ANALYTICAL CHEMISTRY, VOL. 51, NO. 9, AUGUST 1979
Table VII. Comparison of Trace Samples Analyzed Immediately after Loading and after Seven Days Storage
'
~
Concentration (ppb)
1
Peak Height> (Aft? 0 Days
m
1
Peak Height' Afte; 7 Days (mm
1
RSD (%)
1
Composite standard of 100 ml w a s Ioaaed on e a c h ConcenIralO A v e r a a e 0' l h r e e deternlnatlons l o r e a c h ion
be loaded and then stored for a t least 7 days a t room temperature before analysis without significantly affecting results. Table I shows the results of Experiment One which determined t h a t sample ions are quantitatively retained on concentrators, provided the resin capacity is not exceeded. Tables I1 through V show the data obtained from Experiment Two which determined linearity for the ions studied. Response for Po43-, NO3-, and SO4*-was linear over four orders of magnitude (%lo4 ppb). Response for C1- was linear over three orders of magnitude (2-103 ppb). Correlation coefficients for a linear least squares fit were the following: C1-: 0.9999, Pod3-:0,9991, NO3-: 0.9997, S042-:0.9887. The C1- deviation from linearity a t higher levels may be due to the NO3-, lower selectivity of the resin for C1- compared to Po43-, and S042-.During loading, C1- ions may wash through the concentrator a t lower levels than the other ions. Table VI lists the data obtained from Experiment Three
1535
which determined reproducibility of samples loaded remotely on different concentrator columns. Relative standard deand N O i and viation was approximately 17% for Po43I t should be noted that approximately 25% for C1- and SO:-. the precision obtaind from a single concentrator is significantly better than that obtained using several concentrators. (The RSD for Po43-, NOy, and SO4*-using column A is
