The effect of varying short-chain alkyl substitution of the indole nitrogens on the spectroscopic properties of cyanine dyes was examined. Molar absorptivities and fluorescence quantum yields were determined for a set of pentamethine dyes and a set of heptamethine dyes for which the substitution of the indole nitrogen was varied. For both sets of dyes, increasing alkyl chain length resulted in no significant change in quantum yield or molar absorptivity. These results may be useful in designing new cyanine dyes for analytical applications and predicting their spectroscopic properties.

Nitrobenzene, a potentially harmful compound found in tobacco smoke, has been largely excluded from prior analysis due to difficulties with quantification. Quantifying harmful compounds in cigarette smoke is useful to compare products, to examine the impact of design parameters on delivery, and to help estimate exposures. A sensitive high-throughput method has been developed for quantifying nitrobenzene in machine-generated mainstream cigarette smoke using isotope dilution gas chromatography-tandem mass spectrometry (ID-GC-MS/MS). This method has sufficient sensitivity to measure vapor phase nitrobenzene concentrations in the low nanogram range, with a 418 pg/cig method limit of detection. Precision estimates from two quality control cigarette products resulted in percent relative standard deviations of 11.5% and 14.9%; product variability estimates from 13 cigarette products resulted in percent relative standard deviations ranging from 2.8% to 16.9%. Nitrobenzene in the machine-generated, mainstream smoke from 15 cigarette products are reported and range from 18 to 38 ng/cig under the Health Canada Intense smoking regimen.

The use of the NIR spectral region (650-900 nm) is advantageous due to the inherently lower background interference and the high molar absorptivities of NIR chromophores. Near-Infrared (NIR) dyes are increasingly used in the biological and medical field. The binding characteristics of NIR dyes to biomolecules are possibly controlled by several factors, including hydrophobicity, size and charge just to mention a few parameters. Binding characteristics of symmetric carbocyanines and found that the hydrophobic nature of the NIR dye is only partially responsible for the binding strength. Upon binding to biomolecules significant fluorescence enhancement can be observed for symmetrical carbocyanines. This fluorescence amplification facilitates the detection of the NIR dye and enhances its utility as NIR reporter. This manuscript discusses some probe and marker applications of such NIR fluorescent dyes. One application discussed here is the use of NIR dyes as markers. For labeling applications the fluorescence intensity of the NIR fluorescent label can significantly be increased by enclosing several dye molecules in nanoparticles. To decrease self quenching dyes that have relatively large Stokes' shift needs to be used. This is achieved by substituting meso position halogens with amino moiety. This substitution can also serve as a linker to covalently attach the dye molecule to the nanoparticle backbone. We report here on the preparation of NIR fluorescent silica nanoparticles. Silica nanoparticles that are modified with aminoreactive moieties can be used as bright fluorescent labels in bioanalytical applications. A new bioanalytical technique to detect and monitor the catalytic activity of the sulfur assimilating enzyme using NIR dyes is reported as well. In this spectroscopic bioanalytical assay a family of Fischer based n-butyl sulfonate substituted dyes that exhibit distinct variation in absorbance and fluorescence properties and strong binding to serum albumin as its sulfonic acid moiety is modified to less water soluble moiety was identified. In polar solvents, these water soluble compounds are strongly fluorescent, however form the less soluble aggregated species with virtual loss of fluorescence when the sulfonate groups are cleaved by enzymatic activity to form the corresponding straight chain alkyl aldehyde derivatives. To achieve this conversion in vitro photo-reduced riboflavin mononucleotide (FMN) with a glucose/ glucose-oxygenase oxygen scavenging system was utilized. The reduced FMN serves as a key substrate in the enzymatic desulfonation. Once the FMNH 2 was produced the desulfonation reaction was characterized by using Laser Induced Fluorescence Capillary Zone Electropheresis (LIF-CZE). This method can be utilized as an assay to detect the enzyme activity in vitro with the possibilities of in vivo applications.

A quantitative method was developed to measure four harmful carbonyls (acetaldehyde, acrolein, crotonaldehyde, and formaldehyde) in aerosol generated from e-cigarette, or vaping, products (EVPs). The method uses a commercially available sorbent bed treated with a derivatization solution to trap and stabilize reactive carbonyls in aerosol emissions from EVPs to reduce reactive analyte losses and improve quantification. Analytes were extracted from the sorbent material using acetonitrile and analyzed via high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). The method was applied to aerosols generated from products obtained from case patients with EVP use-associated lung injury (EVALI). The method accuracy ranged from 93.6 to 105% in the solvent and 99.0 to 112% in the matrix. Limits of detection (LODs) were in the low nanogram range at 0.735–2.10 ng for all analytes, except formaldehyde at 14.7 ng. Intermediate precision, as determined from the replicate measurements of quality-control (QC) samples, showed a relative standard deviation (RSD) of less than 20% for all analytes. The EVALI case-related products delivered aerosol containing the following ranges of carbonyls: acetaldehyde (0.0856–5.59 μg), acrolein (0.00646–1.05 μg), crotonaldehyde (0.00168–0.108 μg), and formaldehyde (0.0533–12.6 μg). At least one carbonyl analyte was detected in every product. Carbonyl deliveries from EVALI-associated products of all types are consistent with the previously published results for e-cigarettes, and levels are lower than those observed in smoke from combustible cigarettes. This method is rugged, has high throughput, and is well suited for quantifying four harmful carbonyls in aerosol emissions produced by a broad spectrum of devices/solvents, ranging from e-cigarette containing polar solvents to vaping products containing nonpolar solvents.

in Wiley Online Library (wileyonlinelibrary.com).Seven 2,4,6-trisubstituted pyridine derivatives with N,N-diethylaniline substituents at the 4-position were synthesized, and their spectroscopic properties in the absence and presence of acid were studied. The spectral effects of protonation, molar absorptivities, pK a values, and the structural origins of the observed spectral behavior were ascertained. The pyridine nitrogen was found to be more basic than the diethylamino nitrogen atom. Protonation of the pyridine ring nitrogen is associated with the appearance of a red-shifted intramolecular charge transfer peak in the UV-visible spectra. Favorable color indicating properties result from electron-donating substitution at the 2 and 6 positions of pyridine, which provide a greater absorptivity of the red-shifted peak associated with protonation of the pyridine nitrogen. These findings will assist in the design and optimization of these compounds for ion-indicating and pH-sensing applications.