7.3.15
Nitrogen Bases
Non-Metals
157
Trimethylamine [319]. Amines, and basic substances that are not rendered nonreactive by formaldehyde, are released at room temperature from an extract by
potassium hydroxide and extracted into toluene. The toluene phase is separated and
dried and picric acid reagent is added in order to form a coloured complex with
trimethylamine. The absorbance of this solution at 410 nm is a measure of the
concentration of trimethylamine. Other tertiary amines and bases, not completely
rendered non-reactive by formaldehyde under the conditions of the method, may also
give coloured complexes, but normally this interference is small.
Methylamines [319]. The volatile amines in the sample are extracted by means of
perchloric acid. The perchloric acid is made alkaline with sodium hydroxide, and the
amines liberated are steam distilled into hydrochloric acid. The concentration of
amines, including trimethylamine, is determined in the hydrochloric acid solution by
gas-liquid chromatography.
Trimethylamine Oxide [319]. Trimethylamine oxide in an extract of the sample is
reduced with titanium(lII) chloride to trimethylamine, which is then determined. The
value obtained for the trimethylamine content of the sample before reduction is
subtracted from this value to give the trimethylamine oxide.
Hypoxanthine [319]. Hypoxanthine is extracted from the sample by macerating it
with perchloric acid. After neutralisation, the extract is treated with an enzyme that
converts the hypoxanthine quantitatively into uric acid, which is determined by
measuring its absorbance at 290 nm. Both the enzyme and the extract absorb at this
wavelength, and so it is necessary to carry out measurements on blanks. The method
is not specific for hypoxanthine, as similar results will be given by xanthine, which,
although not normally present, should be looked for when unusual samples are being
examined.
Triaryl Phosphate Esters. Murray [476] has described a gas chromatographic method
for the determination in fish tissues of triarylphosphate esters (I mol S-140, tricresyl
phosphate, cresol diphenyl phosphate). These substances are used commercially as
lubricating oil and plastic additives, hydraulic fluids, and plasticizers. The method
involves extraction from the samples, hydrolysis, and measurement of the individual
phenols by gas chromatography as the trimethylsilyl derivatives. The lower detection
limit was about 3 mg kg- 1 of fish.
7.3.16
Organophosphorus Insecticides
Deutsch et al. [477] determined dursban in fish. After a preliminary cleanup, the
extract is chromatographed on a column packed with 3 % Carbowax 20 m on GasChrom (60 to SO-mesh), which gives excellent separation of dursban from other
organophosphorus insecticides. Both thermionic and flame photometric detectors are
satisfactory. Recoveries range from 75 to 105 % (i. e. 90 ± 15 %) depending on the
Nitrogen Bases
Non-Metals
157
Trimethylamine [319]. Amines, and basic substances that are not rendered nonreactive by formaldehyde, are released at room temperature from an extract by
potassium hydroxide and extracted into toluene. The toluene phase is separated and
dried and picric acid reagent is added in order to form a coloured complex with
trimethylamine. The absorbance of this solution at 410 nm is a measure of the
concentration of trimethylamine. Other tertiary amines and bases, not completely
rendered non-reactive by formaldehyde under the conditions of the method, may also
give coloured complexes, but normally this interference is small.
Methylamines [319]. The volatile amines in the sample are extracted by means of
perchloric acid. The perchloric acid is made alkaline with sodium hydroxide, and the
amines liberated are steam distilled into hydrochloric acid. The concentration of
amines, including trimethylamine, is determined in the hydrochloric acid solution by
gas-liquid chromatography.
Trimethylamine Oxide [319]. Trimethylamine oxide in an extract of the sample is
reduced with titanium(lII) chloride to trimethylamine, which is then determined. The
value obtained for the trimethylamine content of the sample before reduction is
subtracted from this value to give the trimethylamine oxide.
Hypoxanthine [319]. Hypoxanthine is extracted from the sample by macerating it
with perchloric acid. After neutralisation, the extract is treated with an enzyme that
converts the hypoxanthine quantitatively into uric acid, which is determined by
measuring its absorbance at 290 nm. Both the enzyme and the extract absorb at this
wavelength, and so it is necessary to carry out measurements on blanks. The method
is not specific for hypoxanthine, as similar results will be given by xanthine, which,
although not normally present, should be looked for when unusual samples are being
examined.
Triaryl Phosphate Esters. Murray [476] has described a gas chromatographic method
for the determination in fish tissues of triarylphosphate esters (I mol S-140, tricresyl
phosphate, cresol diphenyl phosphate). These substances are used commercially as
lubricating oil and plastic additives, hydraulic fluids, and plasticizers. The method
involves extraction from the samples, hydrolysis, and measurement of the individual
phenols by gas chromatography as the trimethylsilyl derivatives. The lower detection
limit was about 3 mg kg- 1 of fish.
7.3.16
Organophosphorus Insecticides
Deutsch et al. [477] determined dursban in fish. After a preliminary cleanup, the
extract is chromatographed on a column packed with 3 % Carbowax 20 m on GasChrom (60 to SO-mesh), which gives excellent separation of dursban from other
organophosphorus insecticides. Both thermionic and flame photometric detectors are
satisfactory. Recoveries range from 75 to 105 % (i. e. 90 ± 15 %) depending on the