Pre-concentration of trace elements in short chain alcohols using different commercial cation exchange resins prior to inductively coupled plasma-optical emission spectrometric detection

Chelex-100, Dowex 50W-x8 and Dowex MAC-3 exchange resins were investigated for separation and pre-concentration of trace amounts of Cd, Cr, Cu, Fe, Mn, Pb, Ti and Zn in alcohols with respect to retention and desorption characteristics. Dowex 50W-x8 was found to be the best sorbent with percentages recoveries >95%. In addition, Chelex-100 appeared to be suitable for the pre-concentration of Cu, Fe and Zn, whereas Dowex MAC-3 was selective for Cu and Fe. Therefore, Dowex 50W-x8 was used for further investigations. The relative standard deviations <4% (n = 20), limits of detection and quantification were 0.1–1.2 μg L⁻¹ and 0.3–1.5 μg L⁻¹, respectively. The SPE method was validated against a certified reference material and the results were in agreement with certified values. The accuracy of the optimized method was verified by the recovery test in the spiked alcohol samples. The accuracy and spike recovery test for different metal ions were in the range 98–102% and 95–105%, respectively. The optimized method was applied to the separation and pre-concentration of metal ions in different commercial alcohol samples.     

Influence of the ratio copper(II) to ligand concentrations and the nature of entering and leaving ligands on the lability of copper(II) complexes

The influence of the ratio Cu : L on the lability of copper(II) complexes with simple ligands of different thermodynamic stabilities (L=EDTA, NTA, cysteine, proline or glycine) was investigated in the range 4:1–1:3. Chelex-100 and chitin were used parallel and batch wise, to cause the dissociation of the complexes, and the results were compared. A few experiments were also performed with the yeast, Saccharomyces cerevisiae. The effect of the exposure time, between 5 and 30 min, and mass (or number of sites) of the particulate matter (PM), always in large excess, were also studied. For all systems, but Cucysteine with chitin, the lability of CuL showed no marked dependence on the mass of PM: when the mass of PM was duplicated, an increase in lability by ≤ 10% was found. For cysteine and proline with Chelex-100, and cysteine and glycine with chitin, the lability of Cu---L complexes markedly increased with the time of exposure, which indicated that the kinetics of the substitution reactions were relatively slow. These results indicate the role of both the leaving and entering ligands in the kinetics of the ligand substitution reactions. The effect of Cu : L on the complex dissociation was more marked with chitin than with Chelex-100. When the leaving ligand is in excess (Cu : L < 1) the magnitude of that excess did not affect markedly the lability. But, when Cu : L> 1, the lability decreased with the increase of the excess of metal for cysteine or glycine with Chelex-100, and for all ligands in presence of chitin. The heterogenous behaviour of the PM may be partially responsible for these results. A maximum lability was observed for 1:1 ratio, particularly for the complexes that are thermodynamically more stable. In the presence of yeast cells, the tendencies mentioned above were confirmed. The present results reinforce the operational character of the speciation studies based on lability data, and that relationship between lability and bioavailability must be analysed for each individual case and should not be extrapolated to different PM or experimental conditions.     

Complexation Kinetics of N‐Alkyl‐Substituted Diamino Diamides with Nickel (II) in Aqueous Solution

Equilibrium constants are deter mined for the protonation and metal complexation of the nickel(II) complexes with 4‐methyl‐4,7‐diazadecanediamide (4‐Me‐L‐2,2,2), 4,7‐dimethyl‐4,7‐diazadecanediamide (4,7‐N,N′‐Me₂‐L‐2,2,2), 4‐ethyl‐4,7‐diazadecanediamide (4‐Et‐L‐2,2,2), and 4‐methyl‐4,8‐ diazaundecane diamide (4‐Me‐L‐2,3,2), in 0.10 M KCl at 25.0°C. The formation kinetics of these nickel (II) complexes have been studied under the same conditions with use of the stopped‐flow technique. The possible path ways for the complexation reaction of nickel (II) with these ligands are discussed. The first metal‐nitrogen bond formation is proposed as the rate‐determining step for the reactions of nickel (II) with the unprotonated ligands; proton loss is the rate‐limiting step in the reactions of nickel (II) with the monoprotonated ligands. Similarly, in dissociation reactions of these nickel (II) complexes, the rate‐determining step for the water dissociation pathway is the break age of the second nickel‐nitrogen bond; the rate‐determining step for the proton‐assisted path way is the protonation of the released amino group. The important factors determining the reactivity of these complexes are considered. The kinetic results of the formation and dissociation reactions of these complexes are consistent with dissociative mechanism.     

Elimination of interferences in determination of platinum and palladium in environmental samples by inductively coupled plasma mass spectrometry

Various approaches were evaluated in order to eliminate the spectral interferences noted when Pt and Pd has to be determined in environmental dust samples by ICP-MS. The chemical separation of Pt and Pd from the matrix components on ion-exchange resins was applied. The performance of cation-exchange resins (Dowex 50 WX-8, Dowex 50 WX-2, Dowex HCR-S, Varion KS, Cellex-P) for the separation of interfering ions was then examined. It was found that Dowex 50 WX-8 shows best performance. The effects of mass, mesh number of resin and concentration of Cl⁻ ions on matrix separation were also studied. Another approach was to use the anion-exchange sorbent Cellex-T, which allows almost total retention of both analytes followed by their elution with 0.1 mol L⁻¹ thiourea in 1 mol L⁻¹ HCl. This procedure however can be used only for platinum determination by ICP-MS. The accuracy of proposed procedures was confirmed by the analysis of certified material BCR-723, and then it was used for determination Pt and Pd in samples of road dust.     

Kinetic speciation of nickel in mining and municipal effluents

This study presents the results of kinetic speciation of nickel in undiluted mining and municipal effluents and effluents diluted with receiving freshwaters from the surrounding environment. The dilution ratios used for the dilution of the effluents were arbitrarily chosen, but were representative of the prevailing mining practices. The purpose of the this dilution was to mimic dilution with natural waters that result from dilution of the mining and municipal effluents with receiving freshwaters, so that this study would reveal environmental realities that are of concern to the managers and regulators of water resources. Ligand exchange kinetics using the competing ligand exchange method (CLEM) was studied using two independent techniques: graphite furnace atomic absorption spectrometry (GFAAS) with Chelex 100 resin as the competing ligand, and adsorptive cathodic stripping voltammetry (AdCSV) with dimethylglyoxime (DMG) as the competing ligand to determine the percentage of Ni metal released from Ni(II)–DOC complexes and the rate of dissociation of Ni(II)–DOC complexes. Using a sample containing a mixture of 30% Copper Cliff Mine effluent, 40% Sudbury municipal effluent and 30% Vermillion River water, both techniques gave results showing that the dilution of the effluent samples increased the percentage of nickel released from Ni(II)–DOC complexes. This increase in the release of nickel from the Ni(II)–DOC complexes may be of concern to managers and regulators of water resources. Agreement between the results of these two techniques has enhanced the validity of the competing ligand exchange method used by both techniques.     

Kinetic study of uranium speciation in model solutions and in natural waters using Competitive Ligand Exchange Method

Kinetic speciation of uranium in model solutions containing uranium and humic acid (HA) and in natural waters has been investigated by Competitive Ligand Exchange Method (CLEM). In alkaline freshwaters, most of uranium species were uranium-carbonate species, which were labile in the CLEM experiment. The uranium speciation of every sample was characterized either as “labile” or “non-labile” uranium complexes depending on the dissociation rate coefficients of the complexes. The results showed that as the U(VI)/HA ratio was decreased, the dissociation rate coefficients decreased and the labile fraction decreased as well. When the U(VI)/HA ratio was 0.1, the labile fraction of the U(VI)-HA increased with increasing pH; however, there was no pH effect on the dissociation of U(VI)-HA complexes at lower U(VI)/HA ratios. Chelex-100 had some limitations in its use for the study of dissociation of U(VI)-HA complex at very low U(VI)/HA ratios. By developing an analytical method and procedure for quantitative determination of kinetic parameters for the dissociation of uranium-HA complexes in model solutions and natural waters, this work has made a substantial contribution to analytical chemistry.     

The CO/PC analogy in coordination chemistry and catalysis

This short account summarizes recent results obtained in the coordination chemistry of phosphinines and emphasizes their analogy with CO ligands. Reduced complexes can be easily assembled through the reaction of reduced 2,2′-biphosphinine dianions with transition metal fragments. Theoretical calculations were performed to establish the oxidation state of the metal in these complexes. Though many reduced complexes are available, phosphinines proved to be too sensitive toward nucleophiles to be used as efficient ligands in most catalytic processes. However, the high electrophilicity of the phosphorus atom can be exploited to synthesize phosphacylohexadienyl anions which exhibit a surprising coordination chemistry. When phosphino sulfide groups are incorporated as ancillary tridentate anionic SPS ligands can be easily produced. These ligands can bind different transition metal fragments such as M-X (M = group 10 metal, X = halogen), Rh-L (L = 2 electron donor ligand), Cu-X and Au-X (X = halogen). Palladium(II) complexes proved to be active catalyst in the Miyaura cross-coupling reaction. Bidentate anionic PS ligands were also synthesized following a similar approach. Their Pd(II) (allyl) derivatives showed a very good activity in the Suzuki catalyzed cross-coupling process that allows the synthesis of biphenyl derivatives through the reaction of phenylboronic acid with bromoarenes.     

Platzwechselvorgänge der Liganden in festen Komplexsalzen. Intermolekularer Ligandenaustausch in gemischten Hexahalogenokomplexen von Osmium(IV)

Ligand Exchange in Solid Complex Salts. II. Intermolecular Ligand Exchange in Mixed Hexahalo-complexes of Osmium(IV) On tempering a pure complex of the type K₂[OsCl_nY_6?n], Y = Br, I; n = 1–5 to 170–200°C all complexes with n = 0–6 are formed by intermolecular solid-state exchange reactions. At equilibrium the ligands are distributed statistically on all species. The rate of exchange is slow for complexes containing many I ligands. It increases with the number of Cl and has its maximum for complexes with many Br ligands. For the exchange mechanism the octahedral vacancies in the anti fluorite lattice are important.     

Kinetic studies of nickel speciation in model solutions of a well-characterized humic acid using the competing ligand exchange method

Publications on the binding characteristics of metals with humic acid (HA) are sparse. Here we investigated the release of nickel from Ni(II)-HA complexes using model solutions of three different [Ni(II)]/[HA] mole ratios at three different pH values; we also compared the results with those of [Ni(II)]/[FA] complexes from previous work in this laboratory. Ligand exchange kinetics using the competing ligand exchange method (CLEM) were studied using two different techniques: graphite furnace atomic absorption spectrometry (GFAAS) with Chelex 100 resin as the competing ligand, and adsorptive cathodic stripping voltammetry (AdCSV) with dimethylglyoxime as the competing ligand to measure the rate of dissociation of Ni(II)-HA complexes. The results of the kinetic studies showed that as the [Ni(II)]/[HA] mole ratio was decreased, the rate of dissociation of Ni(II)-HA complexes decreased, and the proportion of free Ni²⁺ ions plus very labile nickel complexes decreased while the proportion of the less labile kinetically distinguishable components increased. Generally, the rate of dissociation of Ni(II)-HA complexes was slower than that of Ni(II)-FA complexes. Studies on the validity of the kinetic model showed that the concentrations of chemical species varied in a reasonable way with pH and the [Ni(II)]/[HA] mole ratios, indicating that the kinetically distinguishable components have chemical significance and the kinetic model is valid.     

Heterogeneous kinetic studies of the hydrogen peroxide decomposition with some transition metal‐heterocyclic complexes

The heterocyclic compounds piperidine (Pip), piperazine (Pz), morpholine (Morph), and N‐methyl piperazine (N‐MPz) were used as ligands to form transition metal complexes with Ni(II), Cu(II), and Co(II) ions. These complexes were supported on Dowex‐50W resin so as to form new potential active catalysts for H₂O₂ decomposition in an aqueous medium. In all cases the reaction showed a first‐order kinetics with respect to H₂O₂ concentration, except with Co(II) complexes, the reaction showed a second‐order kinetics with 2% divinyl benzene (DVB) (50–100 mesh and 200–400 mesh). The rate constant k (per gram dry resin) was evaluated with a resin of cross‐linkage 2 and 8% DVB (50–100 mesh) and 2% DVB (200–400 mesh) over temperature range 25–40°C. With a given resin cross‐linkage, the rate constant has the following order: Ni(II) complexes < Co(II) complexes < Cu(II) complexes. With Pz ligand, k increased in the following sequence: Ni(II) complexes < Cu(II) complexes < Co(II) complexes. The reaction mechanisms of the first‐ and second‐order kinetics were discussed and the activation parameters were deduced. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 617–624, 2001     

Good linear relationship between logarithms of Eigen’s water exchange constants for several divalent metal ions and activation energies of corresponding metal-catalyzed alkoxysilane hydrolysis in ethylene-propylene copolymer system

Catalytic efficiencies of seven divalent metal acetylacetonate complexes [M(acac)₂; M = Cd(II), Co(II), Cu(II), Fe(II), Ni(II), Pb(II), and Zn(II)] with respect to the water-crosslinking kinetics of vinyltrimethoxysilane-grafted ethylene-propylene copolymer (EPR-g-VTMS) were investigated to examine the effects of progressive changes in metal ion using ATR-FTIR spectroscopy. The hydrolysis activation energies of EPR-g-VTMS follows the order: No catalyst ≈ Ni(acac)₂ > Co(acac)₂ > Fe(acac)₂ ≈ Zn(acac)₂ > Cd(acac)₂ ≈ Cu(acac)₂ > Pb(acac)₂. Interestingly, the kinetics results revealed that the plots of hydrolysis activation energies of EPR-g-VTMS containing M(acac)₂ complexes and Eigen’s water exchange constants for corresponding metal ions showed a excellent linear relationship, suggesting that the reaction pathway for the silane water-crosslinking with hydrous M(acac)₂ complex in EPR-g-VTMS system may be similar to that for water exchange of the metal ion in an aqueous system. Based on the knowledge of traditional kinetics studies by Eigen and Wilkins and hybrid sol-gel chemistry, the plausible catalytic mechanism for M(acac)₂ complexes in EPR-g-VTMS system was proposed.     

Flame atomic absorption spectrometric determination of cadmium(II) and lead(II) after their solid phase extraction as dibenzyldithiocarbamate chelates on Dowex Optipore V-493

An enrichment procedure for cadmium and lead after their solid phase extraction as dibenzyldithiocarbamate chelates on Dowex Optipore V-493 has been established prior to their flame atomic absorption spectrometric determinations. The analytical parameters including pH, amounts of dibenzyldithiocarbamate, sample volume, etc., were investigated. The effects of alkaline and earth alkaline ions and some metal ions on the retentions of analytes on Dowex Optipore V-493 resin were examined. Under the optimized conditions, the detection limits (3s, n = 21) for cadmium and lead were 0.43 μg L⁻¹ and 0.65 μg L⁻¹, respectively. The relative standard deviation (R.S.D.), and the recoveries of standard addition for this method were lower than 5% (n = 11) and 95-102%, respectively. Three standard reference samples (LGC 6010 Hard drinking water, NIST SRM 2711 Montana soil and GBW 07605 Tea) were introduced for accuracy and precision of analytical data. The proposed solid phase extraction system was successfully applied to the analysis of environmental samples.     

Tunable transition metal-ligand complexation for enhanced elucidation of flavonoid diglycosides by electrospray ionization mass spectrometry

A tunable ESI-MS/MS strategy for differentiation of flavone and flavanone diglycoside isomers based on metal complexation with auxiliary ligands is reported. The addition of a metal salt and an auxiliary ligand to a flavonoid solution results in the formation of [M(II) (flavonoid-H) auxiliary ligand](+) complexes, where M(II) is a transition metal. A series of auxiliary ligands with electron-withdrawing substituents were synthesized to tailor the relative metal binding affinities of the ligands and thus directly influence the stabilities, and consequently the dissociation pathways, of the complexes. Upon collisionally activated dissociation, the complexes yield fragmentation patterns in which the abundances of key diagnostic ions are enhanced, thus facilitating isomer differentiation.     

Fractionation analysis of manganese and zinc in beers by means of two sorbent column system and flame atomic absorption spectrometry

In the present article, a method of operational fractionation of Mn and Zn in beer using flame atomic absorption spectrometry was developed. The proposed fractionation scheme was based on use of a hydrophobic adsorbing resin Amberlite XAD7 (first column, 2 g resin bed) connected in a series with a strong cation exchanger Dowex 50Wx4 (second column, 1 g resin bed). After passing the samples of beers through the columns, distinct groupings of Mn and Zn species retained on the sorbents, i.e., hydrophobic fraction of polyphenols bound metal species and cationic metal species fraction, respectively, were determined in respective eluates obtained after complete recovery of Mn and Zn species with 10 ml of 2.0 mol l⁻¹ HNO₃ (first column) and 10 ml of 4.0 mol l⁻¹ HCl (second column). In addition, the effluents collected were analyzed prior to the evaluation of the third, residual fraction, presumably attributed to any hydrophilic anionic and inert metal species. The established fractionation patterns for Mn and Zn were discussed in reference to likely associations of metals with endogenous food bioligands and possible availability of the distinguished metal species classes. The quality of the results was proved by the recovery experiments.     

Development of a new analytical approach based on cellulose membrane and chelator for differentiation of labile and inert metal species in aquatic systems

A new procedure was developed in this study, based on a system equipped with a cellulose membrane and a tetraethylenepentamine hexaacetate chelator (MD-TEPHA) for in situ characterization of the lability of metal species in aquatic systems. To this end, the DM-TEPHA system was prepared by adding TEPHA chelator to cellulose bags pre-purified with 1.0 mol L⁻¹ of HCl and NaOH solutions. After the MD-TEPHA system was sealed, it was examined in the laboratory to evaluate the influence of complexation time (0-24 h), pH (3.0, 4.0, 5.0, 6.0 and 7.0), metal ions (Cu, Cd, Fe, Mn and Ni) and concentration of organic matter (15, 30 and 60 mg L⁻¹) on the relative lability of metal species by TEPHA chelator. The results showed that Fe and Cu metals were complexed more slowly by TEPHA chelator in the MD-TEPHA system than were Cd, Ni and Mn in all pH used. It was also found that the pH strongly influences the process of metal complexation by the MD-TEPHA system. At all the pH levels, Cd, Mn and Ni showed greater complexation with TEPHA chelator (recovery of about 95-75%) than did Cu and Fe metals. Time also affects the lability of metal species complexed by aquatic humic substances (AHS); while Cd, Ni and Mn showed a faster kinetics, reaching equilibrium after about 100 min, and Cu and Fe approached equilibrium after 400 min. Increasing the AHS concentration decreases the lability of metal species by shifting the equilibrium to AHS-metal complexes. Our results indicate that the system under study offers an interesting alternative that can be applied to in situ experiments for differentiation of labile and inert metal species in aquatic systems.     

配合物生成反应速率常数与平衡常数之间的直线自由能关系 II: 镍(II)-N-(对位取代苯基)氨基乙酸配合物的生成反应动力学研究

应用断流分光光度计(Stopped-Flow Spectrophotometer)研究了镍(II)与N-(对位取代苯基)氨基乙酸-(ρ-RC6H4NHCH2COOH, R=CH3O, CH3, H, Cl, 简写为NROH或HL)在25℃及30%(v/v)乙醇溶液中生成配合物的反应动力学. 实验结果表明, 不仅氨基酸配体的负离子(NRO^-或L^-)具有较高的反应活性, 而且两性离子(HN^+RO^-或^+HL^-)也是有效的反应配体. 反应按双途径进行, 即按Eigen-Tamm机理进行的NRO^-途径和以质子迁移为速率控制步骤的两性离子途径. 两性离子的反应活性(以log kHL^±表示)与配体的碱性强度(pK2)之间呈现直线自由能关系. 并发现镍(II)配合物的离解反应速率常数(log k-L^-)与配体的碱性强度(pK2)和配合物的稳定常数(log KNiL^N^i)之间均存在直线自由能关系.     

Investigation on sorption equilibria of Mn(II), Cu(II) and Cd(II) on a carboxylic resin by the Gibbs-Donnan model

Sorption mechanism of bivalent metal ions on a weak cationic resin containing the carboxylic group is studied. The Gibbs-Donnan model is used to describe and then to predict the sorption through the determination of the intrinsic complexation constants. These quantities characterize the sorption being independent of experimental conditions. They are determined according to a well established procedure and using a recently proposed iterative method for calculation of counter ion concentration in the resin phase. Sorption mechanisms are also studied adding appropriate soluble ligands whose complexing properties are exactly known to the solution containing the resin and the metal ion. Competing with the resin for the complexation of the metal, they shift the sorption curve to higher pH and often this allows detecting other complexes between the metal and the resin. In this way for Mn(II), besides the 1:1 complex formed in the more acidic solution, with logbeta(110)=-4.55, the complex ML(2), characterized by logbeta(120)=-9.80, is found; for Cd(II), besides the ML complex, with logbeta(110)=-3.01, at pH higher than 7, the specie MLOH with logbeta(11-1)=-8.28. For Cu(II) the complex ML(2) is detected, confirming previous findings, with logbeta(120)=-7.24. In the presence of two different ligands, sulphosalicylic and malonic acid, a different complex, ML(2)OH, is identified, with the same intrinsic complexation constant for the two ligands, logbeta(12-1)=-13.35. As expected from the model, the intrinsic complexation constants, especially for the 1:1 complex, are in a good agreement with the complexation constants of acetic acid.     

Application of permeation liquid membrane and scanned stripping chronopotentiometry to metal speciation analysis of colloidal complexes

The potential of permeation liquid membrane (PLM) to obtain dynamic metal speciation information for colloidal complexes is evaluated by measurements of lead(II) and copper(II) complexation by carboxyl modified latex nanospheres of different radii (15, 35, 40 and 65 nm). The results are compared with those obtained by a well characterized technique: stripping chronopotentiometry at scanned deposition potential (SSCP). Under the PLM conditions employed, and for large particles or macromolecular ligands, membrane diffusion is the rate-limiting step. That is, the flux is proportional to the free metal ion concentration with only a small contribution from labile complexes. In the absence of ligand aggregation in the PLM channels, good agreement was obtained between the stability constants determined by PLM and SSCP for both metals.     

Magnetism of metal-nitroxide compounds involving bis-chelating imidazole and benzimidazole substituted nitronyl nitroxide free radicals

Coordination compounds based on imidazole and benzimidazole substituted nitronyl nitroxide radicals with transition metal ions and trivalent lanthanide ions are described from the perspective of their magnetic properties.For the transition metal compounds the crystal structures show various metal-nitroxide dimensionalities including mononuclear (0D), one-dimensional (1D) and two-dimensional (2D) complexes. The mononuclear complexes were isolated with most metal ions of the first transition series. One copper(II) complex shows a copper(II)-radical ferromagnetic coupling (J = +75 cm⁻¹) while for the other mononuclear compounds, mainly with manganese(II), the metal-radical interactions are antiferromagnetic. The one-dimensional and two-dimensional complexes are manganese(II) compounds which show canting effects leading to weak ferromagnetism.For the trivalent lanthanide ions [La(III), Gd(III) and Eu(III)], three series of mononuclear complexes were obtained in which the metal center is bound to four, two or one nitroxide radicals depending on the counter ions and ancillary ligands. Unexpectedly, in most gadolinium(III) complexes, the Gd(III)-radical interactions were found to be antiferromagnetic in contradiction with other foundings and previous theoretical models. In support to the magnetic studies, the optical properties of the lantanide complexes have also been investigated and are briefly described.     

Determination of the glycosylation site of flavonoid monoglucosides by metal complexation and tandem mass spectrometry

Metal complexation and tandem mass spectrometry were used to differentiate C- and O-bonded flavonoid monoglucoside isomers. Electrospray ionization of solutions containing a flavonoid glycoside and a metal salt led to the generation of the key [M(II) (L) (L-H)](+) complexes, where M is the metal ion and L is the flavonoid glycoside. Thirteen flavonoid monoglucosides were examined in combination with Ca(II), Mg(II), Co(II), Ni(II), and Cu(II). Collisional activated dissociation (CAD) of the [M(II) (L) (L-H)](+) complexes resulted in diagnostic mass spectra, in contrast to the CAD mass spectra of the protonated, deprotonated, and sodium-cationized flavonoid glucosides. Five common sites of glycosylation could be predicted based on the fragmentation patterns of the flavonoid glucoside/magnesium complexes, while flavonoid glucoside/calcium complexes also were effective for location of the glycosylation site when MS(3) was employed. Cobalt, nickel and copper complexation had only limited success in this application. The metal complexation methods were also applied for characterization of a flavonoid rhamnoside, and the dissociation pathways of the metal complexes indicate that flavonoid rhamnosides have distinctive dissociation features from flavonoid glucosides.