70 Organic compounds in soils, sediments & sludges
To check the enhancement effect in the presence of soil extracts, soil was treated
with ammonium nitrate at a rate equivalent to 200 kg ha
−1 . When 50 g of the soil
were extracted with 100 ml of methanol using the method of Byast et al [47] the
concentration of ammonium nitrate in solution was about 4 µg µL. Injections of
the treated soil extract increased the peak height of a subsequent 60 ng Atrazine
standard by 55–65%. No increase occurred following injections of untreated soil
extracts.
Cotterill et al [46] concluded that the apparent enhancement of response could
lead to large errors in the determination of pesticides residue using the peak-height
method of measurement. The magnitude could depend on the frequency of injection
of standards. Therefore, when a high ammonium nitrate fertiliser concentration is
present in pesticide extracts, peak areas are more likely to give accurate values than
peak heights. It is advisable that extracts from soils containing high fertiliser levels
should be chromatographed using a freshly conditioned column. When ammonium
nitrate is present in the soil in sufficient amounts to cause measurement difficulties,
its presence in the extract should be avoided by the use of an alternative extraction or
partition technique.
Studies have been made of the fate of 3-amino 1,2,4 triazole herbicides in soils
[48], while adsorption of aminotriazole by clay minerals has been postulated, little is
known of the interaction with pure clay minerals, particularly of the montmorillonite
group. The importance of such reactions cannot be overemphasised in view of their
bearing on the persistence of the herbicide in the soil.
While the high solubility of aminotriazole in water (28 g per 100 ml at 23
◦ C)
suggests ready leaching from whole soil, Russell et al [48] showed if the soil contains
a montmorillonite-type mineral, the aminotriazole might be resistant to leaching as a
result of adsorption by the montmorillonite.
The 3-aminotriazole molecule is protonated when adsorbed on montmorillonite
surfaces to produce the 3-aminotriazolium cation. In the case of montmorillonite saturated with polyvalent cations (Ca
2+ , Cu
2+ , Ni
2+ , A1
3+ ) protonation is believed to be
due to the highly polarised water molecules in direct co-ordination to these cations.
The decreasing order of extent of protonation (Ca, Mg, A1) reflects the order of
decreasing polarising power of the cations. Infrared spectra indicate co-ordination of
2-aminotriazole to Ni
2+ and Cu
2+ cations. The infrared absorption band at 1696 cm
−1
is assigned to the C=N stretching vibration of the exocyclic C=N
+ HH group. Shifts
of the 1696 cm
−1 band to 1683 and 1666 cm
−1 upon dehydration and deuteration,
respectively, suggest that the positive charge on the protonated molecule lies on the
exocyclic nitrogen. The protonated molecule undergoes normal exchange reactions
with other cations.
Stransky et al [49] investigated the possibility of determining the triazine herbicides
Atrazine (2-chloro-4ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro
4,6, bis ethylamino 1,3,5 triazine), Atratone (2-ethyl amino-4-isopropylamino 1,3,5
triazine), Prometryne, Desmetryn and Methoprotryne, also the growth regulator
Chlormequat and the quarternery cationic herbicides Paraquat (1,1
dimethyl-4,4bypyridinium chloride) and Diquat(1,1
ethylene-2, 2-bypyridinium bromide in soil
extracts by capillary isotachophoresis. The more basic triazine could be determined
directly using enforced isotachophoresis but very week triazine bases had to be
derivatised by nucleophilic substitution of chlorine by electron-donor or quaternary
To check the enhancement effect in the presence of soil extracts, soil was treated
with ammonium nitrate at a rate equivalent to 200 kg ha
−1 . When 50 g of the soil
were extracted with 100 ml of methanol using the method of Byast et al [47] the
concentration of ammonium nitrate in solution was about 4 µg µL. Injections of
the treated soil extract increased the peak height of a subsequent 60 ng Atrazine
standard by 55–65%. No increase occurred following injections of untreated soil
extracts.
Cotterill et al [46] concluded that the apparent enhancement of response could
lead to large errors in the determination of pesticides residue using the peak-height
method of measurement. The magnitude could depend on the frequency of injection
of standards. Therefore, when a high ammonium nitrate fertiliser concentration is
present in pesticide extracts, peak areas are more likely to give accurate values than
peak heights. It is advisable that extracts from soils containing high fertiliser levels
should be chromatographed using a freshly conditioned column. When ammonium
nitrate is present in the soil in sufficient amounts to cause measurement difficulties,
its presence in the extract should be avoided by the use of an alternative extraction or
partition technique.
Studies have been made of the fate of 3-amino 1,2,4 triazole herbicides in soils
[48], while adsorption of aminotriazole by clay minerals has been postulated, little is
known of the interaction with pure clay minerals, particularly of the montmorillonite
group. The importance of such reactions cannot be overemphasised in view of their
bearing on the persistence of the herbicide in the soil.
While the high solubility of aminotriazole in water (28 g per 100 ml at 23
◦ C)
suggests ready leaching from whole soil, Russell et al [48] showed if the soil contains
a montmorillonite-type mineral, the aminotriazole might be resistant to leaching as a
result of adsorption by the montmorillonite.
The 3-aminotriazole molecule is protonated when adsorbed on montmorillonite
surfaces to produce the 3-aminotriazolium cation. In the case of montmorillonite saturated with polyvalent cations (Ca
2+ , Cu
2+ , Ni
2+ , A1
3+ ) protonation is believed to be
due to the highly polarised water molecules in direct co-ordination to these cations.
The decreasing order of extent of protonation (Ca, Mg, A1) reflects the order of
decreasing polarising power of the cations. Infrared spectra indicate co-ordination of
2-aminotriazole to Ni
2+ and Cu
2+ cations. The infrared absorption band at 1696 cm
−1
is assigned to the C=N stretching vibration of the exocyclic C=N
+ HH group. Shifts
of the 1696 cm
−1 band to 1683 and 1666 cm
−1 upon dehydration and deuteration,
respectively, suggest that the positive charge on the protonated molecule lies on the
exocyclic nitrogen. The protonated molecule undergoes normal exchange reactions
with other cations.
Stransky et al [49] investigated the possibility of determining the triazine herbicides
Atrazine (2-chloro-4ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro
4,6, bis ethylamino 1,3,5 triazine), Atratone (2-ethyl amino-4-isopropylamino 1,3,5
triazine), Prometryne, Desmetryn and Methoprotryne, also the growth regulator
Chlormequat and the quarternery cationic herbicides Paraquat (1,1
dimethyl-4,4bypyridinium chloride) and Diquat(1,1
ethylene-2, 2-bypyridinium bromide in soil
extracts by capillary isotachophoresis. The more basic triazine could be determined
directly using enforced isotachophoresis but very week triazine bases had to be
derivatised by nucleophilic substitution of chlorine by electron-donor or quaternary