Solid-phase extraction of alkylphosphonic and O-alkyl alkylphosphonic acids followed by HPLC separation using porous graphitic carbon sorbent.

An HPLC separation of alkyl phosphonic acids on porous graphitic carbon adsorbent Hypercarb, based upon a step gradient of formic acid concentration in an aqueous mobile phase, was evaluated in this study. Analytes were detected by single quadrupole and triple quadrupole MS. Good separation was achieved for methyl phosphonic acid, ethylphosphonic acid, n-propylphosphonic acid, isopropylphosphonic acid, ethyl methylphosphonic acid, isopropyl methylphosphonic acid, isobutyl methylphosphonic acid, pinacolyl methylphosphonic acid. Solid-phase extraction of these analytes on Hypercarb was also proposed, desorption was carried out with aqueous ammonium formate and water-methanol mixtures. LODs were 0.1-0.2 ng mL-1 for these analytes without SPE; solid-phase extraction resulted in the decrease of LODs at least 100-fold. Accuracy was proven by analyses of spiked samples of river water and snow meltwater.

Solvation characteristics of porous graphitic carbon Hypercarb in subcritical water chromatography.

Retention of 17 organic compounds was studied in high-temperature liquid chromatography mode on Hypercarb porous graphitic carbon with subcritical water as an eluent. Three different eluent temperatures were studied: 150, 175 and 200 °C. Abraham solvation parameters model was used for quantitative evaluation of retention data. It was found that increase of eluent temperature from 150 to 200 °C results in decrease of cavity formation system parameter v from 2.9 to 1.7. No clear tendency can be observed for temperature dependency of other system parameters.

Specificity of noble metals dynamic sorption preconcentration on reversed-phase sorbents.

The reversible sorption preconcentration of noble metals (NMs) using different schemes "sorbent-reagent-eluent" was investigated. The extraction of Au, Pd, Pt, Ir, Rh and Ru chlorocomplexes from hydrochloric acid solutions on hyper-crosslinked polysterene MN-200 in the form of ion associates with tributylamine (TBA) and 4-(n-octyl)diethylenetriamine (ODETA) was investigated. It was found that Pd, Pt and Au were quantitatively and reversibly extracted using TBA on hyper-crosslinked polysterene; the appropriate eluent for desorption was 1M solution of HCl in ethanol. Ir, Rh and Ru under these conditions were not sorbed quantitatively. It was found that sorbent hydrophobicity is not the main characteristic that defines the efficiency of sorption of a particular NM ion associate. Different efficiencies of hyper-crosslinked polysterene MN-200 for sorption of square-planar chlorcomplexes of Pt, Pd and Au and octahedral complexes of Ir, Rh and Ru were found. For the first time, the sorbents with their own N-atoms - StrataX and StrataX-AW - were used for the sorption of Ir, Rh and Ru. Using these sorbents, the sorption of Ir was increased up to 95%, and the sorption of Ru and Rh was increased to about 40%. We can explain these results by nonspecific interaction of chlorcomplexes of Ir, Rh and Ru with ethylenediamine groups of the sorbent. Weak bases with large anions may be applied for desorption of Ir, Rh and Ru. Two schemes of dynamic sorption preconcentration of NMs from hydrochloric acid solutions were proposed - hyper-crosslinked polysterene MN-200 for the determination of Au, Pd, Pt, and StrataX-AW for Ir, Rh and Ru.

Determination of rare earth elements in rock samples by inductively coupled plasma mass-spectrometry after sorption preconcentration using Pol-DETATA sorbent.

Sorption preconcentration of rare earth elements prior to introduction in inductively coupled plasma mass spectrometry is developed. For the first time Pol-DETATA sorbent was used for REEs preconcentration after digestion of wide classes of rock samples. The developed technique is based on lithium metaborate fusion, preconcentration on Pol-DETATA sorbent, elution with nitric acid and flow-injection sample introduction to the ICP-MS spectrometer. The efficiency of REEs extraction from the resulting solutions in the presence of high amounts of iron is examined. 5-sulfosalicylic acid was used as a masking reagent. Flow-injection introduction of 50 µL of eluate obtained after desorption was used to avoid corrosion of the parts of the ICP-MS instrument due to high acidity of the eluate. The accuracy of the developed technique is checked by the analysis of the certified reference materials of rock samples. The REEs recoveries within 85-100% interval were attained for most REEs in tested reference materials.

X-ray fluorescence determination of As, Bi, Co, Cu, Fe, Ni, Pb, Se, V and Zn in natural water and soil extracts after preconcentration of their pyrrolidinedithiocarbamates on cellulose filters.

A simple method for the elements preconcentration on thin-layer paraffin-treated cellulose filters was proposed. It was found that pyrrolydinedithiocarbamates of As(III), Bi, Cd, Co, Cu, Fe(III), Ni, Pb, Se(IV), V(V) and Zn obtained after mixing of sample (3-5 ml min(-1)) and reagent (0.7-1.0 ml min(-1)) streams were quantitatively recovered from 100 ml sample. The sample acidity was adjusted to pH 4.8-5.2 for preconcentration of Cd, Co, Cu, Fe(III), Ni, Pb, V(V) and Zn, and to 2 M HCl for preconcentration of As, Bi and Se. The optimum reagent concentration was found to be 0.1%. The elements were determined on the filters by X-ray fluorescence spectrometry. The detection limits achieved were 0.1-4.0 mug of element on the filter. Relative standard deviation (R.S.D.) was not higher than 0.08 while determining 5-50 mug of elements on filter. Accuracy and precision of the technique proposed were evaluated by the analysis of spiked natural samples.

FIA-FAAS system including on-line solid phase extraction for the determination of palladium, platinum and rhodium in alloys and ores.

A number of aliphatic mono- and triamines have been investigated as potential reagents for solid phase extraction of Rh, Pd and Pt. Platinum group metals are recovered from hydrochloric acid solutions as ionic associates of their chloride complexes with protonated amines. The recovery of metals depends both on hydrophobic properties of amine and sorbent and on sorption behaviour of amine itself. For on-line solid phase extraction of platinum group metals 4-(n-octyl)diethylenetriamine and hyper cross-linked polystyrene sorbent SSPS have been applied. Quantitative recovery of rhodium and platinum in the form of their hexachloride complexes was achieved under non-equilibrium conditions of on-line dilution. Metals recovered are quantitatively eluted with 1 M hydrochloric acid solution in ethanol. A new FIA-FAAS method for the determination of Rh, Pd and Pt in solutions based on the decomposition of ores and alloys has been proposed. The RSD values are 0.03-0.08 at 50-ppb concentration level. The detection limits are 3-8 ppb for 1 min of preconcentration. The accuracy of the procedure was verified by the analysis of standard reference materials of sulfide ores and alloys.