doi:10.1016/j.chroma.2007.12.065 
Copyright © 2007 Elsevier B.V. All rights reserved.
Determination of selenium and tellurium compounds in biological samples by ion chromatography dynamic reaction cell inductively coupled plasma mass spectrometry
Chia-Yi Kuoa and Shiuh-Jen Jiang
, a, 
aDepartment of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Received 9 November 2007;
revised 13 December 2007;
accepted 14 December 2007.
Available online 3 January 2008.
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Abstract
An ion chromatography–inductively coupled plasma mass spectrometric (IC–ICP–MS) method for the speciation of selenium and tellurium compounds namely selenite [Se(IV)], selenate [Se(VI)], Se-methylselenocysteine (MeSeCys), selenomethione (SeMet), tellurite [Te(IV)] and tellurate [Te(VI)] is described. Chromatographic separation is performed in gradient elution mode using 0.5 mmol L−1 ammonium citrate in 2% methanol (pH 3.7) and 20 mmol L−1 ammonium citrate in 2% methanol (pH 8.0). The analyses are carried out using dynamic reaction cell (DRC) ICP–MS. The DRC conditions have also been optimized to obtain interference free measurements of 78Se+ and 80Se+ which are otherwise interfered by 38Ar40Ar+ and 40Ar40Ar+, respectively. The detection limits of the procedure are in the range 0.01–0.03 ng Se mL−1 and 0.01–0.08 ng Te mL−1, respectively. The accuracy of the method has been verified by comparing the sum of the concentrations of individual species obtained by the present procedure with the total concentration of the elements in two NIST SRMs Whole Milk Powder RM 8435 and Rice Flour SRM 1568a. The selenium and tellurium species are extracted from milk powder and rice flour samples by using Protease XIV at 70 °C on a water bath for 30 min.
Keywords: Ion chromatography; Inductively coupled plasma mass spectrometry; Dynamic reaction cell; Speciation analysis; Selenium; Tellurium; Biological samples
Fig. 1. Typical mass-selective chromatogram for selenite, selenate, Se-methylselenocysteine, selenomethione, tellurite and tellurate: (a) with standard mode, each selenium and tellurium species was present at 20 ng Se mL−1 and 10 ng Te mL−1, respectively; and (b) with DRC mode. No reaction gas was used in the standard mode. Other HPLC conditions are given in Table 1.
Fig. 2. Typical chromatogram for the separation of selenium and tellurium species in the (a) diluted urine 1 sample and (b) diluted urine 1 spiked with 5 ng mL−1 each of Se and 0.1 ng mL−1 each of Te mixture standard. The urine was collected before taking selenium dietary supplement. The concentration of Se(IV) and Te (VI) in (a) was about 0.69 and 0.09 ng mL−1, respectively. Chromatographic conditions used are given in Table 1.
Fig. 3. Typical chromatogram for the separation of selenium and tellurium species in the (a) extract of NIST RM 8435 Whole Milk Powder and (b) Whole Milk Powder spiked with Se and Te mixture standard. (b) was obtained by spiking the powder sample with 40 ng g−1 (as element) each of Se and 10 ng g−1 each of Te standard mixture. The concentration of MeSeCys and Te (VI) in (a) was about 0.34 and 0.14 ng mL−1, respectively. Chromatographic conditions used are given in Table 1.
Fig. 4. Typical chromatogram of (a) extract of NIST SRM 1568a Rice Flour and (b) Rice Flour spiked with Se and Te mixture standard. (b) was obtained by spiking the powder sample with 100 ng g−1 (as element) each of Se and 2 ng g−1 each of Te standard mixture. Chromatographic conditions used are given in Table 1.
Table 1.
Equipment and operating conditions
Table 2.
Recoveries and concentrations of selenium and tellurium species in urine samples as measured by IC–ICP–MSa (n = 3)
a Values are means of three measurements ± standard deviation. Recovery was determined as described under Section
2.
b Calculated against MeSeCys.
c Calculated against Se(VI).
d The value shown in parenthesis is the percentage of the sum of the species to the total concentration.
e Determined by pneumatic nebulization DRC ICP–MS.
f n.d.: not detected.
Table 3.
Extraction efficiency of selenium and tellurium species in various samples
Values are means of three measurements ± standard deviation.
a The extraction efficiency was calculated on comparison with total concentration.
b NIST certified value.
c Determined by pneumatic nebulization DRC ICP–MS after sample dissolution.
Table 4.
Recoveries and concentrations of selenium and tellurium species in NIST standard reference materials as measured by IC–ICP–MSa,b (n = 3)
a Values are means of three measurements ± standard deviation.
b Recovery was determined by spiking the 0.5 g of NIST RM 8435 Milk Powder and NIST SRM 1568a Rice Flour samples with 5 and 20 ng (as element) each of Te and Se standard mixture and 1 and 50 ng each of Te and Se standard mixture, respectively.
c The value shown in parenthesis is the percentage of the sum of the species to the total extracted concentration listed in
Table 3.
d Not detected.
Table 5.
Recoveries and concentrations of selenium and tellurium species in milk powder as measured by IC–ICP–MSlk and lk (n = 3)
a Values are means of three measurements ± standard deviation.
b Recovery was determined by spiking the 0.5 g of milk powder with 10 and 50 ng (as element) each of Te and Se standard mixture, respectively.
c The value shown in parenthesis is the percentage of the sum of the species to the total extracted concentration listed in
Table 3.
d Not detected.
Abstract
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