Sample Application

It is seen that the result for contact spotting is strongly dependent of the solvent of the sample, whereas for bandwise spray-on application this is not the case. Furthermore, the separation is significantly improved for the latter.

Heated nozzle of the ATS4 (option)
Raising the temperature to 60 °C reduces the time for application of an aqueous sample to about one halve. Especially in trace analysis the use of an ATS4 with heated nozzle is advantageous because large volumes usually have to be applied in order to increase detection sensitivity.

The selection of a sample application technique and the device to be used depends primarily on:

Sample volume
Number of samples to be applied
Required precision and degree of automation.

In order to maximize the separation power of the layer it is important to restrict the size of the sample origin in the direction of chromatography to a minimum. The maximum sample volume that can be applied spotwise »in one stroke« are 5 microliters on conventional layers and 1 microliter on HPTLC layers. Spotwise application of larger volumes requires a device with controllable delivery speed.

Sample application in the form of bands or rectangles:

Spraying-on samples as narrow bands allows the application of larger volumes. Narrow bands as starting zones always ensure the highest resolution. Very large sample volumes or samples with high matrix content can be sprayed-on in the form of rectangles which, prior to chromatography, are focused into narrow bands with a solvent of high elution strength.

All types of Thin-Layer Chromatography, whether qualitative, quantitative or preparative, benefit from optimized resolution as a result of the appropriate sample application technique.

Sample application is the first step of instrumental Thin-Layer Chromatography and thus determines the quality of the analysis.

ATS 4 or Linomat 5?

The CAMAG Automatic TLC Sampler (ATS 4) is the ideal instrument for fully automatic application of a large number of samples with highest precision, whether in a research or a routine lab. Connected to winCATS it is perfectly integrated to control and monitor the entire TLC process.

Furthermore the ATS 4 is used for application of sample, in which for safety reasons manual contact is strictly prohibited. Such samples may include

extremely toxic solutions (e.g. cytostatics)
microbiologically contaminated samples
radioactive compounds

In combination with CAMAG‘s FreeMode software application schemes not common to TLC are possible, for instance applications onto nitro cellulose membranes for the production of diagnostic kits.

The CAMAG Linomat 5 is an affordable alternative to the ATS 4 without making any concessions to the precision of volume dosage. In part it is operated manually, and can even be used in stand-alone mode, but when connected to winCATS it is as perfectly integrated to control and monitor the TLC process as the ATS 4.