NaOH Eluent Research Articles

Improved ciprofloxacin removal by a novel organohalloysite obtained by phenylphosphonic acid intercalation

Ciprofloxacin (CIP) is extensively used to treat bacterial infections, however, its presence in water can lead to bacterial resistance in pathogens and affect human and animal health through the food chain. We addressed this issue by synthesizing innovative organoclays using Algerian halloysite (H) and phenylphosphonic acid (PA) solutions of varying concentrations, which were used in the adsorption of this ubiquitous emerging contaminant. A bibliographic search did not retrieve any articles on the intercalation of phenylphosphonic acid in clays and its use in the removal of emerging contaminants. The insertion of PA in the interlayer space led to an increase in basal distance from 7.6 to 15.2 Å with an intercalation degree of 60%. The uptakes of CIP at 55 °C were 75.0 and 37.2 mg g−1 for the best organohalloysite (HPA6) and H, respectively. The Redlich-Peterson isotherm showed close agreement with our experimental isotherms. The NaOH eluent was highly effective, desorbing 90.7% of CIP from HPA6 which maintained its adsorption performance for four cycles. Through cross-checking the results of intercalation characterization, CIP adsorption and Fourier transform infrared spectroscopy (FTIR) and Raman investigations, we elucidated the mechanism of the CIP-HPA6 interaction, which includes a hydrogen bond between the CIP carbonyl and the hydrogen of intercalated phenylphosphonic acid, along with a hydrophobic interaction between the CIP aromatic ring and the -Si-O-Si- species. The promising potential of this novel nanohybrid is evident, and we believe it could be a highly efficient solution for eliminating pharmaceuticals from wastewater.

Investigation on structural and adsorptive features of BaO modified zeolite powders prepared by ball milling technique: Removal of tetracycline and various organic contaminants

In the current study, the removal of tetracycline (TC) antibiotic via BaO-doped zeolite (80BaO@zeolite), which synthesized by ball-mill technique, from water by adsorption process was studied. The structure and properties of 80BaO@zeolite was determined by XRD, FTIR, SEM and BET/N2. TC adsorption capacity of 71.4 mg g−1 was obtained for 80BaO@zeolite. The Langmuir isotherm model was found to be compatible for 80BaO@zeolite. The kinetic results indicate that the adsorption rate is compatible with the pseudo second order model and the time for the adsorption to reach equilibrium was achieved as 360 min. Maximum TC removal was obtained at pH:10, in the presence of NaCl and CaCl2 salts, and compared to in tap water drinking water and distilled water. The sorption process has shown thermodynamically exothermic and spontaneous nature. The desorption of TC molecules attached to the 80BaO@zeolite surface was investigated using different eluents. The 88% TC removal and 94% TC recovery rates achieved in the first cycle with the 1 M NaOH eluent decreased to 72% and 70%, respectively, in the fourth cycle. High adsorption capacities of 161.3 mg g−1, 59.3 mg g−1 and 85.5 mg g−1were obtained in the removal of malachite green, murexide and basic violet-16, respectively.

A phosphonium ionic liquid conjugated magnetic graphitic carbon nitride nanocomposite: an effective sample pretreatment tool for selenium separation and determination.

We established an innovative and easy-to-use methodology for selenium (Se) extraction and determination from real water samples utilizing a magnetic nanocomposite adsorbent (MNC-SPE) aided by an inductively coupled plasma mass spectrometry (ICP-MS) approach. The MNC-SPE adsorbent was fabricated by hybridizing Fe3O4 nanoparticles on the surface of carbon nitride nanosheets (GCN NSs) that were coated with 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid (P-IL). A variety of techniques were used to thoroughly analyze the structural and chemical characteristics of MNC-SPE, and appear to have a great number of diverse active surface functional units (imidazole ring and -NH3+). In order to optimize the key factors affecting the Se extraction, parameters including the adsorbent dosage, contact time, eluent type, eluent volume, eluent time, and reusability of adsorbent were extensively studied. The proposed approach was validated under the optimal reaction conditions, and it showed good linearity between 0.15 and 100 pg μL-1 with a significant R2 value (R2 = 0.9994) toward Se metal. Besides, the Se limit of detection (LOD) and limit of quantification (LOQ) are 0.063 pg μL-1 and 0.147 pg μL-1, respectively. Further, by utilizing tap and river water samples, the applicability of the validated method was tested; the approach showed high Se recovery values in the range of 87.6-115.5% for the spiked real-world samples and the interday and intraday precision (RSD%) values of the approach were 4.8% (n = 6). The MNC-SPE can be regenerated and reused for four consecutive extraction-desorption cycles by employing 0.5 M NaOH eluent.

Optimization of Isocratic Ion Chromatography Methods for Simultaneous Inorganic Anions and Carboxylic Acids Determination

As a part of preliminary studies, the possibility of quantitative oxidation of aldehydes to carboxylic acids and their determination by isocratic ion chromatography with conductometric detection has been tested. A methodology for the simultaneous separation of inorganic anions (F-, Cl-, NO2-, Br-, NO3-, PO43-, SO42-) and carboxylic acids (formate, acetate and oxalate) by using isocratic ion chromatography with conductivity detection have been developed and validated. Six anion-exchange columns were tested. The best results were achieved for Dionex IonPac AS10 column with 50mM NaOH eluent and flow rate of 1.0 mL∙min-1.

High-efficient phosphate removal from wastewater by weak magnetic La(OH)3 modified platanus biochar

An adsorbent of weak magnetic La(OH)3 modified platanus biochar (La-MB) was synthesized for phosphate (P) removal by iron lanthanum sequential modification method for the first time. Compared with synchronous modification method, La-MB had higher P adsorption capacity and similar magnetic separation property. The performance of La-MB was evaluated in terms of adsorption isotherms, adsorption kinetics, coexisting competitive substances, regenerative ability, and it as fixed-bed column filler to remove P from actual wastewater. The results showed that La-MB had a monolayer P adsorption capacity of 116 mg/g in the pH range of 3.0–9.0 at 35 ℃ with the contact time of 45 min, and the adsorption capacity was higher than most La-modified magnetic adsorbents. The coexisting SO2–4, NO-3 and Cl- had no effect, while the HCO-3, CO2–3 and humic acid interfered with the removal of P due to competition for active sites on the surface of La-MB. Moreover, approximately removal efficiency of 97% was remained after three adsorption-desorption cycles in 1.0 mol/L NaOH eluent, which showed the outstanding stability and cyclic utilization. The maximum treatment bed-volumes (BV) under influent flow rates of 0.5 mL/min, 1.0 mL/min and 1.5 mL/min were 3050 BV, 2000 BV and 1100 BV, respectively. The characterization results of zeta potential, FTIR and XPS revealed that the P adsorption of La-MB was dominated by ligand exchange, inner sphere complexation and electrostatic attraction. All results indicated that La-MB could serve as a promising adsorbent for the efficient removal of P from actual wastewater.

Desorption of Congo red from dye-loaded Phoenix dactylifera date stones and Ziziphus lotus jujube shells

In this work, desorption of Congo red (CR) from dye-loaded phoenix dactylifera date stones (DS-CR) and Zizyphus lotus jujube shells (JS-CR) was investigated. The effects of operating parameters such as different eluents, volume and concentration of eluent, contact time and temperature on desorption of CR from the DS-CR and JS-CR were studied. Experimental results showed that NaOH eluent had better desorption than HCl, HNO3, H2SO4, H3PO4, KOH, NaHCO3, Na2CO3, H2O, CH3OH, C2H5OH and C3H6O. The desorption efficiency increased with increase in volume and concentration of eluent, contact time and temperature. The maximum desorption efficiency of CR from the DS-CR and JS-CR was 92.89% and 86.27%, respectively. The biosorbents can be easily regenerated using NaOH eluent and reused for the dye sorption for four the consecutive biosorption/desorption cycles with high removal of CR, suggesting their applicability toward the textile industry and water purification purpose.

Development of retention mechanism for the separation of carboxylic acids and inorganic anions in cryptand-based ion chromatography

The ion-exchange and complex forming equilibria were quantitatively described and demonstrated in order to understand major factors in the control of selectivity in the analytical separation of carboxylic acids and inorganic anions in cryptand based ion chromatography. A complex retention model has been developed for the separation on a non-conventional IC column. Changes in retention are treated both theoretically and experimentally. Retention mechanism is employed on a macrocycle-based (cryptand n-decyl-[2.2.2]) ion-exchange chromatographic phase to improve the selectivity for a mixture of model analytes. We introduced an alternative internal gradient method by mixed eluent (i.e. eluents formed by combination of two alkali hydroxide with different molar ratio). The effect of binary mixed eluent (Li/Na, Li/K) on the retention behavior and peak shape of carboxylic acids are also discussed in view of the proposed theory. It was shown that the effects of binary aqueous mobile phases, held isocratically behave very similar to the step gradient mode. The "internal gradient” separation system has advantages over traditional step gradient mode. Twenty-six anions of widely varying chemical character (mono-, di-, tri-valent inorganic anions, mono-, di-, tri-valent aliphatic carboxylic acids, aromatic- and haloacetic carboxylic acids) were investigated on the cryptand-based (D222) stationary phase using different methods by LiOH, NaOH and KOH eluent. The predicted vs measured retention data are in rather good agreement. High degree of linearity was obtained for inorganic anions, multivalent carboxylic acids, and for aromatic and haloacetic acids R2 = 0.992, 0.969, and 0.980, respectively.

Study on the adsorption and desorption performance of magnetic resin for Congo red

ABSTRACT This study was to evaluate the adsorption capability of a magnetic resin (NDMP) to the removal of Congo red (CR) from aqueous solution. The adsorption kinetic and isotherm of NDMP were studied, as well as the desorption performance of NDMP. The results showed that the adsorption process of NDMP on CR was more suitable for Pseudo-second-order kinetic model. The whole adsorption process was affected by intraparticle diffusion and ion exchange. The adsorption isotherm of CR by NDMP was fitted better with Langmuir model. It showed that the adsorption of CR on NDMP resin was single layer adsorption. The maximum adsorption capacity (Qm ) of CR at 308 K can reach 354.29 mg/g. In the desorption, 10% NaCl and NaOH eluents had better desorption rate for CR than other mass fraction. While NaCl(10%)-MeOH mixed eluent with volume ratio of 3:7 had the best regeneration performance. The desorption rate can reach 90% within 30 min. The adsorption performance of NDMP on CR didn't decrease after 13 times successive adsorption–desorption by NaCl(10%)-methanol eluent, indicating that NDMP can be efficiently regenerated. The excellent adsorption–desorption performance of NDMP on CR suggests that the magnetic resin has a great potential for treating CR dye wastewater.

Spiramycin adsorption behavior on activated bentonite, activated carbon and natural phosphate in aqueous solution.

Efficacy of activated bentonite, activated carbon, and natural phosphate under experimental conditions was tested as low-cost adsorbents for spiramycin antibiotic removal from aqueous solution. Equilibrium kinetic and isotherm adsorption process are well described by pseudo-second order and Langmuir isotherm models for activated bentonite and activated carbon, while natural phosphate follows pseudo-first order and Freundlich models, respectively. Obtained results revealed that activated bentonite has the highest adsorption capacity (260.3mg/g) as compared to activated carbon (80.3mg/g) and natural phosphate (1.7mg/g). The adsorption capacity decreases for all adsorbents in the presence of NaCl. The adsorption processes are facilitated in the alkaline pH range for activated bentonite and activated carbon, whereas, for natural phosphate, the acidic pH range is favorable. They are involving ion exchange and hydrogen bond mechanisms as well as Van der Waals forces and also π interactions for activated carbon. Thermodynamic calculation shows that spiramycin adsorption is endothermic and spontaneous on all adsorbents. The activated bentonite reusability is more efficient by more than 95% in two-step desorption using NaOH and HCl eluents compared to activated carbon. Thus, activated bentonite is a promising adsorbent for spiramycin removal from aqueous solution.

Hydrothermal assisted magnetic nano-hydroxyapatite encapsulated alginate beads for efficient Cr(VI) uptake from water

The biopolymer, alginate can be made into various usable forms like beads, membrane and candle for the development of water technology. In the present study, an attempt has been made to prepare the alginate in an usable bead form. Here, magnetic nano-hydroxyapatite encapsulated alginate beads (Fe3O4@n-HApAlg) were synthesized by hydrothermal method for selective chromium removal. The synthesized Fe3O4@n-HApAlg beads have enhanced chromium sorptive capacity (SC) of 29.14 mg/g than the individual components. The synthesized materials were characterized by various instrumental techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) isotherm studies. The Cr(VI) sorptive mechanism of Fe3O4@n-HApAlg beads were interpreted by electrostatic attraction. Sorption behavior of the magnetic beads was explained using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The thermodynamic studies indicate the spontaneous and endothermic nature of Cr(VI) sorption. In the kinetic data demonstration, pseudo-first-order, pseudo-second-order, intra particle diffusion and particle diffusion models were employed. The reusability of Fe3O4@n-HApAlg beads was carried out using NaOH eluent and they can be used upto five cycles. The magnetic alginate hybrid beads showed the promising results against the chromium contaminated groundwater by removing Cr(VI) ions below the tolerance limit.

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.

Two-dimensional ion chromatography for the separation of ionic organophosphates generated in thermally decomposed lithium hexafluorophosphate-based lithium ion battery electrolytes

A two-dimensional ion chromatography (IC/IC) technique with heart-cutting mode for the separation of ionic organophosphates was developed. These analytes are generated during thermal degradation of three different commercially available Selectilyte™ lithium ion battery electrolytes. The composition of the investigated electrolytes is based on 1M lithium hexafluorophosphate (LiPF6) dissolved in ethylene carbonate/dimethyl carbonate (50:50wt%, LP30), ethylene carbonate/diethyl carbonate (50:50wt%, LP40) and ethylene carbonate/ethyl methyl carbonate (50:50wt%, LP50). The organophosphates were pre-separated from PF6− anion on the low capacity A Supp 4 column, which was eluted with a gradient step containing acetonitrile. The fraction containing analytes was retarded on a pre-concentration column and after that transferred to the high capacity columns, where the separation was performed isocratically. Different stationary phases and eluents were applied on the 2nd dimension for the investigation of retention times, whereas the highly promising results were obtained with a high capacitive A Supp 10 column. The organophosphates generated in LP30 and LP40 electrolytes could be separated by application of an aqueous NaOH eluent providing fast analysis time within 35min. For the separation of the organophosphates of LP50 electrolyte due to its complexity a NaOH eluent containing a mixture of methanol/H2O was necessary. In addition, the developed two dimensional IC method was hyphenated to an inductively coupled plasma mass spectrometer (ICP-MS) using aqueous NaOH without organic modifiers. This proof of principle measurement was carried out for future quantitative investigation regarding the concentration of the ionic organophosphates. Furthermore, the chemical stability of several ionic organophosphates in water and acetonitrile at room temperature over a period of 10h was investigated. In both solvents no decomposition of the investigated analytes was observed and therefore water as solvent for dilution of samples was proved as suitable.

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.

DETERMINATION OF SULFATE IN COASTAL SALT MARSH SEDIMENTS WITH HIGH-CHLORIDE CONCENTRATION BY ION CHROMATOGRAPHY: A REVISED METHOD

In order to elucidate the relationship between sulfate reduction and mineralization of organic matter in coastal sediments, the content of sulfate in sediment samples should be measured. Chloride, sulfate, bromide, nitrate, and phosphate are the standard anions in coastal sediment samples. Ion chromatography (IC) is one of the popularly used techniques for determinations of these anions. However, the peaks of the five anions in the IC system coincide with each other under high chloride conditions when using the normal method. In this article, an improved, highly sensitive method for simultaneous separation and determination of sulfate, bromide, nitrate, and phosphate in the samples with high chloride concentration is established and evaluated by IC. In high concentrations of chloride samples, the effects of eluent concentration on the retention time and separation of other anions are studied. The peaks of these anions can be well separated on an AS11 ion-exchange column by a low concentration of NaOH eluent (10 mM). in one injection. Gradient elution is helpful to shorten retention time, especially for phosphate. The method detection limit of sulfate is 0.091 mg · L−1. The recovery of sulfate ranged from 100.5% to 106.8%, when the concentrations of standard solution are close to those of the samples. This technique was validated by determining the content of sulfate and chloride in coastal salt marsh sediment samples.

Evaluation of a liquid chromatography method for compound‐specific δ13C analysis of plant carbohydrates in alkaline media

Isotope analysis of carbohydrates is important for improved understanding of plant carbon metabolism and plant physiological response to the environment. High-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS) for direct compound-specific δ(13)C measurements of soluble carbohydrates has recently been developed, but the still challenging sample preparation and the fact that no single method is capable of separating all compounds of interest hinder its wide-spread application. Here we tested in detail a chromatography method in alkaline media. We examined the most suitable chromatographic conditions for HPLC/IRMS analysis of carbohydrates in aqueous conifer needle extracts using a CarboPac PA20 anion-exchange column with NaOH eluent, paying specific attention to compound yields, carbon isotope fractionation processes and the reproducibility of the method. Furthermore, we adapted and calibrated sample preparation methods for HPLC/IRMS analysis. OnGuard II cartridges were used for sample purification. Good peak separation and highly linear and reproducible concentration and δ(13)C measurements were obtained. The alkaline eluent was observed to induce isomerization of hexoses, detected as reduced yields and (13)C fractionation of the affected compounds. A reproducible pre-purification method providing ~100% yield for the carbohydrate compounds of interest was calibrated. The good level of peak separation obtained in this study is reflected in the good precision and linearity of concentration and δ(13)C results. The data provided crucial information on the behaviour of sugars in LC analysis with alkaline media. The observations highlight the importance for the application of compound-matched standard solution for the detection and correction of instrumental biases in concentration and δ(13)C analysis performed under identical chromatographic conditions. The calibrated pre-purification method is well suited for studies with complex matrices that disable the use of a spiked internal standard for the detection of procedural losses.

Determination of phenols with ion chromatography–online electrochemical derivatization based on porous electrode–fluorescence detection

The current study describes the determination of phenols using ion chromatography–online electrochemical derivatization–fluorescence detection (IC/ED/FD). Six model phenols including 4-methylphenol (pMP), 2, 4-dimethylphenol (DMP), 4-tert-butylphenol (TBP), 4-hydroxylphenolacetic acid (pHPA), 4-acetamidophenol (pAAP), and phenol (P) were well separated on an anion-exchange column under ion exchange mode using NaOH with small amount of acetonitrile added as eluent. Online electrochemical derivatization performed via a laboratory-made electrolytic cell (EC), consisting of porous titanium electrode and cation-exchange membrane (CEM), allows the oxidation products that are strongly fluorescent to be detected by the fluorescence detector. NaOH eluent used in the present method matches well with the maximal fluorescence intensity obtained at alkaline condition for oxidized phenols, thus the addition of specific buffer solution after oxidation encountered in previous report could be eliminated. This process leads to a simplified procedure. The proposed method was sensitive to the limits of detection in the range of 0.4μg/L and 3.8μg/L and the limits of quantification between 1.2μg/L and 13μg/L due to the strong electro-oxidation capacity of porous titanium electrode, as well as the implementation of time-programmed potential over EC. The linear ranges were 2.0–1.0×104μg/L for pAAP and DMP, and 10–1.0×104μg/L for P, pMP, pHPA, and TBP, respectively. The relative standard deviations range from 0.9% to 4.8%. The utilization of the method was demonstrated by the analysis of real samples. The average spiked recoveries of target analytes in pool water were 81.0–118%.

HPLC Separation of All Aldopentoses and Aldohexoses on an Anion-Exchange Stationary Phase Prepared from Polystyrene-Based Copolymer and Diamine: The Effect of NaOH Eluent Concentration

To investigate the separations of all aldopentoses (ribose, arabinose, xylose and lyxose) and aldohexoses (glucose, galactose, allose, altrose, mannose, gulose, idose and talose) on the D6 stationary phase prepared by the reaction of chloromethylated styrene-divinylbenzene copolymer and N,N,N’,N’-tetramethyl-1,6-diaminohexane, we examined the effect of varying the concentration of the NaOH eluent on the elution orders. Separations of these aldoses were achieved using a 20 mM NaOH eluent. The elution behaviors of the aldoses were probably due to not only the individual pKa values, but also the chemical structures of the cyclic aldoses.

Batch Adsorption and Mechanism of Cr(VI) Removal from Aqueous Solution by Polyaniline/Humic Acid Nanocomposite

Polyaniline (PANI) and humic acid (HA) composite sorbents were prepared by adding different amount of HA into the chemical oxidation process of PANI. The sorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and N2 adsorption and desorption. Batch adsorption results showed that the sorbent PANI/HA-1 had the best affinity to Cr(VI) in aqueous solution. The adsorption kinetics results of Cr(VI) indicated that the adsorption reached equilibrium within 120 min, and adsorption rate could be described by pseudo second order kinetics. Sorption of Cr(VI) onto PANI/HA-1 fitted the Freundlich adsorption model better than the Langmuir adsorption model. The results of zeta potential measurement and batch experiments showed that the PANI/HA-1 was stable in the pH range of 4–7. The desorption results indicated NaOH eluent had better desorption rate than HCl eluent. The electrochemical-controlled desorption result showed that the loaded Cr(VI) on the PANI/HA-...

Minor glucans from Laetiporus sulphureus basidiocarps

We have continued research on basidiocarps of Laetiporus sulphureus (Bull.:Fr.) Murr grown by implantation under Irkutsk Oblast conditions [1–3]. Alkaline-soluble polysaccharides (ASPS) of this species were found to contain glucans, the dominant component of which was laetiglucan I, a linear -(1 3)-glucan [3]. Herein we study the structures of minor glucans from L. sulphureus. Basidiocarps of L. sulphureus (80 g) were processed as before in order to isolate ASPS [3]. Separation of the ASPS complex produced fractions LSA-1a (11.62 g, laetiglucan I), LSA-1b (1.80 g), and LSA-2 (0.99 g) [3]. LSA-1b contained two components, LSA-1b-1 and LSA-1b-2, which were isolated by preparative gel chromatography (Sephadex G-200, 3 80 cm, NaOH eluent, 0.01 M). LSA-1b (1.5 g) afforded LSA-1b-1 (1.06 g) and LSA-1b-2 (180 mg). LSA-1b-1. MW 180 kDa. IR and 13C NMR spectra and methylation agreed with those of laetiglucan I [3]. LSA-1b-2. MW 150 kDa, [ ]D –21° (c 0.25, 0.1 M NaOH). IR spectrum ( , cm –1): 3289, 2933, 1645, 1342, 1140, 1021, 922, 890 ( -bond), 819. Only glucose was observed after total hydrolysis. Periodate oxidation consumed 0.266 mol of IO4 – per anhydro unit and released 0.131 mol of HCOOH. The hydrolysate after reduction and Smith degradation of the polysaccharide oxidized by periodate contained glycerine and glucose in a 1:6.7 mole ratio. Glycerine was released from terminal glucose units. The presence of glucose indicated that (1 3)-bonds stable to periodate were present. Hydrolysis of the acetylated derivative of LSA-1b-2 oxidized by CrO3 did not produce hexoses. This was possible if its anomeric centers had the -configuration. Methylation of LSA-1b-2 produced a hydrolysate with permethylate 2,3,4,6-tetra-O-Me-Glcp; 2,4,6-tri-O-Me-Glcp; and 2,4-di-O-Me-Glcp in a 1:5.69:1.02 ratio. This indicated that the structure of LSA-1b-2 was a polysaccharide, the main chain of which consisted of (1 3)-bound glucose units substituted 14.7% at the C-6 position with single glucose units. 13C NMR data conformed that LSA-1b-2 was an O-6 branched -(1 3)-glucan (Table 1) [4–6]. LSA-2 was demineralized and deproteinated before being studied. This produced fraction LSA-2 (82% yield per LSA-2 mass). Low-molecular-weight impurities were removed from LSA-2 over a column of Molselect G-25 (3 20 cm, water eluent) and then over Sephadex G-100 (2 60 cm, water eluent). The resulting LSA-2 (534 mg) was a homogeneous polysaccharide. LSA-2 . MW 110 kDa, [ ]D +211° (c 0.18, 0.1 M NaOH). IR spectrum ( , cm –1): 3447, 2932, 1382, 1274, 1155, 1048, 1018, 917, 841 ( -bond), 763, 611. The polymer consisted only of glucose and did not undergo periodate oxidation. The hydrolysate after oxidation of its peracetate by CrO3 contained glucose. The hydrolysate after methylation of LSA-2 contained 2,4,6-tri-O-Me-Glcp as the main product and traces of 2,3,4,6-tetra-O-Me-Glcp. The 13C NMR spectrum of LSA-2 showed six resonances. The position of the resonance for C-1 (100.51 ppm) corresponded with the -configuration of the glucoses whereas the shift of the resonance of C-3 to weak field was due to glycosylation of this position, indicating a (1 3)-type bond (Table 1). The data enable LSA-2 to be identified as a linear -(1 3)-glucan [7, 8]. The studied polysaccharides LSA-1b-2 and LSA-2 were called laetiglucans II and III and were the type of glucans first isolated from L. sulphureus basidiocarps.

A versatile method for stable carbon isotope analysis of carbohydrates by high‐performance liquid chromatography/isotope ratio mass spectrometry

We have developed a method to analyze stable carbon isotope ((13)C/(12)C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent concentration of 1 mM resulted in low background signals and good separation of most of the typical plant neutral carbohydrates. We also show that more strongly bound carbohydrates such as acidic carbohydrates can be separated by inclusion of NO(3) (-) as an inorganic pusher ion in the eluent. Analyses of neutral carbohydrate concentrations and their stable carbon isotope ratios are shown for plant materials and marine sediment samples both at natural abundance and for (13)C-enriched samples. The main advantage of HPLC/IRMS analysis over traditional gas chromatography based methods is that no derivatization is needed resulting in simple sample treatment and improved accuracy and reproducibility.