Determination of some metal ions using lichen‐modified carbon paste electrodes

Abstract

Lichens have long been used as biomonitors of environmental pollution. We therefore investigated the application of lichen-modified carbon paste electrodes (CPEs) for the determination of lead( 11) and copper( 11) using differential pulse anodic stripping voltammetry. These electrochemical biosensors incorporate the biological selectivity of lichen species such as Cladonia portentosa and Lobaria pulmonauia, and the genus Koccelh, with the sensitivity of electrochemical detection. As such, they may offer new reactivity patterns that could be exploited in the determination of trace metal ions in environmental samples and in speciation studies. The voltammetric responses were evaluated with respect to pH of accumulation (carried out under open circuit conditions), pH of electrolyte solution, metal ion concentration, percentage lichen loading in the carbon paste, interferences, and surface renewal. lNTRODUCTIONLichens are plants formed by the symbiotic association of an alga and a fungus. Their general structure is that of an upper cortex, a protective central fungal medulla (of loosely packed hyphae), and a lower cortex. The algae may form a distinct layer beneath the upper cortex, or they can be dispersed throughout. Most lichens have an extracellular matrix which is a gelatinous secretion containing polysaccharides such as lichenan and isolichenan together with glucans, galactomannose, and lichen acids.For years, lichens have been known to accumulate metal ions and have been used extensively as biomonitors of environmental pollution [ 1, 21. The diversity of lichen species close to a suspected pollution source has been used to assess the levels of gaseous air pollutants, with fewer lichen species being found closer t o the emission source 13, 41. These plants are considered to be useful biomonitors of sulfur dioxide A review by Richardson [22] on the pollution sensitivity of lichens discusses the effects of sulfur dioxide and acid rain on the lichens, along with the mechanism of airborne elemental accumulation by these plants. Since then, Beck and Ramelow [ 231 have used lichens enclosed in porous polyvinyl chloride (PVC) tubes as monitors of dissolved metals in natural waters. The W C tubes were suspended at drfferent sampling points along a river. After 2 weeks, the lichens were analyzed by atomic absorption spectroscopy for a wide variety of metals ions includng Pb(I1) and Cu(I1).Kecently, Wang et al. [ 241 reported on experiments at algae-modified electrodes to investigate the incorporation of anionic and cationic metal complexes by algae. GardeaTorresday et al. [ 2 5 , 261 then reported on voltammetric measurements at algae-modified electrodes capable of preconcentrating Cu(I1) and Au( I). These studies suggested that the development of lichen-modified electrodes might open up a new area of sensor development based on the nonelectrochemical bioaccumulation of metal ions.This article describes the development of lichenmodified carbon paste electrodes (CPEs) for the detection of lead( 11) and copper( 1...

Carbon Paste Electrodes in Facts, Numbers, and Notes: A Review on the Occasion of the 50‐Years Jubilee of Carbon Paste in Electrochemistry and Electroanalysis

“…For both CMCPEs and CP-biosensors, numerous materials of such a origin were used, comprising: i) plants and plant tissues (e.g., alga [131], lichen [132], moss [133], tobacco [134], pea seedlings [135], or grass weed [136]); ii) fruits and vegetables (often as natural sources of enzymes); e.g., banana [137]; orange slice [138], apple [139], pear and peach [140], avocado [141], annona pear [142], pineapple [143], or potatoes [140]; iii) mushrooms [140,144,145], iv) bacteria and viruses [146,147]); v) natural macromolecules (e.g., chitin [148], chitosan [149], or keratin [150]); vi) other materials such as liquid crystals [151,152], metal dispersions [153,154], or pumice (sea foam [155]). …”

Exfoliated Graphite Oxide Modified Electrode for the Selective Determination of Picomolar Concentration of Lead

“…Some of the modified electrodes require additional step [15,23,24,26,29,30]. The moss modified carbon paste electrode [CPE] requires long accumulation time of 15 minutes [24] and the lichen modified CPE requires a renewal time of 5 minutes [23]. The dibenzo-18-crown-6-and cryptand modified CPE [24] has a high detection limit (0.5 pM).…”

“…The ligands used for the modification of electrode in lead analysis include 1-(2-pyridylazo)-2-naphthol [15], dibenzo-18-crown-6-and cryptand [22], lichen [23], moss [24], benzoin oxime [25], zirconium phosphate-amorphous silica [26] and p-chlorophenylcinnamohydroxamic acid [27] and p-phenylenediamine [28]. Some of the modified electrodes require additional step [15,23,24,26,29,30]. The moss modified carbon paste electrode [CPE] requires long accumulation time of 15 minutes [24] and the lichen modified CPE requires a renewal time of 5 minutes [23].…”

Modified carbon-containing electrodes in stripping voltammetry of metals

“…CPE modified by biocatalysts, which are constituents of α-and β-cyclodextrins [223][224][225] or natural lichens [311][312] are used for measurement of ions of heavy metals.…”