222
Phytoplankton
9.4.3
Acrylic Acid
Capillary gas chromatography with electron capture detection has been used [634] for
the trace level determination of acrylic acid in algal cultures (Hymenomonas carterae
and Skeletonema costatum). Acrylic acid was extracted using tri-n-octylphosphine
oxide dissolved in methyl tertiary butyl ether. The extracted acids were analysed
following crown ether (18-crown-6) catalysed derivatization with pentafluorobenzyl
bromide.
9.4.4
Carbohydrates
Cowie and Hedges [635] have described a technique for extraction and quantitative
analysis of neutral monosaccharides from plankton algae, requiring as little as 10 mg
of total organic matter. Acid hydrolysis yields monomeric sugars which may exist in
up to five isomeric forms when in solution. Lithium perchlorate is used to equilibrate
sugar isomer mixtures in pyridine catalytically prior to conversion to their trim ethylsilyl ether derivatives. Analysis is carried out by use of gas-liquid chromatography on
fused-silica capillary columns. Quantification on the basis of a single clearly resolved
peak for each sugar is made possible by the equilibration step.
The freeze dried sample of algae is ground and homogenized, and a weighed
portion treated with 70 % sulphuric acid at 20°C for 2 h, then heated to 100°C for 3 h.
Adonitol and sorbitol are added as internal standards, and the mixture homogenized
prior to neutralization with anhydrous barium hydroxide and centrifugation to remove barium sulphate. The neutralized solution is passed down a column of 1:1 cation:anion exchange resins and the eluate evaporated to dryness at 60°C. The dried residue
is dissolved in pyridine and treated with bis(trimethylsilyl) fluoracetamide and trimethylchlorosilane to form the methyl derivative of carbohydrates which is then gas
chromatographed. Recoveries of carbohydrates from algae put through the entire
analytical procedure ranged from 64 % (ribose) and 98 % (fucose). An 81 % recovery
of glucose from cellulose was obtained. Some typical values obtained for carbohydrates in algae are listed in Table 9.7.
Table 9.7
Carbohydrate contents of algae reproducibility (from [635])
mg of sugar 100 mg- 1 of organic carbon
LXY
ARA
RHA
RIB
XYL
Sediment
SMD
0.02 ± 0.00
0.07 ± 0.01
0.08 ± 0.00
0.30 ± 0.02
0.08 ± 0.00
%RSD
0.00
14.3
0.00
6.67
0.00
FUC
MAN
GAL
GLU
TCHiO
SMD
0.22 ± 0.01
0.60 ± 0.02
0.32 ± 0.02
2.06 ± 0.05
3.75 ± 0.12
%RSD
4.55
3.33
6.25
2.43
3.20
Phytoplankton
9.4.3
Acrylic Acid
Capillary gas chromatography with electron capture detection has been used [634] for
the trace level determination of acrylic acid in algal cultures (Hymenomonas carterae
and Skeletonema costatum). Acrylic acid was extracted using tri-n-octylphosphine
oxide dissolved in methyl tertiary butyl ether. The extracted acids were analysed
following crown ether (18-crown-6) catalysed derivatization with pentafluorobenzyl
bromide.
9.4.4
Carbohydrates
Cowie and Hedges [635] have described a technique for extraction and quantitative
analysis of neutral monosaccharides from plankton algae, requiring as little as 10 mg
of total organic matter. Acid hydrolysis yields monomeric sugars which may exist in
up to five isomeric forms when in solution. Lithium perchlorate is used to equilibrate
sugar isomer mixtures in pyridine catalytically prior to conversion to their trim ethylsilyl ether derivatives. Analysis is carried out by use of gas-liquid chromatography on
fused-silica capillary columns. Quantification on the basis of a single clearly resolved
peak for each sugar is made possible by the equilibration step.
The freeze dried sample of algae is ground and homogenized, and a weighed
portion treated with 70 % sulphuric acid at 20°C for 2 h, then heated to 100°C for 3 h.
Adonitol and sorbitol are added as internal standards, and the mixture homogenized
prior to neutralization with anhydrous barium hydroxide and centrifugation to remove barium sulphate. The neutralized solution is passed down a column of 1:1 cation:anion exchange resins and the eluate evaporated to dryness at 60°C. The dried residue
is dissolved in pyridine and treated with bis(trimethylsilyl) fluoracetamide and trimethylchlorosilane to form the methyl derivative of carbohydrates which is then gas
chromatographed. Recoveries of carbohydrates from algae put through the entire
analytical procedure ranged from 64 % (ribose) and 98 % (fucose). An 81 % recovery
of glucose from cellulose was obtained. Some typical values obtained for carbohydrates in algae are listed in Table 9.7.
Table 9.7
Carbohydrate contents of algae reproducibility (from [635])
mg of sugar 100 mg- 1 of organic carbon
LXY
ARA
RHA
RIB
XYL
Sediment
SMD
0.02 ± 0.00
0.07 ± 0.01
0.08 ± 0.00
0.30 ± 0.02
0.08 ± 0.00
%RSD
0.00
14.3
0.00
6.67
0.00
FUC
MAN
GAL
GLU
TCHiO
SMD
0.22 ± 0.01
0.60 ± 0.02
0.32 ± 0.02
2.06 ± 0.05
3.75 ± 0.12
%RSD
4.55
3.33
6.25
2.43
3.20