Preconcentration of trace metals in environmental and biological samples by cation exchange resin filters for x-ray spectrometry

Abstract

223Table VII. Comparison of Different Methods from Noisy Simulated Data Corresponding to Mixed First-and m-Order (Input Conditions: k,' = k,' = 1 )" noise = 0.5b noise = 5 b k,' 12, ' kl' km' m = 1.5 this work 1.003 0.996 1.027 0,960 Toby 0.979 1.028 0.718 1,365 m = 2 this work 1.002 0.996 1.018 0.963 Toby 0.981 1.030 0.868 1.215 ShankC 1.001 0.999 0.981 1.047 Kelter and Camd 1.008 0.963 a ([AJ, -[AJN)/[A], = 0 . 8 0 ; N = 200 points. Noise = lOOe,,.Shank's method is based on plotting y = 1/ [A]jf vs. x = l/[A]j. Although the variances on the two variables are of the same order of magnitude and are not constant, these rate constants are obtained by using the ordinary least-squares treatment, ignoring the weighting factors which would be needed for rigorous calculations. No significant differences from the graphical procedure were observed.From ref 8 (180 points). ~ ~~ ~carried out calculations for m = 1.5 and m = 2 by using the two methods (input values: kl' = k,'= 1). As shown in Table VII, Toby's method is unsuitable for accurate determination of rate constants from very noisy data and can even lead to significant errors for a noise level as low as 0.5%. This is due to the very small variations with K of the curvature of the drawings obtained by plotting the left-hand term of eq 3 vs. time and consequently to unsignificant variations in the correlation coefficient r used to test the linearity (e.g., the following r values were observed for different arbitrary K input values with m = 2 and emax = 0.005: K = 1.1, r = 0.999933; K = 1.05, r = 0.9999345; K = 1.0, r = 0.9999344). Moreover, taking 2 as a goodness-of-fit parameter does not improve the method.For m = 2, the results obtained here have also been compared with those deduced by using the methods of Shank andKelter and Cam, which deal with this case only. As also shown in Table VII, accuracies of the calculations are of the same range of magnitude. LITERATURE CITED(1) Toby. 6. H.; Toby, F. S.; Toby, S. Int. J. Chem. Kinet. 1078, 70, 12) Linschitz. H.: Sarkanen. K. J. Am. Chem. SOC. 1058. 80. 417-422.. . 4826-4832.(3) Fletcher, R.; Powell, M.A preconcentration method is descrlbed for the X-ray spectrometric analysis of several trace elements In seawater, NBS-SRM 1648 urban particulate, NBS-SRM 1632 trace elements in coal, and nickel in urlne at concentrations as low as 1 ppb. The elements in the coal and urban partlculate samples were loaded quantitatively on catlon exchange resin fllters and subsequently analyzed by energy-dispersive X-ray fluorescence spectrometry using secondary targets for monochromatic excitation of the fllter sample. Prior to the analysis of seawater and urine the trace elements from the matrlx were separated wlth a chelatlng resin. Comparison of the results obtained with NBS-SRM certificate values and/or those of other workers indicated agreement withln &lo%.Detectlon and quantitation llmlts for thls preconcentratlon method are also presented.The application of X-ray fluorescence (XRF) spectrometry to the analysis of environmental and...

Chelation ion chromatography as a method for trace elemental analysis in complex environmental and biological samples

“…It was then shown that the resin could be used, not only to preconcentrate but also to separate elements and groups of elements in seawater prior to instrumental analysis by graphite furnace atomic absorption (GFAAS), inductively coupled plasma (ICP), or spark source 0003-2700/90/0362-1185$02.50/0 © 1990 American Chemical Society isotope dilution mass spectrometry (SSIDMS) (2)(3)(4)(5)(6)(7). The procedure was extended and applied to acid-digested biological and botanical samples and used in conjunction with other instrumental techniques such as X-ray fluorescence (XRF) and neutron activation analysis (NAA) (8)(9)(10)(11)(12)(13). This technique has found general application due to its capability to eliminate the more common alkali and alkaline-earth elements and anion species while retaining many of the analytes of interest.…”

Radiochemical neutron activation analysis of zinc isotopes in human blood, urine, and feces for in vivo tracer experiments

“…Chelex Separation. Chelex-100 resin is frequently used as a preconcentration medium for trace elements in estuarine and seawater samples (21)(22)(23)(24)(25)(26)(27)(28)(29) and has also been used for biological and environmental matrices (30,31). Decontamination factors of >107, >106, and >103 were obtained for Na, Cl, and Br, respectively, by using Chelex-100 as a preirradiation separation medium for NAA determinations (28,29).…”

Total reflection energy-dispersive x-ray fluorescence spectrometry using monochromatic synchrotron radiation. Application to selenium in blood serum

“…The distance from the edge of the NSLS beam at the sample to the detector was 1.7 cm. Samples consisted of thin glass films of known composition, sputter deposited on polycarbonate and on a Si mirror, and known concentrations of manganese ion on cation-exchange resin filters (14). Because of the high Compton scattering in air encountered when the EDXRF secondary target system is operated at high tube power with little collimation, measurements were made in vacuum to obtain optimum performance.…”