84
Marine Sediments
For more specific applications, activated charcoal has been replaced by synthetic
adsorbants such as macroreticular resins, e. g. Amberlite XAD (Riley and Taylor
[722], Harvey [723]) or polyurethane foam (Gesser et al. [724]). These adsorbants
suffer from the drawback of being difficult to clean and of retaining traces of the
material collected rather tenaciously. Therefore, these adsorb ants have to be Soxhlet
extracted in order to remove the sorbate which, for all practical purposes, eliminated
the possibility of fractionated desorption.
In applying the principle of reversed-phase chromatography to the accumulation of
dissolved organic material from water, Ahling and Jensen [725] used a mixture of
n-undecane and Carbowax 4000 monostearate on Chromo sorb W as the collecting
medium. Uthe and Reinke [726] tested porous polyurethane coated with liquid phases
such as SE 3, DC 200, QF-l, DEGS, OV-25, OV-225 for the same purposes. In each
case, the coating is achieved easily and may be modified to the desired adsorption
properties. However, the coating is not chemically bonded to the support and may
thus be removed together with the sorbate. Aue et al. [727] demonstrated the potential
of support-bonded polysiloxanes for a simple, fast, and sensitive analysis of organochlorine compounds in natural aqueous systems.
Derenbach et al. [728] tested a technique for the accumulation of certain fractions
of dissolved organic material from sea water and, subsequently, for the fractionated
desorption of the collected material.
The handling of water extracts and possible sources of contamination would thus
be reduced to a minimum. Furthermore, fractionated desorption of the accumulated
material under mild conditions should result in less complex mixtures with little risk
of denaturation.
These workers investigated the suitability of numerous support materials used in
reversed-phase high performance liquid chromatography for the recovery of nonpolar organic compounds from sea water. Porous glass treated with trichloro-noctadecyl silane was found to permit at least a semi-quantitative recovery of test
compounds. This silanized glass support was found to be easy to keep free from
contamination and, in addition, had a relatively high adsorption capacity, permitting
fractional desorption of the test compounds. Results obtained with this column were
compared with those obtained using Amberlite XAD-2.
Derenbach et al. [728] give full details of the preparation of this support material.
They used 14C labelled spike compounds, 1- 14 C n-hexadecane and di(2-ethylhexyl)
(carboxyl-14C) phthalate) and also non-labelled compounds (n-C 16 -n-C 24 alkanes,
diethyl, di-isobutyl, di-n-butyl, butylbenzyl dicyclohexyl, bisethylhexyl phthalic acid
esters, p, pi DDE, DDMU, Dieldrin, Endrin pesticides) in recovery experiments.
Some 25-1 samples of natural sea water were spiked and 5-1 subsamples of these
were extracted with 20, then 10 ml of pure n-hexane. The hexane phases were allowed
to separate for 30-60 min. The combined extracts were dried over anhydrous sodium
sulphate, reduced in volume with a rotary evaporator at 40°C and tap water vacuum,
and taken for silica gel clean-up followed by gas chromatography. The remaining 20 1
of the sample were drawn through the adsorption system at a pumping rate of 2-5
bedvolumes per minute. The system consisted of a precombusted glass fibre filter
(same type as above: diameter 140 mm) and the adsorption column (length 90 mm;
i. d. 23 mm) was either packed with silanized porsus glass, silanized glass beads, or
Marine Sediments
For more specific applications, activated charcoal has been replaced by synthetic
adsorbants such as macroreticular resins, e. g. Amberlite XAD (Riley and Taylor
[722], Harvey [723]) or polyurethane foam (Gesser et al. [724]). These adsorbants
suffer from the drawback of being difficult to clean and of retaining traces of the
material collected rather tenaciously. Therefore, these adsorb ants have to be Soxhlet
extracted in order to remove the sorbate which, for all practical purposes, eliminated
the possibility of fractionated desorption.
In applying the principle of reversed-phase chromatography to the accumulation of
dissolved organic material from water, Ahling and Jensen [725] used a mixture of
n-undecane and Carbowax 4000 monostearate on Chromo sorb W as the collecting
medium. Uthe and Reinke [726] tested porous polyurethane coated with liquid phases
such as SE 3, DC 200, QF-l, DEGS, OV-25, OV-225 for the same purposes. In each
case, the coating is achieved easily and may be modified to the desired adsorption
properties. However, the coating is not chemically bonded to the support and may
thus be removed together with the sorbate. Aue et al. [727] demonstrated the potential
of support-bonded polysiloxanes for a simple, fast, and sensitive analysis of organochlorine compounds in natural aqueous systems.
Derenbach et al. [728] tested a technique for the accumulation of certain fractions
of dissolved organic material from sea water and, subsequently, for the fractionated
desorption of the collected material.
The handling of water extracts and possible sources of contamination would thus
be reduced to a minimum. Furthermore, fractionated desorption of the accumulated
material under mild conditions should result in less complex mixtures with little risk
of denaturation.
These workers investigated the suitability of numerous support materials used in
reversed-phase high performance liquid chromatography for the recovery of nonpolar organic compounds from sea water. Porous glass treated with trichloro-noctadecyl silane was found to permit at least a semi-quantitative recovery of test
compounds. This silanized glass support was found to be easy to keep free from
contamination and, in addition, had a relatively high adsorption capacity, permitting
fractional desorption of the test compounds. Results obtained with this column were
compared with those obtained using Amberlite XAD-2.
Derenbach et al. [728] give full details of the preparation of this support material.
They used 14C labelled spike compounds, 1- 14 C n-hexadecane and di(2-ethylhexyl)
(carboxyl-14C) phthalate) and also non-labelled compounds (n-C 16 -n-C 24 alkanes,
diethyl, di-isobutyl, di-n-butyl, butylbenzyl dicyclohexyl, bisethylhexyl phthalic acid
esters, p, pi DDE, DDMU, Dieldrin, Endrin pesticides) in recovery experiments.
Some 25-1 samples of natural sea water were spiked and 5-1 subsamples of these
were extracted with 20, then 10 ml of pure n-hexane. The hexane phases were allowed
to separate for 30-60 min. The combined extracts were dried over anhydrous sodium
sulphate, reduced in volume with a rotary evaporator at 40°C and tap water vacuum,
and taken for silica gel clean-up followed by gas chromatography. The remaining 20 1
of the sample were drawn through the adsorption system at a pumping rate of 2-5
bedvolumes per minute. The system consisted of a precombusted glass fibre filter
(same type as above: diameter 140 mm) and the adsorption column (length 90 mm;
i. d. 23 mm) was either packed with silanized porsus glass, silanized glass beads, or