Determination of inorganic arsenic compounds by HPLC/UV method

In this study, generation of hydrides of As(III) and As(V) from the oxo-anions (AsO33- ve AsO43-) species that found in different oxidation species in aqueous system, after that generation of complex with an anionic ligand in appropriate reaction conditions and instrumental rearrangements, and then firstly, quantitative measurement with UV/Vis method and secondly, with reversed phase high performance liquid chromatography on an ODS column was aimed. In the method, As(III) directly and As(V) after reduction into As(III) in acidic media are converted into hydride form by NaBH4 that is pumped from continuous flow system into the hydride generation cell. The As-DDTC is generated by passing the hydride generated with assistance of N2 gas through Ag-DDTC prepared in pyridine which is placed in complex generation cell. Inorganic As(III) and total inorganic arsenic levels are calculated from the absorbance measurements of the complex obtained with UV/Vis Spectrophotometer at 521 nm and then inorganic As(V) level is calculated by taking the difference between inorganic As(III) and total inorganic arsenic levels. Optimization studies for determination of inorganic As(III) and total inorganic arsenic was carried out using UV/Vis spectrophotometer. The concentration of Ag-DDTC, NaBH4 and the pH of the K2HPO4/KH2PO4 buffer in inorganic As(III) determination were defined as % 0.50, % 3.00 (m/v) and 6.5, respectively. The concentration of Ag-DDTC, NaBH4 and HCl in total inorganic arsenic determination were defined as % 0.50, % 1.00 (m/v) and 1.00 M, respectively. In the experiment in which 5 µg L-1 As(III) and 5 µg L-1 As(V) standard arsenic solutions were used as sample solution, the concentration and the relative errors for As(III), As(V) and total arsenic were determined as 4.89, 5.20 and 10.09 µg L-1 and % 2.20, 4.00 and 0.90 respectively. The accuracy and reproducibility of the method of which LOD value defined as 0.04 µg L-1 and LOQ value defined as 0.13 µg L-1, is quite good and can reliably apply to real samples. After that, inorganic arsenic speciation studies in which it was used different mobile phase and column in the HPLC-UV/Vis system, resulted negatively. Because it could not be obtained required sharp complex peak. The reasons mentioned in below. • Pyridine and Ag-DDTC showed a broad absorption peak in wide wavelength range in HPLC system. • As-DDTC complex substance precipitated in many moving phase mediums. • As-DDTC complex substance disintegrated in ODS and CN column. • Nano sized Ag particles did not pass from column. Speciation of inorganic arsenic species in aqueous media with reverse phase HPLC-UV system could not be performed in this step. Finally, UV/Vis spectrophotometer was used in the studies indicated that at various solvent medium and pH values, there were no interaction between As(III) and DPPC, PPTS, TBACl, PTSA, DSPP, APDC, TBAB substances. Key words : Arsenic, Ag-DDTC, Speciation, UV/Vis, HPLC