Lead , colorimetric detection

N.Z. Aracama, A.N. Araujo, R. Perez-Olmos, Sequential injection analysis of lead using time-based colorimetric detection and preconcentration on an anionic-exchange resin, Anal. Sci. 20 (2004) 679. 

The results obtained for the vast majority of the laboratories carrying out the ISO 15061 IC method were considered to be fit for the purpose. In addition to this method, five alternative methods suitable for trace bromate determinations were also considered, namely on-line IC-ICP-MS, simple on-line column chromatography ICP-MS, IC with chlorpromazine post-column reaction and colorimetric detection, and fluorescence quenching with Carbostyril (with pre-treatment), which are all capable of achieving a bromate detection limit below 1 xg/L. A field method with methylene blue and fluorescence quenching with Carbostyril without sample pretreatment did not lead to satisfactory results at this level of bromate concentrations. 

Wang, Z., Lee,J. H., et al. Label-Free Colorimetric Detection of Lead Ions with a Nanomolar Detection Limit and Tunable Dynamic Range by using Gold Nanoparticles and DNAzyme. Advanced Materials,20(17), 3263-3267 (2008). 

The methods most commonly used to detect hydrogen sulfide in environmental samples include GC/FPD, gas chromatography with electrochemical detection (GC/ECD), iodometric methods, the methylene blue colorimetric or spectrophotometric method, the spot method using paper or tiles impregnated with lead acetate or mercuric chloride, ion chromatography with conductivity, and potentiometric titration with a sulfide ion-selective electrode. Details of commonly used analytical methods for several types of environmental samples are presented in Table 6-2. 

A reverse cross-coupling reactions mediated by palladium was used to develop a colorimetric sensitive chemodosimeter for the detection of trace palladium (II) salts [93]. The decolorization of 4 is produced by a nucleophilic attack of ethanethiol in basic DMSO solutions. Palladium detection is done via thiol scavenging from the 4-ethanethiol complex leading to a color turn-on of the parent squaraine. Naked-eye detection of Pd(NC>3)2 is as sensitive as 0.5 ppm in solution, and the instrument-based detection can go as low as 0.1 ppm. 

In addition to test kits used in EPA-approved screening methods, a variety of other test kits are available from several manufacturers, for example, immunoassay test kits for BTEX in soil and water and for chlorinated solvents in water colorimetric kits for the detection of lead kits for a wide range of water quality parameter manufactured by Hach Company. 

In most cases, uronic acids are liberated from acidic polysaccharides by hydrolysis leading to irreproducible concomitant formation of lactones. Several methods to circumvent this problem have been published describing conversion of the uronic acid into methyl esters followed by reduction with borohydride or borodeuteride reagents and subsequent hydrolysis and GC-MS detection [129]. Other techniques are based on the liberation and quantification of carbon dioxide. Direct determination of uronic acid residues in hydrolyzates has frequently been performed according to colorimetric assays, which are rather insensitive and have thus mostly been replaced by high-performance anion exchange chromatography (HP-AEC) methods [130-132]. 

In 1959 Harrison and Gilroy (3) demonstrated the detectability of barium, antimony and lead in firearm discharge residue using a specific "spot" test for each element. Inadequate colorimetric sensitivity for barium and antimony (I4.) has severely restricted the use of the method as a field tool. 

In 1959, Harrison and Gilroy introduced a method based on the detection of the metal-containing components of FDR.124 The metallic components involved, namely, lead, antimony, and barium, originate from the primer and the bullet (lead and antimony). The method is based on colorimetric spot tests and involves swabbing the suspect s hands with cotton cloth damped with 0.1 M hydrochloric acid. The swab is allowed to dry and is then tested with one or two drops of a 10% alcohol solution of triphenylmethylarsonium iodide. The appearance of an orange ring indicates the presence of antimony. 

BIOLOGICAL PROPERTIES the biological half-life for lead in the bones of humans is 10 yrs can be detected in water by atomic adsorption or by colorimetric analysis or by inductively coupled plasma optical emission spectrometry, dissolved lead by 0.45 micron filtration prior to such analysis... 

In addition to the standard Watson-Crick base pairing it has recently been discovered that thymine can selectively bind to mercuric ion (Hg ) via the formation of a thymine-Hg -thymine (T-Hg -T) complex (72). The presence of the Hg at the thymine-thymine mismatch leads to a significant increase ( 10°C) in the T . Mirkin and coworkers (40) incorporated this T-Hg "-T coordination chemistry in the DNA-AuNP system to design a novel colorimetric assay for detecting Hg " "(Fig. 12.15). In a typical assay, two batches of AuNPs were functionalized with two complementary sequences, respectively, and combined to form aggregates. 

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