Protocol to evaluate the efficacy and safety of tolvaptan in patients with refractory ascites after liver resection: an open-label, single-arm phase I/II study

Background

In patients with chronic liver diseases such as cirrhosis, massive ascites after hepatic resection is the cause of prolonged hospitalization and worsening prognosis. Recently, the efficacy of tolvaptan in refractory ascites has been reported; however, there are no reports on the efficacy or safety of tolvaptan for refractory ascites after hepatic resection. This study aims to evaluate the efficacy of early administration of tolvaptan in patients with refractory ascites after hepatic resection.

Materials and methods

This is an open-label, single-arm phase I/II study. This study subject will comprise patients scheduled for hepatic resection of a liver tumor. Patients with refractory ascites after hepatic resection (drainage volume on postoperative day 1 ≥5 ml/body weight 1 kg/day) will be treated with tolvaptan. The primary endpoint will include the maximum change in body weight after hepatic resection relative to the preoperative baseline. The secondary endpoints will include drainage volume, abdominal circumference, urine output, postoperative complication rate (heart failure and respiratory failure), number of days required for postoperative weight gain because of ascites to decrease to preoperative weight, change in improvement of postoperative pleural effusion, total amount of albumin or fresh frozen plasma transfusion, type and amount of diuretics used, and postoperative hospitalization days.

Conclusion

This trial will evaluate the efficacy and safety of tolvaptan prophylaxis for refractory ascites after hepatic resection. As there are no reports demonstrating the efficacy of tolvaptan prophylaxis for refractory ascites after hepatic resection, the authors expect that these findings will lead to future phase III trials and provide valuable indications for the selection of treatments for refractory postoperative ascites.

A Multicenter, Open-Label, Single-Arm Phase I Trial of Dual-Wield Parenchymal Transection: A New Technique of Liver Resection Using the Cavitron Ultrasonic Surgical Aspirator and Water-Jet Scalpel Simultaneously (HiSCO-14 Trial)

PURPOSE

This study evaluated the safety and feasibility of a technique of liver resection named dual-wield parenchymal transection technique (DWT), using cavitron ultrasonic surgical aspirator (CUSA) and water-jet scalpel simultaneously.

METHODS

This multicenter, prospective, open-label, and single-arm phase I trial included patients aged 20 years or older with hepatic tumors indicated for surgical resection and scheduled for open radical resection. This study was conducted at two institutions affiliated with the Hiroshima Surgical Study Group of Clinical Oncology (HiSCO). The primary endpoint was the proportion of massive intraoperative blood loss (≥ 1000 mL). The secondary endpoints were the amount of blood loss, operative time, parenchymal transection speed, postoperative complications, and mortality. The safety endpoints were device failure and adverse events associated with devices.

RESULTS

From June 2022 to May 2023, 20 patients were enrolled; one was excluded and 19 were included in the full analysis set (FAS). In the FAS, segmentectomy was performed in nine cases, sectionectomy in four cases, and hemihepatectomy in six cases. Radical resection was achieved in all patients. Intraoperative blood loss greater than 1000 mL was observed in five patients (26.3%). The median amount of blood loss was 545 mL (range, 180-4413), and blood transfusions were performed on two patients (10.5%). The median operative time was 346 minutes (range, 238-543) and the median parenchymal transection speed was 1.2 cm2/minute (range, 0.5-5.1). Postoperative complications of Clavien-Dindo classification ≥ Grade 3 occurred in four patients (21.1%). No mortalities occurred in this study. In the safety analysis, there were no device failures or adverse events associated with devices.

CONCLUSIONS

This study demonstrated the safety and feasibility of DWT for liver resection. The efficacy of the DWT will be evaluated in future clinical trials.

Preoperative percutaneous or transvascular marking for curative resection of small liver tumours with potential for missing during hepatectomy: a study protocol for an open-label, single-arm phase II study

INTRODUCTION

Small liver tumours are difficult to identify during hepatectomy, which prevents curative tumour excision. Preoperative marking is a standard practice for small, deep-seated tumours in other solid organs; however, its effectiveness for liver tumours has not been validated. The objective of this study is to evaluate the effectiveness of preoperative markings for curative resection of small liver tumours.

METHODS AND ANALYSIS

This is an open-label, single-arm, single-centre, phase II study. Patients with liver tumours of ≤15 mm requiring hepatectomy will be enrolled and will undergo preoperative marking by placing a microcoil near the tumour using either the percutaneous or transvascular approach. The tumours, including the indwelling markers, will be excised. The primary endpoint will be the successful resection rate of liver tumours, defined as achieving a surgical margin of ≥5 mm and ≤15 mm. Secondary endpoints will include the results of preoperative marking and hepatectomy.

ETHICS AND DISSEMINATION

Ethical approval for this trial was obtained from the Ethical Committee for Clinical Research of Hiroshima University, Japan. The results will be published at an academic conference or by submitting a paper to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

jRCTs062220088.

Efficacy and safety of lenvatinib-transcatheter arterial chemoembolisation sequential therapy followed by surgical resection for intermediate-stage hepatocellular carcinoma beyond Up-to-7 criteria: a study protocol for a multicentre, single-arm, prospective study

INTRODUCTION

The feasibility and efficacy of surgical resection following systemic therapy for intermediate-stage hepatocellular carcinoma (HCC) beyond the Up-to-7 criteria is unclear. The combination of lenvatinib (LEN) and transcatheter arterial chemoembolisation (TACE), termed LEN-TACE sequential therapy, has shown a high response rate and survival benefit in patients with intermediate-stage HCC. This trial aims to evaluate the efficacy and safety of LEN-TACE sequential therapy and the feasibility of surgical resection for intermediate-stage HCC beyond the Up-to-7 criteria.

METHODS AND ANALYSIS

This is a multicentre, single-arm, prospective clinical trial. Thirty patients with intermediate-stage HCC beyond the Up-to-7 criteria will be enrolled. Patients eligible for this study will undergo LEN-TACE sequential therapy in which LEN is administered for 4 weeks, followed by TACE, and then further LEN for another 4 weeks. Patients will be assessed for efficacy of LEN-TACE sequential therapy and resectability, and surgical resection will be performed if the HCC is considered radically resectable. The primary outcome of this study is the resection rate after LEN-TACE sequential therapy. The secondary outcomes are the objective response rate of LEN-TACE sequential therapy, safety, curative resection rate, overall survival and recurrence-free survival.

ETHICS AND DISSEMINATION

This trial was approved by the Institutional Review Board of Hiroshima University, Japan (approval no. CRB210003), and has been registered with the Japan Registry of Clinical Trials (jRCTs061220007). The results of this study will be submitted for publication in a peer-reviewed journal and shared with the scientific community at international conferences.

TRIAL REGISTRATION NUMBER

jRCTs061220007 (https://jrct.niph.go.jp/latest-detail/jRCTs061220007).

Proper use of appendiceal stump closure methods for surgical site infection in laparoscopic appendectomy

INTRODUCTION

Although some studies have reported on the relationship between appendiceal stump closure methods and postoperative complications, there is no fixed method for this procedure. This study aimed to compare treatment outcomes of the existing procedures.

METHODS

We retrospectively analyzed the records of 200 patients who underwent urgent laparoscopic surgeries and investigated whether the difference in the appendiceal stump closure method was a risk factor for surgical site infection. The patients were divided into the Endoloop and endostapler groups, and 45 propensity score-matched patients were included. The treatment outcomes of the two groups were compared.

RESULTS

The patients with high body temperature showed significantly developed surgical site infection in multivariate analysis (P = .036). There was no significant difference in the appendix stump methods (Endoloop vs endostapler). Regarding postoperative complications, superficial and deep incisional surgical site infection, organ/space surgical site infection, ileus, and complications of Clavien-Dindo grade IIIa or higher; there was no significant difference between the endoloop and endostapler groups after propensity score matching (P = .725, 1.000, .645 and .557, respectively).

CONCLUSION

By properly using the Endoloop and endostapler according to the severity of inflammation, the Endoloop can be safely performed in many cases. Inexpensive Endoloop as an option for stump closure methods should positively impact medical costs.

Preoperative Endoscopic Tattoo Marking Improves Lymph Node Retrieval in Laparoscopic Rectal Resection: A Retrospective Cohort Study

Purpose

Harvesting at least 12 lymph nodes (LNs) is recommended for adequate tumor staging in colon surgery. Although preoperative endoscopic tattooing has been used for primary localization of tumors, its impact on LN retrieval in colorectal surgery remains controversial. We aimed to investigate the relationship between preoperative tattooing and LN retrieval after laparoscopic rectal resection.

Methods

We reviewed the records of 92 patients with rectal cancer who underwent laparoscopic resection from January 1, 2018 to December 31, 2019. Patients were categorized into 2 groups according to whether preoperative endoscopic tattooing was performed. The rate of adequate LN retrieval (≥12) was compared.

Results

The tattooed and non-tattooed groups comprised 49 and 43 patients, respectively. In the tattooed and non-tattooed groups, the rates of adequate LN retrieval were 75.5% and 55.8%, respectively (P=0.046). Univariate analysis revealed that female sex, tattooing, LN metastasis status, pathological pathological stage (p-stage), and LN dissection were predictive factors for adequate LN retrieval. In the multivariate analysis, female sex (odds ratio [OR], 3.34; 95% confidence interval [CI], 1.15-9.73; P=0.027), tattooing (OR, 2.87; 95% CI, 1.03-7.94; P=0.043), and p-stage (OR, 3.34; 95% CI, 1.04-10.75; P=0.043) were independent predictive factors for adequate LN retrieval after surgery.

Conclusion

This study revealed that preoperative endoscopic tattooing was statistically significantly associated with adequate LN retrieval in patients with rectal cancer who underwent laparoscopic rectal resection. Preoperative endoscopic tattooing should be considered to improve disease assessment and avoid stage migration.

Cutaneous metastasis of cecum cancer with MSI-high and BRAFV600E mutation: a case report

Background

Cutaneous metastases of colorectal cancer (CRC) are rare, occurring in 0.7% to 5% of cancer patients. Furthermore, the molecular subtypes of cutaneous metastasis of CRC are unclear. Here, we present a rare case of cutaneous metastasis of high-frequency microsatellite instability (MSI-high)/BRAFV600E-mutant cecum cancer.

Case presentation

A 77-year-old woman presented at the outpatient clinic with a subcutaneous mass on her left back. An excisional biopsy was performed and metastatic cutaneous adenocarcinoma was diagnosed. A computed tomography scan of the thorax and abdomen showed thickening of the cecum wall, the presence of pericolic lymph nodes, multiple masses in the liver, and a single nodule in the right lung. Right colectomy with D2 lymphadenectomy and functional end-to-end anastomosis was performed because of the almost-complete intestinal obstruction. The expression of KRAS wild type, BRAFV600E mutation, and MSI-high was detected in the cecum cancer using molecular pathological examination. She received chemotherapy with XELOX + BEV regimen (capecitabine + oxaliplatin + bevacizumab). After four administrations, a computed tomography scan showed reduction of distant metastases, which suggested partial response.

Conclusions

We encountered a rare case of cutaneous metastasis of MSI-high and BRAFV600E-mutant cecum cancer. In the future, it will be necessary to accumulate more cases to identify clinical features and more effective treatments for CRCs with cutaneous metastasis.

Reduced-port surgery for right paraduodenal hernia in an adult patient: A case report and review of the literature

Paraduodenal hernia (PDH) is a congenital internal hernia caused by an abnormal rotation of the midgut during embryotic life; it is characterized as right- or left-sided according to the hernial sac location. Herein, we describe a case of a 30-year-old male patient who was preoperatively diagnosed with right PDH and underwent successful laparoscopic repair using reduced-port surgery (RPS). The patient presented with postprandial nausea, vomiting, and upper abdominal pain. Contrast-enhanced CT and an upper gastric series led to the preoperative diagnosis of right PDH associated with intestinal malrotation. Thereafter, laparoscopic repair using RPS was performed. After the small bowels were reduced from the hernial sac, the hernial orifice was opened widely and laterally. The postoperative course was uneventful. This is the first report of a successful laparoscopic surgery on right PDH using RPS.

Radical surgery for anal canal neuroendocrine carcinoma with pagetoid spread: a case report

Anal canal neuroendocrine carcinoma (NEC) with pagetoid spread (PS) is a rare disease, and its treatment strategy remains unclear. The prognosis of anal canal NEC with PS is poor. Resection margin status is very important for anorectal carcinoma because it affects survival. When accompanied by PS, the defect of the resulting perineal wound following radical surgical intervention may be necessarily enlarged to ensure the appropriate margin status. This case report discusses the treatment of a patient with advanced anal canal NEC with PS, inguinal lymph node metastasis and sphincter infiltration in which total pelvic exenteration with plastic surgery was successfully performed. The plastic surgery incorporated a gracilis muscle flap that was useful for the reconstruction of the enlarged perineal defect.

Indocyanine green fluorescence imaging for subtotal esophagectomy due to esophageal stenosis after acute esophageal necrosis: a report of two cases

Although esophageal stricture after acute esophageal necrosis (AEN) is often refractory to dilation therapy, there have been few reports of surgical intervention. We report two rare cases of successful subtotal esophagectomy and esophagogastrostomy for esophageal strictures after AEN using indocyanine green (ICG) fluorescence imaging. In case 1, emergent esophagogastroduodenoscopy (EGD) in a 56-year-old man with coffee-ground emesis revealed black esophageal mucosa in the middle to lower esophagus, indicating AEN. Despite conservative therapy, an esophageal stricture developed after 2 weeks. Repeated endoscopic balloon dilation (EBD) did not resolve the stenosis; esophagectomy was thus performed approximately 6 months after AEN onset. We evaluated the blood flow to the esophagus using ICG fluorescence imaging to determine the proximal surgical resection line. The postoperative course was uneventful. In case 2, an 81-year-old woman with upper gastrointestinal bleeding with hematemesis and chest pain was diagnosed with AEN by EGD and was treated with conservative therapy. An esophageal stricture developed after 3 weeks, and repeated EBD was ineffective. Approximately 2 months after AEN onset, she underwent esophagectomy using ICG fluorescence imaging. The postoperative course was uneventful. Considering that AEN is a blood flow disorder, ICG fluorescence imaging is a useful technology to prevent surgical morbidity.

[Total Pelvic Exenteration and Perineal Reconstruction with a Gracilis Myocutaneous Flap for Local Recurrence of Rectal Cancer]

The case involved a female in her 70s. Six years prior, she had undergone an abdominoperineal rectal resection for rectal cancer. Local recurrence was observed during follow-up so preoperative chemoradiotherapy was performed to shrink the tumor, followed by a total pelvic exenteration, bilateral ureterocutaneous fistula, and perineal reconstruction with a gracilis myocutaneous flap. She was discharged from hospital 39 days following surgery with no major complications. We herein report on a case of a good postoperative course due to surgery including a total pelvic exenteration and perineal reconstruction with a gracilis myocutaneous flap for postoperative local recurrence.

[Outcome of Repeated Surgical Resections of Hepatic and Pulmonary Metastases from Colorectal Cancer]

Previous reports have demonstrated that repeated surgical resections of resectable hepatic and pulmonary metastases from colorectal cancer contribute to a better prognosis. We retrospectively assessed the outcomes of 19 patients with colorectal cancer who underwent repeated resections of hepatic and pulmonary metastases between February 2007 and February 2017. The median observation period was 69.9 months, and 26 liver and 27 lung resections were performed. The cumulative 5-year survival rates after resection of the last metastasis was 75.1% and the median disease-free survival after resection of the last metastasis was 34.7 months. Although 7 patients showed recurrence and 4 patients died, 7 patients exhibited long-term survival. Univariate analysis revealed that simultaneous liver and lung metastases were significantly predictor of poor prognosis(p=0.039). Progress of the patients in the present study were comparable to those in previous reports. Therefore, we propose that repeated surgical resection of hepatic and pulmonary metastasis from colorectal cancer could improve patient prognosis. Further studies should examine to identify more accurate prognostic factor with large series.

Treatment outcomes after splenectomy with gastric devascularization or balloon-occluded retrograde transvenous obliteration for gastric varices: a propensity score-weighted analysis from a single institution

BACKGROUND

Although balloon-occluded retrograde transvenous obliteration (BRTO) is often selected to treat gastric varices caused by portal hypertension, data comparing BRTO and splenectomy with gastric devascularization (Sp + Dev) are limited.

METHODS

From January 2009 to February 2018, 100 patients with gastric varices caused by portal hypertension who underwent Sp + Dev (n = 45) or BRTO (n = 55) were included. Overall survival (OS) and the rebleeding rate were calculated using the inverse probability of a treatment weighting-adjusted log-rank test. Independent risk factors were identified by Cox regression analysis. Changes in liver function and adverse events after the procedures were analyzed.

RESULTS

Patients in the Sp + Dev group tended to have lower platelet counts than those in the BRTO group, but liver function did not differ between these groups. The 5-year OS rates for the Sp + Dev and BRTO groups were 73.4 and 50.0% (p = 0.005), respectively. There were no significant differences in rebleeding rates between the two groups. Multivariate analysis showed that serum albumin level ≤3.6 g/dL, prothrombin time% activity (PT%) ≤80%, and serum creatinine level ≥0.84 mg/dL were poor prognostic factors. Although the Sp + Dev group had more short-term complications after procedures, Sp + Dev tended to be more effective in improving liver function than BRTO.

CONCLUSIONS

Sp + Dev showed better OS and improvement of liver function compared with BRTO for the treatment of gastric varices caused by portal hypertension.

A rare case of a spontaneously ruptured secondary hepatic malignant lymphoma

Background

Although secondary liver involvement of the lymphoma is common and occurs in 50% of patients with non-Hodgkin’s lymphoma, liver tumor rupture in malignant lymphoma is extremely rare. We report a case of a spontaneously ruptured secondary liver involvement of non-Hodgkin’s lymphoma that was successfully treated with transcatheter arterial embolization (TAE) to obtain hemostasis, and subsequent hepatectomy and systemic chemotherapy. To the best of our knowledge, this is only the second reported case of a ruptured hepatic lymphoma.

Case presentation

A 74-year-old man with sudden-onset right shoulder and upper quadrant pain was transferred to our hospital via an ambulance. His vital signs were stable. Contrast-enhanced computed tomography showed a large hypo-enhancing tumor (94 × 81 mm) in the posterior segment of the liver, with intratumoral extravasation and a 12 × 10 mm daughter tumor in segment 5 of the liver. Hemoperitoneum due to rupture of hepatocellular carcinoma with intratumoral hemorrhage was suspected, although the serum alpha-fetoprotein and protein induced by vitamin K absence-II levels were within normal range. TAE was used for hemostasis. Extended posterior segmentectomy including tumor resection in segment 5 was performed on day 23 after embolization. The postoperative course was uneventful. Pathological examination of the resected specimens revealed that the ruptured tumor was diffuse large B-cell lymphoma. Postoperative fluorodeoxyglucose positron emission tomography-computed tomography showed uptake in the left parotid gland, pancreas, and thoracic vertebra. Based on these findings, the final diagnosis was a ruptured secondary hepatic malignant lymphoma. Complete remission was achieved with chemotherapy. He remains alive 30 months after hepatectomy without evidence of relapse.

Conclusions

We report the first case describing a hepatic tumor rupture as the first presentation of a primary or secondary hepatic malignant lymphoma. The patient was successfully treated with TAE, hepatectomy, and subsequent systemic chemotherapy for non-Hodgkin’s lymphoma.

Nutrient recovery from biomass cultivated as catch crop for removing accumulated fertilizer in farm soil

As a result of long-term continuous use of fertilizers in farm land, a large amount of nutrients accumulate in the soil, increasing the risk of eutrophication or nitrate pollution of groundwater. For rehabilitating the farm soil and recovering nutrients such as nitrogen, phosphorus and potassium, a new system has been developed by our research group. This paper discusses the methodology of extracting nutrients from biomass in order to recover phosphorus and other nutrients in crystal form. Around 80% or higher extraction rates were achieved for phosphorus and potassium by soaking the powdered tissue in distilled water or 1% NaOH solution for 24 h. The extracted phosphorus and potassium act as a potential resource for recycled fertilizer or other industrial materials.

Formation of chlorinated aromatics in model fly ashes using various copper compounds

Various copper compounds found in fly ash are related to the formation of chlorinated aromatics. The formation potentials of chlorinated aromatics in different model fly ashes containing various copper compounds and the chemical behavior of such copper compounds were investigated. In model fly ash with copper metal, hydroxide, carbonate, or oxides, the generated amounts of chlorobenzene (CBz) and polychlorinated biphenyls (PCBs) and the average chlorination numbers were low and at the same level, respectively. The maximum generated amounts of chlorinated aromatics were observed at 300 degrees C. Although X-ray absorption near edge structure (XANES) spectra indicated that the chemical form of copper compounds changed little, they were found to promote the formation of chlorinated aromatics. Therefore, these copper compounds play the same role as CuO. On the other hand, in model fly ash with copper chloride, the generated amounts of CBz and PCBs were quite high and the average chlorination numbers was high. Dynamic changes were observed in XANES spectra, and the pre-edge peak attributed to monovalent copper compounds appeared at around 300 degrees C. A large difference was observed between these two groups in the amount of CuCl generated and the homologs of chlorinated aromatics present, indicating that CuCl played an important role in the formation of chlorinated aromatics.

Behaviour and adsorptive removal of siloxanes in sewage sludge biogas

We investigated the behaviour of siloxanes, which adversely affect biogas engines, as well as their concentration levels in sewage sludge biogas in Japan. We also performed experiments on the absorptive removal of siloxanes using various adsorbents and determined the main adsorbent characteristics required for the removal of siloxanes. The results of our study on the concentration and composition of siloxanes in biogas were similar to previous reports. Moreover, we found that the concentration of siloxanes changes in relation to the outside air temperature based on real-time measurements of siloxanes using a continuous analyser. We further speculated that the continuous analyser would accurately indicate the siloxane concentration in model biogas but overestimate the siloxane concentration in actual biogas because of positive interference by VOCs and other biogas components. In the siloxane adsorption experiment, the equilibrium uptake of both cyclic siloxanes, D4 and D5, was positively related to the BET-specific surface area of the adsorbents and the fraction of the external surface area taken up by relatively large diameter pores. We attributed the adsorption results to the fact that the siloxane molecules are generally larger than micropores; therefore, they are less susceptible to adsorption to micropores. Based on these results, we concluded that adsorbents with large BET-specific surface areas, especially those with a high external specific surface area and pores of relatively large diameters, are desired for the removal of siloxanes.

Chemical states of trace elements in sewage sludge incineration ash by using x-ray absorption fine structure

In this study, the chemical states of chromium (Cr), arsenic (As), and selenium (Se) in sewage sludge incineration ash were determined by X-ray absorption fine structure (XAFS) spectroscopy. Sewage sludge incineration ash was sampled from several facilities, and XAFS measurements were carried out with a beam line BL01B1 at the SPring-8 facility. Cr K-edge X-ray absorption near-edge structure (XANES) spectra suggested that Cr compounds were predominantly speciated as Cr(III) and the fraction of Cr(VI) was very minor. Compared to the reference materials, Cr XANES spectra of the incineration ashes were similar to those of FeCr2O4, Cr(OH)3, and CaCr2O4. As K-edge XANES spectra indicated that As(V) compounds were present in incineration ashes. Because the chemical state of As in sewage sludge was As3+ in our previous study, we speculated that the chemical state of As changed into As(V) during the incineration process. According to Se K-edge XANES spectra, Se compounds were predominantly Se(IV), and a slight difference was observed in the chemical states amongst facilities using inorganic or organic coagulants in the dewatering process.

Extraction efficiency of phosphate from pre-coagulated sludge with NaHS

The recovery of phosphorus from sewage and sludge treatment systems is particularly important because it is a limited resource and a large proportion of the phosphorus currently used in Japan must be imported. We have been experimentally evaluating recovery methods with sulphide. In this study, we focussed on the extraction of phosphate from the sludge, and sought to achieve a greater extraction efficiency and to validate the extraction mechanism. We conducted three experiments, i.e. a sludge-type experiment, a coagulant ratio of pre-coagulated sludge experiment, and a concentration of pre-coagulated sludge experiment. Phosphate was extracted not with normal sewage sludge but with pre-coagulated sludge and FePO4 reagent at S/Fe = 1.0-2.0. A coagulant ratio of 23mg Fe L(-1) was required in the precoagulation process to effectively extract phosphate. A high concentration of pre-coagulated sludge was required for the phosphate extraction. The mass balance was calculated, and 44.0% of phosphorus was extracted to supernatant, and 98.5% of iron and 98.3% of sulphur (44.1% of sulphur was sulphide). Thus, phosphate can be selectively separated from iron by the phosphate extraction method with NaHS, and phosphorus and iron can be recovered and reused at sewage treatment plants using ferric chloride as a coagulant.

Complex formation analysis of water-soluble calixarenes by capillary zone electrophoresis

The equilibria of complex formation reactions between various kinds of cations and anionic calixarenes in an aqueous solution were analyzed by capillary zone electrophoresis on the basis of the change in electrophoretic mobility of the calixarenes. The apparent electrophoretic mobility of the calixarenes decreased with increasing concentrations of alkali metal ions and quaternary ammonium ions. Equilibrium constants were determined by a non-liner least-squares analysis using the changes in apparent electrophoretic mobility. The complex formation constants obtained with alkali metal ions were in the order of 10(2.3) - 10(3.0), and those with quaternary ammonium ions were 10(2.9) - 10(4.2), providing less selectivity among them. The selectivity of the calixarene toward alkali metal and quaternary ammonium ions in aqueous solution involves flexible structure, and compensative interactions of electrostatic and hydrophobic interactions. From the results obtained in this work, the electrophoretic method has proved to be useful for analyzing the reactivity of anionic calixarene in aqueous solution.