Determination of inorganic anions in red algae (Eucheuma cottonii ...

R. Suhaili et al. Proceeding of The International Seminar on Chemistry 2008 (pp. 406-410)Jatinangor, 30-31 October 2008chemically the background conductivity of theelectrolyte of an eluent before it enters theconductivity cell [11-12]. Suppressors are used inconjunction with conductivity detectors to improvedetection sensitivity, especially for anion analysisTwo suppressor types are commonly used foranion analysis. They are continuously regeneratedmembrane suppressors and intermittently regeneratedpacked-bed suppressors. Electrochemical andchemical regeneration have been used with both.Packed-bed suppressors are more rugged and reliablethan membrane suppressors [5-13], but intermittentregeneration limits run time and requires mechanicalswitching mechanisms. While more fragile,membrane suppressors offer continuous operation andregeneration. In addition to suppressing the mobilephase and enhancing the analyte signal through acid–base neutralization reactions like traditional ICsuppressors, this new suppressor also removescarbonic acid as CO (g) from the analyte stream,reducing background conductivity with carbonate–hydrogencarbonate mobile phases to near zero. Thisimproves the signal-to-noise ratio, reduces the waterdip that often interferes with early eluting peaks, andenables gradient separations with carbonate–hydrogencarbonate mobile phases with minimalbaseline shift.The propose of this research is to determinationof eight inorganic anions (F - , Cl -, NO 2 - , Br - , NO 3 - ,HPO 4 2- , SO 4 2- , I - ) by using two 6-port switchingvalves and two packed column suppressors tomaintain low conductivity of mobile phase in redalgae (Eucheuma cottonii) and carrageenan withsuppressed ion chromatography for achieving higherselectivity, shorter analysis time, lower quantitationand detection limits via optimization ofchromatographic parameters for the routine analysis.Materials and MethodsChemicalsAnalytical reagent grade chemicals were purchasedfrom Nacalai Tesque (Kyoto, Japan). Standardsolutions (0.3mM for each anion) were prepared bydissolving NaF, NaHPO 4 , NaNO 2 , NaCl, NaBr, NaI,NaNO 3 , and Na 2 SO 4 by using deionized water. Allstandard solutions were stored in polyethylenecontainers and kept under refrigeration at 4 ◦ C. wereprepared. The deionized water used throughout thisstudy was prepared in the laboratory using a GS-590water distillation system (Advantec, Tokyo, Japan).The stock standard solutions for anions contained ionsof interest. The standard solution of anions Na 2 CO 3and NaHCO 3 were obtained from Wako (Osaka,Japan), and used for the eluent. The eluent wasprepared daily before use.he pH of the carbonat eluentwas measured with an IM-20E ion meter (ToaElectronics, Tokyo, Japan). A 0.45 µm membranefilter for IC obtained from GL Sciences (Tokyo,Japan) and stored in polyethylene containers then keptunder refrigeration at 4 ◦ C. The samples were injectedto the chromatographic system without dilution.SamplesRed algae Eucheuma cottonii which was 40 daysages, harvested from, big Aceh sub-province ofNangro Aceh Darussalam, Indonesian. The algaewere extensively washed with distilled water toremove the particulate material from their surface andwere dried under the sunlight Dried biomass of redalgae was cut, ground and then screened to particlesizes of 150-425 µm. Carrageenan was extracted fromred algae by alkaline solution. Dried red algae andcarrageenan were digested with nitric acid andhydrogen peroxide, the solution was filtered with a0.45 µm membrane filter for IC, stored inpolyethylene containers and kept under refrigerationat 4 ◦ C.IC systemThe ion chromatograph consisted of a PU-2080i plusHPLC pump (Jasco, Tokyo, Japan), a Rheodyne 5095injector equipped with a 20- µl sample loop (Cotati,CA, USA), a CM-8020 conductivity detector (Tosoh,Tokyo, Japan), two Model 7610-600-6 port switchingvalve (Rheodyne), and a Computer AidedChromatography data processor (Nippon Filcon,Tokyo, Japan). The column employed was a TSKgelIC-Anion-PW XL column (50 mm×4.6 mm i.d.) andtwo suppressor columns obtained from Tosoh (Tokyo,Japan). One suppressor was being used forchromatographic run, and the other suppressor wasregenerated with 0.5 M sulfuric acid (Wako PureChemical Industries, Osaka, Japan) at a flow rate of2.0µl/min by using pump. The suppressor column wasthen rinsed with deionized water for futurechromatographic run.Operating conditionsThe mixture of (Na 2 CO 3 : NaHCO 3 ) was used as theeluent for the determination of anions. The systemwas operated under isocratic mode. Since the pressurelimit of the columns is 8MPa. To find the optimumcondition of anion separation, the effect of eluentflow-rate, eluent concentration and anionconcentration were studied. The optimum conditionwas applied to determine anion in red algae(Eucheuma cottonii) and carrageenanResults and discussionEffect of sodium carbonate and sodium bicarbonateconcentration on anions separationSodium bicarbonate and sodium carbonate solutionconcentration ratio were evaluated for the efficient407