Question

Suggest the best instrumental method(s) for the following analyses. Also suggest possible sample pre-treatment methods or accessaries if there are any. Consider the sample concentration, possible interferences, sample size, etc.

6) To measure the concentration (about 10-3 M) of Cu2+ samples. 7) To know the crystalline structure of solid samples.

8) To measure Ca2+ concentration (about 1 ppm); the sample volume is very small.

9) To know the molecular structure of a carbonyl-containing organometallic compound [M(CO)n].

10) Roughly estimate the elemental composition of chemical compounds.

Answer 1

6. To measure the concentration of Cu2+ sample – UV spectroscope

            UV spectroscopy refers to absorption spectroscopy or reflection spectroscopy. This spectroscopic make use of the Ultraviolet region and the adjacent visible spectra regions where electromagnetic spectrum, atoms and molecules undergo electronic transitions. The colour of the perceived chemicals might change due to the adsorption or reflectance. Absorption spectroscopy measure the transition of atoms from ground state to excited state.

7. To know the crystalline structure of solid samples – X-ray crystallography (XRC)

            XRC determines the atomic and molecular structure of a crystal. When a bean of X-ray happens to fall on the sample it diffracts these beams into many specific directions with specific angles and directions. A crystallographer measures this angle and directions and produce a three dimensional picture. This 3D picture contains the density of electrons within the sample structure. By knowing this density of electrons we can identify the mean position of atoms, chemical bonds, and various other vital information.

8. To measure Ca2+ concentration – Radiometric methods

            For analysing a small sample of Ca, Radiometric methods can be chosen. Radiometric methods are based on the use of a ratio between two fluorescent intensities.

9. To know the molecular structure of a carbonyl containing organic metallic compound – Infrared spectroscopy

            Infra-Red spectroscopy analysis the interaction of Infrared light with a molecule. It can measure in three ways, by analysing the absorption, emission and reflection methods.

10. Elemental composition of Chemical compounds – X-ray fluorescence spectroscopy (XRF)

            XRF is the emission of characteristic fluorescent (secondary) X-rays from a material that has being excited by bombarding with high energy x-rays or gamma rays. This method can be used for elemental analysis and chemical analysis.