Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography/electron capture detection

Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study, the pyrethroid metabolites in workers’ urine samples were monitored for the first time with a novel sample pretreatment process combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe derivatization (ISD) followed by gas chromatography–electron capture detector (GC-ECD) analysis. A micro-syringe pre-filled with derivatizing agents and syringe needle connected to an extracting solvent impregnated hollow fiber segment was used as the LPME probe. Pyrethroid metabolites were extracted and enriched simultaneously from urine samples by HF-LPME sampling and acid hydrolysis at 70 °C for 10 min. After sampling, the ISD was performed by mixing the extracting solution and derivatizing agents through plunger movements, followed by GC-ECD analysis. Parameters influencing the HF-LPME efficiency and ISD were investigated and optimized. Under optimum conditions, the method provided enrichment factors of 69.8–154.6, repeatability from 5.0 to 12% (n = 5), and good linearity (R ² = 0.9980–0.9998) for interested analytes spiked in urine samples. The method detection limits ranged from 1.6 to 17 ng/mL. A comparison was performed between the proposed method and conventional methods. The proposed method was applied to analyze pyrethroid metabolites in the urine samples collected from workers of pesticide formulation plants. The results suggested that the proposed HF-LPME coupled ISD method was a rapid, simple, efficient, and eco-friendly technique in the biomonitoring of metabolites of pyrethroids in workers’ urine.     

A novel graphene nanosheets coated stainless steel fiber for microwave assisted headspace solid phase microextraction of organochlorine pesticides in aqueous samples followed by gas chromatography with electron capture detection

In this study, a novel graphene nanosheets (GNSs) coated solid phase microextraction (SPME) fiber was prepared by immobilizing microwave synthesized GNSs on a stainless steel wire. Microwave synthesized GNSs were verified by X-ray diffraction, field emission-scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). GNS-SPME fiber was characterized using FE-SEM and the results showed the GNS coating was homogeneous, porous, and highly adherent to the surface of the stainless steel fiber. The performance and feasibility of the GNS-SPME fiber was evaluated under one-step microwave assisted (MA) headspace (HS) SPME followed by gas chromatography with electron capture detection for five organochlorine pesticides (OCPs) in aqueous samples. Parameters influencing the extraction efficiency of MA-HS-GNS-SPME such as microwave irradiation power and time, pH, ionic strength, and desorption conditions were thoroughly examined. Under the optimized conditions, detection limits for the OCPs varied between 0.16 and 0.93 ng L(-1) and linear ranges varied between 1 and 1500 n gL(-1), with correlation coefficients ranging from 0.9984 to 0.9998, and RSDs in the range of 3.6-15.8% (n=5). In comparison with the commercial 100 μm polydimethylsiloxane fiber, the GNS coated fiber showed better extraction efficiency, higher mechanical and thermal stability (up to 290°C), longer life span (over 250 times), and lower production cost. The method was successfully applied to the analysis of real water samples with recoveries ranged between 80.1 and 101.1% for river water samples. The results demonstrated that the developed MA-HS-GNS-SPME method was a simple, rapid, efficient pretreatment and environmentally friendly procedure for the analysis of OCPs in aqueous samples.     

Partial sums and the radius problem for some class of conformal mappings

Let $|\frac{{s_n (z)}} {{f(z)}} - 1| $|\frac{{s_n (z)}} {{f(z)}} - 1| when f ∈ $\left| {f'(z)\left( {\frac{z} {{f(z)}}} \right)^2 - 1} \right| < 1$\left| {f'(z)\left( {\frac{z} {{f(z)}}} \right)^2 - 1} \right| < 1     

Coefficient inequalities for univalent starlike functions

Let A be the class of analytic functions in the unit disk $\mathbb{D}$ with the normalization f(0) = f′(0) ? 1 = 0. In this paper the authors discuss necessary and sufficient coefficient conditions for f ∈ A of the form $$\left( {\frac{z} {{f(z)}}} \right)^\mu = 1 + b_1 z + b_2 z^2 + \ldots$$ to be starlike in $\mathbb{D}$ and more generally, starlike of some order β, 0 ≤ β < 1. Here µ is a suitable complex number so that the right hand side expression is analytic in $\mathbb{D}$ and the power is chosen to be the principal power. A similar problem for the class of convex functions of order β is open.     

A first one-pot synthesis, isomerization and synthetic utility of mono- and bis Morita-Baylis-Hillman adducts of 1,1′-ferrocenedialdehyde

A one-pot synthesis of mono- and bis-Morita-Baylis-Hillman adducts of 1,1′-ferrocenedialdehyde has been achieved. These adducts undergo a facile and efficient stereoselective isomerization with a number of saturated, unsaturated, aromatic alcohols, phenols and thiophenol with a montmorillonite K10 clay catalyst to afford highly functionalized trisubstituted alkene derivatives of ferrocene. The synthetic utility of isomerized derivatives has been demonstrated by a ferrocene appended novel macrocycle synthesis, a ferrocenyl bis-triazole synthesis and an evaluation of the liquid crystalline property of a cholesterol derivative of ferrocene.     

Region of variability for close-to-convex functions-II

For a complex number α with let be the class of analytic functions f in the unit disk with f(0)=0 satisfying in , for some convex univalent function in . For any fixed , and we shall determine the region of variability V(z₀,α,λ) for f(z₀) when f ranges over the class

In the final section we graphically illustrate the region of variability for several sets of parameters z₀ and α.     

Uniformly locally univalent harmonic mappings

The primary aim of this paper is to characterize the uniformly locally univalent harmonic mappings in the unit disk. Then, we obtain sharp distortion, growth and covering theorems for one parameter family \({{\mathcal {B}}}_{H}(\lambda )\) of uniformly locally univalent harmonic mappings. Finally, we show that the subclass of k-quasiconformal harmonic mappings in \({{\mathcal {B}}}_{H}(\lambda )\) and the class \({{\mathcal {B}}}_{H}(\lambda )\) are contained in the Hardy space of a specific exponent depending on \(\lambda \), respectively, and we also discuss the growth of coefficients for harmonic mappings in \({{\mathcal {B}}}_{H}(\lambda )\).     

John disks,the Apollonian metric,and min-max properties

The main results of this paper are characterizations of John disks-the simply connected proper subdomains of the complex plane that satisfy a twisted double cone connectivity property. One of the characterizations of John disks is an analog of a result due to Gehring and Hag who found such a characterization for quasidisks. In both situations the geometric condition is an estimate for the domain’s hyperbolic metric in terms of its Apollonian metric. The other characterization is in terms of an arc min-max property.     

Integral transforms of functions with the derivative in a halfplane

LetA be the class of normalized analytic functions in the unit disk Δ and define the class

Mineralogical role on natural radioactivity content in the intertidal sands of Tamilnadu coast (HBRAs region), India

Activity concentration and mineralogical characterization in the intertidal sand samples of Tamilnadu coast, India have been analyzed. From the gamma spectral analysis, the average value of ²³⁸U, ²³²Th and ⁴⁰K in the intertidal sand samples are 12 ± 4, 59 ± 4 and 197 ± 26 Bq kg⁻¹ respectively. The average value of ²³²Th alone is slightly higher than the world average value. From XRD and FTIR analysis, monazite, zircon, ilmenite, magnetite, hematite, quartz, witherite, calcite, nacrite, microcline feldspar, orthoclase feldspar, gibbsite and organic carbon are identified. Of these minerals, monazite and microcline feldspar are the most associated with the presence of ²³²Th and ⁴⁰K respectively.