Ultramicroanalysis

Ultramicroanalysis 

a method used in analytical chemistry to study extremely small quantities of a substance, of the order of 10~⁶ g or less. In this method, the specimens are dissolved in such volumes (10~³-10~⁶ ml) that solutions of standard analytical concentrations (10”MO”⁴ normal) are formed. Ultrami-croanalysis is used to study small quantities of various natural and synthesized compounds, minerals, meteorites, various corrosion products, and inclusions in metal alloys. It enables scientists to study quantities of substances considerably smaller than those used in microanalysis.

The techniques of ultramicroanalysis are highly specific and individual for each specimen. Operations are carried out in a capillary vessel while viewing through a magnifying glass (volumes of uptol x 10~³ ml) or a microscope (volumes less than 1 x 10~³ml); mechanical devices are used to move the specimens and the various instruments. Experiments under a microscope are carried out with the aid of micromanipulators.

Among the various operations performed on the specimens are (1) sedimentation in a microcone with subsequent separation of the residue by centrifugation (but not filtration), (2) electrolysis on fine-wire microelectrodes, (3) titration in capillary cells, preferably electrometric, and (4) the determination of tinted compounds in capillary vessels by means of microscope-photometers. In biochemical research, one of the principal ultramicroanalytical methods is spectrophotometry, which is used after the chromatographic or electrophoretic separation of the substances being analyzed. In addition to titriphotometric and spectrophotometric methods, elementary ultramicroanalysis of organic substances also involves gas chromatography and gas analysis. Specimens for ultramicroanalysis are weighed on ultramicroscales with an accuracy of 10”M0~⁹ g; a small sample is loaded onto a sagging quartz filament or a quartz balance suspended on a coiled torsion filament.

The solution of many problems related to the analysis of extremely small specimens is ensured by combining ultramicroanalysis with physical methods of local analysis.

REFERENCES

Korenman, I. M. Vvedenie v kolichestvennyi ul’tramikroanaliz. Moscow, 1963.
Belcher, R. Submikrometody analiza organicheskikh veshchestv. Moscow, 1968. (Translated from English.)
Tolg, G. Elementnyi ul’tramikroanaliz. Moscow, 1973. (Translated from English.)
Alimarin, I. P., and M. N. Petrikova. Kachestvennyi i kolichestvennyi ul’tramikrokhimicheskii analiz. Moscow, 1974.
Submicrogram Experimentation. Edited by N. Cheronis. New York-London, 1960.
El-Badri, H. M. Micromanipulators and Micromanipulation. Wash ington, D.C., 1963.

M. N. PETRIKOVA