Radiotracer measurement of the volatilization of organic trace constituents from water.

Abstract The mass-transfer coefficient for the volatilization of organic microconstituents from water can be determined by laboratory radiotracer experiments. Formulation and practical aspects are considered and illustrated by the example of a 5.10(-7) M solution of monochlorobenzene.

Toxic heavy metals and other trace elements in foodstuffs from 12 different countries. An IAEA coordinated research program.

A research program related to the assessment of toxic heavy metals and essential trace elements in foodstuffs has been carried out in 12 countries under the auspices of the IAEA. The main purpose of this program was to obtain data on the elemental concentrations of potentially toxic elements in foodstuffs in various countries, and to compare them with the maximum permissible levels specified in national legislation and international guidelines. High-priority elements for this study were As, Cd, Cr, Pb, Hg, and Se. Also of interest, but of lower priority, were Sb, Cu, and Zn. Emphasis was placed on the use of nuclear and nuclear-related analytical techniques, complemented by conventional methods, and on quality assurance.

Improvement of the reproducibility of ion-pair HPLC of 99mTc(Sn)EHDP complexes and the influence of the Sn(II) concentration on the composition of the reaction mixture.

The use of a non-volatile modifier and the simultaneous exclusion of oxygen by flushing with helium in ion-pair HPLC of 99mTc(Sn)EHDP-complexes prevents spurious oxidation during the separation process. It thus enables the omission of the reducing agent from the eluent solution and the determination of the labelling percentage from the TcO4(1)-peak. In addition, retention times become more reproducible.

On-line radiometric determination of [14C]-urapidil and its main metabolises in rat plasma, using post-column ion-pair extraction and solvent segmentation techniques.

Post-column ion-pair extraction has been applied to the on-line radiometric determination of [(14)C]-urapidil and its main metabolises in reversed-phase liquid chromatography (LC). [(14)C]-remoxipride was used as internal standard. Chromatography was performed isocratically, using acetonitrile-water (pH = 2.2) as eluent on a cyanobonded column. Various ion-pair reagents were tested for their extraction efficiency of the analytes mentioned from the eluent into chloroform. Quantitative extraction was possible using sodium dodecylbenzenesulphonate as ion-pair reagent. The influence of the extraction solvent composition, the percentage organic modifier in the eluent and the flow-rates of eluent and scintillator on the extraction percentage and the (14)C-counting efficiency has been studied. In addition, the enhancement of sensitivity is possible using an on-line radiometric procedure. Finally, the method has been applied to the analysis of rat plasma for [(14)C] -labelled urapidil and its metabolises.

On-line low-level radiometric detection of [14C]remoxipride in liquid chromatographic effluents. Application to urine samples.

A method for on-line radiometric detection in liquid chromatography (LC) is described that permits the detection of low levels of radioactivity in LC effluents by using solvent segmentation and storage of the segmented effluent in a capillary storage loop. The object of the method is to make the flow-rate in the on-line radioactivity monitor (and hence the mean residence time in the monitor) independent of the separation process. Therefore, after storage of the complete chromatogram, the segmented effluent is led through the monitor at flow-rates that can be chosen according to the residence time desired for accurate and precise radioactivity determination. In this system, it is possible to use a flow-cell volume small enough to preserve the chromatographic integrity, while maintaining the possibility of increasing the counting time. Tests have been performed on the reproducibility of 14C detection and the influence of the flow-rate through the monitor on the standard deviation in 14C peak area and, thus, on the detection limit, using 14C-labelled remoxipride. As an application, analyses of urine samples for [14C]remoxipride and one of its potential metabolites are reported.

The effect of the reduction method on the composition of 99mTc-EHDP complexes.

The composition of 99mTc-ethane-1-hydroxy-1, 1-diphosphonate complexes, prepared with the reducing agent NaBH4 and by electrolytic reduction, was analysed by reversed-phase ion-pair chromatography and soft-gel permeation chromatography. The results were compared with corresponding data for complexes prepared with the traditional reducing agent tin(II). Significant differences between the chromatograms of the three preparations were found. They were interpreted in terms of the occurrence of different complexes in the three preparations.

Levels of metals in hair of young children as an indicator of environmental pollution.

In 1982 the levels of lead (Pb), cadmium (Cd), vanadium (V), copper (Cu), and selenium (Se) were determined in hair of 231 four- to five-year-old children. The objective was to explore the feasibility of using metal-in-hair levels in groups of children as an indicator of environmental pollution. The study was carried out in four areas, which were assumed to differ in ambient pollution by metals. A questionnaire on personal data, socioeconomic status, intake of beverages, and life-style was completed by the parents. The metal-in-hair levels covered a large range. The variables pertaining to location together with sex, presence of a garden, and drinking of coffee and/or tea explained 32% of the variance of Pb, 24% of the variance of Cd, and 21% of the variance of V. The total variance explained by all measured questionnaire items was at best 38%. The location was the most important factor. Cu and Se levels did not differ between the locations.

The separation of 99mTc(Sn)EHDP complexes by HPLC and GPC.

For the characterization of the multi-component bone-scan agent 99mTc(Sn)EHDP we have analysed the complex mixture with reversed phase ion pair chromatography (IPC) and soft gel permeation chromatography (GPC). With IPC five major complexes were found within a separation-time of 40 min. To avoid decomposition of the complexes during separation, the concentrations of EHDP and the reductant Sn(II) in the eluent had to be identical to the EHDP and Sn(II) concentrations used for the preparation of the complexes. To investigate the stability of the complexes we applied separation by IPC, followed by re-analysis of the fractions within 1 h and after 21-25 h. It appears that there is a state of equilibrium between the five complexes. Within 1 h after isolation the separated complexes were still more than 90% in their original form while after 20 h considerable amounts of the other complexes are found. The two complexes with the largest retention time with IPC are the most stable ones. When the total mixture was re-analysed after 26 h all five components appeared to be still present, but the relative amount of the most stable component had increased. Using GPC for the separation of the complex mixture, we found four major peaks within a separation time of 14 h. The elution orders of the complexes with the two separation methods are opposite.

The effect of DMSO treatment on the composition of 99mTc(Sn)EHDP.

To find an explanation for the reported positive effect of a dimethyl sulfoxide (DMSO) treatment on the performance of the bone scan agent technetium-(tin)-ethane-1-hydroxy-1, 1-diphosphonate, we compared the composition of the agent, prepared with and without treatment with DMSO by using high performance ion-pair chromatography (IPC). The preparation obtained with the DMSO treatment appeared to contain a larger fraction of large and highly charged polynuclear complexes than the preparation without the DMSO treatment. According to experiments by other investigators the smaller 99mTc(Sn)EHDP complexes (early eluting components in IPC) give lower bone/blood ratios than the larger ones. The results presented in this paper show that the explanation for the effect of the DMSO treatment may be that the Sn-EHDP complexes which are removed by extraction with DMSO, give relatively small 99mTc(Sn)EHDP complexes. Without these small complexes a superior bone scan agent is obtained. From experiments in which an excess of 99TcO4 over Sn(II) was used, it was concluded that at least one of the technetium complexes contains Sn(IV). On the other hand, the absence of Sn from a late eluting technetium complex was proven.

Trace element levels in hair of eight-year-old children.

A study of trace element levels in hair was performed on 183 eight-year-old schoolchildren living in Bijlmermeer, a suburb of Amsterdam, the Netherlands. Microlevel-elements, such as Au, Co, Ag, Se and Cd, and macrolevel-elements, such as Pb, Cu, Fe and Zn, were analyzed using the NAA and AAS methods. The total group of children was divided into subgroups, according to ethnic origins: Caucasian boys and girls, Hindustani children and a Surinamese rest group. The relation between element levels in hair and nutritional status, anthropometric and haematological variables were studied. Most levels corresponded reasonably with literature data. The iron in hair may be positively related to daily dietary intake of iron.

The influence of the method of preparation of the bone scanning agent 99mTc(Sn)EHDP on its tissue distribution in the rat.

The tissue distribution in the rat of the bone scanning agent 99mTc(Sn)EHDP is investigated by three methods, viz. by dissecting the animals 3 and 24 h post injection, by scanning the animals with a rectilinear scanner and by whole body autoradiography, particular of micro-sections of the skeleton. The effect of varying the experimental conditions in the preparation of the bone scanning agent (pH and concentrations of Sn(II) and EHDP) is investigated. In some of the experiments additional amounts of Sn(II) and EHDP are added to the reaction mixture after the preparation of the bone scanning agent. In this way the influence of the Sn(II) and EHDP concentrations on the composition of the bone scanning agent, and their influence as such on tissue uptake can be separately investigated. The 99mTc-uptake in bone is compared with the distribution of the 99mTc over the two main products in the reaction mixture, viz. 99mTc(IV)-Sn-EHDP2 and 99mTc(IV)-Sn-EHDP. In addition, the stability in vitro of some of the preparations in urine and plasma and the in vivo binding of the 99mTc to plasma proteins are determined. A procedure for the preparation of the bone scanning agent is recommended.