ASTM D513-02 pdf free.Standard Test Methods for Total and Dissolved Carbon Dioxide in Water.
Make a blank determination before each series ofCO, determinations.
Empty the reaction tube following completion of ananalysis if the remaining volume is insufficient for the nextsample plus acid.The maximum liquid volume of the sampletube is 12 mL. When the sample tube is replaced, CO, from airthat entered the apparatus must be swept out by the gas streambefore beginning the next analysis. Sixty seconds is normallysufficient for this.To eliminate the necessity of removing thesample tube and the subsequent purge time, a stopcock may beattached to the sample tube to permit draining following ananalysis.
For samples with less than 800 mg/L of CO2, use theprocedure described in for blank determinations on a5.0O-mL untreated portion of the sample.Record the coulometer readout as A.If the CO, content of the sample exceeds 800 mg/L,use a proportionately smaller sample and adjust the calcula-tions accordingly. Do not reduce sample volumes so much thatrepresentative samples cannot be obtained or sample volumescannot be measured with sufficient accuracy.Alternatively, thesample may be diluted using CO2-free water. For samples containing less than 100 mg/L, accuracy may be increased byuse of a larger sample size if a larger sample tube is used. If the volume of the sample tube or scrubbers isincreased, the analysis time may have to be lengthened.At theend of an analysis the titration should be complete and thecoulometer display stable. If the titration is not complete, theanalysis time must be lengthened for both blanks and samples.If desired, samples may be pipetted into acid freereaction tubes positioned on the apparatus to begin the analy-sis. In this case,sufficient time (generally 60 s) must beallowed for CO, from air that entered the apparatus to be sweptfrom the apparatus before acid is added and the analysis begun.Recoveries of known amounts of Co2in aseries of spiked samples of choice were as shown in Table 2.The precision and bias data were derived from resultsof the cooperative tests on samples prepared by laboratoriesspiking a matrix of choice with solutions of NaHCO,. Eightlaboratories participated.Samples of interest chosen by participating laboratories included distilled water， deionized wa-ter, potable water, natural waters, brine, industrial waters，andwaters derived from oil shale retorting.The procedure may notapply to all matrices.It is the user’s responsibility to ensure thevalidity of this test method on other sample matrices and todetermine the effect on the precision and bias when other than5.00-mL sample volumes are used.
Precision and bias for this test method conforms toPractice D 2777, which was in place at the time of collaborative testing. Under the allowances made in 1.4 of PracticeD 2777, these precision and bias data do meet existing require-ments for interlaboratory studies of Committee D19 testmethods.ASTM D513 pdf download.