Introduction
Paraquat (1,1’-dimethyl-4,4’-bipyridylium dichloride, C
12
H
14
N
2
Cl
2
, Figure 1), and
diquat (1,1’-ethylene-2,2’-bipyridilium dibromide, C
12
H
12
N
2
Br
2
, Figure 1), are non-
selective contact herbicideswidely used in agriculture to control broadleaf and
grassyweeds (use of paraquat is restricted in theUnitedStates). Highly charged
dual quaternary amines, they are readily soluble inwater. They also are highly
toxic, and ingestion of either compound can have serious effects, as they can alter
reduction-oxidation activities inbiological systems.
The highly charged herbicides are difficult to retain by standard reversed phase
HPLC, thus ion pairing reversed phasemethods such asUSEPAMethod 549
were developed. Newmaterials and techniques nowallow simplification, better
detection, recovery, and throughput for these analytes.Wehave developeda
simple, effective analysis for paraquat and diquat, based on a newHPLC column
and a uniquemobilephase. This analysis can be performedon a conventional
HPLC systemwithaUV detector. The separationmakes use of a different
analytical property – chaotropism: an ability todisrupt the structure of water and
thereby alter the interactions among analyte, mobilephase, and stationary phase.
In this case, the object is to promote the solubility of the highly polar analytes in a
non-polar substrate (the stationary phase).
