230 Organic compounds in soils, sediments & sludges
Chromosorb W (80–100 mesh), temperature programmed from 80 to 220
◦ C and operated in differential mode with flame ionisation detectors. The signal was fed to a digital
integrator and then to both channels of a dual-pen recorder operated at high and low
sensitivities.
Aue et al [128] determined µg l
−1 of nitriloacetic acid and citric acid in sewage
effluents. Following a preliminary clean-up and concentration procedure the acids are
converted to their butyl esters and chromatographed on a Carbowax on Celite 545
column at 183
◦ C.
Rudling et al [129] determined nitriloacetic acid gas chromatographically at the
0.1 µg l
−1 level in sewage. Following separation of the nitriloacetic acid on an anionexchange column, it is derivatised with boron triflyoride in 2-chloroethanol to produce
2-chloroethylnitrilotracetate and gas chromatographed on a column packed with 2
per cent QF-1 on Varaport 30. Detection is achieved by electron capture. Chloride,
sulphate, calcium and magnesium did not interfere in this procedure.
Rudling et al [130] simultaneously determined 0.0–10.2 µg of nitriloacetic acid,
EDTA, and diethylenetriaminepenta-acetic acid in sewage samples as their methyl
esters by gas chromatography. The sample, adjusted to pH7, is extracted with chloroform, 1,2-diaminocyclohexanetetra-acetic acid, an internal standard added and the
mixture treated with methanolic boron trifluoride. Chloroform extracts are injected
into a column packed with 5% V-17 on Aeropak, temperature programmed from 150
to 285
◦ C at 10
◦ C min
−1 using helium as carrier gas. Cadmium, copper, zinc and nickel,
and iron did not interfere.
Polarography
Afghan et al [131] developed an automated method for the determination of
nitriloacetic acid in natural water and sewage samples. The method is based on the formation of the bismuth nitrilotriacetic acid complex at pH2 followed by determination
by twin cell oscillographic d.c. polarography. As little as 10 µg l
−1 of nitrilotriacetic can
be determined, with no pre-concentration of the sample being required. The coefficient
variation for 100 mg l
−1 was 1.3%.
Miscellaneous
Longman et al [132] compared five procedures for removing interferences in the determination of nitriloacetic acid in sewage and sewage effluents. None of these methods
completely overcame interference by metals. These workers then developed an alternative procedure based on passing the filtered sample through a column of chelex × 100
chelating resin (Na + form). To the eluate was added zircon reagent and the extinction was measured at 620 nm. The method was applicable in the range 0–10 µg l
−1
nitriloacetic acid in sewage. Ferric iron did not interfere.
10.4.2 Ethylene diamine tetracetic acid
Korsunevskil et al [133] has developed a procedure for determining very small amounts
of EDTA, which can be used to analyse turbid samples. The method is based on the
proportionality of the photoelectric current generated in the photogalvanic cell to free
EDTA concentration.
Chromosorb W (80–100 mesh), temperature programmed from 80 to 220
◦ C and operated in differential mode with flame ionisation detectors. The signal was fed to a digital
integrator and then to both channels of a dual-pen recorder operated at high and low
sensitivities.
Aue et al [128] determined µg l
−1 of nitriloacetic acid and citric acid in sewage
effluents. Following a preliminary clean-up and concentration procedure the acids are
converted to their butyl esters and chromatographed on a Carbowax on Celite 545
column at 183
◦ C.
Rudling et al [129] determined nitriloacetic acid gas chromatographically at the
0.1 µg l
−1 level in sewage. Following separation of the nitriloacetic acid on an anionexchange column, it is derivatised with boron triflyoride in 2-chloroethanol to produce
2-chloroethylnitrilotracetate and gas chromatographed on a column packed with 2
per cent QF-1 on Varaport 30. Detection is achieved by electron capture. Chloride,
sulphate, calcium and magnesium did not interfere in this procedure.
Rudling et al [130] simultaneously determined 0.0–10.2 µg of nitriloacetic acid,
EDTA, and diethylenetriaminepenta-acetic acid in sewage samples as their methyl
esters by gas chromatography. The sample, adjusted to pH7, is extracted with chloroform, 1,2-diaminocyclohexanetetra-acetic acid, an internal standard added and the
mixture treated with methanolic boron trifluoride. Chloroform extracts are injected
into a column packed with 5% V-17 on Aeropak, temperature programmed from 150
to 285
◦ C at 10
◦ C min
−1 using helium as carrier gas. Cadmium, copper, zinc and nickel,
and iron did not interfere.
Polarography
Afghan et al [131] developed an automated method for the determination of
nitriloacetic acid in natural water and sewage samples. The method is based on the formation of the bismuth nitrilotriacetic acid complex at pH2 followed by determination
by twin cell oscillographic d.c. polarography. As little as 10 µg l
−1 of nitrilotriacetic can
be determined, with no pre-concentration of the sample being required. The coefficient
variation for 100 mg l
−1 was 1.3%.
Miscellaneous
Longman et al [132] compared five procedures for removing interferences in the determination of nitriloacetic acid in sewage and sewage effluents. None of these methods
completely overcame interference by metals. These workers then developed an alternative procedure based on passing the filtered sample through a column of chelex × 100
chelating resin (Na + form). To the eluate was added zircon reagent and the extinction was measured at 620 nm. The method was applicable in the range 0–10 µg l
−1
nitriloacetic acid in sewage. Ferric iron did not interfere.
10.4.2 Ethylene diamine tetracetic acid
Korsunevskil et al [133] has developed a procedure for determining very small amounts
of EDTA, which can be used to analyse turbid samples. The method is based on the
proportionality of the photoelectric current generated in the photogalvanic cell to free
EDTA concentration.