Heavy metal pollution is one of the most serious environmental problems, which undermines global sustainability. Many efforts have been made to develop portable sensors for monitoring heavy metals in the environment. Incorporation of nanomaterials and nanostructures into sensors leads to significant improvement in the performance of devices in terms of sensitivity, selectivity, multiplexed detection capability and portability. In addition, small molecules, DNA, proteins and bacteria have been integrated with inorganic materials to selectively bind heavy metals as the molecular recognition probes. This review presents a recent advance in optical, electrochemical and field-effect transistor sensors for heavy metal detection. The optical sensors are focused on colorimetric, fluorescent, surface-enhanced Raman scattering and surface plasmon resonance devices. In addition, optofluidic devices which integrate optical components with microfluidic chips are discussed. Furthermore, nanoparticle-modified electrodes...

Nanostructured Sensors for Detection of Heavy Metals: A Review

Sub-nanometer-sized metal clusters, having dimensions between metal atoms and nanoparticles, have attracted tremendous attention in the recent past due to their unique physical and chemical properties. As properties of such materials depend strongly on size, development of synthetic routes that allows precise tuning of the cluster cores with high monodispersity and purity is an area of intense research. Such materials are also interesting owing to their wide variety of applications. Novel sensing strategies based on these materials are emerging. Owing to their extremely small size, low toxicity, and biocompatibility, they are widely studied for biomedical applications. Primary focus of this review is to provide an account of the recent advances in their applications in areas such as environment, energy, and biology. With further experimental and theoretical advances aimed at understanding their novel properties and solving challenges in their synthesis, an almost unlimited field of applications can be foreseen.

Noble Metal Clusters: Applications in Energy, Environment, and Biology

According to the Autism Society of America, autism is now considered to be an epidemic. The increase in the rate of autism revealed by epidemiological studies and government reports implicates the importance of external or environmental factors that may be changing. This article discusses the evidence for the case that some children with autism may become autistic from neuronal cell death or brain damage sometime after birth as result of insult; and addresses the hypotheses that toxicity and oxidative stress may be a cause of neuronal insult in autism. The article first describes the Purkinje cell loss found in autism, Purkinje cell physiology and vulnerability, and the evidence for postnatal cell loss. Second, the article describes the increased brain volume in autism and how it may be related to the Purkinje cell loss. Third, the evidence for toxicity and oxidative stress is covered and the possible involvement of glutathione is discussed. Finally, the article discusses what may be happening over the co...

Evidence of Toxicity, Oxidative Stress, and Neuronal Insult in Autism

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Toxicological profile for malathion

Even though normal exposure levels to Cd may be small, the human body is inefficient at excreting the heavy metal, so it slowly accumulates over the period of a lifetime. Eventually, the Cd level in the body may become toxic and give rise to harmful effects. Cadmium exposure could therefore be linked to diseases associated with aging such as osteoporosis, prostate cancer, and pancreatic cancer. These potential links have driven the development of a myriad of analytical techniques for the determination of Cd in biological samples. Natural biological Cd concentrations are typically low, so preconcentration steps and sensitive instruments are frequently a necessity. In addition, the complex matrices of biological specimens such as blood, urine, serum, and tissue often require a form of matrix modification or separation. This review provides an overview of these methods with 200 references from the literature published between 1995 and 2005. The analytical methods for the determination of Cd in biolo...

Determination of Cadmium in Biological Samples

This paper describes a method for the determination of heavy metals (Co, NI, Cu, Cd, Pb) in urine by inductively coupled plasma atomic emission spectrometry (ICP-AES). The method proposed requires purification of the samples with activated charcoal under acidic conditions before preconcentration by complexation with ammonium pyrrolidlnedithlocarbamate (APDC). The formed complexes are extracted with methyl isobutyl ketone (MIBK) and the resulting residue Is finally digested under acid oxidant conditions. Because of its low detection limit (below 10 I~g/L), this procedure can be applied conveniently for toxicological diagnostic purposes.

Preconcentration of Heavy Metals in Urine and Quantification by Inductively Coupled Plasma Atomic Emission Spectrometry

A method is proposed that uses a polyamine chelating ion exchange resin for preconcentration of Cd, Cu, Pb, Mn, and Ni in urine and their determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES). After adjusting the samples to pH 7.0, the complexed metals can be Eluted from the resin column with 1 M HNO 3 . The uptake of Cd, Cu, Pb, and Mn was quantitative (83-103%). For the determination of Ni, the method of standard additions was necessary. A tenfold concentration factor for the 100-mL sample and the detection limits in the range of 3.7-9.0 mg/L make this procedure applicable for toxicological diagnosis.

A. Camean

Papers

Preconcentration of Heavy Metals in Urine and Quantification by Inductively Coupled Plasma Atomic Emission Spectrometry

Preconcentration of heavy metals in urine using chelating ion exchange resin and quantification by ICP-AES