Comparison of TLRC Detection Methods

As described at the beginning of this article, there are three principal techniques for the analysis of radio active components on TLC plates, autoradiography, zonal analysis and mechanical detectors (e.g. linear analysers, phosphor imagers, MWPC detectors). The technique of choice depends on a number of parameters but of primary consideration are sensitivity and resolution. Other parameters to be considered are quantification, linear dynamic range, speed, sample throughput and preservation of sample. A comparative summary of the detection methods with respect to these parameters is shown in Table 2.

Both autoradiography and zonal analysis have a number of drawbacks, including sensitivity and resolution, but primarily both techniques are extremely time-consuming. Linear analysers offer a good compromise between speed, resolution and quantitative accuracy. However, the performance of the linear analysers falls well below that of the currently available MWPC detectors and phosphor imagers in all respects. Sensitivity, quantification and, particularly, resolution are significantly superior, resulting generally in much better quality chromato-grams. The phosphor imagers have slightly better resolution than the MWPC detectors but the disadvantage of phosphor imagers is that the chromato-

Table 2 Comparison of thin-layer radiochromatography analysis techniques

Parameters

Autoradiography

Zonal analysis

Linear analyser

MWPC detector

Phosphor imager

Sensitivity

+

+ + + + +

# #

+ + + + +

+ + + + +

Resolution

+ + + + +

#

# #

+ + + +

+ + + + +

Quantification

#

+ + + + +

# # # #

+ + + + +

+ + + + +

Dynamic range

# # #

# # #

+ + +

+ + + + +

+ + + + +

Speed

#

# #

+ + + + +

+ + + + +

# # # #

Sample throughput

#

#

+ + #

+ + + +

+ + + + +

Preserves sample

Yes

No

Yes

Yes

Yes

+ + + + +, Excellent; # # # #, very good; # # #, good; # #, satisfactory; #, poor. (Reproduced with permission from Clark and Klein, 1996.)

gram development cannot be seen in real time. Also, for a single plate the analysis time with the MWPC detectors is quicker but when more sample throughput is required, then the phosphor imagers have the advantage since many plates can be exposed simultaneously.

In general, as the newer range of detectors were brought on to the market they were very expensive in comparison to the linear analysers. However, with increasing competition and technological developments, prices are slowly coming down.

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