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A method for determining lead (Pb) and cadmium (Cd) in cosmetic products by an inductively coupled plasma atomic emission spectrometer (ICP-AES) is described. The acid digestion approach using concentrated HNO3, HNO3–HClO4, and aqua regia is performed, and the results show that the digestion of HNO3 is the most suitable procedure for cosmetics. The proposed method is then validated and optimized for Pb and Cd determination in terms of accuracy, repeatability, and day-to-day reproducibility. For diluted cosmetic samples, the limits of detection for Pb and Cd are 0.07 and 0.001 μg/g, respectively. This developed method is then successfully applied to the analysis of different facial cosmetic products, showing the contents of Pb and Cd within the ranges ~(0.11–0.54) and ~(0.01–0.24) mg/kg, respectively. The determination recoveries for Pb and Cd are within 89.7–104.4%, and the relative standard deviations are less than 3.0% (n = 5), showing the good applicability of this proposed method for Pb and Cd quantification in cosmetic samples.

Seven novel dirhodium coordination polymers (Rh2–Ln) (n = 1–7) are prepared by employing bitopic ligands to connect dirhodium nodes. The formation of the framework is confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) and 1H → 13C cross polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) spectroscopy. Defect sites resulting from incomplete ligand substitution are revealed by 19F MAS NMR. The random stacking behavior of the frameworks in the obtained solid is analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Rh2/O interaction in neighboring layers is investigated by diffuse reflectance ultra-violet visible light (DR-UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). This interaction is relevant to understand the catalytic behavior of various Rh2–Ln catalysts in the cyclopropanation of styrene with ethyl diazoacetate (EDA). In this context, the structure-reactivity relationship is discussed by taking into consideration both interlayer Rh2/O interactions and steric effects of side chains.

The interaction mechanisms of catalase (CAT) with pesticides (including organophosphates: disulfoton, isofenphos-methyl, malathion, isocarbophos, dimethoate, dipterex, methamidophos and acephate; carbamates: carbaryl and methomyl; pyrethroids: fenvalerate and deltamethrin) were first investigated by flow injection (FI) chemiluminescence (CL) analysis and molecular docking. By homemade FI-CL model of lg[(I0-I)/I]=lgK+nlg[D], it was found that the binding processes of pesticides to CAT were spontaneous with the apparent binding constants K of 10(3)-10(5) L mol(-1) and the numbers of binding sites about 1.0. The binding abilities of pesticides to CAT followed the order: fenvalerate>deltamethrin>disulfoton>isofenphos-methyl>carbaryl>malathion>isocarbophos>dimethoate>dipterex>acephate>methomyl>methamidophos, which was generally similar to the order of determination sensitivity of pesticides. The thermodynamic parameters revealed that CAT bound with hydrophobic pesticides by hydrophobic interaction force, and with hydrophilic pesticides by hydrogen bond and van der Waals force. The pesticides to CAT molecular docking study showed that pesticides could enter into the cavity locating among the four subdomains of CAT, giving the specific amino acid residues and hydrogen bonds involved in CAT-pesticides interaction. It was also found that the lgK values of pesticides to CAT increased regularly with increasing lgP, Mr, MR and MV, suggesting that the hydrophobicity and steric property of pesticide played essential roles in its binding to CAT.

Luminescently probed by luminol, the interaction behaviors of bovine serum albumin (BSA) with different antibiotics (macrolides, tetracyclines and sulfonamides) at picomolar levels were investigated using flow injection chemiluminescence (FI-CL) analysis. It was found that BSA and antibiotics formed complexes with the binding ratio of 1 : 1, with the binding constants K within the range of 103 to 105 L mol−1 generally following the order of macrolides < tetracyclines < sulfonamides. Results showed that the ester groups of –OOCC3H7 or –OOC(CH2)2COOC2H5 in macrolides led to increased K by factors of 3.1–42.8 times, –OH or –Cl in tetracyclines increased K by 1.1–1.3 times, and the additional –C(NH)NH2 in sulfonamides increased K about 1.3 times. The thermodynamic parameters demonstrated that the BSA–antibiotic binding process should be spontaneous mainly through hydrophobic interaction for macrolides, hydrogen bonding and van der Waals force for tetracyclines, and electrostatic interaction for sulfonamides. The further antibiotics to BSA molecular docking study revealed that the pocket at subdommain IIA of BSA should be the principle binding site for antibiotics, showing that the interaction parameters including K and ΔG agreed well with the results from the proposed FI-CL analysis. The interesting phenomenon that the log K had good linear correlation to molecular volume MV, molar refractivity MR, polarizability POL and partition coefficient log P of antibiotics was also observed.

Based on the linear enhancement of formaldehyde (FA) within 7.0 ∼ 1000 pmol l−1 on luminol—bovine serum albumin (BSA) chemiluminescence (CL) system, FA determination in air and beer samples using CL with flow injection (FI) was proposed. The detection limit was 2.5 pmol l−1 (3σ) and the relative standard deviations were less than 4.5% (n = 7). At a flow rate of 2.0 mL min−1, a whole analysis from sampling to washing only needed 32 s, offering a sample throughput of 112 h−1. This proposed method was successfully utilized to determine FA vapor pressure in liquid (121.8 ± 3.8 Pa), FA content in real air sample (8.93 ± 0.03 mg m−3), and FA levels in beer (199.5 ± 5.6 ∼ 225.2 ± 3.5 mg l−1), giving determination recoveries from 90.7% to 109.3%. The mechanism of BSA—FA interaction was also investigated, showing FA binding to BSA was a spontaneous process mainly through hydrogen bonding and van der Waals force by FI-CL, with binding constant K of 1.89 × 106 l mol−1 and the number of binding sites n of 0.86. Molecular docking analysis further revealed FA could enter into the pocket at subdomain IIA of BSA, with K of 1.71 × 105 l mol−1 and ΔG of -29.68 kJ mol−1.

A sensitive method for the determination of picogram level dibutyl phthalate (DBP) in wine by flow-injection chemiluminescence (FI–CL) analysis is presented for the first time, which was based on the quenching effect of DBP on the luminol–myoglobin (Mb) CL system. The decrement of CL intensity was linearly proportional to the logarithm of DBP concentration in the range of 0.1–100 pg mL −1 with the detection limit of 0.03 pg mL −1 (3 σ ). At a flow rate of 2.0 mL min −1 , a complete determination of DBP including sampling and washing could be accomplished in 0.5 min, giving the maximum sample throughput of 120 h −1 . The proposed method was successfully applied to the determination of DBP in wine, human serum and urine samples with the relative standard deviations (RSDs) of less than 3.0% ( n = 5). The molecule docking results showed that DBP interacted with the amino acid residues near the heme moiety of Mb. The possible CL mechanism of luminol–Mb–DBP reaction should be that the binding of Mb with DBP forming a 1:1 complex (binding constant K = 1.55 × 10 4 L mol −1 ) led to the conformational change of Mb and resulted in the quenching of CL intensity.

A sensitive chemiluminescence (CL) method for the determination of hesperetin at nanogram levels was first presented. It was based on the inhibitory effect of hesperetin on luminol-dissolved oxygen CL reaction in a flow injection system. The decrements of CL intensity were logarithm over the concentrations of hesperetin in a range of 0.5 to 1000 ng mL−1, with a detection limit of 0.2 ng mL−1 (3σ) and the relative standard deviations lower than 2.1%. At a flow rate of 2.0 mL min−1, the whole determining performance including sampling and washing could be accomplished in 30 s, giving a sampling efficiency of 120 h−1. The proposed method was applied successfully to the direct hesperetin determination in human serum with recoveries from 97.0 to 106.6%, and indirect hesperidin quantification in 2.5 g pericarpium citri reticulatae showing that the content is 8.1±0.2%. The possible CL mechanism of luminol-dissolved oxygen-hesperetin reaction was also discussed in detail.

This paper presented the arsenic determination in four different brands of cosmetic face-creams to provide valuable information on the safety levels for consumers. The cosmetic samples were decomposed by acidic digestion method and then taken for arsenic quantification using inductively coupled atomic emission spectrometry (ICP-AES). The digestion efficiency of acid mixtures including concentrated HNO3, HNO3–HClO4, HNO3–H2O2 and aqua regia was discussed in terms of digestion loss and time consumption. The ICP-AES analyzing results, with determination recoveries of 95.4% ~ 105.2% and relative standard deviations less than 3.0% (n = 5), revealed arsenic contents in the face-creams are in the ranges of 0.68 ~ 3.28 mg·kg−1. Obviously, the arsenic contents in some of the studied brands exceed the maximum recommended value of 2.0 mg·kg−1 set by China. These results lead to the conclusion that constant control of arsenic content in cosmetics should be seriously considered. The successful arsenic determination in cosmetic face-creams by digestion pattern of concentrated HNO3, with simplicity, higher efficiency, less reagent consumption and less analytical time well demonstrates the good analytical capability of this method, promising a great possibility for large batches of cosmetic toxic metal monitoring.

It was first found that the intrinsic fluorescence of lysozyme at 340 nm can be quenched by cephalosporin analogues through the static quenching and non-radiative energy transferring procedure. In the acetate buffer solution with pH 7.0 and 298 K, the quenching fluorescence intensity was in a good linearity over the concentration of drugs in the range of 1–100 μmol L−1, 0.1–100 μmol L−1, 0.5–100 μmol L−1 and 0.05–100 μmol L−1 for cefradine, cefuroxime, cefotaxime and ceftriaxone, respectively. The quenching ability or the binding ability of the studied drugs followed the pattern: ceftriaxone > cefotaxime > cefuroxime > cefradine, which was close to the order of their antibacterial ability. The binding parameters including the association constant and the number of binding potential point were calculated at different temperatures (288, 298 and 308 K), and thermodynamic parameters ΔH°, ΔS° and ΔG° were given. The binding mode of lysozyme with cephalosporins showed that the hydrophobic effect might play a major role. The binding distance between cephalosporin and tryptophan residue in lysozyme was obtained. The results provided the quantitative information for the binding of cephalosporin to lysozyme, and it was suggested that the drugs probably bound to the active site near Trp62 in lysozyme.

In this paper, the luminescence behavior of bovine serum albumin (BSA) and luminol was first studied by flow injection chemiluminescence (CL). It was found that the hyperchromic effect of luminol in the presence of BSA led to the acceleration of the electrons transferring rate of excited 3-aminophthalate, which greatly enhanced the CL intensity of luminol/dissolved oxygen reaction. The increments of CL intensity were proportional to the concentrations of BSA with a linear range from 0.01 to 7 nmol L−1. It was also found that azithromycin could inhibit the CL intensity of luminol/BSA reaction. The decrements of CL intensity were logarithm over the concentrations of azithromycin ranging from 0.1 to 700 ng mL−1. At a flow rate of 2.0 mL min−1, a complete analytical process, which included sampling and washing, could be performed within 30 s with relative standard deviations of less than 3.1%. This proposed method was successfully applied in assaying azithromycin in pharmaceutical and human serum samples with recoveries from 91.0 to 104.3%. The possible luminescence mechanism of luminol/BSA/azithromycin reaction was discussed in detail by CL, UV and fluorescence methods.