Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences.

A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03-0.3% have been obtained for the determination of the (11)B/(10)B isotope ratio using nanogram amounts of boron. Ba(OH)(2) has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl(2) better reproducibilities of the measurement have been achieved. A possible interference of BO(-)(2) ions at mass number 42 by CNO(-) could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low (11)B/(10)B ratios (expressed in delta(11)B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low delta(11)B values are normally correlated with high boron and high chloride concentrations. On the other hand, delta(11)B shifts to higher values in less contaminated samples. For ground water with saline influences, only the delta(11)B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination.

[Bilateral adrenal pheochromocytoma. Diagnosis and follow-up using the clonidine test and measurement of plasma neuropeptide Y concentration]. / Bilaterales adrenales Phäochromozytom. Diagnostik und Verlaufskontrolle mittels Clonidintest und Messung der Plasmakonzentration von Neuropeptid Y.

The role of the clonidine suppression test and determination of the plasma concentration of noradrenaline and of neuropeptide Y (NPY) for the diagnosis and monitoring of bilateral pheochromocytoma was studied in a ten year old girl. Prior to tumor removal plasma concentration of noradrenaline (25.9 nmol/l) and NPY (14 pmol/l) were markedly elevated. Inhibition of central sympathetic activity by clonidine (150 micrograms orally) did not lower the plasma concentration of noradrenaline (70.4 nmol/l) and NPY (52.6 pmol/l). However in an adolescent boy with renal hypertension plasma concentration of noradrenaline and NPY fell following clonidine application (noradrenaline from 1.9 to 1.3 nmol/l, NPY from 3.6 to 2.4 pmol/l). After complete removal of the pheochromocytoma noradrenaline and NPY fell back to normal.