The i.r. spectrum of berkelium-249

The spectrum of ²⁴⁹Bk, excited in an electrodeless lamp, has been recorded between 3700 and 12,000 cm^?1 on a Fourier-transform spectrometer. The strongest 90 lines are listed along with the classification for 77 of them. The lowest levels of the 5f⁹6d7s, 5f⁹7s7p, 5f⁹7s8s, 5f⁸6d7s² , 5f⁸7s²7p and 5f⁸6d7s7p configurations of Bk I and of the 5f⁹6d and 5f⁹7p configurations of Bk II have been identified. Lists of the energies and hfs data of the Bk I levels involved in the i.r. transitions are also included.     

Reactions of the cycloheptatrienyl complexes [MX(CO)2(η-C7H7)] (M=Mo, X=Br; M=W, X=I) with CNBu: X-ray crystal structure of [WI(CO)2(CNBu)2(η-C7H7)]

Reaction of [MX(CO)₂(η⁷-C₇H₇)] (M=Mo, X=Br; M=W, X=I) with two equivalents of CNBu^t in toluene affords the trihapto-bonded cycloheptatrienyl complexes [MX(CO)₂(CNBu^t)₂(η³-C₇H₇)] (1, M=Mo, X=Br; 2, M=W, X=I). The X-ray crystal structure of 2 reveals a pseudo-octahedral molecular geometry with an asymmetric ligand arrangement at tungsten in which one CNBu^t is located trans to the η³-C₇H₇ ring. Treatment of 2 with tetracyanoethene results in 1,4-cycloaddition at the η³-C₇H₇ ring to give [WI(CO)₂(CNBu^t)₂{η³-C₉H₇(CN)₄}], 3. The principal reaction type of the molybdenum complex 1 is loss of carbonyl and bromide ligands to afford substituted products [MoBr(CNBu^t)₂(η⁷-C₇H₇)] 4 or [Mo(CO)(CNBu^t)₂(η⁷-C₇H₇)]Br. Reaction of [MoBr(CO)₂(η⁷-C₇H₇)] with one equivalent of CNBu^t in toluene at 60°C affords [MoBr(CO)(CNBu^t)(η⁷-C₇H₇)], 5, which is a precursor to [Mo(CO)(CNBu^t)(NCMe)(η⁷-C₇H₇)][BF₄], 6, by reaction with Ag[BF₄] in acetonitrile. In contrast with the parent dicarbonyl systems [MoX(CO)₂(η⁷-C₇H₇)], complexes of the Mo(CO)(CNBu^t)(η⁷-C₇H₇) auxiliary, 5 and 6, do not afford observable η³-C₇H₇ products by ligand addition at the molybdenum centre.     

PrB7−: A Praseodymium‐Doped Boron Cluster with a PrII Center Coordinated by a Doubly Aromatic Planar η7‐B73− Ligand

The structure and bonding of a Pr‐doped boron cluster (PrB₇⁻) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB₇⁻ is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB₇. Global minimum searches and comparison between experiment and theory show that PrB₇⁻ has a half‐sandwich structure with C_6v symmetry. Chemical bonding analyses show that PrB₇⁻ can be viewed as a Pr^II[η⁷‐B₇³⁻] complex with three unpaired electrons, corresponding to a Pr (4f²6s¹) open‐shell configuration. Upon detachment of the 6s electron, the neutral PrB₇ cluster is a highly stable Pr^III[η⁷‐B₇³⁻] complex with Pr in its favorite +3 oxidation state. The B₇³⁻ ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide M^III[η⁷‐B₇³⁻] complexes.     

Effect of Must Hyperoxygenation on Sensory Expression and Chemical Composition of the Resulting Wines

This paper evaluates the effect of must hyperoxygenation on final wine. Lower concentrations of caftaric acid (0.29 mg·L⁻¹), coutaric acid (1.37 mg·L⁻¹) and Catechin (0.86 mg·L⁻¹) were observed in hyperoxygenated must in contrast to control must (caftaric acid 32.78 mg·L⁻¹, coutaric acid 5.01 mg·L⁻¹ and Catechin 4.45 mg·L⁻¹). In the final wine, hydroxybenzoic acids were found in higher concentrations in the control variant (gallic acid 2.58 mg·L⁻¹, protocatechuic acid 1.02 mg·L⁻¹, vanillic acid 2.05 mg·L⁻¹, syringic acid 2.10 mg·L⁻¹) than in the hyperoxygenated variant (2.01 mg·L⁻¹, 0.86 mg·L⁻¹, 0.98 mg·L⁻¹ and 1.50 mg·L⁻¹ respectively). Higher concentrations of total flavanols (2 mg·L⁻¹ in hyperoxygenated must and 21 mg·L⁻¹ in control must; 7.5 mg·L⁻¹ in hyperoxygenated wine and 19.8 mg·L⁻¹ in control wine) and polyphenols (97 mg·L⁻¹ in hyperoxygenated must and 249 mg·L⁻¹ in control must; 171 mg·L⁻¹ in hyperoxygenated wine and 240 mg·L⁻¹ in control wine) were found in both the must and the control wine. A total of 24 volatiles were determined using gas chromatography mass spectrometry. Statistical differences were achieved for isobutyl alcohol (26.33 mg·L⁻¹ in control wine and 32.84 mg·L⁻¹ in hyperoxygenated wine), or 1-propanol (7.28 mg·L⁻¹ in control wine and 8.51 mg·L⁻¹ in hyperoxygenated wine), while esters such as isoamyl acetate (1534.41 µg·L⁻¹ in control wine and 698.67 µg·L⁻¹ in hyperoxygenated wine), 1-hexyl acetate (136.32 µg·L⁻¹ in control wine and 71.67 µg·L⁻¹ in hyperoxygenated wine) and isobutyl acetate (73.88 µg·L⁻¹ in control wine and 37.27 µg·L⁻¹ in hyperoxygenated wine) had a statistically lower concentration.     

Highly Active Catalysts for the Transfer Dehydrogenation of Alkanes: Synthesis and Application of Novel 7–6–7 Ring‐Based Pincer Iridium Complexes

A series of Ir–PCP pincer precatalysts [(7–6–7‐^RPCP)Ir(H)(Cl)] and [(7–6–7‐^ArPCP)Ir(H)(Cl)(MeCN)] bearing a novel “7–6–7” fused‐ring skeleton have been synthesized based upon the postulate that the catalytic species would have durability due to their rather rigid structure and high activity owing to the low but sufficient flexibility of their backbones, which are not completely fixed. Treatment of these precatalysts with NaOtBu gave rise to the active 14 electron (14e) species [(7–6–7‐^iPrPCP)Ir] and [(7–6–7‐^PhPCP)Ir], which can trap hydrogen and were spectroscopically characterized as the tetrahydride complexes. Both [(7–6–7‐^iPrPCP)Ir] and [(7–6–7‐^PhPCP)Ir] were found to be highly effective in the transfer dehydrogenation of cyclooctane with tert‐butylethylene as the hydrogen acceptor, the initial reaction rate at high temperature (230 °C) being higher for [(7–6–7‐^iPrPCP)Ir] than [(7–6–7‐^PhPCP)Ir], and the turnover number (TON) of the overall hydrogen transfer being higher for the latter. Nonetheless, the estimated TONs were as high as 4600 and 4820 for the two complexes at this temperature, respectively, which are unprecedented absolute values. In terms of durability, the [(7–6–7‐^PhPCP)Ir] complex is the catalyst of choice for this reaction. Structural analysis and computational studies support the importance of the low flexibility of the ligand core.     

Studies in heavy ion activation analysis

⁷Li induced radioactivation was used for the trace determination of hydrogen via the¹H(⁷Li, n)⁷ Be reaction. At 21 MeV⁷Li, only boron and magnesium present small nuclear interferences. An activation curve has been established by bombarding a stack of thin mylar foils. The comparison of this curve with the excitation function for the forward reaction, namely⁷Li(p, n)⁷ Be, shows that the recoil range from the superficial hydrogen atoms is only 1.7 mg·cm^–2, allowing post-irradiation etching. Hydrogen has been determined in titanium and lead bronze at the 100 ppm level with a relative precision of 6 to 10%. Studies of 32 potential interfering elements suggest the extension of Li activation to the trace determination of Na[²³Na(⁷Li,⁶Li)²⁴Na] and K[³⁹K(⁷Li, d)^44m,⁴⁴Sc].     

PrB7−: A Praseodymium-Doped Boron Cluster with a PrII Center Coordinated by a Doubly Aromatic Planar η7-B73− Ligand

The structure and bonding of a Pr-doped boron cluster (PrB₇⁻) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB₇⁻ is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB₇. Global minimum searches and comparison between experiment and theory show that PrB₇⁻ has a half-sandwich structure with C_6v symmetry. Chemical bonding analyses show that PrB₇⁻ can be viewed as a Pr^II[η⁷-B₇³⁻] complex with three unpaired electrons, corresponding to a Pr (4f²6s¹) open-shell configuration. Upon detachment of the 6s electron, the neutral PrB₇ cluster is a highly stable Pr^III[η⁷-B₇³⁻] complex with Pr in its favorite +3 oxidation state. The B₇³⁻ ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide M^III[η⁷-B₇³⁻] complexes.     

Beryllium-7 activity concentration in maize during the growth period

Beryllium-7 (⁷Be) activity in maize was measured in Yangling County, Shaanxi Province, on the Loess Plateau Region of China in 2007. The ⁷Be mass activity concentration in maize leaf samples was significantly greater than in maize stem, maize root and maize grain samples. The ⁷Be activity in maize leaves accounted for 78% of the total maize ⁷Be activity. The ⁷Be mass activity concentration in maize varied from 25.4 to 122.4 Bq kg⁻¹ and areal activity concentration held by maize from 1.2 to 111.5 Bq m⁻² during the growth period. The percentage of ⁷Be areal activity concentration held by maize relative to the ⁷Be areal activity concentration measured in reference soils ranged from 0.4 to 24.2% with a mean of 13.7%.     

Inclusion Interactions of Cucurbit[7]uril with Adenine and its Derivatives

Interactions of cucurbit[7]uril (Q[7] host) with guest adenine (g1), adenosine (g2) and 2′,3′-o-isopropylideneadenosine (g3) were studied in details by ¹H NMR, UV absorption spectroscopy, fluorescence spectroscopy and high performance liquid chromatography (HPLC) methods. We found that the suitable pH range for interaction was between 1 and 7, and the optimal pH range was between 2 and 4. The ¹H NMR analysis indicated that Q[7] selectively interacted with the adenine moiety of the guests g1 and g2, while Q[7] selectively interacted with the D-ribose sugar ring moiety of the guest g3. Moreover, ¹H NMR spectra showed that the exchange between the bound guest and the free guest was fast on the NMR time scale for the Q[7]-g1 and Q[7]-g2 systems. However, an obvious equilibrium between the bound host/guest and the unbound host/guest were observed in the Q[7]-g3 complex. Several methods were used to determine quantitatively the stability of the three host–guest inclusion complexes formed between Q[7] and the guests. The formation constants by UV and fluorescence were 1.90 × 10⁵ L mol^? 1 and 1.34 × 10⁵ L mol^? 1 for Q[7]-g1, 9.41 × 10⁴ L mol^? 1 and 4.24 × 10⁴ L mol^? 1 for Q[7]-g2, 4.50 × 10⁴ L mol^? 1 and 3.62 × 10⁴ L mol^? 1 for Q[7]-g3, respectively. HPLC method was also introduced to explore the interactions between Q[7] and the adenine and its derivatives. The formation constants of the host–guest inclusion complexes, as determined by HPLC, were 6.76 × 10⁴ L mol^? 1 for Q[7]-g1, 1.80 × 10⁴ L mol^? 1 for Q[7]-g2, 3.01 × 10⁴ L mol^? 1 for Q[7]-g3 respectively. Our study suggested that Q[7] could be a suitable host for the delivery of bioactive molecules, such as the adenine and its derivatives.     

Complexation and aromatization of α,β-unsaturated cyclic ketones by Ru(H2O)6 and (Bz)Ru(H2O)3: molecular structure of (η-Tosylate)(η-hydroxycyclopentadienyl)Ru and of (η-Tosylate)(η-1,4-dihydroxy-2,3,5,6-tetramethylbenzene)Ru

Ruaq²⁺(OTs)₂ complexes in aqueous solution to unsaturated cyclic ketones. These aromatized on heating to π-arene Ru complexes. Thus, with cyclohexonone the main product was Ru(η⁶-phenol)₂²⁺, 4, along with some Ru(η⁶-phenol)(η⁶-OTs)⁺, 6. Similarly gave cyclopentenone in the presence of various arenes Ru(η⁵-hydroxycyclopentadienyl)(η⁶-arene)⁺. Duruquinone complexed to Ruaq²⁺ as a monoprotanated hydroquinolate in Ru(η⁶-2,3,5,6-tetramethyl-1,4-hydroquinone)(η⁶-OTs), 14. Ru(η⁵-cyclopentadienyl)(η⁶-OTs), 8, and 14 were characterized by single crystal x-ray structure analyses, data see Table 1. Whereas both ligands in 8 are planar, the 1,4-hydroquinone ligand in 14 shows distinct bending of the COH groups.     

The electronic structure of thorium monoxide: Ligand field assignment of states in the range 0–5 eV

Configuration interaction ligand field theory (CI LFT) calculations of the electronic energy levels of ThO were performed by treating the molecular electronic states as Th ^{2 +} free-ion levels perturbed by the ligand field of O²⁻. Twenty nine experimentally characterized ThO v = 0 energy levels, together with the energy difference between the v = 0 levels of the Y and W states were fitted using a CI LFT model that included Th ^{2 +} 7s ² , 6d7s, 6d², 7s7p, 6d7p, 5f7s, and 7p² configurations. Predictions from these calculations were used to provide tentative assignments for 171 out of 250 ThO band heads listed by Gatterer et al. [“Molecular Spectra of Metallic Oxides”, Specola Vaticana (1957)]. Term energies for 30 electronic states have been determined based on these assignments. Subsequently, the CI LFT model was refined by fitting to a set of 59 electronic term energies. The inclusion of CI effects together with integer valence, atomic-in-molecule, ionic bonding ideas reveals atomic energy level patterns that are multiply replicated in the molecular energy level patterns of six Th ^{2 +} O²⁻ atomic ion configurations (6d7s, 6d², 7s7p, 6d7p, 5f7s, and 7p²) revealing the underlying atomic ion structure that gives rise to the complex and seemingly erratic unassigned bands reported in the Vatican Atlas. © 2018 Wiley Periodicals, Inc.     

Synthesis,Biological Activity of Pyrimidine Linked with Morpholinophenyl Derivatives

A new series of 5‐fluoro‐N⁴‐(3‐(4‐substitutedbenzylamino)phenyl)‐N²‐(4‐morpholinophenyl)pyrimidine‐2,4‐diamine derivatives ( 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j ) are prepared from using an intermediate compound 5‐fluoro‐N⁴‐(3‐(aminophenyl)‐N²‐(4‐morpholinophenyl)pyrimidine‐2,4‐diamine ( 5 ). The structures of the newly synthesized products are established from their spectral ¹H‐NMR, ¹³C‐NMR, ¹⁹F‐NMR, ESI‐MS, and analytical data. Here we report the synthesized compounds and larvicidal activity. All the compounds are screened for their significant larvicidal activity against third instar larvae at 24, 48, and 78‐h time exposure, and values were compared with standard drug Malathion. The Compounds 7i , 7a , 7c , 7f , and 7j exhibited significant activity. However the compounds 7b , 7e , 7d , and 7h showed excellent activity when compared to the above compounds and to standard drug malathion too because of the presence of mild electron withdrawing groups such as trifluoro, fluorine, hydroxy, nitro, and methoxy derivatives which are attached to the benzyl ring.     

Effect of C7-Substituent on Self-Assembly of Chlorosomal Chlorophylls

Abstract

Bacteriochlorophyll d analogues that possessed a series of bulky substituents of OMe, OCOMe, and OCO ^t Bu at the C7¹-position were synthesized (Zn-complexes of methyl 7¹-substituted-3-(1-hydroxy-methyl)pyropheophorbide a). Aggregation behavior of these pigments was examined in comparison with a natural-type compound (C7¹-H) to elucidate the effects of size of the C7¹-moiety on self-assembly of the chlorins. These C7¹-substituted Zn-chlorins formed self-aggregates in 1% THF/hexane. The aggregates gave almost the same visible absorption bands, especially a ca. 2000-cm^?1 red-shifted Q_y peak; the spectra were essentially similar to those of the natural-type Zn-chlorin (C7¹-H). All the aggregates of the C7¹-substituted compounds showed similar exciton-type CD couplets in the red-shifted Q_y region, which were different from the feature of the couplet of the C7¹-H Zn-chlorin aggregate. These spectral data suggested that the C7¹-moiety did not interrupt the intermolecular linkages between chlorin molecules but altered the supramolecular structure which influences the long-range chirality.     

The interaction model between metal cation and tropylium: a quantum chemistry predication

The aromatic cation tropylium, C₇H₇⁺, predicted at the MP2/6-31G** level, is capable of binding with metal cations Be²⁺ or Mg²⁺, forming M²⁺–C₇H₇⁺ complexes. The obstacle for their binding is almost electrostatic repulsion, and the binding is from polarization and charge transfer. The orbital interaction between the M²⁺ and C₇H₇⁺ is mainly the s–π and p–π interactions. Interestingly, Be²⁺ is possible to pass through the ring of C₇H₇⁺, while Mg²⁺ is not. The intrinsic IR band of the M²⁺–C₇H₇⁺ complex is below 600 cm⁻¹, which results from the vibration of the M²⁺ along the normal axis of C₇H₇⁺.     

Light Intensity and Photoperiod Affect Growth and Nutritional Quality of Brassica Microgreens

We explored the effects of different light intensities and photoperiods on the growth, nutritional quality and antioxidant properties of two Brassicaceae microgreens (cabbage Brassica oleracea L. and Chinese kale Brassica alboglabra Bailey). There were two experiments: (1) four photosynthetic photon flux densities (PPFD) of 30, 50, 70 or 90 μmoL·m⁻²·s⁻¹ with red:blue:green = 1:1:1 light-emitting diodes (LEDs); (2) five photoperiods of 12, 14, 16, 18 or 20 h·d⁻¹. With the increase of light intensity, the hypocotyl length of cabbage and Chinese kale microgreens shortened. PPFD of 90 μmol·m⁻²·s⁻¹ was beneficial to improve the nutritional quality of cabbage microgreens, which had higher contents of chlorophyll, carotenoids, soluble sugar, soluble protein and vitamin C, as well as increased antioxidant capacity. The optimal PPFD for Chinese kale microgreens was 70 μmol·m⁻²·s⁻¹. Increasing light intensity could increase the antioxidant capacity of cabbage and Chinese kale microgreens, while not significantly affecting glucosinolate (GS) content. The dry and fresh weight of cabbage and Chinese kale microgreens were maximized with a 14-h·d⁻¹ photoperiod. The chlorophyll, carotenoid and soluble protein content in cabbage and Chinese kale microgreens were highest for a 16-h·d⁻¹ photoperiod. The lowest total GS content was found in cabbage microgreens under a 12-h·d⁻¹ photoperiod and in Chinese kale microgreens under 16-h·d⁻¹ photoperiod. In conclusion, the photoperiod of 14~16 h·d⁻¹, and 90 μmol·m⁻²·s⁻¹ and 70 μmol·m⁻²·s⁻¹ PPFD for cabbage and Chinese kale microgreens, respectively, were optimal for cultivation.     

Mechanism of 7Be scavenging from the atmosphere through precipitation in relation to seasonal variations in Rokkasho Village, Aomori Prefecture, Japan

⁷Be deposition fluxes and atmospheric concentrations were measured at Rokkasho Village, Aomori Prefecture, Japan, from 2000 to 2005. It was confirmed that the ⁷Be deposition fluxes were minimum in summer, and the fallout maximizes in winter. The atmospheric concentration of ⁷Be was especially low in summer, and high in the other three seasons. A positive correlation was observed between the amount of precipitation and ⁷Be deposition. Clear seasonal differences were evident among the ratios of ⁷Be deposition flux to precipitation amounts in the four seasons. The ratios were especially high in winter, higher than those in the other three seasons. ⁷Be deposition flux was estimated by a simple simulation model using atmospheric ⁷Be concentrations and local meteorological data. As a result, the estimated deposition value was relatively lower than the measured value in winter.     

Duplex Stability of 7-Deazapurine DNA: Oligonucleotides containing 7-bromo- or 7-iodo-7-deazaguanine

The oligonucleotide building blocks, the phosphonates 1a, b and the phosphoramidites 2a, b derived from 7-iodo- and 7-bromo-7-deaza-2′-deoxyguanosines 3a, b were prepared. They were employed in solid-phase oligonucleotide synthesis of the alternating octamers d(Br⁷c⁷G-C)₄ ( 8 ) and d(I⁷c⁷G-C)₄ ( 9 ) as well as the homo-oligonucleotides d[(Br⁷c⁷G)₅-G] ( 11 ) and d[(I⁷c⁷G)₅-G] ( 12 ). The melting profiles and CD spectra of oligonucleotide duplexes were measured. The T_m values as well as the thermodynamic data were determined and correlated to the major-groove modification of this DNA. The self-complementary octamers 8 and 9 form more stable duplexes compared to the parent oligomer d(G-C)₄. The heteroduplex of d[(I⁷c⁷G)₅-G] ( 12 ) with d(C₆) is slightly destabilized (ΔT_m = ?12°) over that of d[(c⁷G)₅-G] with d(C₆). However, the complex of 12 with poly(C) is more stable than that of d[(c⁷G₅-G)] with poly(C).     

Syntheses and Characterization of the First Cycloheptatrienyl Transition-Metal Complexes with a M-CF3 Bond

The organometallic chemistry of metal complexes with organocyclic ligands of higher than five hapticity is much more lacking than the chemistry of metal complexes with η⁵-cyclopentadienyl ligands, which has been explored in considerable depth, resulting in novel advances. The main reason for this is stability. In particular, reports indicate that (η⁷-C₇H₇)ML_n complexes are considerably less stable than analogous (η⁵-C₅H₅)ML_n. In perfluoroalkyl metal chemistry, there is currently no reported (η⁷-C₇H₇)ML_n derivative, whereas a number of alkylated ones are known and important conclusions have been drawn about their stability. Responding to this void, and using Morrison’s trifluoromethylating reagent, the present study reports the synthesis and characterization of the first cycloheptatrienyl molybdenum complexes bearing the trifluoromethyl moiety; (η⁷-C₇H₇)Mo(CO)₂CF₃ (I), and (η⁷-C₇H₇)Mo(CO)(PMe₃)CF₃ (II) and discusses their low thermal instability.     

Variation of 7Be concentration in surface air at Nagano, Japan

The concentration of ⁷Be in surface air at Nagano City has been measured during the period from August 2000 to March 2005. The average monthly concentrations of ⁷Be in surface air were in the range of 3.3–14 mBq/m³ with pronounced two peaks in spring and autumn. It took 30–40 hours to recover the ⁷Be concentrations observed before, once ⁷Be was washed out by wet precipitations. For a pronounced increase in the concentrations of ⁷Be found in winter, a low-pressure trough coming close to the Japanese Islands with high concentrations of ⁷Be is responsible under the characteristic distribution of atmospheric pressure around the Japanese Islands.     

Voltammetry and electrochemical stripping analysis for antimony in aqueous and nonaqueous media after extraction

Cyclic voltammetry of antimony was studied in aqueous media (HCl-LiCl) and in nonaqueous media after extraction with 20% tri-n-butylphosphate in toluene, with a rotating glassy carbon disc electrode. Reduction of antimony to the element in aqueous media is nearly reversible, but irreversible in nonaqueous media. Anodic stripping voltammetric and chronopotentiometric determinations were also studied in nonaqueous media; methanol and LiCI, NH₄SCN or NH₄NO₃, were used as base electrolytes. In nonaqueous media, antimony can be determined down to concentrations of 1O⁻⁸ M by stripping voltammetry, and lO⁻⁷ M by stripping chronopotentiometry. Electrochemical stripping determinations of 10⁻⁶ M antimony(III) were not affected by Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺ or As³⁺ (5 · 10⁻³ M), ag⁺ (4 · 10⁺⁴ M in stripping voltammetry or 10⁻³ M in stripping chronopotentiometry), Hg²⁺ (5 · 10⁻⁴M), Pb²⁺ (3 · 10⁻⁴ M), Cu²⁺ (1.5 · 10⁻⁴ M)Sn²⁺ and Sn⁴⁺ (7 · 10⁻⁴ M), Fe³⁺ (4 · 10⁻⁴ M), Au³⁺ (5 · 10⁻⁵ M) and Bi³⁺ (1.5 · 10⁻⁵ M). Thestripping chronopotentiometric determination showed better selectivity.