Detection of Heavy Metals by Immunoassay:  Optimization and Validation of a Rapid, Portable Assay for Ionic Cadmium

Abstract

An immunoassay is described that measured Cd(II) in aqueous samples at concentrations from approximately 7 to 500 ppb. The assay utilized a monoclonal antibody that bound tightly to a cadmium−ethylenediaminetetraacetic acid (EDTA) complex but not to metal-free EDTA. A inhibition immunoassay format was employed for this analysis; ionic cadmium was diluted into an excess of EDTA before being incubated with the antibody in the presence of an immobilized Cd(II)−EDTA conjugate. Ca(II), Na(I), and K(I), cations commonly encountered in ambient water samples, did not interfere with the cadmium immunoassay at concentrations approaching their solubility limit. The assay reliably measured Cd(II) in the presence of a 1 mM excess of Fe(III), Mg(II), and Pb(II). Zn(II) and Ni(II) had minimal effect on the assay at levels below 100 μM, and the immunoassay was relatively insensitive to interferences by In(III) and Mn(II) at concentrations up to 10 μM. Hg(II) had the ability to cause a false positive in the assay, but only at concentrations higher than 1 μM. The assay compared favorably with atomic absorption spectroscopy in its ability to measure cadmium in spiked water samples taken from a Louisiana bayou.

Impact of metals on the biodegradation of organic pollutants.

“…Immunoassays have been developed for cadmium, lead, cobalt, nickel, and zinc. An immunoassay for mercury is commercially available Khosraviani et al 1998). The second tool is the use of bioreporters, which are whole cells that produce a protein with measurable activity (e.g., LacZ) or light in response to bioavailable metal.…”

Detection of hexavalent uranium with inline and field-portable immunosensors

“…Previous work in our laboratory has focused on the isolation/characterization of antibodies that bind to metal-chelate complexes and on the development of antibody-based assays useful for measuring a variety of heavy metals in a given sample (Khosraviani et al, 1998;Delehanty et al, 2003;Darwish and Blake, 2004;Kriegel et al, 2006;Zhu et al, 2007). The work described in this report represents some of the first experiments carried out by our laboratory in a field setting and demonstrates the portability, speed and overall utility of immunosensors for environmental analysis.…”

Facile Synthesis of Galactosamine‐Stabilized Gold Nanoparticles with Sensitive Cd2+ Sensing

“…[1] Experimental and epidemiologic studies provide evidence that chronic exposure to Cd 2+ ions, in combination with other environmental factors, can contribute to an increased risk of cancer. [2][3][4] The standard for the concentration of Cd 2+ ions in drinking water under US and EU guidelines is no more than 44 nm. [5,6] However, the World Health Organization (WHO) standard for the maximum allowable level of inorganic Cd 2+ ions in drinking water is no more than 3 ppb (15 nm).…”

“…To date, several conventional analytical techniques have been used, for example, atomic absorption spectroscopy (AAS). [4] These methods often suffer from disadvantages, for example, time-consuming sample pretreatment or expensive instruments. Many detection sensors have been developed to solve the above defects.…”