Abstract
UDK 631.4:546.19
 A simple and inexpensive method for the determination of inorganic As(III) and As(V) at low ppb levels was developed. The method is based on formation of hydride from a sample solution and its reaction with mercury bromide on a solid support. Formation of a yellow-brownish product was optically detected.
 Amidosulfonic acid was used as a reaction medium for determination of total inorganic arsenic, while citrate buffer (0.1 mol/dm3, pH=5.5) was used as a reaction media for determination of As(III) alone. As(V) was calculated as a difference of total inorganic arsenic and As(III).
 This method has been applied to soil extracts. Extraction of inorganic arsenic from soil samples was done in three-step sequential extraction with the following extractants: NH4H2PO4 (0.05 mol/dm3); NH4-oxalate buffer (0.2 mol/dm3, pH=3.25); and mixture of NH4-oxalate buffer (0.2 mol/dm3) and ascorbic acid (0.1 mol/dm3) at pH=3.25. The method was suitable for determination of inorganic arsenic species in soil extracts covering concentration range of the analyte between 0.2 - 20 ppb.
Highlights
As(V) at low ppb levels was developed
This method has been applied to soil extracts
Extraction of inorganic arsenic from soil samples was done in three-step sequential extraction with the following extractants: NH4H2PO4 (0.05 mol/dm3); NH4-oxalate buffer (0.2 mol/dm3, pH=3.25); and mixture of NH4-oxalate buffer (0.2 mol/dm3) and ascorbic acid (0.1 mol/dm3) at pH=3.25
Summary
Optimizacija eksperimentalnih parametara - Optimization of experimental parameters. Da bi se izvršilo određivanje samog arsenita, redukcija arsenata mora biti svedena na najmanju moguću mjeru ukoliko su obje specije prisutne u rastvoru. Dobiveni rezultati su prikazani na dijagramu 2 kao ovisnost razlike signala (ΔU) od promjene pH rastvora. Zavisnost signala od vremena za As(III) u citratnom puferu (0,1 mol/dm, pH = 5,5). Kalibracione krive - Calibration curves Kako bi se izvršilo određivanje samog As(III), izvršena su mjerenja signala standardnih otopina različite koncentracije As(III) u citratnom puferu (0,1 mol/dm, pH = 5,5). Za svaki uzorak zemljišta ispitivane su tri paralelke, a rezultati su prikazani kao srednja vrijednost tri ponovljena određivanja. Određivanje anorganskog arsena u ekstraktima zemljišta je izvršeno na sljedeći način: ukupan anorganski arsen je određivan u kiselom mediju dodatkom dvije tablete amidosulfonske kiseline i jedne tablete reducenta natrij borhidrida; As(III) je određivan u citratnom puferu (0,1 mol/dm, pH 5,5) uz dodatak jedne tablete natrij borhidrida. Rezultati sekvencijalne ekstrakcije uzoraka zemljišta S1 (Gornja Stavnja) izražene kao srednja vrijednost ±SD tri mjerenja za tri paralelke (n=3).
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