Simultaneous Determination Of Inorganic Anions And Cations In Explosive Residues By Ion Chromatography

The determination of inorganic anions and cations in explosive residues at explosion plot,which was very important to decide explosives types.In our research,we simultaneously determinate and separate eight inorganic ions(Cl^-, NO₂^-,NO₃^-,ClO₃^-,SO₄^2-,K⁺,Na⁺,NH₄⁺)within 16min.Several factors were considered as below:1.The eluent of both hydrophobic group and hydrophilic group should be chosen.Phthalic acid has been chosen as the eluent to determine anions and cations simultaneously,considering that phthalic acid contains strong hydrophobic benzene ring and hydrophilic hydroxyl group.Therefore,the phthalic acid was chosen became eluent.2.The pH of eluent was also the important factor effect the ion-exchange ability of eluent.Under different pH,the eluent have different ionic species and different ion-exchange ability.In the end,the pH=4.0 was chosen in the following experiments.3.The effect of phthalic acid concentration in eluent on the retention time of anions and cations was investigated as well.The increase of the phthalic acid concentration of the phthalic acid caused decrease in the sensitivity of conductivity detection.Therefore,the low phthalic acid concentration should be chosen.Taking the retention time,the resolution and the sensitivity into consideration,the optimal concentration of phthalic acid was 3.5 mM.4.The influence of acetonitrile on the retention time of anions and cations was also investigated in the present work.Acetonitrile can occupy the hydrophobic position of ion exchange resin,and reduce the non-ion exchange reaction of target inorganic ions and ion exchange resin,at the same time; acetonitrile possesses hydrophobic character,and increase the hydrophobicity of eluent.5.The order of the columns connected was considered in our studies.In the end,simultaneous determination of inorganic anions and cations by connecting anion-exchange/cation-exchange columns was obtained within 16min using a eluent composed of 3.5 mM phthalic acid,2%acetonitrile,pH= 4.0.