Contrast Transthoracic Echocardiography Using 50% Glucose as a Contrast Agent for Screening of a Patent Foramen Ovale.

A patent foramen ovale (PFO) is considered a risk factor for neurologic events. The goal of the study described here was to assess the feasibility, advantages, diagnostic sensitivity and accuracy of contrast transthoracic echocardiography examination (cTTE) using 50% glucose as a contrast agent in comparison with the use of agitated saline as contrast to screen for PFO. In our study, we found that the peak time, effective duration and duration of microbubbles produced by 50% glucose were all longer than those produced by the physiologic saline. The sensitivities for detection of PFO with cTTE using physiologic saline and 50% glucose as contrast were 83% (20/24) and 100% (24/24), respectively. TEE suggested a PFO in 24 patients in two groups. Use of 50% glucose as a contrast agent in cTTE examination enables ultrasound technicians to easily observe the right-to-left shunt across the PFO. However, the sensitivities for detection of PFO with cTTE using 50% glucose did not statistically significantly differ from those for physiologic saline.

Comparative study of contrast-enhanced ultrasound qualitative and quantitative analysis for identifying benign and malignant breast tumor lumps.

BACKGROUND: To compare the value of contrast-enhanced ultrasound (CEUS) qualitative and quantitative analysis in the identification of breast tumor lumps. MATERIALS AND METHODS: Qualitative and quantitative indicators of CEUS for 73 cases of breast tumor lumps were retrospectively analyzed by univariate and multivariate approaches. Logistic regression was applied and ROC curves were drawn for evaluation and comparison. RESULTS: The CEUS qualitative indicator-generated regression equation contained three indicators, namely enhanced homogeneity, diameter line expansion and peak intensity grading, which demonstrated prediction accuracy for benign and malignant breast tumor lumps of 91.8%; the quantitative indicator-generated regression equation only contained one indicator, namely the relative peak intensity, and its prediction accuracy was 61.5%. The corresponding areas under the ROC curve for qualitative and quantitative analyses were 91.3% and 75.7%, respectively, which exhibited a statistically significant difference by the Z test (P<0.05). CONCLUSIONS: The ability of CEUS qualitative analysis to identify breast tumor lumps is better than with quantitative analysis.

Impact of microbubble enhanced, pulsed, focused ultrasound on tumor circulation of subcutaneous VX2 cancer.

BACKGROUND: Intravascular microbubble-enhanced acoustic cavitation is capable of disrupting the vascular walls of capillaries and small vessels. This study was designed to investigate the impact of microbubble-enhanced, pulsed and focused ultrasound (MEUS) on the blood perfusion of subcutaneous VX2 tumors in rabbits. METHODS: Subcutaneous VX2 cancers in twenty New Zealand rabbits were treated by combining high-pressure amplitude, pulsed and focused therapeutic ultrasound (TUS) and intravenous microbubble injections. The TUS transducer was operated with a peak negative pressure of 4.6 MPa and a duty cycle of 0.41%. Controls were subcutaneous VX2 cancers treated with TUS or microbubbles only. Contrast-enhanced ultrasound (CEUS) and intravenous Evans Blue (EB) perfusion were performed to assess the tumor circulation. The tumor microvascular disruption was assessed by histological examination. RESULTS: CEUS showed that the tumor circulation almost vanished after MEUS treatment. The average peak grayscale value (GSV) of tumor CEUS dropped significantly from 84.1±22.4 to 15.8±10.8 in the MEUS-treated tumors but no significant GSV changes were found in tumors in the two control groups. The mean tumor EB content of the MEUS-treated tumors was significantly lower than that of the controls. Histological examination found scattered tumor microvascular disruption with intercellular edema after MEUS treatment. CONCLUSION: The tumor circulation of VX2 cancers can be arrested or significantly reduced by MEUS due to microvascular disruption.

[Biological properties of lateritic red soil and their relationships with soil fertility in Southern China under different land use types].

Taking the lateritic red soil on a typical slopeland in Southern China as test object, this paper studied the soil microbial properties, enzyme activities, and their relationships with soil fertility under four land use types (newly cultivated dryland, shrub land, Eucalyptus land, and orchard). There existed significant differences in the soil biological properties under different land use types, among which, orchard soil had the highest microbial quantity and enzyme activities, newly cultivated dryland soil had the fastest soil respiration rate, the fewest soil microorganism quantity, and the lowest enzyme activities, whereas shrub land and woodland soils had the biological properties ranged between newly cultivated dryland and orchard soils, and there was a high similarity in the biological properties between shrub land and woodland soils. Under different land use types, the soil microbial quantity and enzyme activities were positively correlated with soil organic carbon and most of the soil nutrients. It was suggested the soils with high soil organic matter content and high fertility level were beneficial to the soil microbial growth and enzyme activities.

Effects of diagnostic ultrasound-targeted microbubble destruction on permeability of normal liver in rats.

This work investigated the effect of diagnostic ultrasound-targeted microbubble destruction (UTMD) on the permeability of normal liver tissue and the safety of this technique. One hundred and four rats were divided into four groups: the control group, the microbubble-only (MB) group, the ultrasound-only (US) group, and the ultrasound-targeted microbubble destruction group (UTMD). The permeabilities of capillaries and cell membranes were determined using Evans blue and lanthanum nitrate as tracers, respectively. The amount of Evans blue was approximately fourfold higher in the UTMD group than in the control, MB-only, and US-only groups (all P<0.01). Evans blue extravasation, visualized as red fluorescence, was detectable by laser confocal scanning microscopy in the parenchyma only in the UTMD group. Lanthanum nitrate-tracing transmission electron microscopy examination indicated that intracellular lanthanum was detectable in the cytoplasm only in the UTMD group. Blood chemical analysis indicated that the effect of diagnostic ultrasound-targeted microbubble destruction on the rats' serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels was transient and recoverable and that this technique had no obvious effect on renal function. Cellular swelling was observed in liver cells in the UTMD group at 0.5 h, but this swelling was no longer apparent after 1 week. These results suggest that diagnostic ultrasound-targeted microbubble destruction can increase the capillary and cell membrane permeabilities in normal liver tissue without a significant increase in hepatic and renal toxicity.

Contrast-enhanced ultrasound diagnosis of splenic artery steal syndrome after orthotopic liver transplantation.

The aim of this study was to investigate the use of contrast-enhanced ultrasound (CEUS) for the detection of splenic artery steal syndrome (SASS) after orthotopic liver transplantation (OLT). Two hundred forty-seven patients underwent OLT. Blood tests and color Doppler flow imaging (CDFI) were performed at various time points after the operation. CEUS and celiac angiography were used for patients suspected of having SASS. If the diagnosis of SASS was confirmed, splenic artery embolization was performed to enhance hepatic artery flow. CEUS and angiography were performed for the assessment of postinterventional clinical outcomes. Three of the 247 patients died postoperatively, and 8 patients were suspected of having SASS because of elevated liver enzyme levels and slim or undetectable hepatic artery blood signals by CDFI at various points after the operation. In these 8 patients, CEUS showed a delayed and weak contrast-enhanced blood signal in the hepatic artery associated with a rapid and intense enhancement of the portal vein blood. No narrowing of the hyperintense signal was observed in the hepatic artery by CEUS. The 8 diagnoses of SASS were proven by celiac angiography, which showed delayed perfusion of the hepatic artery and rapid filling of the splenic artery. Immediately after the interventional procedure, CEUS demonstrated a significantly enlarged hyperintense blood signal in the hepatic artery. In conclusion, approximately 3.27% of SASS cases occur after OLT. SASS can be identified as a sluggish and weak hyperintense blood signal in the hepatic artery without the narrowing and interruption of the hypointense signal in CEUS imaging. CEUS is an effective imaging modality for the detection of SASS after OLT.

Molecular imaging of vulnerable plaques in rabbits using contrast-enhanced ultrasound targeting to vascular endothelial growth factor receptor-2.

PURPOSE: Increased neovascularization has been identified as a feature of atherosclerotic plaque vulnerability and can be traced by microbubble ultrasound contrast agents (UCA). We investigated the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR-2) targeted UCA and VEGFR-2 expression in a vulnerable plaque model in rabbits. METHODS: Microbubbles targeting to VEGFR-2 were prepared by conjugation of biotinylated microbubbles with biotinylated VEGFR-2 antibody via streptavidin. Vulnerability was created by delivering recombinant p53 adenovirus to atherosclerotic plaques obtained in abdominal aorta by a high cholesterol diet and balloon endothelial injury. Twelve week later, the average video intensity of pre- and postcontrast ultrasound images was measured. VEGFR-2 expression and vascular density were quantified by immunohistochemical staining. RESULTS: Retention of targeted UCA in plaques was higher than that of nontargeted UCA (144 ± 18 dB versus 107 ± 9 dB; Z= -3.984, p = 0.000). VEGFR-2 expression was correlated with video intensity of targeted (r(2) = 0.78, p = 0.001), but not of nontargeted, UCA (r(2) = 0.17, p ≥ 0.05). CONCLUSIONS: The magnitude of the sonographic signal from retained VEGFR-2 targeted UCA correlates with VEGFR-2 expression. These results validate the use of targeted UCA for sonographic imaging of vulnerable abdominal artery plaques in rabbits.

Preparation and characterization of a nanoscale ultrasound contrast agent.

OBJECTIVE: The purpose of the present study is to prepare a nanoscale ultrasound contrast agent and to investigate its characterization and ultrasonic imaging in vivo. METHODS: Nanoscale ultrasound contrast agent was prepared by machine vibration and low speed centrifugation, and the appearance, distribution, diameter, and zeta potential of the nanoscale ultrasound contrast agent were measured. Contrast-enhanced ultrasonography was performed on normal rabbit liver to observe the duration and intensity of enhancement. RESULTS: The nanoscale ultrasound contrast agent had a good shape and uniform distribution by light microscope and transmission electron microscope, with average diameters of 623.4 nm and average zeta potential of 1.3 mV. The contrast imaging study in vivo showed that the nanoscale ultrasound contrast agent could significantly enhance the duration and echo intensity of the vessels and parenchyma in rabbit livers, and there were no obvious difference with micro-scale microbubbles. CONCLUSIONS: The nanoscale ultrasound contrast agent is stable and effective for the enhancement of ultrasound imaging. This study provides an important platform for miniaturizing and improving the targeting performance of ultrasound contrast agents.

Construction of thrombus-targeted microbubbles carrying tissue plasminogen activator and their in vitro thrombolysis efficacy: a primary research.

Thrombosis is the common mechanism of various diseases of heart and vasculature and their major morbility and mortality. An efficient, safe and easy thrombolysis method is needed. We tried to develop a new type of ultrasound microbubbles carrying thrombolytics and simultaneously targeting to thrombus, which could bind with thrombus specifically and release the encapsulated drug locally under the ultrasound exposure. Microbubbles carrying tissue plasminogen activator (tPA) and Arg-Gly-Asp-Ser tetrapeptide (RGDS) were prepared by lyopyilization. Their properties were detected, including morphology, particle size, surface potential and pH. The results showed that the microbubbles were suitable for intravenous injection. The envelope rate of tPA, detected by ELISA, was (81.12 +/- 2.44%), and the conjugate rate of RGDS, detected by flow cytometer, was (94.49 +/- 6.19%). The tPA encapsulated in microbubbles kept fibrinolysis activity under the conditions of both natural releasing and ultrasound exposure, checked by agarose fibrin plate process. The contrast-enhanced ultrasonography (CEU) in rabbit liver showed that they were good for enhanced ultrasound imaging. The in vitro thrombolysis of the microbubbles to the blood clots from healthy human was detected with a mimical flowing model propelled by peristaltic pump. The drug-loaded microbubbles plus ultrasound irradiation got higher thrombolysis with the lowest dosage. The tPA-loaded microbubbles targeting to thrombus can be prepared by lyopyilization, which will bring out a novel way for the targeting drug-released thrombolysis therapy.

Resveratrol inhibits right ventricular hypertrophy induced by monocrotaline in rats.

1. Resveratrol (RSV), a polyphenol in red wine, exhibits cardioprotective effects in vitro, such as inhibition of angiotensin II- or phenylephrine-induced cardiomyocyte hypertrophy in rat neonatal myocyte cultures and suppression of cardiac fibroblast proliferation. The aim of the present study was to investigate the protective effects of RSV against monocrotaline (MCT)-induced right ventricular (RV) hypertrophy in rats. 2. Male Sprague-Dawley rats were given a single injection of MCT (50 mg/kg, s.c.) and were then treated with either vehicle (normal saline) or RSV (10 and 30 mg/kg, i.g., twice daily) for 21 days. A separate group of control rats were not injected with MCT and were treated with normal saline for 21 days. At the end of the treatment period, all rats were subjected to echocardiography and haemodynamic measurements. In addition, after rats had been killed, the hearts were subjected to histopathological, untrastructural and immunohistochemical analyses. 3. In vehicle-treated rats, MCT injection resulted in 33% mortality, whereas mortality in RSV-treated MCT-injected rats was 0%. In vehicle-treated rats, MCT increased RV free wall thickness and RV systolic pressure and decreased pulmonary arterial acceleration time at the end of the experimental period. These dynamic changes were ameliorated by RSV in a dose-dependent manner. Histologically, MCT injection resulted in RV hypertrophy, swollen mitochrondria and cardiomyocyte apoptosis; all these morphological changes were dose-dependently improved in rats treated with RSV. 4. In conclusion, RSV inhibits the RV hypertrophy induced by MCT in rats and this effect is mediated by both a direct effect of RSV on cardiomyocytes and an indirect effect mediated via a reduction in pulmonary hypertension.

Myocardium-targeted transplantation of mesenchymal stem cells by diagnostic ultrasound-mediated microbubble destruction improves cardiac function in myocardial infarction of New Zealand rabbits.

BACKGROUND: Therapeutic ultrasound-mediated microbubble destruction has been applied in the targeted delivery of genes, drugs and stem cells. We intended to study whether diagnostic US irradiating lipid-coated microbubble destruction combined with bone-marrow derived MSC infusion could enable the targeted delivery of MSCs into the myocardium and improve cardiac function of the myocardial infarction of New Zealand rabbits. METHODS: Diagnostic ultrasound was applied to the anterior chest for 10 min after intravenous injection of lipid-coated microbubble followed by infusion of BM-MSCs. Echocardiography, histological examination, and western blotting were performed 4 weeks after cell transplantation. RESULTS: The cardiac function (assessed by fractional shortening and ejection fraction) was markedly improved by US+Microbubble+MSC treatment. The number of capillaries stained by HE in US+Microbubble+MSC group (47+/-23) was much greater than that of the MSCs infusion group (26+/-7), US+Microbubble group(22+/-5) and PBS infusion group (19+/-10), P<0.01. US+Microbubble stimulation induced the expression of adhesion molecule (VCAM-1) in capillaries and enhanced the myocardial permeability of microvessels. US+Microbubble-mediated supply of MSCs increased the level of VEGF in ischemic myocardium. Area of cardiac fibrosis in the US+Microbubble+MSC group was significantly decreased by 25.6%,40.1% and 46.8% when compared with MSC infusion group, US+Microbubble group and PBS infusion group, respectively. CONCLUSIONS: This non-invasive cell delivery system may be useful as a novel and efficient approach for angiogenic cell therapy to the infarcted myocardium.

Galphaq-protein carboxyl terminus imitation polypeptide (GCIP)-27 inhibits right ventricular hypertrophy induced by monocrotaline in rats.

This study was to investigate the probable inhibitory effect of Galphaq-protein carboxyl terminus imitation polypeptide-27 (GCIP-27), the optimized form of GCIP, which is a competition candidate of the activated binding sites on Galphaq, on the right ventricular (RV) hypertrophy induced by monocrotaline (MCT) in rats. We have previously shown that GCIP-27, can prevent the hypertrophyc responses in cultured rat cardiomyocytes induced by noradrenaline and angiotensin II. Male Sprague-Dawley rats were given a single dose (50 mg/kg) of MCT subcutaneouly to induce pulmonary hypertension (PH) and RV hypertrophy. GCIP-27 (30, 90 microg/kg) or vehicle was administered (twice daily, intraperitoneally) from day 1 to day 21. GCIP-27 (90 microg/kg) inhibited the elevated pulmonary arteria systolic pressure (PASP) and mean pulmonary arteria pressure induced by MCT, but its dose at 30 microg/kg only reduced the elevated PASP. And no effect could be seen on the pulmonary arteria diastolic pressure at both two doses. On the other hand, the two doses of GCIP-27 improved significantly the weight ratio of RV to left ventricle plus septum, the RV free wall thickness and pulmonary arteria acceleration time (PAAT). In morphometric observation, GCIP-27 (30, 90g/kg) could attenuate cardiomyocytes hypertrophy, interstitium fibrosis, mitochondria swelling and malformation markedly in RVs of MCT-treated rats. Furthermore, GCIP-27 (30, 90 mug/kg) significantly reduced the overexpression of the proliferating cell nuclear antigen (PCNA) induced by MCT in RV cardiocytes. The results suggest that GCIP-27 can effectively attenuate the RV hypertrophy induced by MCT in rats, which may be mediated by both the direct effect on cardiomyocyte and the secondary effect by reducing PH, and may be involved in its influence on the Gq signal pathway.

Value of myocardial regional perfusion on long-term function in collateral-dependent myocardium.

BACKGROUND: Collateral circulation is considered key for left ventricular (LV) function recovery in patients with chronic total occlusion (CTO). However, there are conflicting reports about the influence of collaterals on LV recovery after revascularization. METHODS: Echocardiographic assessment of regional myocardial perfusion, wall motion score (WMS), and left ventricular ejection fraction (LVEF) were performed in patients with angiographically visible collateral circulation of grades 2 and 3. RESULTS: The WMS and LVEF of group B (with presence of myocardial regional perfusion) were significantly improved at one month and six months compared to those of group A (with absence of myocardial regional perfusion). The correlation between myocardial regional blood flow and changes in WMS and LVEF was significant at 6 months in patients with angiographically visible collateral circulation of grade 2 and 3. Similar correlations were observed on myocardial contrast echocardiography (MCE) score index. CONCLUSION: Myocardial function recovery in patients with CTO is determined by myocardial regional perfusion. MCE has important value for prognosis and risk stratification in patients with CTO undergoing cardiac catheterization.

Functionalization of chitosan with 3,4-dihydroxybenzoic acid for the adsorption/collection of uranium in water samples and its determination by inductively coupled plasma-mass spectrometry.

A chitosan resin derivatized with 3,4-dihydroxybenzoic acid moiety (CCTS-DHBA resin) was newly synthesized for the collection/concentration of trace uranium by using cross-linked chitosan (CCTS) as base material, and the adsorption behavior of uranium as well as 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the collected elements on the resin with 1M HNO(3), the eluates were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The CCTS-DHBA resin can adsorb several metal cations and several oxoanionic elements at appropriate pH. Among these metal ions, uranium shows an excellent adsorption behavior on this resin. Uranium as UO(2)(2+) species can be adsorbed on the resin by chelating mechanism with adsorption capacity of 330 mg g(-1) resin. Through the column treatment, the complete removal of large amounts of alkali and alkaline earth matrices without any loss of adsorption efficiency over prolonged usage were achieved with this resin. The CCTS-DHBA resin was applied to the adsorption/collection of uranium in tap water, river water and seawater samples with satisfactory results. The validation of the proposed method was carried out by analyzing uranium in the standard reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-DHBA resin, and the results showed good agreement with the certified values.

Sequential-injection on-line preconcentration using chitosan resin functionalized with 2-amino-5-hydroxy benzoic acid for the determination of trace elements in environmental water samples by inductively coupled plasma-atomic emission spectrometry.

A new chelating resin using chitosan as a base material was synthesized. Functional moiety of 2-amino-5-hydroxy benzoic acid (AHBA) was chemically bonded to the amino group of cross-linked chitosan (CCTS) through the arm of chloromethyloxirane (CCTS-AHBA resin). Several elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and rare earth elements (REEs), could be adsorbed on the resin. To use the resin for on-line pretreatment, the resin was packed in a mini-column and installed into a sequential-injection/automated pretreatment system (Auto-Pret System) coupled with inductively coupled plasma-atomic emission spectrometry (ICP-AES). The sequential-injection/automated pretreatment system was a laboratory-assembled, and the program was written using Visual Basic software. This system can provide easy operation procedures, less reagent consumption, as well as less waste production. Experimental variables considered as effective factors in the improvement sensitivity, such as an eluent concentration, a sample and an eluent flow rate, pH of samples, and air-sandwiched eluent were carefully optimized. The proposed system provides excellent on-line collection efficiency, as well as high concentration factors of analytes in water samples, which results in highly sensitive detection of ultra-trace and trace analysis. Under the optimal conditions, the detection limits of 24 elements examined are in the range from ppt to sub-ppb levels. The proposed method was validated by using the standard reference material of a river water, SLRS-4, and the applicability was further demonstrated to the on-line collection/concentration of trace elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and REEs in water samples.

Preparation of human hepatocellular carcinoma-targeted liposome microbubbles and their immunological properties.

AIM: To prepare the human hepatocellular carcinoma-(HCC)-targeted liposome microbubbles and to investigate their immunological properties. METHODS: Human hepatocarcinoma specific monoclonal antibody HAb18 was attached to the surface of home-made liposome microbubbles by static attraction to prepare the targeted liposome microbubbles. The combination of HAb18 with liposome microbubbles was confirmed by the slide agglutination test and immunofluorescent assay. Their immunological activity was measured by ELISA. Rosette formation test, rosette formation blocking test and immun-ofluorescent assay were used to identify the specific binding of targeted liposome microbubbles to SMMC-7721 hepatoma cells, and cytotoxicity assay was used to detect their effect on human hepatocytes. RESULTS: The targeted liposome microbubbles were positive in the slide agglutination test and immunofluorescent assay. ELISA indicated that the immunological activity of HAb18 on the liposome microbubbles was similar to that of free HAb18. SMMC-7721 cells were surrounded by the targeting liposome microbubbles to form rosettes, while the control SGC-7901 gastric cancer cells were not. Proliferation of SMMC-7721 cells and normal human hepatocytes was not influenced by the targeted liposome microbubbles. CONCLUSION: The targeted liposome microbubbles with a high specific biological activity have been successfully prepared, which specifically bind to human hepatocarcinoma cells, and are non-cytotoxic to hepatocytes. These results indicate that the liposome microbubbles can be used as a HCC-targeted ultrasound contrast agent that may enhance ultrasound images and thus improve the diagnosis of HCC, especially at the early stage.

[A novel microbeads-based chemiluminescence immunoassay for detecting human thyrotropin].

AIM: To establish a low cost and sensitive microbeads-based chemiluminescence immunoassay (CLEIA) for detecting human thyrotropin. METHODS: Thyrotropin in sera was captured by an alkaline phosphase-labeled mAb against TSH beta subunit and a FITC-labeled mAb against TSH alpha subunit. Captured thyrotropin was then isolated with immuno-magnetic beads conjugated with anti-FITC antibody and then quantified by chemiluminescence using adamanatane amine as luminescent substrate. RESULTS: The sensitivity of this assay is 0.004 mIU/L. The intra-assay CV and the inter-assay CV of the assay were 7.45% and 10.45%, respectively. The recovery rate was 91.4% -102.4%. The examination result of the assay correlates well with that of ACS-180 system. CONCLUSION: The CLELA for detecting TSH is low-cost, sensitive, specific and stable, and therefore may have a promising prospect in clinical application.

Grey scale enhancement of rabbit liver and kidney by intravenous injection of a new lipid-coated ultrasound contrast agent.

AIM: To assess the grey scale enhancement of a new lipid-coated ultrasound contrast agent in solid abdominal organs as liver and kidney. METHODS: Size distribution and concentration of the lipid-coated contrast microbubbles were analyzed by a Coulter counter. Two-dimensional (2D) second harmonic imaging of the hepatic parenchyma, the inferior vena cava and the right kidney of the rabbits were acquired before and after contrast agent injection. Images were further quantified by histogram in Adobe Photoshop 6.0. Time-intensity curves of hepatic parenchyma, inferior vena cava and renal cortex were generated from the original grey scale. RESULTS: The 2D images of hepatic parenchyma and cortex of the kidney were greatly enhanced after injection and the peak time could last more than 50 min. CONCLUSION: This new lipid ultrasound contrast agent could significantly enhance the grey scale imaging of the hepatic parenchyma and the renal cortex for more than 50 min.

Adsorption behavior of mercury and precious metals on cross-linked chitosan and the removal of ultratrace amounts of mercury in concentrated hydrochloric acid by a column treatment with cross-linked chitosan.

Cross-linked chitosan was synthesized with chitosan and ethylene glycol diglycidyl ether. The adsorption behavior of trace amounts of metal ions on the cross-linked chitosan was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The cross-linked chitosan adsorbed mercury and precious metals (Pd, Pt, and Au) at pH values from acidic to neutral. Especially, mercury in concentrated hydrochloric acids could be adsorbed on cross-linked chitosan quantitatively by an anion-exchange mechanism in the form of a stable chloride complex. This method was applied to the removal of mercury from commercially available hydrochloric acid; more than 97% of mercury was removed, and the residual mercury in the hydrochloric acid (Grade: for trace analysis) was found to be 0.15 ppb. Mercury adsorbed on the cross-linked chitosan could be easily desorbed with an eluent containing I M hydrochloric acid and 0.05 M thiourea. The thus-refreshed cross-linked chitosan could be repeatedly used for the removal of mercury in hydrochloric acid.