Calculation of Intensity and Efficiency of Nutrition
117
measurement in several parallel subsamples is calculated per 1 mg of body
organic carbon of the consumer, having estimated the values of wet weight of
animal material per 1 ml of its hydrolyzate, the volume of hydrolyzate taken
into the counting samples, and the percentage of organic carbon in the wet
animal material. The latter is estimated as described above (see Sect. 3.4.1).
Thus, the radioactivity of consumers' body material is estimated (Ra, cpmJ.lg
C- 1 ). For small animals, the values of Ra are calculated having estimated their
body carbon content (W), as described above (see Sect. 3.4.1).
An alternative method of Ra estimation can also be used: the combustion
of animals or portions of homogenates of their bodies and the subsequent
radioassay of 14C02 formed by gas flow radiometry or by measuring radioactivity in the absorbing solution of hyamine or some other organic ammonium
base (see Sect. 2.5.5). For such a procedure we have used the wet chromic combustion of animals in the apparatus shown in Fig. 2.3 (Sorokin 1986). An
important advantage of this latter method is that it permits measuring Ra and
W values simultaneously. The animal material (~0.5-2 mg C) is placed into the
combustion test tube of the apparatus. The absorber is filled with 5 or lOml of
0.1 N KOH solution (exact volumes) in the case of W also being estimated. If
not, it is filled with 5 ml 5% hyamine solution in toluene or methanol. When
a slow flow of air through the apparatus is established, 3 ml 0.2 N solution
of K2Cr207 containing traces of AgS04 as catalyzer are added into the test
tube, and the mixture is boiled for 10min. After cooling, the air flow is
increased and the CO2 formed is distilled for another 5-10min. Then all taps
are closed and the contents of the absorber discharged into the measuring
cylinder to measure the total volume of the liquid. On using hyamine solution
as the absorber, the remains of the absorbing liquid is washed out with toluene
or methanol and exact aliquots of 1-5ml are extracted from the measured
volume of absorbing solution and poured into the scintillation vial for radio assay to determine the Ra value. When both values, Ra and W, are to be measured, the solution of KOH used in this case is washed out from the absorber
with boiled hot distilled water into the same measured cylinder to adjust
the volume exactly to 30 ml. Then, two identical aliquots are taken from this
solution to estimate Ra either by direct injection into the scintillation vial
and radioassay with the use of a water-miscible scintillation cocktail or by
measuring the radioactivity of 14C02 in the BaC03 sediment after its sedimentation in the presence of BaCl2 and subsequent collection of BaC03
sediment on the membrane filter (see Sect. 2.5.5). In this case, it is possible to
determine also the value of W, by transferring the remains of the still hot KOH
solution from the cylinder into a closed flask with 1 ml 10% BaCtz solution
added. After precipitation of BaC03 lOmin later, the mixture is titrated with
0.1 N HCI in the presence of phenolphthalein as indicator. The Wvalue is then
calculated as follows: W = 600 x Vo - VrlNJ.lgCsp.-t, where Vo is the volume
of 0.1 N HCI spent by titration of blank standard volume of 0.1 N KOH solution in the presence of BaCtz, ml; VI the same after CO2 distillation, ml; 600
the amount of organic carbon corresponding to 1 ml of 0.1 N HCI, J.lg C, and N
117
measurement in several parallel subsamples is calculated per 1 mg of body
organic carbon of the consumer, having estimated the values of wet weight of
animal material per 1 ml of its hydrolyzate, the volume of hydrolyzate taken
into the counting samples, and the percentage of organic carbon in the wet
animal material. The latter is estimated as described above (see Sect. 3.4.1).
Thus, the radioactivity of consumers' body material is estimated (Ra, cpmJ.lg
C- 1 ). For small animals, the values of Ra are calculated having estimated their
body carbon content (W), as described above (see Sect. 3.4.1).
An alternative method of Ra estimation can also be used: the combustion
of animals or portions of homogenates of their bodies and the subsequent
radioassay of 14C02 formed by gas flow radiometry or by measuring radioactivity in the absorbing solution of hyamine or some other organic ammonium
base (see Sect. 2.5.5). For such a procedure we have used the wet chromic combustion of animals in the apparatus shown in Fig. 2.3 (Sorokin 1986). An
important advantage of this latter method is that it permits measuring Ra and
W values simultaneously. The animal material (~0.5-2 mg C) is placed into the
combustion test tube of the apparatus. The absorber is filled with 5 or lOml of
0.1 N KOH solution (exact volumes) in the case of W also being estimated. If
not, it is filled with 5 ml 5% hyamine solution in toluene or methanol. When
a slow flow of air through the apparatus is established, 3 ml 0.2 N solution
of K2Cr207 containing traces of AgS04 as catalyzer are added into the test
tube, and the mixture is boiled for 10min. After cooling, the air flow is
increased and the CO2 formed is distilled for another 5-10min. Then all taps
are closed and the contents of the absorber discharged into the measuring
cylinder to measure the total volume of the liquid. On using hyamine solution
as the absorber, the remains of the absorbing liquid is washed out with toluene
or methanol and exact aliquots of 1-5ml are extracted from the measured
volume of absorbing solution and poured into the scintillation vial for radio assay to determine the Ra value. When both values, Ra and W, are to be measured, the solution of KOH used in this case is washed out from the absorber
with boiled hot distilled water into the same measured cylinder to adjust
the volume exactly to 30 ml. Then, two identical aliquots are taken from this
solution to estimate Ra either by direct injection into the scintillation vial
and radioassay with the use of a water-miscible scintillation cocktail or by
measuring the radioactivity of 14C02 in the BaC03 sediment after its sedimentation in the presence of BaCl2 and subsequent collection of BaC03
sediment on the membrane filter (see Sect. 2.5.5). In this case, it is possible to
determine also the value of W, by transferring the remains of the still hot KOH
solution from the cylinder into a closed flask with 1 ml 10% BaCtz solution
added. After precipitation of BaC03 lOmin later, the mixture is titrated with
0.1 N HCI in the presence of phenolphthalein as indicator. The Wvalue is then
calculated as follows: W = 600 x Vo - VrlNJ.lgCsp.-t, where Vo is the volume
of 0.1 N HCI spent by titration of blank standard volume of 0.1 N KOH solution in the presence of BaCtz, ml; VI the same after CO2 distillation, ml; 600
the amount of organic carbon corresponding to 1 ml of 0.1 N HCI, J.lg C, and N