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1

Quick and simple speciation analysis of chromium in cements

Grabarczyk Malgorzata, Wardak Cecylia

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 2

art. no. 144445

EN

The extraction of total Cr(VI) from commercially available cements, based on DTPA + 0.2 mol dm-3 (NH4)2SO4/NH4OH mixture solution and subsequent selective determination of Cr(VI) has been proposed. The determination was carried out using the adsorptive voltammetric stripping method. The study was conducted using three different commercially available cement samples. It has been checked that the proposed extraction procedure guaranteed no changes of chromium speciation during cement analysis. For comparison extraction was also carried out with the use of recommended by United States Environmental Protection Agency (EPA) Method 3060A, based on 0.28 mol dm-3 Na2CO3 + 0.5 mol dm-3 NaOH). Additionally, the extraction process was carried out using only distilled water as an extraction mixture which allows to evaluate concentration of only soluble Cr(VI) forms contained in cement. In all three cements, the content of soluble Cr(VI) was below 2 ppm, i.e. the limit value by European Union Directive 2003/53/EC.

2

Multicommutation flow analysis with chemiluminescence detection: application to the chromium(III) determination

Koronkiewicz S., Sobczuk M.

Environmental Biotechnology

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2008

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Vol. 4, No. 1

25-31

EN

The study deals with the application of multicommutation flow analysis for determination of Cr(III) concentration in environmental samples at a trace level. The detection method was based on the luminol-H2O2 chemiluminescence reaction in basic aqueous solution using Cr(III) ions as a catalyst. The experimental part of investigation focused on the optimization of equipment conditions, i.e. reagent flow rate, injected sample volume and the work of solenoid valves. The specificity of the method was tested with respect to selected heavy metal ions. The presented method allowed determination of Cr(III) over the range from 2.5 to 50ng*cm-3, with a low detection limit (under optimum conditions: 0.15ng*cm-3). Multicommutation is one of the best methods of analytical procedure automation. The main advantages of multicommutation method, compared with classical flow injection analysis (FIA), is the ability to achieve more repeatable analytical signal, which in turn allows to improve the method precision (relative standard deviation, RSD, was 1.8% for 10 determinations of 20ng*cm-3 Cr(III)). Moreover, it is excellent from the point of view of environmental protection because it offers very low reagent consumption: luminol 0.26; H2O2 2.16; sample 0.15 (cm3 per peak). The sampling rate was about 90 samples*h-1.

3

Investigations of Chemical Speciation of Cr in Solutions and Soil Eluates with Hydroxylamine Hydrochloride

Kalembkiewicz J., Soco E.

Chemia i Inżynieria Ekologiczna

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2003

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Vol. 10, nr 3-4

253-258

EN

The investigations leading to determination of conditions of Cr(VI) to Cr(III) reduction and coexistence of these species in solutions and soiI eluates with [formula] after the sequential extraction of soil were carried out. Influence of: pH, temperature, mixing time and Cr(VI) concentration on the course of reaction was studied. It was found of influence of the parameters on Cr(VI) reduction. Moreover, it was found that total reduction of Cr(VI) to Cr(III) in soiI eluates after the sequential extraction of soil (0.04 M NH2OH . HCI in 25% CH]COOH, t = 96°C, GCXIn = 6 h, oxides fraction of soil) does proceed.

PL

Wykonano badania prowadzące do określenia warunków redukcji Cr(VI) do Cr(III) i współistnienia form w roztworach i eluatach glebowych z [wzór] po ekstrakcji sekwencyjnej gleby. Badano wpływ pH, temperatury, czasu mieszania oraz stężenia Cr(VI) na przebieg reakcji. Stwierdzono wpływ badanych parametrów na redukcję Cr(VI). Stwierdzono ponadto, że w eluatach glebowych po ekstrakcji sekwencyjnej gleby (0,04 M NH2OH . HCI w 25% CH)COOH, t = 96°C, 9.xln = 6 h, trakcja tlenkowa gleby) zachodzi całkowita redukcja Cr(VI) do Cr(III).