Introduction - Determination of Anions in Natural and Treated Waters - page 44

detector Roth Scientific - Chrom-A-

Scope

Cecil Instruments CE 1400 Series 1000

Differential viscosity
mass detection
(evaporative)

Roth Scientific
Applied
Chromatography
system

-
750/14

Chrom-A-
Scope
-

Diode array Varian 9060 200L and

5001
5500 series

Perkin-Elmer LC 135, LC 235

and LC 480

-

LKB 2140

Hewlett Packard Multiple

wavelength
detector

1050 series

Source: Own files

absorb in the ultraviolet-visible region, nor do they possess natural fluorescence. Each of
the major methods has its own particular advantages and disadvantages. Since the variety
of available chemistries can be confusing, the method itself should govern the choice that
meets requirements, rather than the equipment or systems offered. The optimal method is
best selected by a comprehensive and objective review of all commonly used techniques.
Overriding criteria which will influence the selection are resolution, sensitivity and
speed. While the very best chromatogram for any given method will inevitably be a
compromise, only the fullest evaluation of all the alternatives offered will guarantee a
correct selection.
Certainly, a vast amount of experience has been gained by the widespread use of
conventional amino acid analysers. They offer high reliability, accuracy, reproducibility
and can separate complex samples. Because conventional analysers can be fully
automated, they are widely used in routine analysis. However, the method is limited by
the sensitivity which can be achieved using ninhydrin as the derivatising agent.
Sensitivity can be increased by using ortho -phthaldialdehyde (OPA) instead, but where
extremely high sensitivity is required, high performance liquid chromatography is the
method of choice.
The other reagents used in high performance liquid chromatography are 9-fluorenyl
methoxycarbonyl chloride (FMOC) and phenyliso-thiocyanate (PITC). Fluorenyl
methoxycarbonyl chloride is becoming increasingly popular in protein chemistry research
because it reacts with secondary amines and also offers rapid analysis of protein
hydrolsylates.
One aspect governing the choice of method is the sensitivity required. If only a small
amount of sample is available, then for the LKB Alpha Plus and the LKB high