Determination of phthalate esters from food-contacted materials by on-line microdialysis and liquid chromatography

Toxicity of Dibutyl phthalate (DBP) toward isolated human blood lymphocytes: Apoptosis initiated from intracellular calcium enhancement and mitochondrial/lysosomal cross talk

Dibutyl phthalate (DBP) is a phthalate ester with wide application in industrial products, so human exposure can happen in workplaces and environment. Conflicting results have been acquired in researches which measured the influences of phthalates contact on immune responses in laboratory animals. Nevertheless, the straight influence of DBP on human lymphocytes and entire mechanisms of its effect against these cells continue to be unexplored. The major purpose of present research was to evaluate the mechanisms which lead to the DBP toxicity on human lymphocytes using accelerated cytotoxicity mechanisms screening (ACMS) technique. Cell viability was determined following12h incubation of lymphocytes with 0.05-1 mM DBP, and mechanistic parameters were assessed after 2, 4 and 6 h of lymphocyte treatment with ½ the IC5012h (0.3 mM), the IC5012h (0.6 mM) and twice the IC5012h (1.2 mM) of DBP. The IC5012 h of a chemical/toxicant is defined as concentration that kills 50 % of cells after 12 h of exposure. The results indicate that DBP exerts toxic effects on isolated human lymphocytes, probably through mitochondrial and lysosomal damage induced by glutathione depletion and oxidative stress. In this study, suppression of cytokines (IL2, INF-gamma and TNF-alpha) production and increase in intracellular calcium were also related to DBP induced lymphocyte toxicity.

Dietary microplastics: Occurrence, exposure and health implications

The increasing use of plastic materials generates an enormous amount of waste. In the aquatic environment, a significant part of this waste is present in the form of microplastics (MPs)- particles with a diameter of between 0.1 μm and 5 mm. The arrival of these small plastics in the food chain has been recently documented. MPs have been reported in fishery products, drinking water and sea salt among other foods. Their intestinal absorption is considered limited due to their size, however, they contain a mixture of chemicals intentionally added during their manufacture, which could cross the intestinal barrier. Currently there are not enough data to allow an accurate assessment of the risk associated with dietary exposure to MPs. The lack of robust methodologies is undoubtedly one of the main problems. There is limited information on occurrence in dietary sources (drinking water and food), human intake, toxicokinetics and long term toxicity of these contaminants. The present review describes the studies published so far and points to the need for improved knowledge in order to have a more accurate view of the problems posed by MPs.

Magnetic dispersive solid phase extraction based on carbonized cellulose-ferromagnetic nanocomposite for screening phthalate esters in aqueous samples

In this work, a sorbent of the carbonized cellulose-ferromagnetic nanocomposite has been proposed for the magnetic dispersive solid phase extraction of some plasticizers in aqueous samples. Carbonized cellulose nanoparticles were prepared by treatment of cellulose filter paper with concentrated sulfuric acid and then loaded on Fe₃O₄ nanoparticles using coprecipitation. This sorbent is compatible with aqueous samples and can be considered as a viable sorbent for extraction of plasticizers from aqueous samples. In this study, magnetic dispersive solid phase extraction is followed by a dispersive liquid-liquid microextraction method. This combination makes the proposed approach as an efficient clean-up method with high enrichment factors for the selected analytes. The enriched analytes are monitored by gas chromatography equipped with a flame ionization detector. Parameters affecting the method efficiency were investigated in details. Under the optimized extraction conditions, limits of detection could reach up to of 0.15-0.50 µg L^-1. The satisfactory enrichment factors of 286-403 were obtained, and the extraction recoveries were found to be in the range of 57-80%. Relative standard deviations were in the range of 3-7% for intra-day and inter-day precisions for six replicate extractions at 25 µg L^-1 of each plasticizer. Calibration curves were linear in wide ranges with coefficients of determination ≥ 0.995. Eventually, efficiency of the prepared sorbent was confirmed by the extraction of some plasticizers from real samples including fruit juices, mineral water, injection solution, cola, and yoghourt drink packed in plastic containers.

Methods for the Determination of Endocrine-Disrupting Phthalate Esters

Phthalates are endocrine disruptors frequently occurring in the general and industrial environment and in many industrial products. Moreover, they are also suspected of being carcinogenic, teratogenic, and mutagenic, and they show diverse toxicity profiles depending on their structures. The European Union and the United States Environmental Protection Agency (US EPA) have included many phthalates in the list of priority substances with potential endocrine-disrupting action. They are: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), diethylhexyl phthalate (DEHP), di-iso-nonyl phthalate (DINP), di-iso-decyl phthalate (DIDP), di-n-decyl phthalate (DnDP), and dioctyl phthalate (DOP). There is an ever-increasing demand for new analytical methods suitable for monitoring different phthalates in various environmental, biological, and other matrices. Separation and spectrometric methods are most frequently used. However, modern electroanalytical methods can also play a useful role in this field because of their high sensitivity, reasonable selectivity, easy automation, and miniaturization, and especially low investment and running costs, which makes them suitable for large-scale monitoring. Therefore, this review outlines possibilities and limitations of various analytical methods for determination of endocrine-disruptor phthalate esters in various matrices, including somewhat neglected electroanalytical methods.

Are nails a valuable non-invasive alternative for estimating human exposure to phthalate esters?

Most human biomonitoring studies conducted in the past year for assessing the human exposure to phthalate esters (PEs) employed measurements of PE metabolites in urine. Although urine is recognized as a valuable non-invasive matrix, it has also limitations regarding the short time window for exposure. Therefore, in this pilot feasibility study we aimed to assess the human exposure to seven PE metabolites (including mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monoethyl phthalate (MEP) and mono-benzyl phthalate (MBzP)) using human nails. Paired nails and urine samples from the same individuals were used for comparison. Median levels of specific PE metabolites measured in nails and in spot urine of twenty Belgian individuals ranged from <LOQ_m to 146ng/g and from 0.2 to 6.7ng/mL (creatinine adjusted), respectively. The major PE metabolites found in nails were MEHP (average 146ng/g), sum (MnBP, MiBP) (average 212ng/g) and MEP (average 205ng/g). Significant correlations were achieved between different metabolites in nails and urine, i.e., MEHP levels in nails correlate well with sum (MnBP, MiBP) (r=0.73, p <0.01) and with MBzP (r=0.52, p <0.05) levels in urine. Moderate correlations were observed between 5-OH-MEHP and sum (MnBP, MiBP) (r=0.62, p <0.01) as well as with MEP (r=0.56, p <0.05) in both matrices. However, no significant correlation was observed for the same metabolite measured in both matrices. Based on participant questionnaires and after performing multivariate statistics, the relevant parameters of exposure positively associated with PE metabolites in nails were the use of hand care products, weight of the individuals and sport activity hours. Based on the detected levels and aforementioned predictors, nails seem a valuable non-invasive matrix for estimating human long-term exposure to DEP, DBnP and/or DIBP and DEHP.

Ant cuticular response to phthalate pollution

Phthalates are common atmospheric contaminants used in the plastic industry. Ants have been shown to constitute good bioindicators of phthalate pollution. Hence, phthalates remain trapped on ant cuticles which are mostly coated with long-chain hydrocarbons. In this study, we artificially contaminated Lasius niger ants with four phthalates: dibutyl phthalate (DBP), diisobutyl phthalate (DiBP), di(2-ethylhexyl) phthalate (DEHP), and benzyl butyl phthalate (BBP). The first three have previously been found on ants in nature in Touraine (France), while the fourth has not. The four phthalates disappeared rapidly (less than 5 days) from the cuticles of live ants. In contrast, on the cuticles of dead ants, DEHP quantities remained unchanged over time. These results indicate that phthalates are actively absorbed by the cuticles of live ants. Cuticular absorption of phthalates is nonspecific because eicosane, a nonnatural hydrocarbon on L. niger cuticle, was similarly absorbed. Ants are important ecological engineers and may serve as bioindicators of ecosystem health. We also suggest that ants and more generally terrestrial arthropods may contribute to the removal of phthalates from the local environment.

The immunotoxicity of dibutyl phthalate on the macrophages in mice

OBJECTIVE

Dibutyl phthalate (DBP), a widely used phthalate chemical, is commonly used as plasticizer. It is well known that DBP causes reproductive and developmental diseases, but the effect of DBP on the immune system remains to be determined. We assessed the effect of DBP on immune functions of murine macrophages, which constitute a key component in the immune response.

MATERIALS AND METHODS

Murine peritoneal exudate macrophages (PEMs) were treated with 0, 1, 5, 10, 50 or 100 μM DBP in vitro for 24 h and then the viability of PEMs were measured by flow cytometry (FCM) and trypan blue count. To investigate the effect of DBP on the functions of PEMs, we treated the PEMs with moderate dose of DBP (0, 1, 5 or 10 μM) in vitro for 24 h. The phenotypes, phagocytosis and cytokine production of PEMs were measured by FCM or real-time PCR. The immunogenicity and antigen presenting capacity of PEMs treated with DBP in vitro were assessed both by the mixed lymphocytereaction (MLR) in vitro assay and through the injection of exposed cells in mice by the delayed-type hypersensitivity (DTH) assay.

RESULTS

High dose of DBP (50-100 μM) showed cytotoxicity on PEMs, whereas after the treatment with moderate dose of DBP (1-10 μM) in vitro, PEMs expressed low level of CD36, CD80 and MHC-II molecules, and showed significantly decreased phagocytosis on apoptotic cells and Escherichia coli. In addition, DBP treatment exhibited a decrease in the cytokine production, immunogenicity and antigen-presenting capacity of PEMs.

CONCLUSIONS

The present study shows the effects of DBP on macrophages, demonstrating immunogenicity and decreased antigen presentation in vitro.

Determination of Phthalate Plasticisers in Palm Oil Using Online Solid Phase Extraction-Liquid Chromatography (SPE-LC)

Contamination of phthalates plasticisers to food has raised concern as some of the phthalates are suspected to be endocrine disruptors. The phthalates have high affinity with oily environment and analysing these chemicals in such matrices is difficult because of the trace amount of the analyte and interference from matrix. An online solid phase extraction (SPE) technique using a large volume (3.5 mL) injection was developed for the analysis of 6 common plasticisers in palm oil. A simple sample preparation involving alumina as a fat retainer and methanol : acetonitrile (1 : 1) as the extraction solvent was performed prior to the usage of online SPE-LC system. This system consists of two columns, C16for the solid phase extraction (SPE) and C18as the analytical column, and a photo diode array detector. The calibration curves were linear from 5 to 1000 μg L−1, with correlation coefficients above 0.99. The instrumental limit of detection was 3 μg L−1and satisfactory recovery was obtained. A screening on a few samples in the retail market revealed the presence of dibutyl phthalate (DBP) and butylbenzylphthalate (BBP) in the palm oil, with concentration less than 1 mg L−1.

Analysis of phthalate migration to food simulants in plastic containers during microwave operations

Phthalates used as plasticizers in the manufacture of household containers can potentially be transferred to foods that are stored or heated in these plastic containers. Phthalates are endocrine disruptor compounds (EDC) and are found in very low concentrations in foods, thus, highly sensitive analytical techniques are required for their quantification. This study describes the application of a new method developed for analyzing the migration of dibutylphthalate (DBP) and benzylbutylphthalate (BBP) from plastic food containers into liquid food simulants. This new method employs the technique of solid phase microextraction cooled with liquid nitrogen. The analysis was conducted by gas chromatography/mass spectrometry (GC/MS) using a polyacrylate fiber. Ultrapure water was used as a simulant for liquids foods, and both new and used plastic containers were placed in a domestic microwave oven for different periods of time at different power levels. The limits of detection for DBP and BBP were 0.08 µg/L and 0.31 µg/L, respectively. BBP was not found in the samples that were analyzed. DBP was found in concentrations ranging from <LOQ to 7.5 µg/L. In general, an increase in migration was observed in containers that were used for a prolonged time, which correlated with increasing heating time.

Effects of push/pull perfusion and ultrasonication on the extraction efficiencies of phthalate esters in sports drink samples using on-line hollow-fiber liquid-phase microextraction

In previous studies, we developed a process, on-line ultrasound-assisted push/pull perfusion hollow-fiber liquid-phase microextraction (UA-PPP-HF-LPME), combining the techniques of push/pull perfusion (PPP) and ultrasonication with hollow-fiber liquid-phase microextraction (HF-LPME), to achieve rapid extraction of acidic phenols from water samples. In this present study, we further evaluated three more-advanced and novel effects of PPP and ultrasonication on the extraction efficiencies of neutral high-molecular-weight phthalate esters (HPAEs) in sports drinks. First, we found that inner-fiber fluid leakage occurs only in push-only perfusion-based and pull-only perfusion-based HF-LPME, but not in the PPP mode. Second, we identified a significant negative interaction between ultrasonication and temperature. Third, we found that the extraction time of the newly proposed system could be shortened by more than 93%. From an investigation of the factors affecting UA-PPP-HF-LPME, we established optimal extraction conditions and achieved acceptable on-line enrichment factors of 92-146 for HPAEs with a sampling time of just 2 min.

Development of an enzyme-linked immunosorbent assay for dibutyl phthalate in liquor

A monoclonal antibody specifically recognizing dibutyl phthalate (DBP) was prepared based on a hapten (di-n-butyl-4-aminophthalate). After optimizing various parameters such as concentrations of antibody, coating antigen and composition of the assay buffer, an inhibition curve was plotted with the 50% inhibition concentration value (IC₅₀) 33.6 ± 2.5 ng/mL. A low level of cross-reactivity (<5%) was found for other phthalate esters. Recovery tests were conducted using liquor simulant (a mixture of water and ethanol) at two fortification levels (100 ng/mL and 300 ng/mL). The recovery rates ranged from 84.7% to 94.5% with a coefficient of variation between 7.1% and 12.8%. Nine liquor samples of different alcoholic strengths were detected using the proposed measure and confirmatory analysis was performed using liquid chromatography-mass spectroscopy (LC-MS). The detection results showed good consistency between the two measures and all the data above indicated that the proposed ELISA could be applied in DBP screening.

Approach to distribution and accumulation of dibutyl phthalate in rats by immunoassay

Dibutyl phthalate (DBP) is mainly taken up by the general population from food intake. To estimate intake of phthalates, determining distribution and accumulation of DBP in biological materials was a critical need. In this work, we set up two novel approaches with a monoclonal antibody specific to DBP to determine the distribution and accumulation of DBP in vivo. The contents of DBP in liver, kidney, stomach and testes were detected by immunofluorescence assays and indirect competitive ELISA. This data give directly evidence that indicates the distribution and accumulation of DBP in vivo. Double-label immunofluorescence assay provides with a visual approach to determination of the distribution and accumulation of DBP. It indicated that DBP accumulated in subcutaneous tissue such as sweat gland, hair follicle. Both of immunofluorescence assay and ELISA can be used to detect the content of DBP in biological materials. Our assays showed that DBP accumulated in viscera being rich in fat, such as liver, kidney and could overcome physiological barriers to penetrate testes. The date suggested that the accumulations of DBP exposed through dermal route were less than that of oral route and most of DBP was metabolized in 2 or 3 days.

Ant cuticles: a trap for atmospheric phthalate contaminants

Phthalates are universal contaminants. We show that they are trapped by the ant cuticles and maintained permanently at a low level, generally less than 1% of cuticular components. They are found throughout the interior of the insect, predominately in the fat body, which suggests that they are adsorbed by the cuticle. In open plastic boxes free of phthalates the ants became more contaminated with phthalates over a period of time, whereas in closed glass jars they did not. This finding suggests that the main source of pollutants is the atmosphere. Different ant species collected from multiple places showed similar levels of contamination. It appeared that in some pristine places the contamination was lower, but this needs to be confirmed. Ants can be considered as bio-indicators of phthalate pollution.

Development of one-step hollow fiber supported liquid phase sampling technique for occupational workplace air analysis using high performance liquid chromatography with ultra-violet detector

In this study, a simple and novel one-step hollow-fiber supported liquid-phase sampling (HF-LPS) technique was developed for enriched sampling of gaseous toxic species prior to chemical analysis for workplace air monitoring. A lab-made apparatus designed with a gaseous sample generator and a microdialysis sampling cavity (for HF-LPS) was utilized and evaluated to simulate gaseous contaminant air for occupational workplace analysis. Gaseous phenol was selected as the model toxic species. A polyethersulfone hollow fiber dialysis module filled with ethylene glycol in the shell-side was applied as the absorption solvent to collect phenol from a gas flow through the tube-side, based on the concentration distribution of phenol between the absorption solvent and the gas flow. After sampling, 20 μL of the extractant was analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-UV). Factors that influence the generation of gaseous standards and the HF-LPS were studied thoroughly. Results indicated that at 25 °C the phenol (2000 μg/mL) standard solution injected at 15-μL/min can be vaporized into sampling cavity under nitrogen flow at 780 mL/min, to generate gaseous phenol with concentration approximate to twice the permissible exposure limit. Sampling at 37.3 mL/min for 30 min can meet the requirement of the workplace air monitoring. The phenol in air ranged between 0.7 and 10 cm³/m³ (shows excellent linearity) with recovery between 98.1 and 104.1%. The proposed method was identified as a one-step sampling for workplace monitoring with advantages of convenience, rapidity, sensitivity, and usage of less-toxic solvent.

Determination of alkylphenols and phthalate esters in vegetables and migration studies from their packages by means of stir bar sorptive extraction coupled to gas chromatography-mass spectrometry

This paper describes a method for the determination of three alkylphenols (APs), 4-tert-octylphenol (tOP), 4-n-octylphenol (OP) and 4-nonylphenol (NP), and six phthalate esters (PEs), dimethylphthalate (DMP), diethylphthalate (DEP), di-n-butylphthalate (DBP), n-butylbenzylphthalate (BBP), di-2-ethylhexylphthalate (DEHP) and di-n-octylphthalate (DOP), in vegetables using stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Ultrasonic radiation was used to extract the analytes from the solid food matrix, and the extract obtained was preconcentrated by SBSE. The different parameters affecting both stages were carefully optimized. The method was applied to analyze commercial vegetables, in the form of plastic packed salads and canned greens, as well as the corresponding filling liquids of the canned food. Quantification of the samples was carried out against aqueous standards using an internal standard (anthracene). The analysis of a 2 g vegetable sample provided detection limits between 12.7 and 105.8 pg g⁻¹ for OP and DEHP, respectively. Migration studies from the plastic packages of the vegetables samples analyzed were carried out. DEP, DBP and DEHP were found to have migrated from the bags to the simulant and the same compounds were quantified in lettuce, corn salad, arugula, parsley and chard, at concentration levels in the 8-51 ng g⁻¹ range. However, OP and NP were found in only two vegetable samples and one filling liquid, but neither was detected in any package. The proposed method provided recoveries of 83-118%.

An immunoassay for dibutyl phthalate based on direct hapten linkage to the polystyrene surface of microtiter plates

BACKGROUND

Dibutyl phthalate (DBP) is predominantly used as a plasticizer inplastics to make them flexible. Extensive use of phthalates in both industrial processes and other consumer products has resulted in the ubiquitous presence of phthalates in the environment. In order to better determine the level of pollution in the environment and evaluate the potential adverse effects of exposure to DBP, immunoassay for DBP was developed.

METHODOLOGY/PRINCIPAL FINDINGS

A monoclonal antibody specific to DBP was produced from a stable hybridoma cell line generated by lymphocyte hybridoma technique. An indirect competitive enzyme-linked immunosorbent assay (icELISA) employing direct coating of hapten on polystyrene microtiter plates was established for the detection of DBP. Polystyrene surface was first oxidized by permanganate in dilute sulfuric acid to generate carboxyl groups. Then dibutyl 4-aminophthalate, which is an analogue of DBP, was covalently linked to the carboxyl groups of polystyrene surface with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Compared with conjugate coated format (IC(50)=106 ng/mL), the direct hapten coated format (IC(50)=14.6 ng/mL) improved assay sensitivity after careful optimization of assay conditions. The average recovery of DBP from spiked water sample was 104.4% and the average coefficient of variation was 9.95%. Good agreement of the results obtained by the hapten coated icELISA and gas chromatography-mass spectrometry further confirmed the reliability and accuracy of the icELISA for the detection of DBP in certain plastic and cosmetic samples.

CONCLUSIONS/SIGNIFICANCE

The stable and efficient hybridoma cell line obtained is an unlimited source of sensitive and specific antibody to DBP. The hapten coated format is proposed as generally applicable because the carboxyl groups on modified microtiter plate surface enables stable immobilization of aminated or hydroxylated hapten with EDC. The developed hapten coated icELISA can be used as a convenient quantitative tool for the sensitive and accurate monitoring DBP in water, plastic and cosmetic samples.

Mitochondrial permeability and toxicity of diethylhexyl and monoethylhexyl phthalates on TK6 human lymphoblasts cells

Phthalates are ubiquitous compounds used in the manufacturing industry. Some are known endocrine disruptors, acting as xenoestrogens, others induce reproductive toxicity and damage to DNA among other effects. Studies on apoptosis induction and mitochondrial damage capacity of phthalates on the immune system are limited. This study aims to determine cell viability inhibition and apoptosis induction of diethylhexyl phthalate (DEHP) and monoethylhexyl phthalate (MEHP) on the human TK6 lymphoblast cell line at concentrations found in the environment. Key hallmark events, such as mitochondrial membrane permeability, generation of reactive oxygen species (ROS) and activation of caspase 3 and 7 were measured. Concentrations that inhibit viability of 50% (IC50) of the cells were determined at 24, 48 and 72 h with doses ranging from 10 to 500 μM. Changes in mitochondrial membrane permeability, ROS generation and activation of caspases 3 and 7, were measured as part of the cell death mechanism. The IC50 at 24 h was approximately 250 μM for both phthalates; at 48 h were 234 and 196 μM for DEHP and MEHP, respectively and at 72 h IC50s were 100 and 80 μM for DEHP and MEHP, respectively. Overall the longer the time of exposure the lower the IC50's for both compounds. Both compounds affected mitochondrial membrane potential, promoted ROS generation and activated caspases 3 and 7. MEHP is more toxic, promotes higher level of ROS production and caspases activation. Our findings suggest that DEHP and MEHP have the capacity to induce apoptosis in cells of the immune system at concentrations found in the environment.

Determination of alachlor and its metabolite 2,6-diethylaniline in microbial culture medium using online microdialysis enriched-sampling coupled to high-performance liquid chromatography

In this study, a simple and novel microdialysis sampling technique incorporating hollow fiber liquid phase microextraction (HF-LPME) coupled online to high-performance liquid chromatography (HPLC) for the one-step sample pretreatment and direct determination of alachlor (2-chloro-2',6'-diethyl-N -(methoxymethyl)acetanilide) and its metabolite 2,6-diethylaniline (2,6-DEA) in microbial culture medium has been developed. A reversed-phase C-18 column was utilized to separate alachlor and 2,6-DEA from other species using an acetonitrile/water mixture (1:1) containing 0.1 M phosphate buffer solution at pH 7.0 as the mobile phase. Detection was carried out with a UV detector operated at 210 nm. Parameters that influenced the enrichment efficiency of online HF-LPME sampling, including the length of the hollow fiber, the perfusion solvent and its flow rate, the pH, and the salt added in sample solution, as well as chromatographic conditions were thoroughly optimized. Under optimal conditions, excellent enrichment efficiency was achieved by the microdialysis of a sample solution (pH 7.0) using hexane as perfusate at the flow rate of 4 μL/min. Detection limits were 72 and 14 ng/mL for alachlor and 2,6-DEA, respectively. The enrichment factors were 403 and 386 (RSD < 5%) for alachlor and 2,6-DEA, respectively, when extraction was performed by using a 40 cm regenerated cellulose hollow fiber and hexane as perfusion solvent at the flow rate of 0.1 μL/min. The proposed method provides a sensitive, flexible, fast, and eco-friendly procedure to enrich and determine alachlor and its metabolite (2,6-DEA) in microbial culture medium.

A comparative cytotoxicity study of isomeric alkylphthalates to metabolically variant bacteria

This work investigated the toxicity of two isomeric alkylphthalates, i.e., di-n-octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) to two model bacteria, Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), which have been previously used to study the toxicity of environmental pollutants. Microcalorimetry was used as the key analytical tool alongside scanning electron microscopy (SEM) and traditional microbiology techniques. The thermokinetic parameters from microcalorimetry showed that the phthalates had a biphasic effect on the metabolic activities of the bacteria; serving as energy sources for the bacteria thereby stimulating their growth at low dosages (< or = 150 microg/mL), but displaying inhibitory effects at higher dosages (> or = 300 microg/mL), indicated by a sharp decrease in growth rate constants at 450 microg/mL. The SEM revealed that the bacterial cells were morphological deformed, with shrunk cells and elongated strands at 600 microg/mL of both phthalates. The elongated strands inferred that the phthalates inhibited the reproductive processes of the bacteria by possibly impeding some stages of cell division. The half inhibitory concentrations of the phthalates showed that DEHP was more toxic than DOP. Additionally, E. coli, a facultative anaerobe, was more susceptible to the toxic effects of phthalates than B. subtilis, an obligate aerobe capable of forming endospores crucial for tolerating extreme environmental conditions.

Structural characterisation of degradation products formed upon di-n-butyl phthalate radiolysis by high-performance liquid chromatography electrospray tandem mass spectrometry

Structural characterisation of 15 degradation products, formed upon di-n-butyl phthalate (DBP) radiolysis, has been achieved using a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) coupling. The dissociation behaviour of protonated DBP was first established to be further used to characterise structural deviation in the degradation products. Based on accurate mass measurements, compounds shown by HPLC-MS analysis were all found to be DBP oxidation products, amongst which various sets of isomers could be distinguished. Collision-induced dissociation experiments performed on each electrosprayed molecule first allowed unambiguous definition of the location of the additional oxygen atoms; that is, in the alkyl branch or on the aromatic ring. Although location of the oxygen atom in the alkyl branches could not always be precisely determined, relative abundances of some product ions allowed oxygenated functions to be identified.