A Comparative Study of Metal Readsorption in the Application of a Three-Stage Sequential Extraction Scheme and Two Accelerated Versions (Ultrasonic and Single Extractions)

Abstract

Accelerated methods for partitioning of Cd, Cr, Cu, Ni, Pb and Zn, such as the use of single and ultrasonic extractions are assessed in terms of readsorption and compared with the three-stage sequential extraction scheme (SES) of the Standards Measurements and Testing Programme (SM&T). The standard addition approach was employed for characterising the readsorption artefact by applying the above fractionation methods over different certified reference materials (CRMs), BCR 701, BCR 601 (lake sediments), and BCR 141R soil. Ultrasonic extractions provided higher readsorption, mainly for BCR 141R and 601 as compared to conventional SES, the role of ultrasound in the activation of adsorptive sites being significant. The single extraction approach seemed to be inadequate with samples containing large amounts of carbonates such as BCR 141 R but worked well with both lake sediments.The readsorption phenomena are mainly occurring in the most labile fraction (i.e. acid soluble) and has been observed to be matrix dependent. The extent of such phenomenon is also dependent on the extraction methodology, i.e conventional vs accelerated.

An ultrasound-assisted procedure for fast screening of mobile fractions of Cd, Pb and Ni in soil. Insight into method optimization and validation

“…Nevertheless, concentrations of all metal fractions in BCR-701 determined by UASE procedure are within the results reported in the literature and compiled by Sutherland (2010). Good agreement of the results with certified values was also obtained for overall metal recoveries in fractions FI-FIII (93–103 %), except for Ni extraction (89 %), that was also reported by Pérez et al (2008) and Ipolyi et al (2002). These studies indicate a great potential of UASE procedure for fast monitoring of mobile metal fractions in soil.…”

“…The effective recovery of Cd was obtained using 5 min sonication time (with mean value for all soil samples of 102.5 %), while for Pb and Ni, more efficient recoveries were obtained using 7 min sonication (97 % for Pb and 94 % for Ni). Longer ultrasonic treatment of samples, 10 min for Pb (L, M and H soil) and 10 and 12 min for Ni (L and M soil), resulted in partial re-adsorption of Pb and Ni on soil particles, what was also demonstrated by Pérez et al (2008). For the next study, the treatment of soil with ultrasounds for 7 min at power of 15 W was chosen for simultaneous extraction of Cd, Pb and Ni into an acid-soluble fraction (FI).…”

“…More complex situation was observed for extraction of Cd; as for sample L, the recovery was low, in the range 60–80 %, while for sample H, the recovery was very high, in the range 120–160 %. Such high results obtained for sample H were probably an effect of re-adsorption of Cd in the first step of extraction (Penilla et al 2005; Pérez et al 2008). The reason for low recovery of Cd in sample L is unknown, especially in view of the fact that the affinity of Cd to ≡FeOH is low (log β  = −2.22).…”

“…Even this protocol is widely accepted and often used for fractionation of metals in various matrices, it still has some limitations (e.g. lack of specificity or species redistribution) as was discussed elsewhere (Bacon and Davidson 2008; Gleyses et al 2002; Pérez et al 2008). Moreover, this standardized protocol is very time consuming.…”

Fast and simple procedure for fractionation of zinc in soil using an ultrasound probe and FAAS detection. Validation of the analytical method and evaluation of the uncertainty budget

“…These effects shorten the operation times necessary to extract soil fraction and enhance “green” aspects of such procedure in terms of time and energy requirements (Bendicho et al 2012 ). A literature review (Table 1 ) shows that both ultrasound bath (Davidson and Delevoye 2001 ; Arain et al 2008 ; Kazi et al 2006 ; Relić et al 2013 ; Péreza et al 2008 ) and ultrasound probe (Davidson and Delevoye 2001 ; Pérez-Cid et al 1999 ) have been applied in sequential extraction procedures as sources of ultrasonic energy (Catalado and Wildung 1978 ; Ross 1994 ; Prasad and Freitas 2003 ). The extraction conditions vary in power/frequency of ultrasounds and sonication time.…”