Determination of total chromium in seawater with isotope dilution sector field ICP-MS following on-line matrix separation

Abstract

An on-line matrix separation and concentration was undertaken for the direct determination of total Cr in seawater using isotope dilution with detection by sector field inductively coupled plasma mass spectrometry (ID SF-ICP-MS). A mini-column packed with 50 ml silica-immobilized diphenylcarbazone (I-DPC) resin was used to extract Cr(III) from seawater following on-line pH adjustment with a pH 9.3 solution of NH 4 OH/HNO 3 . A preliminary reduction of chromium to Cr(III) was achieved with hydroxylamine hydrochloride. Medium resolution was used to efficiently separate argon polyatomic species and any possible oxide interferences. Using a 7.5 ml volume of sample, throughput was 10 samples h À1 with a detection limit (3 s) of 0.005 ng g À1 . Method validation was demonstrated by determination of total chromium in seawater CRMs NASS-5 and CASS-4, yielding concentrations of 0.111 AE 0.011 and 0.1296 AE 0.0094 ng ml À1 (U, 95% confidence interval, k ¼ 4.30, n ¼ 3) in agreement with certified values. The method was applied to the determination of total Cr in candidate seawater CRMs NASS-6 and CASS-5, yielding concentrations of 0.1132 AE 0.0047 and 0.0942 AE 0.0040 ng g À1 (U, 95% confidence interval, k ¼ 2.57, n ¼ 6), respectively. A complete evaluation of uncertainty is presented. Experimental section InstrumentationA Thermo Fisher Scientific Element2 sector field ICP-MS instrument (Bremen, Germany) equipped with a Scott-type double pass glass spray chamber and a PFA self aspirating

Determination of rare earth elements and other trace elements (Y, Mn, Co, Cr) in seawater using Tm addition and Mg(OH)2 co-precipitation

“…This provides assurance that these two elements can be successfully measured in seawater samples using our recommended procedure, despite the fact that they exhibit co-precipitation yields slightly different than those for the REEs. Similarly, our measured concentration for Cr in NASS-5 (110 ± 7 ng.kg -1 ) is in agreement with the certified value (107 ± 15 ng.kg -1 ) and other published high-quality Cr data [27,28]. Additional analyses would be needed to further validate whether total Cr in seawater can be routinely measured using our recommended procedure (e.g.…”

Determination of trace metals in high-salinity petroleum produced formation water by inductively coupled plasma mass spectrometry following on-line analyte separation/preconcentration

“…46 However, contamination introduced by sample manipulation and reagents must be properly corrected for in order to obtain accurate results. 37 The following equation was used for the quantitation of Cd, Pb, Ni, U, Fe, Mo and Zn in the samples: 37…”

“…A PerkinElmer (Norwalk, CT, USA) FIAS-400 MS flow injection accessory was used for on-line column separation and concentration, as described previously. 29,37 An additional threeway solenoid valve (Cole Parmer, Part No. P-98300-02) was activated by a home-made 12 V dc power supply controlled by remote switches on the FIAS 400.…”

“…As PFW presents a more complex matrix than seawater, earlier methods 29,37 used to sequester trace metals were examined to assess recoveries using separation/preconcentration with columns of various sorbents. In general, spike recoveries decreased for all analytes as the salinity of the PFW samples increased over the range 16.6&-166.6&.…”

Atomic spectrometry update. Environmental analysis

“…Isotope dilution as a calibration strategy has been investigated for the determination of total Cr in seawater. 171 All the Cr present was reduced to Cr III with hydroxylamine hydrochloride, before the sample pH was adjusted to 9.3. The Cr III was retained on silica immobilized diphenylcarbazone and subsequently eluted with 1.5 M HNO 3 .…”