ABSTRACT
The design of a sensor array that uses a single entity as both the host and the indicator (squaraine dye, SQ) to differentiate a series of metal ions and a series of thiols is reported. The metal ions and thiols act as both analytes and "modulators" of the squaraine response allowing pattern-based discrimination. Mercury(II), palladium(II), copper(II), iron(II), and nickel(II) can be discriminated when combining SQ with five thiols: propane thiol (PT), 3-mercaptopropionic acid (MPA), naphthalene-2-thiol (NT), 2,3-dimercaptopropanol (DMP), and 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM). Likewise, the five thiols can be discriminated using SQ and the five metals. For example, SQ in combination with 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM) afforded very good differentiation of all five metal ions. However, propanethiol, 3-mercaptopropionic acid, and naphthalene-2-thiol produced very similar differentiation of the considered metal ions. On the other hand, all metal ions considered in this study are able to discriminate 2,3-dimercaptopropanol (DMP) and 2-acetylamino-3-mercaptopropionic acid methyl ester (ACM) clearly and completely, both from one another and from the other three thiols (PT, NT, MPA). Importantly, mercury(II) is the only metal ion able to effect the discrimination of naphthalenethiol (NT) from PT and MPA, thus giving the best discrimination overall. The study shows that complex discrimination of widely diverse classes, metal ions and thiols, can be achieved via a single receptor/indicator.
ABSTRACT
A colorimetric chemodosimeter (SQ1) for the detection of trace palladium salts in cross-coupling reactions mediated by palladium is described. Decolorization of SQ1 is affected by nucleophilic attack of ethanethiol in basic DMSO solutions. Thiol addition is determined to have an equilibrium constant (K(eq)) of 2.9 × 10(6) M(-1), with a large entropic and modest enthalpic driving force. This unusual result is attributed to solvent effects arising from a strong coordinative interaction between DMSO and the parent squaraine. Palladium detection is achieved through thiol scavenging from the SQ1-ethanethiol complex leading to a color "turn-on" of the parent squaraine. It was found that untreated samples obtained directly from Suzuki couplings showed no response to the assay. However, treatment of the samples with aqueous nitric acid generates a uniform Pd(NO(3))(2) species, which gives an appropriate response. "Naked-eye" detection of Pd(NO(3))(2) was estimated to be as low as 0.5 ppm in solution, and instrument-based detection was tested as low as 100 ppb. The average error over the working range of the assay was determined to be 7%.
ABSTRACT
A glow assay technology for the detection of a chemical warfare simulant is presented, which is based on modulating the peroxyoxalate chemiluminescence pathway by way of utilising an oximate super nucleophile that gives an "off-on" glow response.
