355. The Zeta potential was--1.83 mV. The drug was highly entrapped into the liposomes with good reproduction and stability. The in vitro release of Iohexol liposomes was significantly slower than that of Iohexol,and was 98.57% at 24 h. Iohexol liposomes may reduce the dosage, prolong the effective time of the developing agent, and could reduce the side effects of Iohexol on the blood vessels and cerebral nerves.

Radiographic and computed tomographic evaluation of experimentally induced lung aspiration sites in dogs

This study was performed to radiographically examine the prevalence of aspiration sites and to evaluate their atomical correlation with the bronchial pattens. Ten healthy beagle dogs were repeatedly radiographed, at weekly intervals, in the left and right lateral, ventrodorsal (VD) and dorsoventral (DV) positions. Three mililiters of iohexol distilled with same volume of saline was infused into the tracheal inlet. Which lung lobe was aspirated was decided upon by the presence of a significant alveolar pattern due to the contrast medium. Alveolar patterns were identified at the left (100%) and right cranial lung lobes (77%) with the dogs in dependant lateral recumbency, at the right caudal lung lobe (71%) with the dogs in VD recumbency and at the right middle lung lobe (59%) with the dogs in DV recumbency, respectively. The anatomical correlation was evaluated by performing computed tomography. The right principal bronchus (165.8 ± 1.6°) was more straightly bifurcated than was the left principal bronchus (142.7 ± 1.8°, p < 0.01). In VD position, the right side lung had a greater opertunity to become aspirated. The ventrally positioned right middle lobar bronchial origin was more easily to be aspirated the other laterally positioned ones. We think that these anatomical characteristics can be one of the causes for aspiration pneumonia to occur more frequently in the right side lung.

Ozonation and reductive deiodination of iopromide to reduce the environmental burden of iodinated X-ray contrast media

The potential of ozonation for the removal of iodinated X-ray contrast media (ICM) with focus on the oxidation products was examined. Iopromide used as model compound was dissolved in tap water, respectively in the effluent of a membrane bioreactor and was ozonated. Ozone (10 mg/L) was continuously introduced into a semi-batch reactor (35 L/h). After 30 minutes the ozone concentration was increased to 30 mg/L. In all experiments the iopromide concentration decreased very fast, whereas the decrease of the amount of organic bound iodine (AOI) was much lower. The concentration of iodate, the inorganic oxidation product increases with time, depending on the AOI decrease. The data clearly show that the ozonation of iopromide using a common applied ozone dosage leads to the formation of numerous iodinated transformation products, which are detectable by LC-ESI-MS. As an alternative treatment, especially for the treatment of urine or hospital waste water, the source for the contamination, it was tested if iopromide can be deiodinated by zero-valent iron. First experiments done in stirred batch reactors using iopromide dissolved in ultra pure water and urine with an initial pH of 2 showed that iopromide can be deiodinated completely by zero-valent iron. Even in contaminated urine collected in a hospital a deiodination of ICM was possible. Kinetic studies at constant pH showed that the deiodination can be described by pseudo-first order for equal iopromide and iron concentrations. The observed rate constant kobs increased with decreasing pH with a maximum at pH 3 with 4.76x10(-4) s(-1). The concentration of iopromide can be decreased by ozonation and by the reductive dehalogenation. In case of ozonation iodinated organic compounds are the main reaction products, whereas the reductive dehalogenation leads to transformation products which are not iodinated and are thus most probable biodegradable.

Enhanced biodegradation of iopromide and trimethoprim in nitrifying activated sludge

Iopromide (an X-ray contrast agent) and trimethoprim (an antibacterial drug) are frequently detected pharmaceuticals in effluents of wastewater treatment plants (WWTPs) and in surface waters due to their persistence and high usage. Laboratory-scale experiments showed that a significantly higher removal rate in nitrifying activated sludge as compared to conventional activated sludge was observed for both iopromide and trimethoprim. When the activity of the nitrifying bacteria was inhibited, the percent removal of iopromide decreased from 97 to 86% while trimethoprim removal decreased from 70 to 25%. The metabolite of iopromide identified when nitrification was not inhibited was a dehydroxylated iopromide at the two side chains. However, when the nitrifying bacteria were inhibited the metabolite identified was a carboxylate, formed during the oxidation of the primary alcohol on the side chain of iopromide. These results suggest that the nitrifying bacteria are important in the observed biodegradation of iopromide in the activated sludge with higher solid retention time (SRT). Results from the laboratory-scale study were corroborated by the observed removal efficiencies in a full-scale municipal WWTP, which showed that iopromide (ranging from 0.10 to 0.27 microg/L) and trimethoprim (ranging from 0.0.08 to 0.53 microg/L) were removed more effectively in the nitrifying activate sludge which has a higher SRT (49 days) than in the conventional activated sludge (SRT of 6 days). In nitrifying activated sludge, the percent removal of iopromide in the WWTP reached 61%, while in conventional activated sludge, average removal was negligible. For trimethoprim, removal was limited to about 1% in the conventional activated sludge, while in the nitrifying activated sludge, the removal was increased to 50%.