Toxicity of Ocimum americanum L. extracts against Aedes aegypti larvae (Diptera: Culicidae) and their impact on insecticide resistance.

Mosquitoes are a key threat to millions of people worldwide. They spread the pathogens that cause deadly diseases among humans and animals. Synthetic pesticides are the best agents to control mosquitoes, but they cause several problems for the environment as well as public health. Continuous usage of commonly available insecticides develops multiple resistances among pests. In search of alternatives to synthetic pesticides, botanicals could be one of the best alternatives to control mosquitoes. The present study explores the insecticidal activity of Ocimum americanum against Aedes aegypti larvae and their effect on detoxification enzymes. Leaves of O. americanum were sequentially extracted using hexane, chloroform, and methanol. Among these, hexane extract showed 100% larvicidal activity at 1 g/L concentration for 24 h and the LC50 value was 0.3 g/L. The phytochemical screening of hexane extract was performed through gas chromatography-mass spectrometry analysis, which showed 27 compounds. The major compounds are squalene (13.03%), camphor (9.77%), and 1-Iodohexadecane (8.02%). The toxicity of active hexane extract was tested against third instar larvae of Chironomus costatus (nontarget organism). Results revealed less toxicity (12.2%) at 1 g/L concentration on the nontarget organism. The enzyme activity of acetylcholinesterase and ß-carboxylesterase was significantly inhibited by the hexane extract. The present study reveals the insecticidal potential of O. americanum with minimum effects on nontarget organisms. The O. americanum extract inhibited the activity of A. aegypti's major insecticide-resistant enzymes. O. americanum could be one of the best alternatives to controlling mosquitoes.

LC-MS/MS and GC-MS profiling, antioxidant, enzyme inhibition, and antiproliferative activities of Thymus leucostomus H ausskn. & V elen. extracts.

The chemical composition as well as antioxidant, antiproliferative, and enzyme inhibition activities of extracts from aerial parts of Thymus leucostomus H ausskn. & V elen. obtained with hexane, methanol, and water were evaluated. Results showed that the methanol extract had significantly (p < 0.05) the highest total phenolic content (TPC; 107.80 mg GAE/g) and total flavonoids content (TFC; 25.21 mg RE/g) followed by the aqueous extract (102.72 mg GAE/g and 20.88 mg RE/g, respectively). LC-MS/MS-guided profiling of the three extracts revealed that rosmarinic acid (34.8%), hesperetin (42.9%), and linoleic acid (18%) were the dominant compounds in the methanol, aqueous and hexane extracts, respectively. GC-MS analysis of the hexane extract showed that É£-sitosterol (29.9%) was the major constituent. The methanol extract displayed significantly (p < 0.05) the highest Cu++ , Fe+++ , and Mo(VI) ions scavenging and reducing properties while the aqueous extract exerted significantly (p < 0.05) the highest metal chelating power (42.51 mg EDTAE/g). Both the hexane and methanol extracts effectively inhibited the acetylcholinesterase enzyme (2.63 and 2.65 mg GALAE/g, respectively) while the former extract exerted significantly (p < 0.05) the highest butyrylcholinesterase (2.32 mg GALAE/g), tyrosinase (19.73 mg KAE/g), and amylase (1.16 mmol ACAE/g) inhibition capacity. The aqueous extract exhibited the best glucosidase inhibition property (0.49 mmol ACAE/g). The methanol and hexane extracts exerted a higher cytotoxic effect on HT-29 (IC50 : 8.12 µg/mL) and HeLa (IC50 = 8.08 µg/mL) cells, respectively. In conclusion, these results provide valuable insight into the potential use of T. leucostomus bioactive extracts in different pharmaceutical applications.

Cuticular hydrocarbons for the identification and geographic assignment of empty puparia of forensically important flies.

Research in social insects has shown that hydrocarbons on their cuticle are species-specific. This has also been proven for Diptera and is a promising tool for identifying important fly taxa in Forensic Entomology. Sometimes the empty puparia, in which the metamorphosis to the adult fly has taken place, can be the most useful entomological evidence at the crime scene. However, so far, they are used with little profit in criminal investigations due to the difficulties of reliably discriminate among different species. We analysed the CHC chemical profiles of empty puparia from seven forensically important blow flies Calliphora vicina, Chrysomya albiceps, Lucilia caesar, Lucilia sericata, Lucilia silvarum, Protophormia terraenovae, Phormia regina and the flesh fly Sarcophaga caerulescens. The aim was to use their profiles for identification but also investigate geographical differences by comparing profiles of the same species (here: C. vicina and L. sericata) from different regions. The cuticular hydrocarbons were extracted with hexane and analysed using gas chromatography-mass spectrometry. Our results reveal distinguishing differences within the cuticular hydrocarbon profiles allowing for identification of all analysed species. There were also differences shown in the profiles of C. vicina from Germany, Spain, Norway and England, indicating that geographical locations can be determined from this chemical analysis. Differences in L. sericata, sampled from England and two locations in Germany, were less pronounced, but there was even some indication that it may be possible to distinguish populations within Germany that are about 70 km apart from one another.

Exploring the utility of the Threshold of Toxicological Concern (TTC) as a screening approach for complex substances.

The Threshold of Toxicological Concern (TTC) has been applied to assess chemical safety for use, particularly in the food safety area. Although the TTC was developed for application to an individual chemical structure, more recently this concept has been suggested for the assessment of combined exposures to multiple chemicals. This study evaluated the potential for applying the TTC to a specific type of co-exposure, that of a complex substance of variable composition which contains multiple constituents, following the World Health Organization/International Programme on Chemical Safety framework for risk assessment of combined exposure to multiple chemicals. The results indicated that the TTC threshold was lower (i.e., more conservative) than regulatory thresholds derived for the same substance or even its most toxic constituent, providing assurance that the TTC could meet the requirements for a conservative screening process. This case study indicates that the TTC concept can be a useful tool to screen for potential risks from complex substances, with the consideration of additional aspects such as variability in chemical constituents and their relative proportions within the substance.

Inside-tube solid-phase microextraction as an interlink between solid-phase microextraction and needle device for n-hexane evaluation in air and urine headspace.

Monitoring the trace amount of chemicals in various samples remains a challenge. This study was conducted to develop a new solid-phase microextraction (SPME) system (inside-tube SPME) for trace analysis of n-hexane in air and urine matrix. The inside-tube SPME system was prepared based on the phase separation technique. A mixture of carbon aerogel and polystyrene was loaded inside the needle using methanol as the anti-solvent. The air matrix of n-hexane was prepared in a Tedlar bag, and n-hexane vapor was sampled at a flow rate of 0.1 L/min. Urine samples spiked with n-hexane were used to simulate the sampling method. The limit of detection using the inside-tube SPME was 0.0003 µg/sample with 2.5 mg of adsorbent, whereas that using the packed needle was 0.004 µg/sample with 5 mg of carbon aerogel. For n-hexane analysis, the day-to-day and within-day coefficient variation were lower than 1.37%, with recoveries over 98.41% achieved. The inside-tube SPME is an inter-link device between two sample preparation methods, namely, a needle trap device and an SPME system. The result of this study suggested the use of the inside-tube SPME containing carbon aerogel (adsorbent) as a simple and fast method with low cost for n-hexane evaluation.

Qualitative analysis of flavors and fragrances added to tea by using GC-MS.

A precise identification method was developed to identify the flavors and fragrances added to tea matrix artificially using gas chromatography with mass spectrometry and gas chromatography with quadrupole time-of-flight mass spectrometry. The proposed method was based on the corresponding "three-column retention indices, two exact mass numbers, one mass spectrum matching degree" database of 40 kinds of common flavors and fragrances. The intraday and the interday relative standard deviation of the retention indices were less than 0.048 and 0.093%, respectively. The accuracy of exact mass was between 0.15 and 6.22 ppm. And the validation of the created database was performed by analyzing the tea samples. Thus, the proposed method is suitable for the precise identification of the flavors and fragrances added to tea matrix artificially without standard substances as a reference.

Acquired Color Vision Defects and Hexane Exposure: A Study of San Francisco Bay Area Automotive Mechanics.

Occupational exposure to solvents, including n-hexane, has been associated with acquired color vision defects. Blue-yellow defects are most common and may be due to neurotoxicity or retinal damage. Acetone may potentiate the neurotoxicity of n-hexane. We present results on nonhexane solvent and hexane exposure and color vision from a cross-sectional study of 835 automotive repair workers in the San Francisco Bay Area, California (2007-2013). Cumulative exposure was estimated from self-reported work history, and color vision was assessed using the Lanthony desaturated D-15 panel test. Log-binomial regression was used to estimate prevalence ratios for color vision defects. Acquired color vision defects were present in 29% of participants, of which 70% were blue-yellow. Elevated prevalence ratios were found for nonhexane solvent exposure, with a maximum of 1.31 (95% confidence interval (CI): 0.86, 2.00) for blue-yellow. Among participants aged ≤50 years, the prevalence ratio for blue-yellow defects was 2.17 (95% CI: 1.03, 4.56) in the highest quartile of nonhexane solvent exposure and 1.62 (95% CI: 0.97, 2.72) in the highest category of exposure to hexane with acetone coexposure. Cumulative exposures to hexane and nonhexane solvents in the highest exposure categories were associated with elevated prevalence ratios for color vision defects in younger participants.

Hexane Extract of Echinops spinosissimus Turra subsp. spinosus from Tunisia: A Potential Source of Acetylated Sterols - Investigation of its Biological Activities.

The hexane extract of Echinops spinosissimus Turra subsp. spinosus flower heads was analyzed for its fatty acid and sterol composition. Its physicochemical characteristics were also studied. The saponification, iodine and peroxide values were determined as 255 mg KOH/g, 42.57 g I2 /100 g and 110 m equiv. O2 /kg of oil, respectively. The oleic (C18:1; 61.14%), palmitic (C16:0; 21.36%) and linoleic (C18:2; 10.45%) acids were the dominant fatty acids. This extract was also found to contain high levels of ß-sitosterol and stigmasterol (44.97% and 34.95% of total sterols, respectively). On the other hand, the identification of terpenoid compounds was investigated by using GC/MS, which revealed fourteen major terpenoids mainly taraxasterol, lupeol, pseudotaraxasterol, lup-22(29)-en-3-yl acetate, taraxasteryl acetate, α-amyrin, ß-amyrin, pseudotaraxasteryl acetate, hop-20(29)-en3-ß-ol, α-amirenone, along with ß-sitosterol and stigmasterol. Moreover, we have evaluated the in vitro antibacterial and antifungal activities of the unsaponifiable matter and a fraction isolated from this extract. These activities were conducted using the diffusion disc methods and broth microdilution assay. The resulted fraction from this extract showed the highest antibacterial activity with significant minimum inhibitory concentrations (MIC) values 125.0 µg/ml against Staphylococcus aureus, Micrococcus luteus and Bacillus cereus. However, it did exhibit no substantial antifungal activity.

Volatile organic compounds in bile for early diagnosis of cholangiocarcinoma in patients with primary sclerosing cholangitis: a pilot study.

BACKGROUND: The diagnosis of cholangiocarcinoma (CCA) in patients with primary sclerosing cholangitis (PSC) is particularly difficult. The role of volatile organic compounds (VOCs) for diagnosis of CCA in patients with PSC is not known. OBJECTIVE: Our aim was to identify potential VOCs in the headspaces (gas above the sample) in bile that may predict CCA in patients with PSC. DESIGN: Prospective cross-sectional study. SETTING: Referral center. PATIENTS: A total of 32 patients undergoing ERCP for PSC and for CCA complicating PSC. INTERVENTIONS: ERCP, bile aspiration. MAIN OUTCOME MEASUREMENTS: Selected ion flow tube mass spectrometry was used to analyze the concentration of 22 prevalent VOCs in bile samples. Logistic regression analysis was performed to build a predictive model for diagnosis of CCA. RESULTS: Levels of several compounds (ethanol, acrylonitrile, acetonitrile, acetaldehyde, benzene, carbon disulfide, dimethyl sulfide, 2-propranolol) were significantly different in patients with CCA complicating PSC compared with those having PSC (P < .05). By using receiver operating characteristic curve analysis, we developed a model for the diagnosis of CCA adjusted for age and sex based on VOC levels of acrylonitrile, 3-methyl hexane, and benzene. The model (2.3239*log [acrylonitrile] + 0.9871*log [3-methyl hexane] + 0.8448*log [benzene]) < -0.12 identified the patients with CCA (area under the curve [AUC] = 0.89), with 90.5% sensitivity and 72.7% specificity (P = .02). LIMITATIONS: Sample size. CONCLUSION: The measurement of VOCs in biliary fluid may be useful to diagnose CCA in patients with PSC. A larger study with a longitudinal study design is required to confirm our pilot observations to diagnose CCA early in patients with PSC. ( CLINICAL TRIAL REGISTRATION NUMBER: NCT01565460.).

Biomimetic superhelical conducting microfibers with homochirality for enantioselective sensing.

Chiral amplification and discrimination are great challenges in both scientific and technological research fields such as chemical synthesis, chiral catalysis, and biomedicine. By mimicking protein superstructures in nature, chiral conducting polyaniline (PANI) molecules induced by chiral dopants were self-assembled to ultra-ordered superhelical microfibers. The induced homochirality is observed to be amplified into different hierarchies, from chiral molecules to helical nanostructures, and to superhelical microstructures. Furthermore, both experimental and theoretical results indicated that the gas sensor made from a single PANI helical microfiber showed enantioselective discrimination to chiral aminohexane, giving it great potential for applications in online chiral discrimination.

Surgical smoke may be a biohazard to surgeons performing laparoscopic surgery.

BACKGROUND: Surgical smoke production is inevitable during surgical procedures. Although many workplaces have adopted smoke-free environments, healthcare workers, especially surgeons, continue to be exposed to surgical smoke. METHODS: From February 2013 to March 2013, a total of 20 patients underwent transperitoneal laparoscopic nephrectomy for renal cell carcinoma. A 5-L gas sample was collected 30 min after the electrocautery device was first used and was analyzed by gas chromatography and mass spectrometry. Cancer risk was calculated for carcinogenic compounds and hazard quotient was calculated for noncarcinogenic compounds using US Environmental Protection Agency guidelines. RESULTS: Twenty patients with a median age of 57.5 years were enrolled in the study. Eighteen volatile organic compounds were detected by Japanese indoor air standards mix analysis. The cancer risks were ethanol, 5.10 × 10(-5) ± 6.35 × 10(-5); 1,2-dichloroethane, 4.75 × 10(-3) ± 7.42 × 10(-4); benzene, 1.09 × 10(-3) ± 4.33 × 10(-4); ethylbenzene, 2.87 × 10(-5) ± 1.32 × 10(-5); and styrene, 2.94 × 10(-6) ± 1.16 × 10(-6). The hazard quotients were acetone, 1.88 × 10(-2) ± 7.63 × 10(-3); hexane, 1.48 × 10(-1) ± 8.70 × 10(-2); benzene, 4.66 ± 1.85; toluene, 2.61 × 10(-2) ± 7.23 × 10(-3); p-xylene, 1.81 × 10(-1) ± 6.45 × 10(-2); o-xylene, 2.40 × 10(-2) ± 3.33 × 10(-2); and styrene, 5.15 × 10(-3) ± 2.03 × 10(-3). CONCLUSIONS: For five carcinogenic compounds detected, the cancer risk was greater than negligible. For 1,2-dichloroethane and benzene, the risk was classified as unacceptable. Analysis of noncarcinogenic compounds showed that risk reduction measures are needed for benzene. Even though surgical smoke is not an immediate health hazard, operating room personnel should be aware of the potential long-term health risks associated with exposure.

The mammalian toxicological hazards of petroleum-derived substances: an overview of the petroleum industry response to the high production volume challenge program.

Petroleum-derived substances are complex and composed of aliphatic (normal-, iso-, and cycloparaffins), olefinic, and/or aromatic constituents. Approximately 400 of these complex substances were evaluated as part of the US Environmental Protection Agency voluntary High Production Volume (HPV) Challenge program. The substances were separated into 13 groups (categories), and all available data were assessed. Toxicology testing was conducted as necessary to fully address the end points encompassed by the HPV initiative. In a broad sense, volatile hydrocarbons may cause acute central nervous system effects, and those that are liquids at room temperature pose aspiration hazards if taken into the lungs as liquids and may also cause skin irritation. Higher boiling substances may contain polycyclic aromatic constituents (PACs) that can be mutagenic and carcinogenic and may also cause developmental effects. Substances containing PACs can also cause target organ and developmental effects. The effects of aliphatic constituents include liver enlargement and/or renal effects in male rats via an α-2u-globulin-mediated process and, in some cases, small but statistically significant reductions in hematological parameters. Crude oils may contain other constituents, particularly sulfur- and nitrogen-containing compounds, which are removed during refining. Aside from these more generic considerations, some specific petroleum substances may contain unusually toxic constituents including benzene, 1,3-butadiene, and/or n-hexane, which should also be taken into account if present at toxicologically relevant levels.

Removal of sulfur compounds from diesel using ArF laser and oxygen.

A laser-based technique for deep desulfurization of diesel and other hydrocarbon fuels by removal of dimethyldibenzothiophene (DMDBT), a persistent sulfur contaminant in fuel oils has been developed. We report a selective laser excitation of DMDBT in diesel and model compounds such as n-hexane in a reaction chamber under oxygen environment where oxidative reactions can take place. ArF laser emitting at 193 nm was employed for excitation of oxygen and DMDBT, while for process optimization, the laser energy was varied from 50 to 200 mJ/cm(2). The laser-irradiated DMDBT solution under continuous oxygen flow was analyzed by UV absorption spectrometer to determine the photochemical oxidative degradation of DMDBT. In just 5 min of laser irradiation time, almost 95% DMDBT was depleted in a diesel containing 200 ppm of DMDBT. This article provides a new method for the removal of sulfur compounds from diesel by laser based photochemical process.

Phytochemical prospection and larvicidal bioactivity of the janaguba (Himatanthus drasticus) Mart. Plumel (Apocynaceae) latex against Aedes aegypti L. (Diptera: Culicidae).

The aim of this study was to carry out phytochemical prospecting and evaluate the larvicidal activity of Himatanthus drasticus latex extracts against Aedes aegypti. The extracts were obtained by maceration from 5 g of latex powder concentrated separately in 100 mL of methanol, ethyl acetate, and hexane solvents. The concentrations of 100, 200, 300, 400, and 500 ppm of each extract were tested in triplicate with a solution of pyriproxyfen as the positive control and distilled water and dimethylsulfoxide as the negative control. The phytochemical prospection of the methanolic extract showed the presence of phenolic compounds, such as anthocyanins, anthocyanidins, catechins, chalcones, aurones, leucoanthocyanidins, and condensed tannins. The insecticidal bioactivity was most significant for the methanolic extract. The methanolic extract lethal concentrations (LC) of 50 and 90% were 190.76 and 464.74 ppm, respectively. After 48 hours of exposure, the extracts using methanol, ethyl acetate, and hexane at their highest concentrations (500 ppm) caused larval mortality of 100, 73.33, and 66.67%, respectively. These extracts also promoted changes in the external morphology of the larvae, such as damage to the anal papillae, darkening of the body, and reduction in the number of bristles. The methanolic extract showed greater expressivity for morphological changes. The latex of H. drasticus has larvicidal activity against third-stade larvae of A. aegypti and it is more significant when obtained through maceration in methanol. The methanolic extract of H. drasticus latex contains phenolic compounds with insecticidal activity against A. aegypti larvae.

Effects of covered solid sorbent tube sample holders on organic vapor measurements.

A study was conducted to examine whether there are significant differences between organic vapor concentrations measured using charcoal tubes with three different configurations: uncovered sample holder (open tube), SKC, and Buck brand covered sample holders. A fractional factorial experimental design was used with the following factors and levels: vapor (n-hexane vs. m-xylene), pump type (pulsating vs. continuous), exposure profile (variable vs. constant), flow rate (30 mL/min vs. 200 mL/min), duration (30 min vs. 80 min), and sample placement (mannequin vs. free hanging). Two of each sampler configuration (six total) were placed in an exposure chamber, and a dynamic test-atmosphere generation system was used to prepare atmospheres containing approximately 12-15 ppm n-hexane or m-xylene with exposure profiles and sampling conducted according to a run sheet generated for the experimental design. A total of 24 runs were completed with six samplers per run, yielding 144 samples that were analyzed by gas chromatography/flame ionization detector. Concentration results for each pair of SKC and Buck covered sample holders were averaged and normalized by dividing by the average result for the open tube sampler from the same run to eliminate the effect of daily variation in chamber concentrations. The resulting ratio of covered sample tube holder and open tube concentrations was used as the response variable. Results of analysis of variance using the general linear model (MINITAB 16) identified statistically significant main effects and/or interactions for pump type, exposure profile, flow rate, and sample holder. However, the magnitude of the effects was generally less than 10%, and overall mean concentration ratios were 0.989 and 1.02 for the Buck and SKC sample holders, respectively. These results show good agreement between covered sample holder results and open tube measurements and demonstrate that exposure assessment errors resulting from the use of covered sorbent tube sample holders for organic vapor monitoring are relatively small (<10%) and not likely to be of practical importance.

Characterization and evolution of exposure to volatile organic compounds in the Spanish shoemaking industry over a 5-year period.

This study measured inhalation exposure to 13 volatile organic compounds (VOCs) among workers in the leatherwear industry in Spain, examined the changes in those exposures over a 5-year period, and documented local exhaust ventilation practices that affected exposure. In collaboration with an occupational risk prevention company, air samples were collected from 849 workers' personal breathing zones using personal air pumps with activated charcoal tubes. VOCs were analyzed using a GC/MS-optimized method modified in our laboratory from that proposed by Spanish authorities (INSHT). Airborne concentrations were compared with occupational exposure limit (OEL) values from the European authorities. The most frequently detected VOCs were acetone (98.1%), toluene (94.8%), n-hexane (71.2%) and other C6-C7 branched alkyl hydrocarbons (97.5%). Other frequently detected VOCs were MEK (64.9%), ethylacetate (60.7%), and cyclohexane (29.3%). Benzene was detected in 24.6% of samples. Although all the samples were taken while workers performed tasks judged to have the highest VOC exposure potential, only 14% of samples showed excessive aggregate exposure, and chemical-specific OELs were exceeded in a relatively small number of cases: 7.2% for n-hexane, 2.8% for toluene, 0.6% for acetone, and 0.4% for hexane isomers. Over the study period, a diminished use of n-hexane in solvent formulations and an increased use of branched hexane and heptane isomers were observed. Six factors relating to work location conditions and types were evaluated. Most high-exposure cases were associated with three task types. The presence of local exhaust ventilation was an important exposure control, but significant exposures despite the use of local exhaust were observed. Although n-hexane exposures significantly decreased over the study period, the overall level of VOC exposure did not decrease. More effective exposure prevention measures need to be implemented.

Residues of HCHs and DDTs in soils and sediments of preconstructing urban wetland.

Residues of hexachlorohexanes isomers (HCHs) and dichlorodiphenyltrichloroethane and metabolites (DDTs) in the soils and sediments of Dayanghan Wetland in Wuhu, China were investigated. The concentrations of ΣHCH in soils and sediments averaged 1.35 and 3.77 µg/kg with the predominance of ß-HCH and δ-HCH, respectively. The concentrations of ΣDDT in soils and sediments averaged of 7.80 and 2.80 µg/kg, respectively, with the dominance of o, p'-DDT. The concentrations of HCHs in the soils and sediments and DDTs in the sediments were categorized as no pollution, but the level of DDTs in the soils was classified as low pollution.

[Regulation and control of hexane level in air of workplace].

The article covers discussion on necessity of changing MAC for hexane in air of workplace. That is justified by health disorders in the workers, supported by the authors' experimental studies. The authors analyzed methods to control hexane levels in air of workplace, suggested specific standardized method assessing hexane in air of workplace and in ambient air.

Quantitative analysis of thiamylal and its metabolite secobarbital using liquid chromatography-tandem mass spectrometry in adipose tissue, serum, and liver.

Thiamylal is an ultrashort-acting barbiturate used for intravenous administration or general anesthesia induction. However, some cases of poisoning and suicide with thiamylal administration have been reported. Additionally, there are few reports on its analysis in the organs and adipose tissue, which requires purification by column chromatography and evaporation. A rapid and sensitive method was developed for quantifying thiamylal and its metabolite, secobarbital, in the adipose tissue, serum, and liver using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were prepared using modified QuEChERS extraction. For adipose tissue samples, an acetonitrile-hexane partitioning step was added to the extraction. This method was applied to investigate a suspected self-poisoning autopsy case. The quantitation accuracy for thiamylal added to porcine pericardial fat (0.18 µg/g), human serum (0.015 µg/mL), and porcine liver (0.18 µg/g) was 103%, 113%, and 95.3%, respectively. The quantitation limits calculated for porcine pericardial fat, human serum, and porcine liver at a signal-to-noise ratio of 10 were 0.06 µg/g, 0.005 µg/mL, and 0.06 µg/g, respectively. In addition, the thiamylal and secobarbital levels in the forensic autopsy case were 140 and 1.5 µg/g, respectively, in myocardial fat; 3.5-4.9 and 0.12-0.20 µg/mL, respectively, in serum; and 6.2-42 and 0.58-1.1 µg/g, respectively, in liver tissue. Thiamylal is especially distributed in the adipose tissue. The thiamylal-to-fat ratio may help estimate the time from administration to death. The developed modified QuEChERS extraction method with acetonitrile-hexane partitioning is suitable for analyzing hydrophobic compounds, such as thiamylal, in the adipose tissue.

[Determination of polychlorinated naphthalenes in ambient air by isotope dilution gas chromatography-triple quadrupole mass spectrometry].

Polychlorinated naphthalenes (PCNs) have a structure similar to that of polychlorinated biphenyls (PCBs) and represent a new type of persistent organic pollutants (POPs) that are widely present in the environment and biological communities. PCNs can migrate and transform via different environmental media, which severely affects the health of humans and organisms. Researchers have devoted considerable focus on ambient air pollution. Although the current ambient air quality has not yet limited the concentration of PCNs, the Stockholm Convention has required parties to prohibit and eliminate their production and use. As one of the contracting parties, China is obligated to improve its environmental monitoring. In other words, the development of a method for monitoring PCNs in ambient air is important for understanding ambient air quality and safeguarding human health. PCNs are generally present at trace levels (pg/m3) in ambient air. To achieve accurate quantification of PCNs, high demands are raised on the methods for extraction, purification, and instrumental analysis, which can directly affect the efficiency, accuracy, and sensitivity of a method. Considering the trace-level presence of PCNs in ambient air and the high efficiency and accuracy of the analytical method, accelerated solvent extraction (ASE), combined with column chromatography using a multilayer silica gel column and a neutral alumina column, was established for the extraction and purification of PCNs in ambient air. The important parameters involved in the aforementioned steps, such as the type of extraction and volume of elution solvent, were optimized. The results indicated that dichloromethane-hexane (1∶1, v/v) was the best extraction solvent for the recovery of PCNs. Hexane and dichloromethane-hexane (5∶95, v/v) were used as the elution solvents for the multi-silica gel column and neutral alumina column, respectively. Isotope dilution gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was used to quantify the target compounds. Gas chromatographic parameters, such as temperature program conditions and inlet temperature, were also optimized. The oven temperature program was as follows: 80 ℃ for 1 min, 80 ℃ to 160 ℃ at 15 ℃/min, 160 ℃ to 265 ℃ at 3 ℃/min, and 265 ℃ to 280 ℃ at 5 ℃/min, followed by holding the temperature at 280 ℃ for 10 min. The inlet temperature was set at 260 ℃. The optimal characteristics of ion pair, collision energy, and ion source temperature were determined by optimizing the key mass spectrometry parameters. The developed instrumental method, combined with suitable sample preparation techniques, was used to determine the concentrations of PCNs in ambient air samples. Quality control (QC) and quality assurance (QA) were performed by adding isotope internal standards before sampling, extraction, and injection analysis to monitor the entire analysis process. The relative standard deviations (RSDs) of the relative response factors (RRFs) for trichloronaphthalene to octachloronaphthalene were less than 16% in the concentration range of 2-100 ng/mL. The method detection limits (MDLs) for PCN homologues were in the range of 1-3 pg/m3(calculated using a sample volume of 288 m3). The precision and accuracy of this method for determining PCNs in ambient air samples were evaluated using a spiked matrix. The average spiked recoveries of trichloronaphthalene to octachloronaphthalene were 89.0%-119.4%, 98.6%-122.5% and 93.7%-124.5% at low, medium, and high spiked concentrations (20, 50, and 90 ng/mL), respectively. The RSDs of the assay results were 1.9%-7.0%, 1.6%-6.6%, and 1.0%-4.8%, respectively. During the entire analysis process, the average recoveries of the sampling and extracted internal standards were 136.2%-146.0% and 42.4%-78.1%, respectively, and the corresponding RSDs were 5.6%-7.5% and 2.7%-17.5%. Thus, this method meets the requirements of trace analysis and exhibits good parallelism, high sensitivity, high accuracy, and good precision, and it is suitable for the accurate quantitative determination of trichloronaphthalene to octachloronaphthalene in ambient air.