S. Jeyakumar

Simultaneous determination of trace amounts of borate, chloride and fluoride in nuclear fuels employing ion chromatography (IC) after their extraction by pyrohydrolysis

An accurate and sensitive method based on the combination of pyrohydrolysis-ion chromatography (PH-IC) is proposed for the simultaneous separation and determination of boron as borate, chloride and fluoride in nuclear fuels such as U(3)O(8), (Pu,U)C and Pu-alloys. The determination is based on the initial pyrohydrolytic extraction of B, Cl and F from the samples as boric acid, HCl and HF, respectively, which are subsequently separated by ion chromatography (IC). The proposed method significantly improves the existing analytical methodology as it combines the determination of boron, a critical trace constituent in nuclear materials, along with F(-) and Cl(-) for chemical quality control measurements. Various experimental parameters were optimized to achieve maximum recoveries of the analytes during the pyrohydrolysis and to get better ion chromatographic (IC) separation of borate, F(-) and Cl(-) along with other anions such as CH(3)COO(-), NO(2)(-), NO(3)(-), Br(-), PO(4)(3-) and SO(4)(2-). Recoveries of more than 93% could be obtained for all the analytes in the sample (0.5-1.5 g) at 1200+/-25K and distilled with pre-heated steam at the flow rate of 0.3 mL/min. An isocratic elution with a mobile phase of 0.56 M d-mannitol in 6.5mM NaHCO(3) was used for the IC separation. The detection limits for B (as borate), F(-) and Cl(-) were 24, 13 and 25 microgL(-1), respectively. Precision of about 5% was achieved for determination of boron, Cl(-) and F(-) in the samples containing 1-5 ppm(w) of boron, and 10-25 ppm(w) of Cl and F. The method was validated with reference materials and successfully applied to the nuclear fuels. The methodology is easy to adapt on routine basis.

Separation behavior of U(VI) and Th(IV) on a cation exchange column using 2,6‐pyridine dicarboxylic acid as a complexing agent and its application for the rapid separation and determination of U and Th by ion chromatography

The retention behavior of U and Th as their 2,6-pyridine dicarboxylic acid (PDCA) complexes on a cation exchange column was investigated under low pH conditions. Based on the observed retention characteristics, an ion chromatographic method for the rapid separation of uranium and thorium in isocratic elution mode using 0.08 mM PDCA and 0.24 M KNO(3) in 0.22 M HNO(3) as the eluent was developed. Both uranium and thorium were eluted as their PDCA complexes within 2 min, whereas the transition and lanthanide metal cations were eluted as an unresolved broad peak after thorium. Under the optimized conditions both U and Th have no interference either from alkali and alkaline earth elements up to a concentration ratio of 1:500 or from other elements up to 1:100. The detection limits (LOD) of U and Th were calculated as 0.04 and 0.06 ppm, respectively (S/N=3). The precision in the measurement of peak area of 0.5 ppm of both U and Th was better than 5% and a linear calibration in the concentration range of 0.25-25 ppm of U and Th was obtained. The method was successfully applied to determine U and Th in effluent water samples.

Study on the identification of organic and common anions in the pyrohydrolysis distillate of mixed uranium-plutonium carbide for the interference free determination of chlorine and fluorine by ion chromatography

Abstract Identification of various soluble organic acids formed during the pyrohydrolysis of uranium-plutonium mixed carbide [(U,Pu)C] was carried out using ion chromatography. This has significant importance as the soluble organic acids can cause severe interferences during the ion chromatography separation and determination of Cl− and F− in the pyrohydrolysis distillate of (U,Pu)C. Determination of Cl and F is important in the chemical quality control of nuclear materials as these two elements can cause corrosion and hence, their concentrations in all nuclear materials are restricted to certain specified values. Since the pyrohydrolysis distillates contain both inorganic and organic acid anions, for the sake of separating and identifying organic acid anions from the common inorganic anions, three independent isocratic elutions using varying concentrations of NaOH eluent were employed for the separation of weakly, moderately and strongly retained anions. It was observed that pyrohydrolysis of (U,Pu)C also produced soluble organic acids as in the case of nitric acid dissolution of UC. The present investigation revealed the presence of formic, acetic, propionic, butyric, oxalic acid anions in the pyrohydrolysis distillate of (U,Pu)C in trace or ultra-trace concentrations. The presence of each organic acid identified in the chromatogram was confirmed with spike addition as well as by separating them by capillary electrophoresis method. The presence of lower aliphatic acids viz. formic and acetic acids was reconfirmed by carrying out an independent separation with tetraborate eluent. It is suggested that nitric acid being formed during pyrohydrolysis could be responsible for the formation of organic acids. Based on the findings, an ion chromatography separation method has been proposed for the interference-free determination of chloride and fluoride in pyrohydrolysis distillate of (U,Pu)C.

Separation of Boron from Borated Paraffin Wax by Pyrohydrolysis and Alkali Extraction Methods and Its Determination Using Ion Chromatography

A method based on the pyrohydrolysis extraction of boron and its quantification with ion chromatography was proposed for paraffin waxes borated with H3BO3 and B4C. The optimum pyrohydrolysis conditions were identified. Wax samples were mixed with U3O8, which prevents the sample from flare up, and also accelerates the extraction of boron. Pyrohydrolysis was carried out with moist O2 at 950°C for 60 and 90 min for wax with H3BO3 and wax with B4C, respectively. Two simple methods of separation based on alkali extraction and melting wax in alkali were also developed exclusively for wax with H3BO3. In all the separations, the recovery of B was above 98%. During IC separation, B was separated as boron-mannitol anion complex. Linear calibration was obtained it between 0.1 and 50 ppm of B, and LOD was calculated as 5 ppb (S/N = 3). The reproducibility was better than 5% (RSD).

Separation and determination of trace thorium in uranium matrix using chelation ion chromatography

ABSTRACT A simple chromatographic method for the determination of trace thorium in uranium matrix has been reported after studying the retention behavior of U(VI) and Th(IV) as their 2,6-pyridine dicarboxylic acid (PDCA) complexes on a reversed phase column. The method does not require pre-separation of uranium matrix. A mobile phase consisting of PDCA, KNO3, and HNO3 in 5% methanol was used. A calibration plot was constructed in the presence of uranium matrix (r2 = 0.9978). The precision of the method is 5% at 1 ppm of Th and LOD was obtained at 0.1 ppm (S/N =3). The accuracy of the method was checked by comparing the results with neutron activation analysis.

Direct Separation of Molybdenum from Solid Uranium Matrices Employing Pyrohydrolysis, a Green Separation Method, and Its Determination by Ion Chromatography.

Pyrohydrolysis is a well-established separation method, and it is being used as a sample preparation method for several materials for further determination of non-metals such as halogens, boron, and sulfur. Analytes are retained in a diluted solution that is suitable for carrying out analysis by several determination techniques and minimizing the use of concentrated reagents. Pyrohydrolysis separation of metals has not been reported yet. The present study demonstrates the pyrohydrolysis separation of Mo as MoO4(2-) from uranium materials and its subsequent determination using ion chromatography coupled with suppressed conductivity detector. With use of TGA and XRD the volatilization behavior of Mo was studied. Important parameters for the pyrohydrolysis method required for the quantitative separation of Mo were evaluated. The precision of the method was better than 5% at 25 ppm of Mo. The accuracy was evaluated by analysis of a CRM (U3O8-ILCE-IV). The method was applied to determine Mo in ammonium diuranate samples, where the conventional methods suffer from the loss of Mo.

Development of ion chromatography and capillary electrophoresis methods for the determination of Li in Li–Al alloy

Two methods were developed for determination Li content in Li–Al alloy by employing ion chromatography (IC) and capillary electrophoresis (CE) without any prior separation of Al matrix. In absence of suitable certified reference material the two methods were used to validate each other. Using a high capacity column and a weaker eluent methane sulphonic acid, it was possible to separate Li in IC without eluting strongly retained Al. The method showed good precision and sensitivity and was extended for analysis of routine samples. In the case of CE using imidazole as co-ion, Li was detected in CE by indirect detection. In view of no interference from Al, samples were analyzed without any matrix separation. The CE method was used successfully for sample analysis and results were compared with IC results.

Simultaneous determination of borate, chloride and molybdate in pyrohydrolysis distillates of plant and soil samples by ion chromatography

Determination of concentrations of micronutrients in plant samples is important in order to assess the growth and quality of plants. An ion chromatography (IC) method was developed for the simultaneous determination of B, Cl and Mo (micronutrients present in their anionic form in aqueous samples) using a gradient elution with d-mannitol and NaOH. Despite their different chemical nature, these elements could be separated from the matrix by employing pyrohydrolysis. IC was employed for their sequential determination from single aliquot injection into the IC column. It was observed that the optimised procedures developed earlier in our laboratory for the separation of B and halogens using d-Mannitol-NaOH or bicarbonate eluents could not be extended to B-Mo-Cl separation. The concentration levels of d-mannitol in the eluent required for separation of boron impeded the conductivity detection of Mo and the peak sensitivity was seen to be critically dependent on d-mannitol concentration in the eluent. In addition, d-mannitol in NaOH eluent altered the retention times of analytes (B, F-, Cl-, NO3-, SO42-and MoO42-) which were not observed in the case of bicarbonate eluent. The current study deals with the investigation on the influence of d-mannitol on the molybdate as well as its role on the retention time. Formation of Mo-mannitol complex at different pH conditions and de-protonation of mannitol were correlated to the observed effects. Based on the observations, a gradient elution method was proposed for the simultaneous separation and determination of B, Cl and Mo in the pyrohydrolysis distillates of plant samples. The method was calibrated for B (0.05-1 mg/L), Cl (0.1-10 mg/L) and Mo (0.5-10 mg/L) and the linear regression coefficients obtained were 0.9992, 0.9998 and 0.997 respectively. The limit of detection (LOD) for B, Cl and Mo was calculated to be 19, 23 and 96 μg/L, respectively. The developed IC method after pyrohydrolytic separation of B, Cl and Mo was successfully applied for the analysis of real samples.

Analysis of Predictive Factors Influencing Early Patency in Adult Autogenous Arterio Venous Accesses

Arteriovenous(AV) accesses are the lifeline for Chronic kidney disease (CKD) patients and providing a durable access is a challenge for every vascular surgeon. The maturation of autogenous AV accesses at 4-6 weeks is the biggest hurdle more than the creation of AV access. There are many traditional preoperative predictors for Arteriovenous fistula( AVF) maturation including old age female sex, obesity, smoking, presents of atherosclerotic risk factors like Coronary Artery Disease(CAD), Cerebrovascular Disease(CVD), Peripheral Vascular Disease(PAD), Diabetes Mellitus. In this study in addition to the evaluation of the above risk factors routine duplex was done to see additional parameters like artery diameter reactive hyperemia, and venous diameter, venous distensibility and to rule out central venous stenosis. Preoperative mean arterial pressure and blood pressure between the two upper limbs were also taken into consideration after thorough physical examination. A new concept of spiral laminar flow detected by post op duplex was also included in this study. With all the parameters and routine postoperative antiplatelets with clopidogrel 75mg once daily in all patients the influence of such factors on early patency of adult autogenous AV accesses were assessed at 2 weeks post procedure.

Traditional pig rearing practices among the Nicobari tribes of Nicobar group of Islands, India

The Andaman & Nicobar Islands are a group of 572 big and small Islands & Islets in the South Eastern part of Bay of Bengal. Nicobari pigs (Sus scrofa Nicobaricus) which are indigenous to these islands got domesticated and well adapted to the island ecosystem. A study was conducted on pig rearing system among the Nicobari tribes of Nicobar group of islands viz. Car Nicobar, Katchal, Nancowry, Kamorta, and Teressa. Results of the current study revealed that the Nicobari pigs were reared under traditional system by the Nicobari tribal community and the pigs were concentrated only in Nicobar group of islands. The pigs were reared and considered as family asset among the tribal. The phenotypic characters showed that the Nicobari pigs were indigenous to these islands and their existence was noted since many centuries. These pigs were reared under free range system. Nicobari tribes use various indigenously made materials/utensils for housing and feeding. Pigs were fed mainly with coconut and other locally available feed resources and in addition, pigs feed through scavenging and rooting. No commercial farms or sale of meat was practiced. It is concluded that the Nicobari pigs are considered as an indigenous pig germplasm (Sus scrofa Nicobaricus) belonging to this island territory and Nicobari tribes practices century old established indigenous technical knowledge in pig rearing and they are passed through many generations. ITK would significantly contribute to the generation and pave the way for exploitation of technology to benefit tribal/rural populations.