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In this paper, a boron–mannitol complex wet acid digestion method proposed for the accurate determination of boron in silicate samples by inductively coupled plasma mass spectrometry (ICP-MS) was investigated in detail for the first time. With the addition of 50 μL of mannitol (2% wt.) into the mixture of 0.6 mL of concentrated HF and 30 μL of concentrated HNO3, the 50 mg of silicate sample was effectively decomposed after being heated overnight with optional pre-ultrasonic treatment. Following fluoride formation prevention by 8% HNO3 (wt.) and fluoride decomposition using 6% HCl (wt.), the samples were fluxed in 2.0 mL of 40% HNO3 (wt.) for 4 h and aged overnight. By diluting 1000-fold using 2% HNO3 (wt.) solution, the samples were directly quantified by an ICP-MS, showing boron recoveries of the standard materials including diabase W-2, basalt JB-2a, and rhyolite JR-2 in the range of 95.5–105.5% (n = 5). For this wet acid method, it was found that the contents of boron had no obvious difference under digestion temperatures of 65, 100, and 140 °C. It was also found that the ICP-MS quantification accuracy deteriorated at the mass of 11B when boron content was about 7250 ng yielding positive bias with average recoveries of 115.5–119.8% (n = 5), while the determination results remained unaffected at the mass of 10B. Furthermore, the digestion efficiency of boron by laboratory high-pressure closed digestion method was assessed. The boron recoveries with samples treated by the high-pressure closed digestion method were found to vary within 49.5–98.0% (n = 5) and even lowered down to 31.1% when skipping pressure relief procedure. The long-term quantification stability study showed that the boron content generally declined in one month for the high-pressure closed digestion method and exhibited no significant changes for the proposed method. By applying such an improved boron–mannitol complex digestion method, the boron concentration in the studied silicate standard materials were accurately determined, providing critical data for further boron isotope analyses and associated geochemical studies. This in-depth method investigation for silicate boron determination demonstrates the feasibility of this boron–mannitol complex strategy under a wide digestion temperature of 65–140 °C, and also sheds light on the extensive applications of boron as a geological tracer.

This work presents the long-term determination accuracy study of ICP-QMS for rare earth elements (REEs) in geological matrices. Following high-pressure closed acidic decomposition, REEs are measured repetitively across seven months by ICP-QMS. Under optimum experimental conditions (including spray chamber temperature, gas flow rate, sampling depth, etc.), the REE contents in geological standard materials from basic (basalt BCR-2 and BE-N) to intermediate (andesite AGV-2) and up to acidic (granite GSR-1) show good agreement with the certified values, giving relative errors below 10%. Here, the influence of two storage materials (perfluoroalkoxy PFA and polypropylene PP) on the long-term determination accuracy of REEs has also been monitored. It is found that the relative errors of REEs using a PFA container range from &minus, 6.6 to 6.3% (RSDs &lt, 6.0%), while that using a PP container are within &minus, 4.0 to 3.9% (RSDs &lt, 4.6%). By using PP material as a solution storage container, the accuracy of REEs quantification in a series of real geological samples are checked, showing the RSDs of less than 5.0%. This work first clarifies the long-term stability of REEs quantification by ICP-QMS covering two types of storage materials, confirming the reasonability of PP material as a daily storage container in terms of higher data precision and lower cost.

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.

In this work, in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analysis with non-matrix-matched calibration is proposed for determining the composition of spodumene samples. Accuracy of the quantification in dependence on instrument operating conditions and the signal beat effect on quantification accuracy have been investigated in detail. Using NIST SRM 610 as reference material for external calibration, the mass fractions of major, minor and trace elements (Li, Si, Al, Na, Mg, Mn, Fe, Ga, and others) were determined using femtosecond-LA-ICPMS and compared with nanosecond-LA-ICPMS. Helium (He) was employed as the carrier gas in the ablation cell, and the aerosols produced under hole drilling ablation condition are then transported to a quadrupole ICPMS by a mixture of He and Ar as the make-up gas. Results show that the carrier gas flow rate had a substantial effect on both transient signal structure and LA-ICPMS quantification. With different He flow rates, both synchronized and non-synchronized acquisition with and without aliasing in the transient signals recorded were compared. Synchronized acquisition settings could attenuate the oscillations in the transient signals substantially but showed large variability (up to 18% RSD for Li2O) among individual acquisitions. Non-synchronized acquisition, with and without visible aliasing, on the other hand, was producing reproducible results without systematic biases when averaging ion signals from a sufficient number of scans (>100) for quantification. For the latter it was found that non-aliasing methods allowed for a direct identification of heterogeneities or inclusions in the transient signals and these were thus preferred for analysis. The accuracy of the analyses with non-matrix matched calibration was evaluated by comparing the matrix Al2O3/SiO2 mass fraction ratios with those obtained by electron probe microanalysis (EPMA). It was found that operation with only 0.2 L/min of He achieved the best agreement, while higher gas flow rates caused an increase in Al2O3/SiO2 and Li2O/SiO2 mass fraction ratios. This is considered to be a result of differences in ionization efficiency within the ICP caused by the higher abundance of easily ionized elements in the spodumenes compared to the calibration standard. By selecting appropriate acquisition settings for sequential MS detection and robust operating conditions, the repeatability of the analyses could be improved to values less than 1% for the Li2O mass fractions determined. When using the proposed settings for the analysis of 11 spodumene samples of different origin, the Al2O3/SiO2 mass fraction ratios agreed within −2% to +4% to those obtained by EPMA. These results confirm that spodumenes can be accurately analyzed in situ by LA-ICPMS without matrix-matched calibration standards. While matrix elements of the studied spodumenes were all in a comparable range, minor and trace elements showed substantial intra- and inter-sample variabilities.

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 of bovine serum albumin with doxycycline was investigated using chemiluminescence and molecular docking. Doxycycline at concentrations from 1.0 to 2.5 × 103 pmol · L−1 quenched the chemiluminescence from the luminol–bovine serum albumin system. The data were analyzed using a chemiluminescence mathematic model for protein–ligand interaction, log[(I0 – I)/I] = logK + nlog[D]. The binding constant of bovine serum albumin with doxycycline was 3.36 × 105 L · mol−1 at 298 K with one binding site. The binding constant, enthalpy change, entropy change, and binding free energy change showed that the bonding of doxycycline to bovine serum albumin was spontaneous and enthalpy driven via hydrogen bonding and van der Waals forces. Further molecular docking analysis substantiated that doxycycline was well positioned in the pocket at the subdomain IIA (site I) of bovine serum albumin with a binding constant of 3.31 × 105 L · mol−1. Doxycycline served as both a hydrogen acceptor and donor and main...

An ultrasensitive, quick, and simple approach for the determination of pg levels of diphacinone (DPN) by flow injection chemiluminescence (CL) analysis is proposed for the first time. It is based on the quenching effect of DPN on the CL intensity from a luminol–bovine serum albumin (BSA) CL system, for which the CL intensity decrease was linearly proportional to the logarithm of DPN concentration in the range of 5.0 to 5000 pg/mL. The LOD for DPN determination was as low as 2.0 pg/mL (3σ), and the RSD values were less than 5.0%. One determination cycle that included sampling and washing could be performed in 0.5 min with a sample throughput of 120/h under the optimum experimental conditions. This proposed method was successfully applied to determining DPN in human gastric juice and serum samples with recoveries from 91.8 to 114.3%, and to continuous monitoring of the degradation of DPN in water samples exposed to sunlight during 43 h with a variation ratio of 99.99%. The possible interaction behavior of BSA–DPN is briefly discussed.

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.

Human saliva quantitative monitoring of clarithromycin (CLA) by chemiluminescence (CL) with flow injection analysis was proposed for the first time, which was based on the quenching effect of CLA on luminol–bovine serum albumin (BSA) CL system with a linear range from 7.5 × 10−4 to 2.0 ng/ml. This proposed approach, offering a maximum sample throughput of 100 h−1, was successfully applied to the quantitative monitoring of CLA levels in human saliva during 24 h after a single oral dose of 250 mg intake, with recoveries of 95.2∼109.0 % and relative standard deviations lower than 6.5 % (N = 7). Results showed that CLA reached maximum concentration of 2.28 ± 0.02 μg/ml at approximately 3 h, and the total elimination ratio was 99.6 % in 24 h. The pharmacokinetic parameters including absorption rate constant (0.058 ± 0.006 h−1), elimination rate constant (0.149 ± 0.009 h−1) and elimination half-life time (4.66 ± 0.08 h) were obtained. A comparison of human saliva and urine monitoring was also given. The mechanism study of BSA–CLA interaction revealed the binding of CLA to BSA is an entropy driven and spontaneous process through hydrophobic interaction, with binding constant K BSA–CLA of 4.78 × 106 l/mol and the number of binding sites n of 0.82 by flow injection–chemiluminescence model. Molecular docking analysis further showed CLA might be in subdomain IIA of BSA, with K BSA–CLA of 6.82 × 105 l/mol and ΔG of −33.28 kJ/mol.

Human saliva quantitative monitoring of roxithromycin (ROX) at picomolar-level by flow injection (FI) chemiluminescence (CL) analysis is described for the first time, to our knowledge. Monitoring was based on the CL intensity from luminol-BSA reaction, which can be quenched in the presence of ROX, with the decreasing CL intensity linearly proportional to the logarithm of the ROX concentration, ranging from 0.6 to 1000 pmol·L-1. The detection limit of the proposed method for the determination of ROX was as low as 0.2 pmol·L-1 (3?), and the relative standard deviations were less than 4.0% (n = 7). A complete analytical process, including sampling and washing for ROX determination, conducted at a flow rate of 2.0 mL·min-1, was performed completely within 30 s, yielding a sample efficiency of 120 h-1. The proposed method was successfully applied to the determination of ROX in human saliva and serum samples with recoveries from 90.9% to 110.1%. The continuous monitoring of ROX in human saliva after oral intake showed that the total elimination ratio was 87.1% during 24 h, and the pharmacokinetic parameters were 0.97 ± 0.18 h-1 for the absorption rate constant Ka, 0.082 ± 0.010 h-1 for the elimination rate constant Ke, and 8.56 ± 1.11 h for the elimination half-life time t1/2. It was also found that ROX in human saliva and urine simultaneously reached the maximum at 2 h with the concentration correlate ratio of 0.97.

An ultrasensitive method for determining picomolar midecamycin (MID) by flow injection (FI) chemiluminescence (CL) was first described based on the inhibitory effect of MID on luminol–BSA reaction. It was found that the CL intensity decrements were linear with the logarithm of MID concentrations in the range of 1.0–5000 pmol · l–1with a detection limit as low as 0.3 pmol · l–1(3σ). The relative standard deviation of seven repetitive measurements for 10 pmol · l–1MID was 3.0%. At a flow rate of 2.0 ml · min–1, the whole analysis procedure including sampling and washing could be finished in 30 s, offering the sample efficiency of 120 h–1. This proposed method was successfully applied to determine MID in human serum samples with the recoveries from 96.0 to 110.0%. The CL mechanism of luminol–BSA–MID reaction was also given.

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.