High-repetition fast-scan cyclic voltammetry and chronoamperometry were used to quantify and characterize the kinetics of dopamine and dopamine-o-quinone adsorption and desorption at carbon-fiber microelectrodes. A flow injection analysis system was used for the precise introduction and removal of a bolus of electroactive substance on a sub-second time scale to the disk-shaped surface of a microelectrode that was fabricated from a single carbon fiber (Thornel type T650 or P55). Pretreatment of the electrode surfaces consisted of soaking them in purified isopropyl alcohol for a minimum of 10 min, which resulted in S/N increasing by 200−400% for dopamine above that for those that were soaked in reagent grade solvent. Because of adsorption, high scan rates (2000 V/s) are shown to exhibit equivalent S/N ratios as compared to slower, more traditional scan rates. In addition, the steady-state response to a concentration bolus is shown to occur more rapidly when cyclic voltammetric scans are repeated at short in...

Subsecond adsorption and desorption of dopamine at carbon-fiber microelectrodes.

Honey contains a variety of metals. Major metals are primarily derived from soil and nectar-producing plants, but consideration also needs to be given to environmental pollution or other anthropogenic sources of metals in honey, especially of Cd, Cr, Cu, Fe, Ni, Pb and Zn, which may present hazards to human health and adversely affect the quality and the safety of honey. This review surveys the literature from the past 15 years on determination of the metal content of honey by atomic absorption and emission spectrometries. It pays particular attention to sample treatment, sample preparation and measurement techniques. It also discusses the suitability of information on the composition of metals in honey for classifying according to botanical and geographical origin or indicating and controlling environmental pollution.

Determination of metal content in honey by atomic absorption and emission spectrometries

High levels of arsenic (As) in rice grain are a potential concern for human health. Variability in total As in rice was evaluated using 204 commercial rice samples purchased mostly in retail stores in upstate New York and supplemented with samples from Canada, France, Venezuela, and other countries. Total As concentration in rice varied from 0.005 to 0.710 mg kg(-1). We combined our data set with literature values to derive a global "normal" range of 0.08-0.20 mg kg(-1) for As concentration in rice. The mean As concentrations for rice from the U.S. and Europe (both 0.198 mg kg(-1)) were statistically similar and significantly higher than rice from Asia (0.07 mg kg(-1)). Using two large data sets from Bangladesh, we showed that As contaminated irrigation water, but not soil, led to increased grain As concentration. Wide variability found in U.S. rice grain was primarily influenced by region of growth rather than commercial type, with rice grown in Texas and Arkansas having significantly higher mean As concentrations than that from California (0.258 and 0.190 versus 0.133 mg kg(-1)). Rice from one Texas distributor was especially high, with 75% of the samples above the global "normal" range, suggesting production in an As contaminated environment.

http://pubs.acs.org/doi/pdf/10.1021/es702747y

Arsenic in Rice: I. Estimating Normal Levels of Total Arsenic in Rice Grain

https://opus.lib.uts.edu.au/bitstream/10453/14761/1/2010005083.pdf

M. Alessandrelli

Papers

Arsenic content of various types of rice as determined by plasma- based techniques

A pilot study for the production of a certified reference material for trace elements in honey

Trace elements in bovine muscle: an ongoing project for a new certified reference material

The handbook of analytical methods for trace elements as adopted by the national reference laboratories for residues

The Cardbox/Cardview Database for residues in live animals and their products