Instant Notes: Analytical Chemistry

peak height ¥retention time. Integrated peak areas are directly proportional to the amount of analyte chromatographed when worki ...

Section D – Separation techniques D3 THIN-LAYER CHROMATOGRAPHY Thin-layer chromatographyis a form of planar chromatography simil ...

stand for several minutes to allow the atmosphere in the tank to become saturated with the solvent vapor; ● small volumes of liq ...

thick. Commercially produced plates are available in several sizes between 5 cm and 20 cm square and may incorporate an insolubl ...

Solute detection Solutes separated by TLCremain on the surface of the plate after development. As the majority of solutes are co ...

Rfvalues, e.g. amino acids. A single sample is spotted close to one corner of the plate and, after development, there is a parti ...

in clinical and forensic studies, and testing for the presence or absence of specific substances (limit tests) are additional ap ...

Section D – Separation techniques D4 GAS CHROMATOGRAPHY: PRINCIPLES AND INSTRUMENTATION Principles Gas chromatography(GC) is a s ...

pressures and hence their boiling points. Solutes are therefore generally eluted in order of increasing boiling point, except wh ...

● gas supply and controls; ● sample injection port; ● column housed in a thermostatically-controlled oven; ● detection and recor ...

Alternative methods of sample injection are summarized below and in Table 1 , with schematic diagrams in Figures 2and 3. ● Split ...

very small fraction of injected sample reaching the column. A slow purge stream of gas prevents substances bleeding from the sep ...

● Capillary(open tubular) columns have become the most widely-used in recent years. They consist of long, narrow bore, high-puri ...

overloading causes peaks to tail and resolution to deteriorate. Special injec- tion systems are therefore required, as described ...

are specific interactions with a solute, e.g. on a nonpolar stationary phase, t-butyl alcohol (bp 82.6∞C) elutes before cyclohex ...

Temperature control is essential in ensuring reproducible separations by GC. The column is enclosed in an insulated and thermost ...

(i) Thermal conductivity detector(TCD). This is one of the oldest types, and is known also as a katharometeror hot-wire detector ...

(ii) Flame ionization detector (FID). This is the most important of a group of detectors where the signal is related to the ioni ...

The ECDis one of the most sensitive of GC detectors, especially if argon replaces nitrogen as the carrier gas, but traces of air ...

Section D – Separation techniques D5 GAS CHROMATOGRAPHY: PROCEDURES AND APPLICATIONS The effect of column temperature on chromat ...