a. The suppressor in Figure 26-8 enables low parts per billion conductivity detection for anions such as Cl-Cl^- and Br-,Br^-. but very poor detection limits for anions such as CN-CN^- and borate. Explain why.

b. Mixtures of sodium carbonate and bicarbonate can be used as eluent in suppressed-ion anion chromatography. Detection limits are poorer than with hydroxide eluent due to a higher background conductivity. Explain why.

Figure 26-8

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Anode H₂O 2H+ + O₂ +2e H₂O + O₂ out H+ H₂O in K+ X™ in KOH eluent from separator column H+ + OH™ + H₂O K+ H+ X-out to detector KOH + H₂O + H₂ out H₂O in H₂ + 2OH- Cathode 2H₂O + 2e Cation-exchange membrane (negatively charged) Harris/Lucy, Quantitative Chemical Analysis, 10e, © 2020 W. H. Freeman and Company FIGURE 26-8 Electrolytic suppression for anion chromatography replaces K+OH KOH eluent with H2O. H₂OH+H* generated at the anode passes through the cation-exchange membrane and replaces K+K+ in the eluent. Anions such as X-X do not pass through the cation exchange membrane due to Donnan exclusion.