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Determination of boron isotopic variations in aquatic systems by negative thermal ionization mass spectrometry as a tracer for anthropogenic influences (CAT#: STEM-ST-0218-LJX)

Introduction

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 11B/10B 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 MgCl2 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.




Principle

Thermal ionization mass spectrometry exploits the thermochemical reactions that occur in molecules in a sample when they are irradiated by a beam of high energy electrons. This reaction usually takes place at high temperatures, resulting in the formation of ions. The ionized species are accelerated in an electric field and then analyzed by mass spectrometry through the ion-focusing lens of a mass spectrometer. The mass spectrometer will separate and detect the ions according to their mass and charge.

Applications

For analyzing the distribution of molecules, atoms and molecular groups.
For studying the chemical structure of Earth's minerals and rocks.
For studying the structure and function of biomolecules.
For studying problems in physics.

Procedure

1. The sampling system sends the sample to be analyzed into the ion source;
2. The ion source ionizes the atoms and molecules in the sample into ions;
3. The mass analyzer separates ions according to the size of the mass-charge ratio;
4. The detector is used to measure and record the intensity of the ion current to obtain the mass spectrum.

Materials

• Sample Type:
Boron

Notes

Before starting the machine, check whether the water (water cooler), electricity, gas (argon/nitrogen), temperature, humidity, and exhaust air of the instrument are normal.
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