E. Ivanova

Flow injection on-line preconcentration of palladium by ion-pair adsorption in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection (FI) method for the preconcentration/separation of palladium, coupled with electrothermal atomic absorption spectrometry (ETAAS), is presented. The preconcentration was performed by on-line formation of an ion-pair between the positively charged potassium complex of 1,4,7,10,13,16-hexaoxacyclooctadecane (K+18-crown-6) and the palladium thiocyanate anion (Pd(SCN)42−) and its sorption on the inner walls of a PTFE knotted reactor (KR). The elution was achieved by methanol acidified with 1% (v/v) HNO3. An enhancement factor of 29 and a sampling frequency of 14 h−1 were obtained for a preconcentration time of 90 s and a sampling flow rate of 4.4 ml min−1. The detection limit (3σ) is 16 ng l−1 and precision (RSD) for 0.4 µg l−1 Pd is 2.3%. The method was validated by recovery measurements on spiked blood and road dust samples.

Simultaneous on-line preconcentration and determination of Pt, Rh and Pd in urine, serum and road dust by flow injection combined with inductively coupled plasma time-of-flight mass spectrometry

In this work, ICP-time of flight (TOF)-MS with ultrasonic nebulisation (USN) was combined on-line with a flow injection (FI) system for the determination of Pt, Rh and Pd in biological fluids (urine and blood serum) and road dust. Simultaneous and selective preconcentration of the 3 analytes was performed by sorption of their complexes formed on-line with diethylthiourea (DET) on the inner walls of a PTFE knotted reactor (KR), in a wide range of sample acidity (0.1–0.5 M HNO3 for Pd and Rh and 0.05–0.2 M HNO3 for Pt). A quantitative elution was achieved using 500 µl methanol acidified with 1% HNO3. The detection limits obtained were 0.54, 2.12 and 0.36 ng l−1 for Pt, Rh and Pd, respectively, and the relative standard deviation RSD (for 50 ng l−1 of Pt, Rh and 25 ng l−1 of Pd, n = 6) was ≤ 3%. Using a preconcentration time of 120 s and a sample flow rate of 5 ml min−1, enrichment factors of 55, 5 and 2 for Pd, Pt and Rh, respectively, were obtained in comparison with direct determination by ICP-MS without preconcentration. Special attention was paid to the study of the adverse effects of potentially interfering species present in the matrix (Cd, Cu, Pb, Sr, Fe, Y, Zn, Ni, Rb, Mn and Mo) on the preconcentration and the mass-spectrometric determination of the analytes. The accuracy of the method was demonstrated by the analysis of urine, blood serum and road dust certified reference materials. The method was applied to urine and serum samples of healthy subjects. The concentrations of Pt, Rh and Pd determined in these samples were comparable to reported values.

Determination of trace elements in natural waters by inductively coupled plasma time of flight mass spectrometry after flow injection preconcentration in a knotted reactor

A flow injection on-line sorption system was developed for the separation and preconcentration of traces of Ag, Cd, Co, Ni, Pb, U and Y from natural water samples with subsequent detection by ICP TOF MS. Simultaneous preconcentration of the analytes was achieved by complexation with the chelating reagent 1-phenyl-3-methyl-4-benzoylpyrazol-5-one immobilized on the inner walls of a (200cm x 0.5mm) PTFE knotted reactor. The analytes were eluted and transported to an axial ICP TOF MS system with 1% (v/v) HNO(3) containing 0.3microg l(-1) of Rh as an internal standard using ultrasonic nebulization. The detection limits (3sigma) varied from 0.3ng l(-1) for Y to 15.2ngl(-1) for Ni and the precision (R.S.D.) was better than 4%. Using a loading time of 90s and a sample flow rate of 4.5ml min(-1), enhancement factors of 3-14 were obtained for the different analytes in comparison with their direct determination by ICP TOF MS with ultrasonic nebulization without preconcentration. The accuracy of the method was demonstrated by analysis of water based certified reference materials.

Inductively coupled plasma mass spectrometry for trace analysis using flow injection on-line preconcentration and time-of-flight mass analyser

Abstract Flow injection (FI) methodologies extend the performance of atomic spectroscopic techniques particularly when on-line preconcentration and separation procedures are involved. This article reviews some of the most relevant aspects of the coupling of FI procedures with inductively coupled plasma-mass spectrometry (ICP-MS), as an attractive approach to perform ultra-trace metal determinations in samples containing a high proportion of total dissolved solids. The capabilities of ICP-time-of-flight (TOF) MS as a fast transient detector for simultaneous determination of a large number of isotopes in a FI peak are also reviewed.

Air driven on-line separation and preconcentration on a C18 column coupled with thermospray flame furnace AAS for the determination of cadmium and lead at μg l−1 levels

A simple and sensitive method for the determination of cadmium and lead at μg l−1 and sub-μg l−1 levels by on-line separation and preconcentration coupled with thermospray flame furnace AAS (TS-FF-AAS) was developed. Compressed air was used to drive the sample through the 3 cm HPLC C18 RP column and the 500 μl eluate to the TS-FF-AAS. The chelating reagent ammonium pyrrolidinedithiocarbamate was immobilized onto the column as a solution in the eluent (60% v/v methanol) simultaneously with the elution of the previous preconcentrated sample. Loading of sample volumes up to 20 ml was possible. The detection limits for cadmium and lead using 20 ml sample volume were 0.007 and 0.17 μg l−1, respectively. RSD values were typically about 4%. The combined effect of preconcentration and TS-FF-AAS yielded enhancement factors towards conventional flame AAS of 1960 and 610 for cadmium and lead, respectively.

New chelating sorbents based on pyrazolone containing amines immobilized on styrene-divinylbenzene copolymer-I Synthesis and analytical characterization.

A series of new cheating sorbents has been prepared by modification of styrene-divinylbenzene copolymer with different pyrazolone-containing amines. The substances were characterized by elemental analysis and infared spectroscopy. The complexation ability of the sorbents towards alkali, alkaline-earth, transition and precious metals has been studied. The new sorbents may successfully be applied to the simultaneous preconcentration of alkaline-earth and transition elements in neutral medium and to the selective separation of precious metals in acidic medium.

Flame AAS determination of dopants and trace metal impurities in single crystals of potassium titanylphosphate.

A flame AAS method is used for the determination of dopants and impurities in potassium titanylphosphate (KTP) single crystals. Sample digestion using sulphuric acid and hydrofluoric acid is proposed as being the most appropriate procedure. The effect of major and minor components in the sample solution on the analytical signal is studied. The content of the dopants Cr, Mn and Ni (at a level of about 1 mg g(-1)) as well as the content of the impurities Fe, Na, Mg, W and Al (from 4 mug g(-1), depending on the trace metal) in the KTP single crystals is determined. The precision of the method is characterized by a relative standard deviation of 3-10%. The accuracy is checked by comparison with ICP-AES data for the trace element content in the KTP single crystals.

Flame AAS determination of As, Cd and Tl in soils and sediments after their simultaneous carbodithioate extraction

SummaryThe extraction system ammonium tetramethylenecarbodithioate/isobutylmethylketone is applied to the simultaneous preconcentration of the toxic trace elements As, Cd and Tl from soil digests at an acidity of 2–3 mol/l sulphuric acid and to their separation from the major soil components. The extraction procedure is easily coupled to AAS. The accuracy of the method is checked by the analysis of a certified reference material. RSD is between 4 and 10%.

Total reflection X-ray fluorescence analysis of trace elements in Bulgarian bottled mineral waters of low and high mineral content

The trace elements S, Cl, K, Ca, Mn, Fe, Ni, Cu, Zn, As, Br, Rb and Ba in Bulgarian bottled mineral waters of low and high total dissolved solids (TDS) content were determined by total reflection X-ray fluorescence (TXRF) analysis using gallium as internal standard. The water samples were analysed after simple preparation consisting in three-fold sequential pipetting/drying of 5 μL portions of the water sample mixed with the internal standard on the quartz holders. The precision of the obtained results is characterised by an RSD of 5–16%. The lower limits of detection (LLDs) in waters of TDS content of 160–420 mg L−1 were in the low µg L−1 range, whereas those in the water with TDS content of 2900 mg L−1 were higher by a factor of 5–15. There is a good agreement between the results for the trace element content obtained by TXRF and inductively coupled plasma optical emission spectrometry (ICP-OES) for mineral waters with TDS content in the range from 160 to 2900 mg L−1.

Improved ET-AAS determination of alkaline and earth alkaline elements with a simple low-cost tungsten coil atomizer

SummaryThe ET-AAS determination of elements which form hardly atomizing carbides or oxides and of elements with resonance lines in the visible part of the spectrum, e.g. alkaline and earth alkaline elements, was studied using the tungsten coil atomizer; the detection limits were between 0.02 and 1.6 ng/ml. The advantages of the new atomizer are illustrated by the determination of Ba, Ca and Mg traces in ammonium paratungstate, which, as a carbide-forming matrix, is less suitable for the analysis with conventional AAS techniques.