Determination of phenylenediamine isomers in hair dyes by coal cinders micro-column extraction and MEKC

Metal Cation-Doped ns-Cucurbit[10]uril: Adsorption of Para-Phenylenediamine

The separation of phenylenediamine (PDA) isomers is crucial in the field of chemical manufacturing. Herein, we presented a strategy for the separation of PDA isomers (para-phenylenediamine, p-PDA; meta-phenylenediamine, m-PDA; ortho-phenylenediamine, o-PDA) using four supramolecular framework materials of ns-cucurbit[10]uril (ns-Q[10]), (1) ns-Q[10](Cd), (2) ns-Q[10](Mn), (3) ns-Q[10](Cu), (4) ns-Q[10](Pb). Our findings indicated that these supramolecular framework materials of ns-Q[10] showed remarkable selectivity for para-phenylenediamine (p-PDA) in p-PDA, m-PDA, and o-PDA mixtures, respectively. The variations in selectivity observed in these four single-crystal structures arose from variations in the thermodynamic stabilities and binding modes of the host-guest complexes. Importantly, the supramolecular framework based on ns-Q[10] exhibited selective accommodation of p-PDA over its isomers. This study highlighted the practical application of ns-Q[10] in effectively separating PDA isomers and demonstrated the potential utility of ns-Q[10] in isolating other organic molecules.

Chiral dual-emission composite material fluorescein/CCQDs @ZIF-8 for highly efficient recognition of phenylenediamine isomers and their oxidized product

As a new type of fluorescent nanomaterial, chiral carbon quantum dots (CCQDs) have the advantages of wide source, good water solubility and high chemical stability, and have been widely used in drug detection, bioimaging and chemical sensing. In this work, a chiral dual-emission hybrid material fluorescein/CCQDs@ZIF-8 (1) was synthesized by in-situ encapsulation strategy. Luminescence emission position of CCQDs and fluorescein are almost unchanged after the encapsulation into ZIF-8. The luminescent emissions of CCQDs and fluorescein can be observed to be located at 430 nm and 513 nm, respectively. When 1 is soaked in pure water, ethanol, dimethylsulfoxide, DMF, DMA and targeted substances solution for 24 h, 1 can maintain its structural stability. Photo-luminescent (PL) studies show that 1 can discriminate p-phenylenediamine (PPD) from m-phenylenediamine (MPD) and o-phenylenediamine (OPD), which can detect the presence of PPD with high sensitivity and selectivity (ratiomeric fluorescent probe with K_BH: 1.85 × 10³ M^-1 and detection limit: 8.51 μM). Further, 1 also effectively distinguish the oxidized product of these phenylenediamine(PD) isomers. 1 can be used as a "turn-off" fluorescent probe to detect oxidized product of PPD (ratiomeric fluorescent probe with K_SV: 6.82 × 10² M^-1 and detection limit: 0.112 mM) and a "turn-on" fluorescent probe to detect oxidized product of MPD (ratiomeric fluorescent probe: K_BH: 1.65 × 10³ M^-1 and detection limit: 35.03 μM) and oxidized product of OPD (ratiomeric fluorescent probe: K_BH: 2.40 × 10⁶ M^-1 and detection limit: 0.105 μM). Further, for the convenience of practical application, 1 can be developed as fluorescence ink and be prepared into a mixed matrix membrane. When the target substances are gradually added to the membrane, significant luminescence change with obvious color change can be observed.

Current trends in sample preparation for cosmetic analysis

The widespread applications of cosmetics in modern life make their analysis particularly important from a safety point of view. There is a wide variety of restricted ingredients and prohibited substances that primarily influence the safety of cosmetics. Sample preparation for cosmetic analysis is a crucial step as the complex matrices may seriously interfere with the determination of target analytes. In this review, some new developments (2010-2016) in sample preparation techniques for cosmetic analysis, including liquid-phase microextraction, solid-phase microextraction, matrix solid-phase dispersion, pressurized liquid extraction, cloud point extraction, ultrasound-assisted extraction, and microwave digestion, are presented. Furthermore, the research and progress in sample preparation techniques and their applications in the separation and purification of allowed ingredients and prohibited substances are reviewed.

Exploring versatile applications of cyclodextrins: an overview

CONTEXT

Ever since the discovery of cyclodextrins, a family of cyclic oligosaccharides based on α (1 → 4) linkage among glucopyranose subunits, these versatile supramolecular hosts have received tremendous attention for scientific explorations. Due to their property of forming host-guest type inclusion complex, cyclodextrins and their synthetic derivatives exhibit wide range of utilities in different areas viz. pharmaceuticals, drug delivery systems, cosmetics, food and nutrition, textile and chemical industry etc.

OBJECTIVE

The purpose of this review is to highlight properties, advantages, recent studies and versatile benefits of cyclodextrins and to re-strengthen their prospective applications in novel directions for future research.

METHODS

This article summarizes a variety of applications of cyclodextrins in various industrial products, technologies, analytical and chemical processes and recent industrial advancements by extensively literature search on various scientific databases, Google and websites of various associated pharmaceutical industries and patenting authorities across the world.

RESULTS AND CONCLUSION

Due to possibility of multidimensional changes in physical and chemical properties of molecules upon inclusion complexation in cyclodextrins, these compounds are of great commercial interest and may offer solution to many of the scientific problems of the current world.

An efficient and rapid thin-layer chromatography method for the identification of 32 dye substances in hair dye products

OBJECTIVE

The use of dye substances in hair dye products has led to controversial public and scientific discussions about their impact on human health. This study aimed to explore a rapid method for identification of dye substances in hair dye products.

METHODS

Thin layer chromatography (TLC) method was conducted in this study. We developed basic data of 32 dye substances by 4 developing solvents and 2 indicator sprays. The dye substances were identified by comparing the Rf values and colors between samples and reference substances.

RESULTS

Thirty samples were identified by the established method. 22 hair dye substances were detected in 16 formula known samples, 15 hair dye substances were detected in 14 formula unknown samples. Four laboratories participated in the validation and the results showed good interlaboratory reproducibility.

CONCLUSION

The developed TLC method is simple, rapid, reliable and can be finely used for identification of dye substances in hair dye products.

Recent advances in enrichment techniques for trace analysis in capillary electrophoresis

CE is gaining great popularity as a well-established separation technique for many fields such as pharmaceutical research, clinical application, environmental monitoring, and food analysis, owing to its high resolving power, rapidity, and small amount of samples and reagents required. However, the sensitivity in CE analysis is still considered as being inferior to that in HPLC analysis. Diverse enrichment methods and techniques have been increasingly developed for overcoming this issue. In this review, we summarize the recent advances in enrichment techniques containing off-line preconcentration (sample preparation) and on-line concentration (sample stacking) to enhancing sensitivity in CE for trace analysis over the last 5 years. Some relatively new cleanup and preconcentration methods involving the use of dispersive liquid-liquid microextraction, supercritical fluid extraction, matrix solid-phase dispersion, etc., and the continued use and improvement of conventional SPE, have been comprehensively reviewed and proved effective preconcentration alternatives for liquid, semisolid, and solid samples. As for CE on-line stacking, we give an overview of field amplication, sweeping, pH regulation, and transient isotachophoresis, and the coupling of multiple modes. Moreover, some limitations and comparisons related to such methods/techniques are also discussed. Finally, the combined use of various enrichment techniques and some significant attempts are proposed to further promote analytical merits in CE.