Life cycle exposure to titanium dioxide nanoparticles (TiO2-NPs) induces filial toxicity and population decline in the nematode Caenorhabditis elegans.

Titanium dioxide nanoparticle (TiO2-NP) exposure has raised significant concern due to their potential toxicity and adverse ecological impacts. Despite their ubiquitous presence in various environmental compartments, the long-term consequences of TiO2-NPs remain poorly understood. In this study, we combined data of in vivo toxicity and modeling to investigate the potential negative impacts of TiO2-NP exposure. We employed the nematode Caenorhabditis elegans, an environmental organism, to conduct a full life cycle TiO2-NP toxicity assays. Moreover, to assess the potential impact of TiO2-NP toxicity on population dynamics, we applied a stage-constructed matrix population model (MPM). Results showed that TiO2-NPs caused significant reductions in reproduction, survival, and growth of parental C. elegans (P0) at the examined concentrations. Moreover, these toxic effects were even more pronounced in the subsequent generation (F1) when exposed to TiO2-NPs. Furthermore, parental TiO2-NP exposure resulted in significant toxicity in non-exposed C. elegans progeny (TiO2-NPs free), adversely affecting their reproduction, survival, and growth. MPM analysis revealed decreased transition probabilities of surviving (Pi), growth (Gi), and fertility (Fi) in scenarios with TiO2-NP exposure. Additionally, the population growth rate (λmax) was found to be less than 1 in both P0 and F1, indicating a declining population trend after successive generations. Sensitivity analysis pinpointed L1 larvae as the most vulnerable stage, significantly contributing to the observed population decline in both P0 and F1 generations under TiO2-NP exposure. Our findings provide insight into the potential risk of an environmental organism like nematode by life cycle exposure to TiO2-NPs.

Nonpolar Side Chains Affect the Photochemical Redox Reactions of Copper(II)-Amino Acid Complexes in Aqueous Solutions.

Photochemical redox reactions of Cu(II) complexes of eight amino acid ligands (L) with nonpolar side chains have been systematically investigated in deaerated aqueous solutions. Under irradiation at 313 nm, the intramolecular carboxylate-to-Cu(II) charge transfer within Cu(II)-amino acid complexes leads to Cu(I) formation and the concomitant decomposition of amino acids. All amino acid systems studied here can produce ammonia and aldehydes except proline. For the 1:1 Cu(II) complex species (CuL), the Cu(I) quantum yields at 313 nm (ΦCu(I),CuL) vary by fivefold and in the sequence (0.10 M ionic strength at 25 °C) alanine (0.094) > valine (0.059), leucine (0.059), isoleucine (0.056), phenylalanine (0.057) > glycine (0.052) > methionine (0.032) > proline (0.019). This trend can be rationalized by considering the stability of the carbon-centered radicals and the efficient depopulation of the photoexcited state, both of which are dependent on the side-chain structure. For the 1:2 Cu(II) complex species (CuL2), the Cu(I) quantum yields exhibit a similar trend and are always less than those for CuL. The photoformation rates of ammonia, Cu(I), and aldehydes are in the ratio of 1:2.0 ± 0.2:0.7 ± 0.2, which supports the proposed mechanism. This study suggests that the direct phototransformation of Cu(II)-amino acid complexes may contribute to the bioavailable nitrogen for aquatic microorganisms and cause biological damage on cell surfaces in sunlit waters.

Markedly Enhanced Surface Hydroxyl Groups of TiO2 Nanoparticles with Superior Water-Dispersibility for Photocatalysis.

The benefits of increasing the number of surface hydroxyls on TiO2 nanoparticles (NPs) are known for environmental and energy applications; however, the roles of the hydroxyl groups have not been characterized and distinguished. Herein, TiO2 NPs with abundant surface hydroxyl groups were prepared using commercial titanium dioxide (ST-01) powder pretreated with alkaline hydrogen peroxide. Through this simple treatment, the pure anatase phase was retained with an average crystallite size of 5 nm and the surface hydroxyl group density was enhanced to 12.0 OH/nm², estimated by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Especially, this treatment increased the amounts of terminal hydroxyls five- to six-fold, which could raise the isoelectric point and the positive charges on the TiO2 surface in water. The photocatalytic efficiency of the obtained TiO2 NPs was investigated by the photodegradation of sulforhodamine B under visible light irradiation as a function of TiO2 content, pH of solution, and initial dye concentration. The high surface hydroxyl group density of TiO2 NPs can not only enhance water-dispersibility but also promote dye sensitization by generating more hydroxyl radicals.

Vortex-assisted liquid-liquid microextraction of strontium from water samples using 4',4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 and tetraphenylborate.

A vortex-assisted liquid-liquid microextraction method was developed for the chromatographic determination of strontium in aqueous samples. In the method, strontium was complexed with 4',4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 in the presence of tetraphenylborate as the counter anion, which increased the hydrophobicity of the ion-association complex, resulting in its improved extraction into 1-octanol. Strontium from the organic phase was stripped with nitric acid back to aqueous solution and determined by ion chromatography. The optimum microextraction conditions were as follows: 2.0 mL aqueous samples with 3 mM tetraphenylborate; 150 µL of 1-octanol as the extractant phase with 10 mM DtBuCH18C6; vortex extraction time for 10 s; centrifugation at 6000 rpm for 4 min; stripping by 0.1 M nitric acid. Under the optimum conditions, the detection limit for strontium was 0.005 mg/L. The calibration curves showed good linearity over the range between 0.01 and 2.5 mg/L. Intra- and interday precisions of the present method were satisfactory with relative standard deviations of 1.7 and 2.1%, respectively.

Influence of silver and titanium dioxide nanoparticles on in vitro blood-brain barrier permeability.

An in vitro blood-brain barrier (BBB) model being composed of co-culture with endothelial (bEnd.3) and astrocyte-like (ALT) cells was established to evaluate the toxicity and permeability of Ag nanoparticles (AgNPs; 8nm) and TiO2 nanoparticles (TiO2NPs; 6nm and 35nm) in normal and inflammatory central nervous system. Lipopolysaccharide (LPS) was pre-treated to simulate the inflammatory responses. Both AgNPs and Ag ions can decrease transendothelial electrical resistance (TEER) value, and cause discontinuous tight junction proteins (claudin-5 and zonula occludens-1) of BBB. However, only the Ag ions induced inflammatory cytokines to release, and had less cell-to-cell permeability than AgNPs, which indicated that the toxicity of AgNPs was distinct from Ag ions. LPS itself disrupted BBB, while co-treatment with AgNPs and LPS dramatically enhanced the disruption and permeability coefficient. On the other hand, TiO2NPs exposure increased BBB penetration by size, and disrupted tight junction proteins without size dependence, and many of TiO2NPs accumulated in the endothelial cells were observed. This study provided the new insight of toxic potency of AgNPs and TiO2NPs in BBB.

Sensitivity enhancement in the fluorometric determination of aliphatic amines using naphthalene-2,3-dicarboxaldehyde derivatization followed by vortex-assisted liquid-liquid microextraction.

A highly sensitive liquid chromatographic method was developed for the fluorometric determination of trace amounts of linear aliphatic primary amines. Prior to extraction, amines were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide ion (CN) and extracted by vortex-assisted liquid-liquid microextraction (VALLME). The optimum conditions were as follows: derivatization reaction time for 5 min in 2.0 mL aqueous donor samples with 50 µM NDA/CN, and 10mM borate buffer at pH 9; vortex extraction time for 20s in the VALLME step with 50 µL of isooctane as the extractant phase; centrifugation for 1 min at 6000 rpm. Under the optimum conditions, the limits of detection (LOD) were between 0.01 and 0.04 nmol L(-1). The calibration curves showed good linearity in the range of 0.1-20 nmol L(-1). In comparison with previous work using o-phthalaldehyde/2-mercaptoethanol derivatization, the method has much more stable fluorescent derivatives, higher fluorescence intensities, and greater extraction efficiencies. The sensitivity enhancement factors (SEF) were between 2 and 70, which is in good agreement with the theoretical values calculated from partition coefficients in VALLME system.

Photochemical redox reactions of copper(II)-alanine complexes in aqueous solutions.

The photochemical redox reactions of Cu(II)/alanine complexes have been studied in deaerated solutions over an extensive range of pH, Cu(II) concentration, and alanine concentration. Under irradiation, the ligand-to-metal charge transfer results in the reduction of Cu(II) to Cu(I) and the concomitant oxidation of alanine, which produces ammonia and acetaldehyde. Molar absorptivities and quantum yields of photoproducts for Cu(II)/alanine complexes at 313 nm are characterized mainly with the equilibrium Cu(II) speciation where the presence of simultaneously existing Cu(II) species is taken into account. By applying regression analysis, individual Cu(I) quantum yields are determined to be 0.094 ± 0.014 for the 1:1 complex (CuL) and 0.064 ± 0.012 for the 1:2 complex (CuL2). Individual quantum yields of ammonia are 0.055 ± 0.007 for CuL and 0.036 ± 0.005 for CuL2. Individual quantum yields of acetaldehyde are 0.030 ± 0.007 for CuL and 0.024 ± 0.007 for CuL2. CuL always has larger quantum yields than CuL2, which can be attributed to the Cu(II) stabilizing effect of the second ligand. For both CuL and CuL2, the individual quantum yields of Cu(I), ammonia, and acetaldehyde are in the ratio of 1.8:1:0.7. A reaction mechanism for the formation of the observed photoproducts is proposed.

Vortex-assisted liquid-liquid microextraction coupled with derivatization for the fluorometric determination of aliphatic amines.

A new one-step derivatization and microextraction technique was developed for the fluorometric determination of C(1)-C(8) linear aliphatic primary amines in complex sample solutions containing high levels of amino acids. In this method, amines were derivatized with o-phthalaldehyde (OPA) and 2-mercaptoethanol (2-ME) in aqueous solution and extracted simultaneously by vortex-assisted liquid-liquid microextraction (VALLME). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: 50 µL of isooctane as the extractant phase; 2.0 mL aqueous donor samples with 12 mM OPA, 24 mM 2-ME, and 0.1 M borate buffer at pH 10; 1 min vortex extraction time; centrifugation for 4 min at 6000 rpm. After centrifugation, the enriched analytes in the floated extractant phase were determined by HPLC-FL in less than 14 min. Under the optimum conditions, the limits of detection were of the order of 0.09-0.31 nM. The calibration curves showed good linearity over the investigated concentration range between 0.4 and 40 nM. The proposed method has been applied to the determination of aliphatic amines in acidophilus milk, beer, and Cu(II)/amino acid solution.

Determination of linear aliphatic aldehydes in heavy metal containing waters by high-performance liquid chromatography using 2,4-dinitrophenylhydrazine derivatization.

A simple and sensitive method is described for the determination of picomolar amounts of C(1)-C(9) linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7-28 nM. The detection limit can be further lowered by using off-line C(18) adsorption cartridge enrichment. The recoveries of C(1)-C(9) aldehydes were 93-115% with a relative standard deviation of 3.6-8.1% at the 0.1 microM level for aldehydes. The HPLC-DNPH method has been applied for determining aldehyde photoproducts from Cu(II)-amino acid complex systems.

Purge-and-trap ion chromatography for the determination of trace ammonium ion in high-salinity water samples.

It has always been assumed that purge-and-trap (P&T) method is only used for the analysis of volatile organic compounds (VOCs) in aqueous samples. In this paper, a novel P&T preconcentrator has been developed for the determination of trace amounts of ammonium ion in high-salinity water samples by ion chromatography (IC). Method performance is evaluated as a function of concentration of assistant purging material, purging time, and flow rate. Under the optimum P&T conditions with the purified nitrogen gas at flow rate 40 mL/min for 15.0 min at 40 degrees C, the overall collection efficiency is independent of the concentration of ammonium over the range 1.2-5.9 microM. The enrichment factor (EF) of ammonium correlates the ratio of the sample volume to the acceptor solution volume in the trap vessel, providing potentially unlimited increase of the ammonium signal. Our results indicate that environmental samples with low levels of ammonium in matrices with high concentrations of sodium can be easily analyzed and the detection limit down to 75 nM (1.35 ppb) level, corresponding to picomole of ammonia in the injected sample. Calibration graph was constructed with ammonium standards ranging from 0.05 to 6.0 microM and the linearity of the present method was good as suggested by the square of correlation coefficients being better than 0.997. Thus, we have demonstrated that the P&T-IC method allows the routine determination of ammonium ion in seawater samples without cation interferences.

Removal of benzene and toluene by carbonized bamboo materials modified with TiO2.

Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance its removal efficiency of harmful gases. Carbonized bamboo-TiO(2) composite (CBC) was prepared by heating mixtures of carbonized bamboo powder (CB) and TiO(2) nanoparticles, denoted as CBM, under nitrogen condition. TiO(2) nanoparticle and carbonized bamboo powder were mixed with the mass ratios of 1/1 and 2/1, respectively. At the same mass ratio of TiO(2) to CB, the benzene and toluene removal efficiencies follow the trend: CBC>CBM>CB, which is consistent with the amount of TiO(2) validated by elemental analysis. Sorption mechanism of benzene and toluene by CB, CBM and CBC might belong to hydrophobic-hydrophobic interaction, observed by depletion of untreated bamboo (UB) carbohydrates during carbonization. Sorption kinetics was further analyzed, and optimal correlation was found by fitting with the Elovich kinetic equation.

Entrapment of horseradish peroxidase in sugar-modified silica monoliths: toward the development of a biocatalytic sensor.

A miniaturized HRP-entrapped bioreactor was prepared by a one-step enzyme immobilization method using a biocompatible sol-gel processing method employing either diglycerylsilane (DGS) or sodium silicate (SS) as precursors and a covalently tethered sugar, N-(3-triethoxysilylpropyl)gluconamide (GLS) as a silica modifier. Factors such as leaching, catalytic efficiency and long-term stability were examined to assess the role of the precursor and modifier in influencing enzyme performance. The results showed that sodium silicate derived materials modified with covalently bound sugars at a level of 10 mol% were optically transparent and provided the highest catalytic turnover rate for entrapped HRP. The stability and reusability of the entrapped HRP was found to be satisfactory for at least 1 month in the GLS-doped SS materials, and the entrapped HRP was able to respond linearly to the presence of peroxide over the concentration range of 0-750 microM with a detection limit of 6 microM, demonstrating the potential of this material for the development of a reusable optical biosensor.

Open tubular capillary electrochromatography using capillaries coated with films of alkanethiol-self-assembled gold nanoparticle layers.

We have used alkanethiol self-assembly and dithiol layer-by-layer (LBL) self-assembly processes to prepare an Au nanoparticle (NP)-coated open tubular capillary electrochromatography (OTCEC) column for the separation of three neutral steroid drugs (testosterone, progesterone, and testosterone propionate). The CEC column was fabricated through LBL self-assembly of Au NPs on a 3-aminopropyltrimethoxysilane (APTMS)-modified fused-silica capillary and subsequent surface functionalization of the Au NPs through self-assembly of alkanethiols. We investigated the electrochromatographic properties of the resulting Au NP-coated CEC column using a "reversed phase" test mixture of three steroid drugs. We found that the key factors affecting the separation performance were the number of Au NP layers, the length of the carbon-atom chain of the alkanethiol self-assembled on the Au NPs, the percentage of organic modifier, and the pH of the running electrolyte. This study reveals that the self-assembly of alkanethiols and dithiols onto Au NPs provides stationary phases for CEC separation that are easy to prepare and whose retention behavior is highly controllable and reproducible. We believe that our findings will contribute to further studies of the application of nanotechnology to separation science.

Fluorometric determination of ammonium ion by ion chromatography using postcolumn derivatization with o-phthaldialdehyde.

A postcolumn fluorometric derivatization method for the determination of trace amounts of ammonium ion (microg/L level) under matrices with high concentrations of sodium and amino acids has been developed. In this method, ammonium ion was determined by ion chromatography combined with fluorometric detection (IC-FL) in less than 16 min. IC was performed in a high-capacity cation-exchange Dionex IonPac CS16 analytical column (250 mm x 5 mm) under isocratic conditions with 30 mM methanesulfonic acid (MSA) as mobile phase at flow-rate 1.0 mL/min. To remove amino acid interference, the postcolumn derivatization based on the reaction of ammonia with o-phthaldialdehyde (OPA) and sulfite was applied. The excitation and emission wavelengths were 364 and 425 nm, respectively. The effects of pH, reaction temperature and time, OPA-reagent composition and concentration, and sample matrix were studied. The linear range and detection limit of this method were similar to the standard method. The IC-FL method with a postcolumn fluorometric derivatization allows the routine determination of ammonium ion in extreme matrices where the ratios of sodium and amino acids to ammonium are up to 2,800,000:1 and 28,000:1, respectively.

Studying the size/shape separation and optical properties of silver nanoparticles by capillary electrophoresis.

This paper describes the feasibility of employing capillary electrophoresis (CE) to separate silver particles in nanometer regimes. We have found that the addition of an anionic surfactant, sodium dodecyl sulphate (SDS), to the running electrolyte prevents coalescence of the silver particles during the process, which improves the separation performance; the concentration of SDS required for optimal silver nanoparticle separation is ca. 20 mM. By monitoring the electropherograms using a diode-array detection (DAD) system, we have also investigated the separation of suspended silver nanorods with respect to their shapes. Our results demonstrate that the combination of CE and DAD is a powerful one for the separation and characterization of various silver nanoparticles.

Degradation of MTBE in dilute aqueous solution by gamma radiolysis.

The radiolytic degradation of methyl tert-butyl ether (MTBE) in air-equilibrated dilute solution was investigated. Complete degradation of MTBE can be achieved within 5 min of irradiation at 59.7 Gy/min. The observed first-order degradation rate constant, called dose constant, increased from 0.04 to 0.56 Gy(-1) as the concentration of MTBE decreased from 92500 to 19 microg/L. Tert-butyl formate, tert-butyl alcohol, acetone and methyl acetate were found to be the primary intermediates of the degradation reaction with yields of 47%, 11%, 6.4% and 9.1%, respectively. The degradation of MTBE or its intermediates was also found to depend on the concentrations of benzene and cupric ion. The study shows that the removal of MTBE can be significantly decreased with increasing concentration of benzene. Little affects were observed with the presence of cupric ions, while the degradation of TBF was apparently reduced. These results indicate that gamma radiolysis can be a potentially effective treatment for the removal of MTBE in contaminated water systems.

Determination of volatile organic compounds in workplace air by multisorbent adsorption/thermal desorption-GC/MS.

Investigation of volatile organic compounds (VOCs) was first conducted in the air of class-100 cleanrooms at liquid crystal display (LCD) fabrication facilities. Air samples were collected on multisorbent tubes (including Carbopack B, Carbopack C, and Carbosieve S-III) and analyzed using adsorption/thermal desorption coupled with gas chromatography-mass spectrometry (GC-MS). Optimal conditions lead to average recoveries in the range of 96.2-98.2%, and method detection limits between 0.38 and 0.78 ppb, under the condition of 1-l sampling volume and 80% relative humidity. The method appears to be accurate, sensitive, simple and well-suited for determining VOC distributions from various stages of LCD manufacturing process and temporal variations of the analyte concentrations. About 15 VOCs were identified in workplace air. The major pollutants such as propylene glycol methyl ether acetate (PGMEA), butyl acetate, and acetone that are commonly used in the opto-electronics industry were detected and accurately quantified with the established method.

Capillary electrophoretic analysis of the derivatives and isomers of benzoate and phthalate.

A capillary electrophoretic method for the analysis of 12 commonly found derivatives and isomers of benzoate and phthalate, including p-toluic acid, p-acetamido and p-hydroxy derivatives of benzoic acid, salicylic acid and its acetyl ester, 2- and 4-isomers of carboxybenzaldehyde, meta-, para-, and ortho-isomers of phthalic acid, and monomethyl terephthalic acid was developed. Capillary electrophoresis (CE) was performed in the free zone electrophoresis mode. Performing CE in 10 mM phosphate buffer, pH 7.0 could separate most of the benzoic acid derivatives except the structural or positional isomers. The positional isomers of phthalic acids could be completely separated with co-addition of alpha- and beta-cyclodextrins. Addition of poly(ethylene glycol) 600 (4%) could further resolve some structural isomers. The CE method developed here is rapid, i.e. complete separation could be achieved in less than 8 min for the nine monoanionic benzoate derivatives and in less than 14 min for the three dianionic phthalate isomers. The new method has good precision and linearity and can be readily applied to real samples for quantitative analysis. It is sensitive and can detect sub-ppm (w/w) level of impurity in real terephthalic samples.

Measurement of toxic volatile organic compounds in indoor air of semiconductor foundries using multisorbent adsorption/thermal desorption coupled with gas chromatography-mass spectrometry.

A method for the qualitative and quantitative analysis of volatile organic compounds (VOCs) in the air of class-100 clean rooms at semiconductor fabrication facilities was developed. Air samples from two semiconductor factories were collected each hour on multisorbent tubes (including Carbopack B, Carbopack C, and Carbosieve SIII) with a 24-h automatic active sampling system and analyzed using adsorption/thermal desorption coupled with gas chromatography-mass spectrometry. Experimental parameters, including thermal desorption temperature, desorption time, and cryofocusing temperature, were optimized. The average recoveries and the method detection limits for the target compounds were in the range 94-101% and 0.31-0.89 ppb, respectively, under the conditions of a 1 L sampling volume and 80% relative humidity. VOCs such as acetone, isopropyl alcohol, 2-heptanone, and toluene, which are commonly used in the semiconductor and electronics industries, were detected and accurately quantified with the established method. Temporal variations of the analyte concentrations observed were attributed to the improper use of organic solvents during operation.

Analysis of alkyl organoiodide mixtures by high-performance liquid chromatography using electrochemical detection with a post-column photochemical reactor.

A method for the analysis of six alkyl organoiodides (iodomethane, iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane) commonly found in acetic acid process was developed. In this method the target analytes were determined by high-performance liquid chromatography (HPLC) using a post-column photochemical reactor with electrochemical detection (ED) in less than 30 min. HPLC was performed in ODS C18 reversed-phase column (5 microm, 250 x 4.6 mm I.D.) under isocratic conditions with methanol-0.067 M acetate buffer (70:30, v/v), pH 6.2 as mobile phase at flow-rate 1.1 ml/min. Alkyl organoiodides, which are electrochemically inactive, were made oxidizable at potential of 120 mV after post-column irradiation with low-pressure mercury lamp in a knitted PTFE tube. The photoreactor was placedin an aluminum housing full of nitrogen in order to prevent from the interference of oxygen. The detection limit for most analytes was of the order of 1-2 microg/l. The HPLC-ED method with a post-column photochemical reactor has good precision and linearity and can be readily applied to the routine determination of alkyl organoiodides in real acetic acid samples.