Pickering Laboratories Pinnacle PCX - Page 115

6.3-2
Section 6
ApplicAtions
Pinnacle Operators Manual
Pickering Laboratories Inc.
The separation of the 12 carbamates shown in Figure 6.3-A is achieved with the Pickering Carbamate Column
maintained at constant temperature and a water/methanol gradient. The carbamates elute principally in
relation to their relative hydrophobicity. Aldicarb sulfone, which is minimally hydrophobic, elutes early while
methiocarb, which is more hydrophobic, elutes towards the end of the gradient.
The separated carbamates are first hydrolysed by sodium hydroxide (NaOH) at 100°C to release an alcohol,
carbonate, and methylamine. In the second post-column reaction, methylamine reacts with o-phthalaldehyde
(OPA) and the nucleophilic Thiofluor™ to form a highly fluorescent isoindole derivative (Figure 6.3-B).
Note: 1-naphthol fluoresces without derivatization and the hydrolysis of carbaryl in the post-column reactor
also produces 1-naphthol, but at a different retention time. This observation is useful for troubleshooting.
Basic Sample Preparation
The following is a general sample preparation for Water samples containing carbamate. For details, consult the
EPA 531.2 method for drinking water and the AOAC method for Vegetables.
HS
OPA
Fluorescent Isoindole
Carbamate
pH>9
CHO
CHO
S
N
CH
3
NH
2
CH
3
N
CH
3
CH
3
N
CH
3
CH
3
2.
1.
+
O
O
R
NH
CH
3
H
2
O
OH
-
100°C
CH
3
NH
2
+
R OH
CO
3
2
-
+
+
Figure 6.3-B