Addition Of DTPA Research Articles

Simplification of organic matter before voltammetric determination of Tl(I) and Tl(III) in water using nanostructured photocatalyst and solar light

The crucial point of this study was to verify the hypothesis that both thallium species are not affected by the procedure of photolysis when it is applied as a method of simplification of sample matrix containing surfactants, and that this method of sample pretreatment leads to reliable results of Tl speciation analysis. It is important especially because of high instability of Tl(III), which makes partial reduction of Tl(III)DTPA complex unavoidable. After conservation of Tl speciation by addition of DTPA the photolysis assisted with nanostructured hierarchically organized film was performed using “solar lamp” (Fe2O3/WO3/Fe2O3 film, pH 6, 380–800 nm). The results imply that under proposed photolysis conditions Tl(I) is not oxidized in the presence of water matrix, SDS nor DTPA. Also, even 100-fold excess of Fe(III) ions over Tl(I) ions does not accelerate the oxidation of Tl(I) to Tl(III), and already 2 h of heterogeneous photolysis allow to limit the interferences caused by SDS and obtain reliable results. The data obtained by anodic stripping voltammetry (ASV) were verified using an inter-method comparison with SEC ICP MS. Moreover, after 2 h irradiation the reduction rate of Tl(III)DTPA standard solution increased only slightly from 2-3% to 4–6%. The presence of river water matrix causes a slightly higher (9%) reduction of the trivalent form. These changes are irrelevant in the context of instability of Tl(III) compounds. This study indicates that “soft decomposition” can be applied in speciation analysis of thallium in water matrix.

Quantitative Determination of Arsenate in Dried Shrimp by Spectrophotometric Measurement of its Heteropoly Blue

A cost-effective and sensitive spectrophotometric method for the determination of arsenate in dried shrimp has been developed using molybdenum blue as a chromogenic reagent. The method is based on arsenate conversion to arsenomolybdate heteropoly blue having an absorbance maximum at 870 nm. The effects of pH, time, temperature and light on its complex formation were investigated. The optimal complex formation condition at pH 4 in 90 min at 15+1°C was obtained and the blue color was favorable developed in daylight. The proposed method has been successfully applied for the determination of arsenate in samples with the addition of DTPA to eliminate the interferences resulting in increased selectivity. The standard addition calibration graph was constructed with the linear range extended to 40 μgL-1 (r2 = 0.9987). The detection limit (S/N = 3) of 3.21 μgL-1, and the precision of 3.13% (RSD) were obtained. The method has good recovery of 95% for the determination of arsenate. The amounts of arsenate in dried shrimp samples compared with those obtained from ICP-OES were shown to be in good agreement (r = 0.998).

Continuous separation of Sr, Y and some actinides by mixed solvent anion exchange and determination of 89,90Sr, 238,239Pu and 241Am in soil and vegetation samples

Methodology for the determination of 89,90Sr, Am and Pu isotopes in complex samples is given. Methodology is based on simultaneous isolation of Sr, Y and actinides from samples by mixed solvent anion exchange chromatography, mutual separation of 89,90Sr and 90Y from actinides, mutual separation of Th, Pu and Am by extraction chromatography, quantitative determination of 89,90Sr by Cherenkov counting and quantitative determination of Pu and Am isotopes in soil and vegetation samples by alpha spectrometry. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25 M HNO3 in mixture of ethanol and methanol as eluent. It is also shown that Pu, Am and Th strongly binds on the mentioned column, can be separated from number of elements and easily be eluted from column by water. After elution actinides were mutually separated on TRU column and electrodeposited on stainless steel disc. Examination of conditions of electrodeposition was shown that chloride-oxalate electrolyte with addition of DTPA in presence of sodium hydrogen sulphate in cell with cooling and rotating platinum anode enables deposition of actinides within 1 h by 0.8 A cm−2 current density. Obtained peaks FWHM for Pu, Am and Th isotopes are between 27 and 40 keV. Scanning electron microscopy picture and ED XRF analysis of electroplated discs showed that actinide deposition is followed by iron oxide formation on disc surface. The methodology was tested by determination of 89,90Sr, Am and Pu isotopes in ERA proficiency testing samples (low level activity samples). Obtained results shows that 89,90Sr, 241Am and 238,239Pu can be simultaneously separated on anion exchange column, 89,90Sr can be determined by Cherenkov counting with a satisfactory accuracy and limit of determination within 1–3 days after separation. 241Am and 238,239Pu can easily be separated on TRU column and determined after electrodeposition with acceptable accuracy within 1 day.

Indirect Anodic Stripping Voltammetric Determination of Tl(I) and Tl(III) in the Baltic Seawater Samples Enriched in Thallium Species

AbstractThe sensitive method DPASV with HMDE in the presence of DTPA and acetic buffer was used for determination of Tl(I) and Tl(III) in spiked seawater sample. The proposed method was based on the appropriate chemical conservation of Tl speciation. To determine the total amount of Tl, an addition of ascorbic acid to sub‐sample was necessary, but to determine Tl(I) to the second sub‐sample addition of DTPA was needed. Various factors influencing the stability of Tl(III) and electrochemical parameters were investigated. The quantification limit of 1.8 ng mL−1 Tl(I) was found for 8 min preconcentration. The procedure was validated using recovery study and HPLC ICP MS determinations.

Separation and Quantification of Tl(I) and Tl(III) in Fresh Water Samples

The two oxidation states of thallium, Tl(I) and Tl(III), were quantified by IC-ICP-MS using complexation of Tl3+ with DTPA (penta-carboxymethyl-diethylenetriamine) and separation on a cation exchange column according to a modification of the method devised by Coetzee et al. In order to avoid successively lowered separation efficiency and loss of resolution during a run, a gradient elution was made using HCl instead of HNO3. With an ultrasonic nebuliser instead of a V-groove nebuliser the limit of detection for Tl(I) and Tl(III) could be lowered from 25 ng/L and 3.0 ng/L to 9.0 ng/L and 0.7 ng/L, respectively, which is adequate for many fresh water systems. The stability of Tl(III) in acidic solutions was found to be concentration dependent, with an initially high reduction rate of Tl(III). Exposure of the sample to light further increased the reduction rate. Addition of DTPA (0.01 mM) and acid (HNO3, 1%) to a sample with 1 μg/L Tl(III) stabilised the Tl(III) content for at least 48 h. Analysis of field samples showed that only acidification is inadequate to maintain the original distribution of Tl(I) and Tl(III). Internal calibration (standard addition) and correction of the analytical signal (205Tl) with a non-ionic internal standard (11B) yielded almost quantitative recoveries of both Tl(I) and Tl(III). A scheme for field sample preparation is proposed, including sampling, storage and pre-analysis treatment.

Determination of micronutrients and heavy metals in soils using electro–ultrafiltration (EUF) technique by addition of DTPA

AbstractWith the electro–ultrafiltration (EUF) technique, the plant availability of several plant nutrients in soils can be characterized. The basic principle of EUF is that an electric field is induced using platinum electrodes. Ions in the soil suspension move either to the cathode or to the anode and are filtrated through ultra‐membrane filters. In the standard EUF procedure, two extractions steps are used: 30 min at 20°C and 5 min at 80°C. However, the determination of micronutrients and heavy metals with the standard EUF procedure is not possible, because the solubility of these elements in water is low and most of the watersoluble elements are precipitated when passing the platinum electrodes.The addition of DTPA, a well known complexing agent, during a third EUF fraction (5 min at 80°C) enables extraction of micronutrients and heavy metals. Highest concentrations in the 33 soils of the study were found for iron, followed by zinc, manganese, lead, copper, and nickel. Lower concentrations were obtained for cobalt, chromium, cadmium, and molybdenum. For two soils, the EUF/DTPA procedure was compared to CaCl2/DTPA and EDTA soil extraction methods, showing that higher or comparable amounts were found with CaCl2/DTPA and much higher amounts with the EDTA method.These results reveal that the EUF/DTPA technique in principle can be used for the determination of plant‐available micronutrients and heavy metals. However, in a next step the relationship between EUF/DTPA‐extractable elements and their availability for plants needs to be quantified.

Reduction of skeletal accumulation of radioactivity by co-injection of DTPA in [ 90Y-DOTA 0,Tyr 3]octreotide solutions containing free 90Y 3+

Peptide receptor-targeted radionuclide therapy is nowadays being performed with radiolabeled DOTA-conjugated peptides, such as [ 90Y-DOTA 0,Tyr 3]octreotide (also known as OctreoTher® or 90Y-DOTATOC). The incorporation of 90Y 3+ is typically ≥99%, however, since a total patient dose can be as high as 26 GBq or 700 mCi the amount of free 90Y 3+ (=non-DOTA-incorporated) can be substantial. Free 90Y 3+ accumulates in bone with undesired radiation of bone marrow as a consequence. 90Y-DTPA is excreted rapidly via the kidneys. Incorporation of free 90Y 3+ into 90Y-DTPA might prevent this fraction from being accumulated into bone, therefore we have investigated: the biodistribution in rats of 90YCl 3, [ 90Y-DOTA 0,Tyr 3]octreotide, and 90Y-DTPA; possibilities to complex 10% of free 90Y 3+ in a [ 90Y-DOTA 0,Tyr 3]octreotide containing solution into 90Y-DTPA prior to intravenous injection; and effects of 10% free 90Y 3+ in [ 90Y-DOTA 0,Tyr 3]octreotide solution, in the presence and in the absence of excess DTPA, on the biodistribution of in rats. The following results are presented: 90YCl 3 showed high skeletal uptake (i.e., 1% ID (injected dose) per gram femur, with main localization in the epiphyseal plates) and a 24 h total body retention of 74% ID; 90Y-DTPA had rapid renal clearance, and 24 h total body retention of <5% ID; added free 90Y 3+ in [ 90Y-DOTA 0,Tyr 3]octreotide solution could rapidly be incorporated into 90Y-DTPA at room temperature; and accumulation of 90Y 3+ in femur, blood, and liver was related to the amount of free 90Y 3+, whereas these accumulations could be prevented by the addition of DTPA. In conclusion, the addition of excess DTPA to [ 90Y-DOTA 0,Tyr 3]octreotide with incomplete 90Y-incorporation is recommended.

Using DTPA to Decrease Manganese-Induced Peroxide Decomposition

The catalytic activity of Mn(+II) and Mn(+III) in decomposing hydrogen peroxide was studied by using DTPA as the only stabilizer. It was found that the addition of DTPA to a Mn(+II) containing system is more effective than if it is added to a Mn(+III) containing system. To decrease the catalytic effect of Mn(+III), sodium borohydride and DTPA under an acidic condition were considered to reduce Mn(+III) to Mn(+II). The effect of pH on using DTPA to decrease Mn-induced peroxide decomposition is discussed.

Chelation of Zinc Amplifies Induction of Growth Hormone mRNA Levels in Cultured Rat Pituitary Tumor Cells

Zinc is thought to be an integral part of nuclear receptor proteins, stabilizing them in a conformation required for binding to target genes. However, we have recently shown that restriction of zinc availability with a chelator (diethylenetriaminepenta-acetic acid, DTPA) enhances, rather than inhibits, the ability of thyroid hormone to induce growth hormone mRNA expression in GH3 rat pituitary tumor cells. In this report, we have extended these observations by showing that a prolonged (48 h) exposure to DTPA is required to see these effects. The induction by DTPA can be reversed by subsequent addition of zinc, but again, this reversal is slow. A second chelator, EDTA, can also induce growth hormone gene expression in the presence of thyroid hormone, though it is less potent than DTPA. Other agents which act via the nuclear receptor pathway, all-trans and 9-cis retinoic acid, also induce expression of growth hormone mRNA. Addition of DTPA amplifies these effects in a zinc-dependent manner. Thus chelation of zinc potentiates the action of ligands acting via nuclear receptors on growth hormone gene expression. The delayed nature of the response suggests an indirect effect.

Improvement of Hydrogen Peroxide Bleaching of Kraft Pulp by Acid Pre-treatment

The influence of manganese oxidation state on the decomposition of hydrogen peroxide was investigated, and a method to minimize the manganese induced hydrogen peroxide decomposition under an alkaline condition was developed. The inclusion of such a method for the production of fully bleached pulp was investigated.Upon the addition of DTPA (diethylenetriamine-N, N, N′, N″, N″-pentaacetic acid) to Mn (II) containing solution, the manganese induced hydrogen peroxide decomposition under a typical peroxide bleaching condition is minimized. On the other hand, manganese at a higher oxidation state, such as Mn (III, IV) exhibits a strong catalytic effect in decomposing hydrogen peroxide under the alkaline condition. Furthermore, it was confirmed that the higher valency manganese in pulp fibers can be reduced to lower valency form by carbohydrate in pulp fibers. This can be achieved under the conditions of pH2-2.5, 70t and 30-60 min.By applying such a concept to the bleaching of polysulphide-anthraquinone (PS-AQ) pulp from eucalyptus (Eucalyptus camaldulensis) wood in an Eop stage, i. e., acid pre-treatment (A), then the addition of DTPA, followed by an Eop stage, the performance of the Eop stage is improved. Following the AEOP HDP sequence produces a fully bleached pulp with a brightness of 88.8% ISO and a viscosity of 15.5cP.

Inhibition of 2,3-dimethyl-1,4-naphthohydroquinone auto-oxidation by copper and by superoxide dismutase

2,3-Dimethyl-1,4-naphthohydroquinone undergoes auto-oxidation to the corresponding quinone at pH 7.4, with stoichiometric consumption of oxygen and formation of hydrogen peroxide. In an unpurified buffer, the rate of oxidation was low, but it increased nearly 9-fold when trace metals were removed from the buffer by treatment with Chelex resin. A similar increase in rate was achieved by addition of DTPA or bathophenanthroline sulfonate to unpurified buffer, whereas EDTA and desferal were less effective. Addition of copper to purified buffer led to inhibition of oxidation, with a 50% decrease in rate being observed at a metal concentration of 7.1 nM, and it is likely that the low auto-oxidation rate recorded in unpurified buffer was due to copper contamination of the latter. The auto-oxidation of 2,3-dimethyl-1,4-naphthohydroquinone was exceptionally sensitive to inhibition by superoxide dismutase, with a concentration of only 4.5 ng/ml being sufficient for a 50% decrease in rate, and the inhibitory effect of copper may be due to the ability of this metal to catalyse the dismutation of superoxide. Previous studies have shown that the rates of auto-oxidation of 1,4-naphthohydroquinone and 2-methyl-1,4-naphthohydroquinone are influenced by copper contamination of buffer and the present study shows that this is also true for a di-substituted naphthohydroquinone. For accurate assessment of rates of naphthohydroquinone auto-oxidation, it is important that purified buffers or appropriate chelating agents are employed.

Biphasic increase in cytosolic free calcium induced by bradykinin and histamine in cultured tracheal smooth muscle cells: is the sustained phase artifactual?

The effects of bradykinin (BK) and histamine on intracellular Ca2+ ([Ca2+]i) were studied in fura-2-loaded guinea-pig tracheal smooth muscle cells in culture. BK, at 10 nM, and histamine, at 100 microM, induced a rise in [Ca2+]i which was inhibited by the B2 antagonist Hoe 140 and by the H1 antagonist triprolidine, respectively. This rise in [Ca2+]i is biphasic, consisting of a rapid transient phase followed by a sustained phase. The transient phase, induced by either BK or histamine, was strongly inhibited by thapsigargin, a microsomal Ca(2+)-ATPase inhibitor, usually used to deplete certain intracellular Ca(2+)-stores. Ni2+ (4 mM) did not affect the transient phase but abolished the sustained phase when cells were stimulated by BK, further supporting the fact that the transient phase was only dependent on intracellular Ca2+ pools. The sustained phase was partially (for BK) and completely (for histamine) inhibited by 30 microM Mn2+. This effect could be completely reversed by the addition of DTPA, a cell-impermeant chelator of Mn2+, indicating that the Mn2+ exerted its effect extracellularly. The presence of 1 mM probenecid (an inhibitor of a membrane organic anion transporter that extrudes fura-2) drastically inhibited the sustained phase by more than 77% for BK and 88% for histamine. Our results suggest that the effects of BK and histamine on airway smooth muscle cells are mediated via bradykinin B2 receptors and histamine H1 receptors, respectively whose activation allows the rapid transient rise in [Ca2+]i from thapsigargin-sensitive intracellular Ca2+ pools. The sustained phase is proposed to be drastically influenced by an acceleration of fura-2 extrusion during the increase of [Ca2+]i via a probenecid-sensitive mechanism.

Correlation of immunoreactivity and polymer formation to DTPA modification of a monoclonal antibody

The protocol used for coupling of monoclonal antibodies with mixed anhydride of DTPA for subsequent radiolabeling with indium-111 affects the integrity of the immunoreactivity of the antibody preparations. To analyze the effect of minor methodological variations on coupling characteristics, a two-step addition of DTPA to antimyosin antibody with gentle mixing was compared to a single addition with vigorous stirring. The molar ratios of DTPA to antibody were also varied. The polymer formation was assessed by SDS-PAGE and immunoreactivity was assessed by solid phase radioimmunoassay using human heart myosin as the antigen. The immunoreactivity was significantly decreased in the two-step, gentle-mixing method where polymer formation was evident. The one-step, vigorous-stirring method of DTPA incorporation produced no polymerization and no loss of immunoreactivity.

EFFECT OF MOBILE CHELATING AGENTS ON DIFFUSION OF ZINC IN SOILS

The effect of DTPA, EDTA, and fulvic acid (FA) on the self-diffusion of Zn in an alkaline and a calcareous soil was studied. The apparent diffusion coefficient of Zn in soil increased significantly with addition of DTPA, EDTA, FA, and the respective Zn-chelates at the rate of 8 x 10-8 mole/g soil. T