Forensic analysis of mosquito blood meal digestion process and the impact of heroin opiate: determination of the post-feeding interval as a PMI estimation.

Females of some mosquito species are anthropophilic, as they feed on human blood to support egg production and, hence, are forensically valuable if found at a crime scene. The present study investigated the blood meal digestion process in Culex pipiens L. both with and without heroin and proposed a method for estimating the post-feeding interval (PFI). Mosquitoes were fed on a control mouse, a heroin-injected mouse, or in vitro heroin-treated mouse blood. The blood meal digestion was then investigated at different hours post-feeding. Data showed that the blood meal size ingested by control mosquitoes was 0.681 ±â€…0.04 mg/mosquito and was completely digested within 45 h post-feeding. An estimation of the PFI was proposed in terms of the rate of hemoglobin (Hb) digestion. The blood meal size of the mosquitoes fed on the in vitro heroin-treated blood and the heroin-injected mouse was 0.96 ±â€…0.06 and 0.79 ±â€…0.01 mg/mosquito and was completely digested within 50 and 55 h post-feeding, respectively. The digestion of Hb started similarly in all experimental mosquitoes until 10 h post-feeding, after which it significantly decreased in heroin-treated blood meals compared with the control ones. This may suggest that heroin impacted the digestion process, as it took an extra 5-10 h to complete. These findings could be valuable in the forensic context since an estimation of PFI is proposed as a potential estimation of the postmortem interval (PMI). However, care should be taken as heroin in the host blood has significantly impacted the overall digestion process and, hence, may bias the PFI/PMI estimation.

Physicochemical Composition of Local and Imported Honeys Associated with Quality Standards.

The compliance with honey standards is crucial for its validity and quality. The present study evaluated the botanical origin (pollen analysis) and physicochemical properties: moisture, color, electrical conductivity (EC), free acidity (FA), pH, diastase activity, hydroxymethylfurfural (HMF), and individual sugar content of forty local and imported honey samples. The local honey exhibited low moisture and HMF (14.9% and 3.8 mg/kg, respectively) than imported honey (17.2% and 23 mg/kg, respectively). Furthermore, the local honey showed higher EC and diastase activity (1.19 mS/cm and 11.9 DN, respectively) compared to imported honey (0.35 mS/cm and 7.6 DN, respectively). The mean FA of local honey (61 meq/kg) was significantly naturally higher than that of imported honey (18 meq/kg). All local nectar honey that originated from Acacia spp. exhibited naturally higher FA values that exceeded the standard limit (≤50 meq/kg). The Pfund color scale ranged from 20 to 150 mm in local honey and from 10 to 116 mm in imported honey. The local honey was darker, with a mean value of 102.3 mm, and was significantly different from imported honey (72.7 mm). The mean pH values of local and imported honey were 5.0 and 4.5, respectively. Furthermore, the local honey was more diverse in pollen grain taxa compared to imported honey. Local and imported honey elicited a significant difference regarding their sugar content within individual honey type. The mean content of fructose, glucose, sucrose, and reducing sugar of local honey (39.7%, 31.5%, 2.8%, and 71.2%, respectively) and imported honey (39.2%, 31.8%, 0.7%, and 72.0%, respectively) were within the permitted quality standards. This study indicates the necessity of increasing the awareness regarding quality investigations for healthy honey with good nutritional value.

New Method Based on the Direct Analysis in Real Time Coupled with Time-of-Flight Mass Spectrometry to Investigate the Thermal Depolymerization of Poly(methyl methacrylate).

In this work, the isothermal decomposition of poly(methyl methacrylate) synthesized in bulk by the radical route of methyl methacrylate in the presence of azobisisobutyronitrile as the initiator was carried out and monitored for the first time with the DART-Tof-MS technique at different temperatures. Nuclear magnetic resonance (NMR) analysis revealed a predominantly atactic microstructure, and size-exclusion chromatography (SEC) analysis indicated a number average molecular weight of 3 × 105 g·mol-1 and a polydispersity index of 2.47 for this polymer. Non-isothermal decomposition of this polymer carried out with thermogravimetry analysis (TGA) showed that the weight loss process occurs in two steps. The first one starts at approximately 224 °C and the second at 320 °C. The isothermal decomposition of this polymer carried out and monitored with the DART-Tof-MS method revealed only one stage of weight loss in this process, which begins at approximately 250 °C, not far from that of the second step observed in the case of the non-isothermal process conducted with the TGA method. The results obtained with the MS part of this technique revealed that the isothermal decomposition of this polymer regenerates a significant part of methyl methacrylate monomer, which increases with temperature. This process involves radical chain reactions leading to homolytic chain scissions and leading to the formation of secondary and tertiary alkyl radicals, mainly regenerating methyl methacrylate monomer through an unzipping rearrangement. Although they are in the minority, other fragments, such as the isomers of 2-methyl carboxyl, 4-methyl, penta-2,4-diene and dimethyl carbate, are also among the products detected. At 200 °C, no trace of monomer was observed, which coincides with the first step of the weight loss observed in the TGA. These compounds are different to those reported by other researchers using TGA coupled with mass spectrometry in which methyl isobutyrate, traces of methyl pyruvate and 2,3-butanonedione were detected.

Montmorillonite-based polymethacrylate composite monoliths as stationary phase materials for food and pharmaceutical analysis in capillary liquid and gas chromatography.

This work relates to the preparation of novel and promising stationary phases containing inorganic-organic composites for capillary liquid and gas chromatography. A naturally occurring montmorillonite was introduced to polymethacrylate monoliths, then used under different conditions of GC and HPLC at the same time. The performance of the columns was evaluated for the separation of alkane and alkylbenzene series in GC and capillary HPLC, respectively. While the bare monoliths failed to separate the model analytes, montmorillonite-based polymethacrylate allowed a full separation of the mixtures with Rs≥1.42. The columns were applied for the determination of myrcene and limonene isomers in the peel extracts of some fruits using GC, and for the analysis of active ingredients including aspirin, vitamin-C, caffeine, and ibuprofen extracted from common drugs using capillary HPLC. In GC, fast separation was achieved in 1.0 min with Rs of 6.53. The columns exhibited the best efficiency for myrcene with 20,900 plates/m. Using the capillary HPLC columns, the active ingredients were resolved in 10 min with Rs≥5.72. The efficiency values located between 12,800-21,700 plates/m in all cases. The developed methods were found to be linear in the range of 0.10-10.0 and 0.20-180 µg/mL for GC and HPLC, respectively. In comparison with commercial columns, the results in GC methods reveal that, despite their much shorter length, the prepared columns proved a faster separation with higher efficiency and comparable detection limits and chromatographic resolution. The prepared HPLC capillaries exposed lower run times and detection limits with comparable efficiency and resolution, and consume fewer samples and mobile phase solvents. The results demonstrate that the montmorillonite-based polymethacrylate composites are applicable as stationary phases for routine analysis and quality control of important fields such as food and pharmaceutical samples.

Impact of Different Storage Regimes on the Levels of Physicochemical Characteristics, Especially Free Acidity in Talh (Acacia gerrardii Benth.) Honey.

This study investigates how storage conditions (temperature and duration) may affect the physicochemical parameters, especially free acidity (FA), of Talh honey originating from Acacia gerrardii that have naturally high FA levels. Fresh Talh honey samples were kept at 0, 25, 35, and 45 °C, and analyzed monthly over a period of eight months. The Talh honey was monofloral with 69% A. gerrardii pollen content. The free acidity (FA) of freshly harvested Talh honey samples was higher (93 ± 0.3 meq/kg) than that of standard limits (≤50 meq/kg) and remained stable at 0 °C throughout the storage period. A significantly increase in FA started to occur after storage for 6 months at 25 °C (103 ± 0.2 meq/kg), 2 months at 35 °C (108 ± 0.3 meq/kg), and 1 month at 45 °C (112 ± 0.3 meq/kg). After 8 months of storage, the highest FA level was recorded at 45 °C (159 ± 0.5 meq/kg), followed by 127 ± 0.3 meq/kg at 35 °C, 105 ± 0.2 meq/kg at 25 °C, and 94 ± 0.3 meq/kg at 0 °C. It was found that 0 °C was an appropriate temperature for storing honey for long time. The electrical conductivity (EC) of fresh Talh samples (1.46 ± 0.0 mS/cm) was above the accepted limit (≤0.8 mS/cm), which was slightly increased (non-significant) throughout the storage period under all the storage temperatures. Hydroxymethylfurfural (HMF), diastase activity (DN), and reducing sugars (RSs) showed normal levels only at 0 °C and 25 °C throughout the storage period. However, HMF exceeded the standard limits after the first month at 45 °C (127 ± 9.6 mg/kg) and after the second month at 35 °C (90 ± 23.5 mg/kg), DA decreased below standard limits after the second month (5 ± 1 DN) under 45 °C and after the seventh month under 35 °C (7 ± 2 DN, and RSs decreased below 60% after 2 months under 45 °C and after 6 months at 35 °C. The physicochemical parameters (moisture content, pH, color, and sucrose) were the least affected and were within the standard range throughout the storage period under all the storage temperatures. The levels of FA and EC in fresh Talh samples were higher than the acceptable limits. The moisture content, pH, color, and sucrose content were not affected by storage conditions and remained within the acceptable limits. HMF, DA, and RSs were significantly affected by storage conditions only at 35 and 45 °C. The storage of honey at low temperatures (0 and 25 °C) for up to eight months presented the least amount of changes in the honey, and the honey was unchanged from its fresh status. Honey storage at 35 and 45 °C resulted in significant changes. It is recommended that Talh honey, which normally has high acidity levels, should be stored at temperatures not exceeding 25 °C.

Determination of phthalates in bottled waters using solid-phase microextraction and gas chromatography tandem mass spectrometry.

Phthalates are synthetic chemicals widely used, mainly as plasticizers, which are ubiquitous and recognized as endocrine-disrupting chemicals. For investigation of phthalate residues leached from PET bottles into drinking water, a simple and sensitive method was developed, validated and applied to a series of real samples. Solid-phase microextraction (SPME) was used in direct immersion mode for concentration of phthalate traces from 10 mL of each water sample. Four commercially available SPME fibers were tested and compared, while six dialkyl phthalates were investigated: dimethyl phthalate (DMP), diethyl phthalate (DEP), diisopropyl phthalate (DiPP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di-ethylhexyl phthalate (DEHP). The extracted phthalic acid esters were separated and quantified by gas chromatography hyphenated with tandem mass spectrometry (GC-MS/MS) and a detection method based on multiple reaction monitoring (MRM) mode was fully developed, optimized and validated. The fiber which showed the highest ability for extraction of phthalates was DVB/CAR/PDMS which combines a liquid polymeric coating (polydimethyl siloxane and divinylbenzene) with a carboxen porous sorbent layer. The obtained limit of detection was in the range between 0.3 and 2.6 ng mL-1. Thus, this fiber was used for extraction of phthalates from twelve commercial PET bottled water samples. All investigated water brands showed the presence of two to six phthalates at concentrations between 6.3 and 112.2 ng mL-1. The highest level was observed for DnBP, followed by DEHP, DiBP, DMP, DEP and DiPP.

Preparation of value-added metal-organic frameworks for high-performance liquid chromatography. Towards green chromatographic columns.

This work applies the concepts of green chemistry, where polyethylene terephthalate (PET) bottles were used as the acid-dicarboxylic linker source for the synthesis of MIL-53(Al) metal organic frameworks (MOFs) and then used as a stationary phase for the separation of various solutes and compared with MIL-53(Al) synthesized from traditional terephthalic acid. Both synthesized MIL-53(Al) MOFs were characterized by scanning electron microscopy (SEM), FT-IR, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and specific surface area analysis. Eight groups of standard analytes in addition to real samples were tested to evaluate the separation performance of the MIL-53(Al) packed columns in HPLC under various chromatographic conditions. Based on elution order of the studied compounds and the effects of mobile phase composition, the working mechanism was reversed phase mode in the presence of size-exclusion effects for large molecules, which exceeded the dynamic diameter of MIL-53(Al) (~7.6 Å). The effects of stationary phase sieving, mobile phase flow rate and composition, injected sample mass, and temperature were investigated relative to the chromatographic behavior of MIL-53(Al). MIL-53(Al) particle sieving before packing reduced peak broadening and significantly enhanced the chromatographic performance of the prepared columns up to 2.26 times relative to the number of theoretical plates. The MIL-53(Al) packed columns offered high-resolution separation for all studied mixtures with Rs >2 and good stability and long-term durability. At optimal conditions, the prepared columns exhibited efficiencies between 5600-63200 plates m-1. Higher efficiencies were observed for alkylbenzenes and polyaromatic hydrocarbons as the organic linker in the MIL-53(Al) structure, which improved retention and separation of aromatics through π-π interactions. Thermodynamic parameters including ΔH, ΔS, and ΔG for the transfer of analyte from the mobile phase to the MIL-53(Al) stationary phase were studied. Compared with previously cited MOFs packed columns, the present MIL-53(Al) columns gave comparable selectivity and much better efficiency for most of the studied chemicals at optimum conditions, indicating the feasibility of MIL-53(Al) as a stationary phase for HPLC applications.

GC-MS profiling and assessment of antioxidant, antibacterial, and anticancer properties of extracts of Annona squamosa L. leaves.

BACKGROUND: The research and application of plants in food supplements and drugs have attracted great interest. This study aimed to examine the efficiency of several solvents for the extraction of the main compounds from Annona squamosa leaves and to evaluate the antioxidant, antibacterial, and anticancer activities of these extracts. METHODS: Gas chromatography-mass spectrometry was used to screen the bioactive compounds of A. squamosa methanolic extract. The free radical, hydrogen peroxide, and nitric oxide scavenging activities of the extracts were investigated. Furthermore, MTT, nuclear staining, LDH, and monolayer wound repair assays were performed to evaluate the potential anticancer activity of the extracts in colon cancer cells while the antibacterial activity was tested by using a well diffusion assay. RESULTS: A. squamosa leaves extracts were found to contain several bioactive compounds, of which the majority were sesquiterpenes (C15H24). These extracts exhibited strong antioxidant activity and antibacterial potency against both gram-positive and gram-negative bacteria. Different A. squamosa leaves extracts displayed remarkable antiproliferative, cytotoxic, antimigration, and apoptotic activities in colon cancer cells. CONCLUSIONS: A. squamosa leaves contain major bioactive compounds that inhibit the growth of several types of bacteria and colon cancer cell lines, which demonstrated their efficacy as an alternative source of antibiotics and for the development of novel drugs for colon cancer therapy.

Rapid and Sensitive Determination of Methylxanthines in Commercial Brands of Tea Using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry.

Recently, chromatographic techniques have the potential to be greener in order to reduce the environmental impact. In this work, a new simple, sensitive, efficient, and green analytical method based on UHPLC-MS has been developed for a quick determination of methylxanthines including caffeine, theobromine, and theophylline in tea. Under the optimum conditions, a baseline separation has been achieved within 30 seconds, using isocratic elution consisting of 90% water and only 10% acetonitrile at 0.5 mL/min flow rate (3 mL acetonitrile per hour). The mass spectrometer was operated with the SIR mode in ESI+. The developed method was found to be linear in the range of 0.03-5 µg/mL, with correlation coefficients greater than 0.9995 for the three compounds. The respective values of LOD were found to be 0.025, 0.015, and 0.01 µg/mL for caffeine, theobromine, and theophylline, respectively. The proposed assay was applied to 30 commercial tea samples of different brands. Both caffeine and theobromine were found in all tea samples with maximum concentration in sample no. 15, corresponding to 32.6 and 2.72 mg/g of caffeine and theobromine, respectively. On the contrary, theophylline was not detected at all in most samples. When compared with all previous studies that dealt with the same compounds in different matrices, the developed method was found to be the fastest, allowing high-throughput analyses with more than 100 samples/h. The results prove that the method is suitable for routine analysis of methylxanthines and to distinguish the quality of tea samples of various brands.

Microwave Irradiation Assists the Synthesis of a Novel Series of bis-Arm s-Triazine Oxy-Schiff Base and Oxybenzylidene Barbiturate Derivatives.

A novel series of s-triazines incorporating 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde was prepared and fully characterized. The reaction was carried out via stepwise nucleophilic aromatic substitution of chlorine atoms in cyanuric chloride. The first chlorine was substituted by different amines (morpholine, piperidine, or diethylamine) to afford 2,4-dichloro-6-substituted-1,3,5-triazine. The second and third chlorines were substituted by benzaldehyde derivatives in the presence of Na2CO3 as a HCl scavenger to afford the target products: s-triazine oxyaldehyde derivatives (dipodal). The dipodal derivatives were reacted with acid hydrazide, hydralazine, barbituric, or thiobarbituric acid derivatives using conventional heating or microwave irradiation to afford the di-arm s-triazine oxy-Schiff base and oxybenzylidene barbiturate derivatives in good yields. Microwave irradiation done in less solvent afforded the target product in less reaction time with good yield and purity. These types of derivatives might have special interest in coordination and medicinal chemistry.

Carbon nanotube-based benzyl polymethacrylate composite monolith as a solid phase extraction adsorbent and a stationary phase material for simultaneous extraction and analysis of polycyclic aromatic hydrocarbon in water.

A composite of multi-walled carbon nanotubes incorporated into a benzyl methacrylate-co-ethylene dimethacrylate porous monolith was prepared, characterized and used as solid phase adsorbent and as stationary phase for simultaneous extraction and separation of ten polycyclic aromatic hydrocarbons, followed by nano-liquid chromatography analysis. The extraction and chromatographic parameters were optimized with regard to the extraction efficiency and the quality of chromatographic analytes separation. Under the optimized conditions, all PAHs were separated in 13 min with suitable resolution values (Rs = 1.74-3.98). Addition of a small amount of carbon nanotubes (0.1% with respect to monomers) to the polymerization mixture increased the efficiency for the separation column to over 41,700 plates m-1 for chrysene at flow rate of 0.5 µL min-1. The method showed a wide linear range (1-500 µg L-1 with R2 more than 0.9938), acceptable extraction repeatability (RSDs < 6.4%, n = 3) and reproducibility (RSDs < 12.6%, five parallel-made solid phase extraction cartridges) and satisfactory detection limits (0.02-0.22 µg L-1). Finally, the proposed method was successfully applied to the detection of polycyclic aromatic hydrocarbons in environmental water samples. After a simple extraction procedure with preconcentration factor equal to 100, the average recovery values in ultra-pure, tap and sea water samples were found to be in the range 81.3-95.4% with %RSD less than 6.4. Again, the presence of carbon nanotubes (0.3% relatively to monomers) in native polymer enhanced the extraction performance for the solid phase adsorbent up to 78.4%. The application of the monoliths modified with CNTs in extraction and nano-scale liquid chromatography for analysis of environmental samples offered several advantages; it demonstrated an acceptable precision, low detection limits, good reproducibility, satisfying recoveries and wide dynamic linear ranges.

Zeolitic imidazolate framework-methacrylate composite monolith characterization by inverse gas chromatography.

UNLABELLED: Thermodynamic characterization of butyl methacrylate-co-ethylene dimethacrylate neat monolith and zeolitic imidazolate framework-8 incorporated with butyl methacrylate-co-ethylene dimethacrylate composite monolith were studied using inverse gas chromatography at infinite dilution under 1MPa column pressure and various column temperatures. The free energy of adsorption (ΔGA), enthalpy of adsorption (ΔHA) and entropy of adsorption (ΔSA) were determined using a series of n-alkanes. The dispersive component of surface energy (γS(D)) was estimated by Dorris-Gray and Schultz et al. METHODS: The composite monolith showed a more energetic surface than the neat monolith. The acidic, KA, and basic, KD, parameters for both materials were estimated using a group of polar probes. A basic character was concluded with more basic behavior for the neat monolith. Flory-Huggins parameter, χ, was taken as a measure of miscibility between the probes with the low molecular weight and the high molecular weight monolith. Inverse gas chromatography provides a better understanding of the role of incorporated zeolitic imidazolate framework (ZIF-8) into the polymer matrix in its monolithic form.

Monolithic metal-organic framework MIL-53(Al)-polymethacrylate composite column for the reversed-phase capillary liquid chromatography separation of small aromatics.

A monolithic capillary column containing a composite of metal-organic framework MIL-53(Al) incorporated into hexyl methacrylate-co-ethylene dimethacrylate was prepared to enhance the separation of mixtures of small aromatic compounds by using capillary liquid chromatography. The addition of 10 mg/mL MIL-53(Al) microparticles increased the micropore content in the monolithic matrix and increased the Brunauer-Emmett-Teller surface area from 26.92 to 85.12 m(2) /g. The presence of 1,4-benzenedicarboxylate moieties within the structure of MIL-53(Al) as an organic linker greatly influenced the separation of aromatic mixtures through π-π interactions. High-resolution separation was obtained for a series of alkylbenzenes (with resolution factors in the range 0.96-1.75) in less than 8 min, with 14 710 plates/m efficiency for propylbenzene, using a binary polar mobile phase of water/acetonitrile in isocratic mode. A reversed-phase separation mechanism was indicated by the increased retention factor and resolution as the water percentage in the mobile phase increased. A stability study on the composite column showed excellent mechanical stability under various conditions. The higher resolution and faster separation observed at increased temperature indicated an exothermic separation, whereas the negative values for the free energy change of transfer indicated a spontaneous process.

Fabrication of zeolitic imidazolate framework-8-methacrylate monolith composite capillary columns for fast gas chromatographic separation of small molecules.

A composite zeolitic imidazolate framework-8 (ZIF-8) with a butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250µm i.d.) was fabricated to enhance the separation efficiency of methacrylate monoliths toward small molecules using conventional low-pressure gas chromatography in comparison with a neat butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5cm long×250µm i.d.). The addition of 10mgmL(-1) ZIF-8 micro-particles increased the BET surface area of BuMA-co-EDMA by 3.4-fold. A fast separation of five linear alkanes in 36s with high resolution (Rs≥1.3) was performed using temperature program. Isothermal separation of the same sample also showed a high efficiency (3315platesm(-1) for octane) at 0.89min. Moreover, the column was able to separate skeletal isomers, such as iso-octane/octane and 2-methyl octane/nonane. In addition, an iso-butane/iso-butylene gas mixture was separated at ambient temperature. Comparison with an open tubular TR-5MS column (30m long×250µm i.d.) revealed the superiority of the composite column in separating the five-membered linear alkane mixture with 4-5 times increase in efficiency and a total separation time of 0.89min instead of 4.67min. A paint thinner sample was fully separated using the composite column in 2.43min with a good resolution (Rs≥0.89). The perfect combination between the polymeric monolith, with its high permeability, and ZIF-8, with its high surface area and flexible 0.34nm pore openings, led to the fast separation of small molecules with high efficiency and opened a new horizon in GC applications.

Identification of wild collected mosquito vectors of diseases using gas chromatography-mass spectrometry in Jazan Province, Saudi Arabia.

Thirty-three species of mosquitoes have been reported from the Kingdom of Saudi Arabia. Several of these mosquitoes, Anopheles gambiae Giles s.l., Anopheles stephensi Liston, Culex pipiens Linnaeus, Culex quinquefasciatus Say, Culex tritaeniorhynchus Giles, Stegomyia aegypti (Linnaeus) and Aedimorphus vexans arabiensis (Patton) are known vectors of human and animal diseases. In this study, the cuticular hydrocarbon profiles of eight mosquito species using gas chromatography-mass spectrometry were analyzed. Wild collected fourth-instar larvae were reared, and single, newly emerged, unfed adult females were used for the analysis. A total of 146-160 peaks were detected from the cuticular extracts by gas chromatography. Repeated analysis of variance (ANOVA) and Tukey HSD Post Hoc test was used to test for quantitative differences in relative hydrocarbon quantity. In addition, a linear regression model was applied using Enter method to determine the diagnostic peaks for the eight mosquito specimens. The ANOVA test indicated that relative peaks were significant (P < 0.05) when selected pairs of peaks were compared. Also, seven compounds showed qualitative differences among the five mosquito vectors tested. The classes of constituents present were n-alkanes, monomethylalkanes, dimethylalkanes, trimethylalkanes, alkenes, branched aromatic hydrocarbons, aldehydes and esters. These compounds have a carbon chain length ranging from 8 to 18 carbons. The most abundant compound in all adult mosquito specimens was n-hexylacrylate [retention time (RT) 6.73 min], which was not detected in Cx. pipiens. In Cx. pipiens, the most abundant peak was benzaldehyde (RT 2.98 min). Gas chromatography-mass spectrometry is a suitable method to identify adult mosquitoes, especially from focal areas of public health concern such as Jazan Province, Saudi Arabia. This method allows a wide range of adult collected material to be identified with high accuracy.

Preparation and characterization of alkyl methacrylate-based monolithic columns for capillary gas chromatography applications.

Gas chromatography (GC) is considered the least common application of both polymer and silica-based monolithic columns. This study describes the fabrication of alkyl methacrylate monolithic materials for use as stationary phases in capillary gas chromatography. Following the deactivation of the capillary surface with 3-(trimethoxysilyl)propyl methacrylate (TMSM), the monoliths were formed by the co-polymerization of either hexyl methacrylate (HMA) or lauryl methacrylate (LMA) with different percentage of ethylene glycol dimethacrylate (EDMA) in presence of an initiator (azobisisobutyronitrile, AIBN) and a mixture of porogens include 1-propanol, 1,4-butanediol and water. The monoliths were prepared in 500mm length capillaries possessing inner diameters of 250µm. The efficiencies of the monolithic columns for low molecular weight compounds significantly improved as the percentage of crosslinker was increased, because of the greater proportion of pores less than 50nm. The columns containing lower percentages of crosslinker were able to rapidly separate a series of 8 alkane members in 0.7min, but the separation was less efficient for the light alkanes. Columns prepared with the lauryl methacrylate monomer yielded a different morphology for the monolith-interconnected channels. The channels were more branched, which increased the separation time, and unlike the other columns, allowed for temperature programming.

Highly sensitive chiral analysis of amino acids by in-line single drop microextraction and capillary electrophoresis with laser-induced fluorescence detection.

A highly sensitive method for chiral analysis of amino acids by in-line single drop microextraction (SDME) and chiral capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was developed. In SDME, a drop of a basic aqueous acceptor phase covered with a thin organic layer was formed at the tip of a capillary by simple combination of sample-handling sequences of a CE apparatus. Then fluorescein isothiocyanate (FITC)-derivatized amino acids in an acidic donor solution were enriched into the drop through the organic layer. The enriched enantiomers were then resolved using a dual chiral selector of ß-cyclodextrin (ß-CD) and sodium taurodeoxycholate (STC). Here, in addition to serving as a labeling reagent providing high fluorescence signal, hydrophobic FITC was primarily used as a modifier aiding the extraction of zwitterionic amino acids by blocking the amino groups and increasing the hydrophobicity, yielding 220 times increase in extraction efficiency. Several hundred-fold enrichments were achieved with 10 min SDME, yielding LODs of 30-60 pM and enabling direct analysis of d-AAs in a 99% enantiomeric excess mixture. In view of no additional modification of the existing commercial CE instrument, this method without stirring can be easily realized using known operations. When a microstirrer was customized to the CE instrument several thousand-fold enrichments could be obtained with LODs in the low picomolar range of 1-3 pM.

Preparation and chromatographic properties of a multimodal chiral stationary phase based on phenyl-carbamate-propyl-beta-CD for HPLC.

A phenylcarbamate derivative of 2-hydroxypropyl-beta-CD bonded stationary phase was prepared by a previously described method. Its enantiomeric recognition abilities were evaluated as chiral stationary phase (CSP) in normal, polar organic and RP conditions by HPLC. The relevant structural features of the prepared stationary phase which make it an effective chiral selector are discussed. This material seems to have an excellent enantioselectivity for a variety of racemic analytes in the three modes. Hence it can be considered a highly effective multimodal column. Retention factor (k), selectivity (alpha) and resolution (R(s)) were the chosen parameters to describe the column performance. Optimization of these separations was discussed in terms of mobile phase composition, flow rate and structural patterns of the injected analytes.

Enantiomeric separation of drugs and herbicides on a beta-cyclodextrin-bonded stationary phase.

A chemically bonded beta-cyclodextrin chiral stationary phase for HPLC was prepared in a "one pot" process by the reaction of a phenylated beta-cyclodextrin with silica gel. Various racemic analytes such as drugs (aminoalcohol adrenergic beta-blockers, benzodiazepine anxiolytics, arylpropionic acid antiinflammatory agents) and herbicides (aryloxypropionic acids and esters) were separated on the prepared material. The column showed good chiral recognition ability for most of the solutes tested when using heptane and either 2-propanol or chloroform as organic mobile phase modifiers.