Stripping voltammetric techniques a

Stripping voltammetric techniques are an interesting alter-native for the detection of trace levels of heavy metals in
high saline matrices. These techniques present a significant
sensitivity due to their unique ability to preconcentrate tar-get species during the accumulation step on the working
electrode, next to its combination with pulse measurement
techniques that generate a highly favourable signal-to-background ratio. Mercury-based electrodes, such as mercury
film electrodes (MFE), and hanging mercury drop electrodes
(HMDE), have traditionally been used in stripping techniques
because of their advantages, such as high sensitivity, repro-ducibility, purity of the surface, high hydrogen overpotential,
and possibility of amalgam formation. Therefore, they have
been recognized as the most sensitive electrodes for the deter-mination of heavy metals[5]. In particular, the HMDE has
successfully been used for the determination of Pb and Cd in
seawater samples[6,7]. More recently, Süren et al. introduced
a modification in the system by preceding the differential
pulse stripping voltammetry (DPSV) by adsorptive collection
of complexes with 8-hydroxyquinoline (oxine) on to the mer-cury electrode[2]. On the other hand, several studieswith MFE
are reported[8–13]. For example, Khoo and Guo investigated
various mercury(I)/(II) salts as modifiers for carbon paste elec-trodes[8]. Inanattempt toworkwithenvironmentally friendly
metals, a comparative study of the simultaneous determina-tion of heavy metals in highly saline samples by ASV using
both mercury and bismuth film electrodes as working elec-trodes was carried out[9].
Various designs based on graphite–epoxy composite elec-trodes (GECE) for electrochemical stripping analysis of metals
have been used in our laboratories. GECE without any modi-fication have firstly been applied in metal analysis[14–16].A
GECE in the presence of bismuth in the measuring solution
[17] as well as a Bi(NO3)3–GECE[18] that represents a GECE
modified internally with bismuth nitrate salt have also been
studied and applied[19].
The couplingof disposable screen-printedelectrodes (SPEs)
with stripping techniques presents an attractive alternative to
conventional stripping analysis. SPE is related to a mass pro-duction technology based on screening of electroconductive
and insulating inks onto planar substrates (plastic, ceramic,
etc.) at a controlled thickness. The use of stripping analy-sis based SPEs eliminates the problems related to the use
of conventional electrochemical cells: the associated cum-bersome handling, the lengthy cleaning procedures and the
need for a de-aeration step, using electrochemical techniques
less influenced by oxygen interference. Moreover, SPEs related
instruments can be portable by including a compact battery
achieving a user friendly field-deployable device that allows
thedirectmonitoring of heavymetal traces inanin situcontrol
of pollution[20–23].
ASV coupled to SPEs using a variety of electrode designs
and experimental protocols were used for the detection of
Pb and Cd contained in different matrices such as natural
waters[21–27], soil extracts [21,22,27], wastewater [21,26]and
drinking waters[23,25]. On the other hand, Zen et al. devel-oped a Cu/Hg-plated screen-printed electrode for single Pb
determination contained in various waters samples, includ-ing seawater, by square wave anodic stripping voltammetry
[28]. To the best of our knowledge, simultaneous determina-tion of Cd and Pb in seawater has not been reported up to
date.
The present study focuses on the evaluation of the feasi-bility of using SPEs for the simultaneous determination of Pb
and Cd in seawater. Several parameters affecting the system,
such as the matrix effect upon the SPE response and the sta-bility of the measuring system have been studied. The results
obtained for the determination of the metal contents in real
and spiked seawater samples will be shown.
2. Experimental
2.1. Chemicals and apparatus
Heavy metals solutions were prepared by diluting AAS grade
(Panreac) Pb, Cd, Cu and Zn standard solutions. HCl (32%) was
obtained from Fluka. NaCl (99.5%) was purchased from Pan-reac. The pH was adjusted by using CaCO3(99%) (Merck).
A certified reference material (LGC6016) consisting of
estuarine water was used for validation purposes. The
certified metal values: 101±2g/kgCd, 190±4g/kgCu,
196±3g/kgPb, and 976±31g/kgMn.
The SPE sensors (from University of Florence—available
from PalmInstruments,http://www.palmsens.com) consisted
of a screen-printed electrochemical cell with three electrodes
in one single strip: a graphite working electrode modified with
a plasticizer mixed with mercury acetate, a graphite counter
electrode and a silver pseudo-reference electrode[21].
A computer-controlled Autolab PGSTAT-12 (302N-High per-formance) (potentiostat/galvanostat) with general-purposes
electrochemical software operating system (GPES version
4.9.007) from Eco Chemie B.V., The Netherlands, was used

Kết quả (Việt) 1:

Kỹ thuật voltammetric bóc là một thú vị thay đổi người bản xứ để phát hiện dấu vết mức độ của kim loại nặng trongma trận mặn cao. Các kỹ thuật trình bày một quan trọngđộ nhạy cảm do khả năng duy nhất preconcentrate tar-get loài trong bước tích lũy ngày làm việcđiện cực, bên cạnh của nó kết hợp với xung đo lườngkỹ thuật tạo ra một tỷ lệ tín hiệu đến nền rất thuận lợi. Dựa trên Mercury điện cực, chẳng hạn như thủy ngânphim điện cực (MFE), và treo thủy ngân thả điện cực(HMDE), theo truyền thống đã được sử dụng trong tước kỹ thuậtdo lợi thế của họ, chẳng hạn như độ nhạy cảm cao, repro-ducibility, độ tinh khiết của hydro bề mặt, cao overpotential,và khả năng hình thành hỗn hợp. Do đó, họ cóđược công nhận là các điện cực nhạy cảm nhất cho deter mination của kim loại nặng [5]. Cụ thể hơn, HMDE cóthành công được sử dụng trong việc xác định Pb và đĩa Cd trongnước biển mẫu [6,7]. Gần đây, Süren et al. giới thiệumột sửa đổi trong hệ thống bởi ngay trước vi phânxung tước voltammetry (DPSV) của bộ sưu tậpcủa tổ hợp với 8-hydroxyquinoline (oxine) vào các điện cực mer cury [2]. Mặt khác, một số studieswith MFEđược báo cáo [8-13]. Ví dụ, Khoo và Quách điều traCác muối mercury(I)/(II) như gia cường cho carbon dán elec-trodes [8]. Inanattempt toworkwithenvironmentally thân thiệnmetals, a comparative study of the simultaneous determina-tion of heavy metals in highly saline samples by ASV usingboth mercury and bismuth film electrodes as working elec-trodes was carried out[9].Various designs based on graphite–epoxy composite elec-trodes (GECE) for electrochemical stripping analysis of metalshave been used in our laboratories. GECE without any modi-fication have firstly been applied in metal analysis[14–16].AGECE in the presence of bismuth in the measuring solution[17] as well as a Bi(NO3)3–GECE[18] that represents a GECEmodified internally with bismuth nitrate salt have also beenstudied and applied[19].The couplingof disposable screen-printedelectrodes (SPEs)with stripping techniques presents an attractive alternative toconventional stripping analysis. SPE is related to a mass pro-duction technology based on screening of electroconductiveand insulating inks onto planar substrates (plastic, ceramic,etc.) at a controlled thickness. The use of stripping analy-sis based SPEs eliminates the problems related to the useof conventional electrochemical cells: the associated cum-bersome handling, the lengthy cleaning procedures and theneed for a de-aeration step, using electrochemical techniquesless influenced by oxygen interference. Moreover, SPEs relatedinstruments can be portable by including a compact batteryachieving a user friendly field-deployable device that allowsthedirectmonitoring of heavymetal traces inanin situcontrolof pollution[20–23].ASV coupled to SPEs using a variety of electrode designsand experimental protocols were used for the detection ofPb and Cd contained in different matrices such as naturalwaters[21–27], soil extracts [21,22,27], wastewater [21,26]anddrinking waters[23,25]. On the other hand, Zen et al. devel-oped a Cu/Hg-plated screen-printed electrode for single Pbdetermination contained in various waters samples, includ-ing seawater, by square wave anodic stripping voltammetry[28]. To the best of our knowledge, simultaneous determina-tion of Cd and Pb in seawater has not been reported up todate.The present study focuses on the evaluation of the feasi-bility of using SPEs for the simultaneous determination of Pband Cd in seawater. Several parameters affecting the system,such as the matrix effect upon the SPE response and the sta-bility of the measuring system have been studied. The resultsobtained for the determination of the metal contents in realand spiked seawater samples will be shown.2. Experimental2.1. Chemicals and apparatusHeavy metals solutions were prepared by diluting AAS grade(Panreac) Pb, Cd, Cu and Zn standard solutions. HCl (32%) wasobtained from Fluka. NaCl (99.5%) was purchased from Pan-reac. The pH was adjusted by using CaCO3(99%) (Merck).A certified reference material (LGC6016) consisting ofestuarine water was used for validation purposes. Thecertified metal values: 101±2g/kgCd, 190±4g/kgCu,196±3g/kgPb, and 976±31g/kgMn.The SPE sensors (from University of Florence—availablefrom PalmInstruments,http://www.palmsens.com) consistedof a screen-printed electrochemical cell with three electrodesin one single strip: a graphite working electrode modified witha plasticizer mixed with mercury acetate, a graphite counterelectrode and a silver pseudo-reference electrode[21].A computer-controlled Autolab PGSTAT-12 (302N-High per-formance) (potentiostat/galvanostat) with general-purposeselectrochemical software operating system (GPES version4.9.007) from Eco Chemie B.V., The Netherlands, was used