Fast HPLC Method for Determination of Fenoxycarb and Permethrin in Antiparasitic Veterinary Shampoo Using Fused-Core Column

A new and fast high-performance liquid chromatography (HPLC) method using technology of fused-core columns for separation of fenoxycarb and cis-, trans-permethrin has been developed and used for their determination in antiparasitic veterinary shampoo. Separation of insecticides and internal standard sudan II was achieved on the fused-core column Ascentis Express RP-Amide (100 × 3.0 mm), particle size 2.7 μm, with mobile phase acetonitrile/water (55:45, v/v) at a flow rate of 1.0 mL min^?1 and at temperature 60 °C. The detection wavelength of detector was set at 225 nm for both compounds and internal standard sudan II. Under the optimum chromatographic conditions standard calibration curves were measured with good linearity [r ² = 0.99991 for fenoxycarb, r ² = 0.99987 for trans-permethrin, and r ² = 0.99984 for cis-permethrin (n = 8)]. Commercial samples of antiparasitic veterinary shampoo were extracted with ethanol in ultrasound bath for 5 min. A 2-μL sample volume of the filtered solution was directly injected into the HPLC system. Accuracy of the method defined as a mean recovery of insecticides from shampoo matrix was in the range 100.43–103.85 % for both insecticides.     

Determination of cis-permethrin,trans-permethrin and associated metabolites in rat blood and organs by gas chromatography–ion trap mass spectrometry

An analytical method was developed to measure cis-permethrin and trans-permethrin in different biological rat matrices and fluids (whole blood, red blood cells, plasma, brain, liver, muscle, testes, kidneys, fat and faeces). The method was also suitable for the simultaneous quantification of their associated metabolites [cis-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis-DCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (trans-DCCA) and 3-phenoxybenzoic acid (3-PBA)] in blood (whole blood, red blood cells, plasma) and liver. The target analytes were derivatised in samples using a methanolic/hydrochloric acid solution and then extracted with toluene. The analysis was performed by gas chromatography, and detection using ion trap tandem mass spectrometry. The selectivity obtained for complex matrices such as rat organs allowed the use of a purification step to be avoided for most of the matrices investigated. In the case of fat, where permethrin is suspected to accumulate, a dedicated purification step was developed. In fluids, the limits of quantification were at the 50 ng/mL level for the parent compounds and 3-PBA and at 25 ng/mL for cis-DCCA and trans-DCCA. For solid matrices excluding fat, the limits of quantification ranged from 50 ng/g for muscle to 100 ng/g for brain and testes for both cis-permethrin and trans-permethrin. The extraction recoveries ranged primarily between 80 and 120 % for the matrix tested. The stability of blood samples was tested through the addition of 1 % v/v formic acid. The methods developed were applied in a toxicokinetic study in adult rats. cis-Permethrin and the metabolites were detected in all corresponding matrices, whereas trans-permethrin was detected only in blood, plasma and faeces.     

Light-induced cis/trans isomerization of cis-[Pd(L-S,O)2] and cis-[Pt(L-S,O)2] complexes of chelating N,N-dialkyl-N′-acylthioureas: key to the formation and isolation of trans isomers

Irradiation cis-[M(Lⁿ-S,O)₂] complexes (M = Pt^II, Pd^II) derived from N,N-dialkyl-N′-benzoylthioureas (HLⁿ) with various sources of intense visible polychromatic or monochromatic light with λ < 500 nm leads to light-induced cis?→?trans isomerization in organic solvents. In all cases, white light derived from several sources or monochromatic blue-violet laser 405 nm light, efficiently results in substantial amounts of the trans isomer appearing in solution, as shown by ¹H NMR and/or reversed-phase HPLC separation in dilute solutions at room temperature. The extent and relative rates of cis/trans isomerization induced by in situ laser light (λ = 405 nm) of cis-[Pd(L²-S,O)₂] was directly monitored by ¹H NMR and ¹⁹⁵Pt NMR spectroscopy of selected cis-[Pt(L-S,O)₂] compounds in chloroform-d; both with and without light irradiation allows the δ(¹⁹⁵Pt) chemical shifts cis/trans isomer pairs to be recorded. The cis/trans isomers appear to be in a photo-thermal equilibrium between the thermodynamically favored cis isomer and its trans counterpart. In the dark, the trans isomer reverts back to the cis complex in what is probably a thermal process. The light-induced cis/trans process is the key to preparing and isolating the rare trans complexes which cannot be prepared by conventional synthesis as confirmed by the first example of trans-[Pd(L-S,O)₂] characterized by single-crystal X-ray diffraction, deliberately prepared after photo-induced isomerization in acetonitrile solution.     

Development of a New Dynamic Headspace Liquid-Phase Microextraction Method

A new technique, namely dynamic headspace liquid-phase microextraction, has been developed for the extraction of 1,4-dioxane in cosmetic and hygiene samples followed by gas chromatography–flame ionization detection. In this method, the sample is mixed with acetone as a diluent solvent. Then, a few microliters of n-octanol are added into a home-made extraction vessel placed in the headspace of the sample. By heating, the target analyte is transferred to the headspace of the sample and then extracted into n-octanol. Under the optimized conditions, the method showed a good linearity in the range of 3.24–1000 μg kg⁻¹ with a coefficient of determination 0.998. Figures of merit such as enrichment factor of 375, extraction recovery of 94 %, limits of detection and quantification 0.97 and 3.24 μg kg⁻¹, respectively, and relative standard deviation 4.7 % (n = 6, C = 30 μg kg⁻¹) of the proposed method were satisfactory for determination of the target analyte. Finally, the method was successfully applied in determination of 1,4-dioxane in various cosmetic and hygiene samples including shampoo, toothpaste, lotion, washing liquid, and dishwashing liquid.

     

Pharmacokinetics and Tissue Distribution Study of Tryptanthrin in Rats by RP-HPLC with DAD Detector

A simple RP-LC-UV method was established for the determination of tryptanthrin in plasma and different tissues of rats. The separation was achieved by HPLC on a C₁₈ column with a mobile phases composed of acetonitrile–water (47:53, v/v), UV detection was used at 251 nm. Good linearity was found between 0.0183–1.1712 μg mL⁻¹ (r ² = 0.999) for plasma and 0.0937–1.7568 μg mL⁻¹ for the tissue samples, respectively (r ² ≥ 0.9932). The intra- and inter-day precisions expressed as the relative standard deviation for the method were 0.92–6.01 and 1.06–9.11 %, respectively. The relative recoveries of tryptanthrin ranged from 95.26 to 97.89 % for plasma and 82.55 to 114.99 % for tissue homogenates (except heart). The developed method was successfully applied to the pharmacokinetics and tissue distribution research after orally administration of a 56-mg kg⁻¹ dose of tryptanthrin to healthy SD rats. The main pharmacokinetics distribution results showed that liver, lung, small intestine, and large intestine were the major distribution tissues of tryptanthrin in rats, and that tryptanthrin had difficulty in crossing the blood–brain barrier.

     

Fast Analysis of Synthetic Pyrethroid Metabolites in Water Samples Using In-Syringe Derivatization Coupled Hollow Fiber Mediated Liquid Phase Microextraction with GC-ECD

A fast and efficient method has been demonstrated for the trace determination of six important metabolites of synthetic pyrethroids including cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis- and trans-Cl₂CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-Br₂CA), 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), 3-phenoxybenzoic acid (3-PBA), and 2-phenoxybenzoic acid (2-PBA) in environmental water samples using hollow fiber (HF)-mediated liquid-phase microextraction (LPME) coupled with in-syringe derivatization (ISD) followed by gas chromatography (GC) with electron capture detector (ECD) analysis. This method utilizes a HF membrane segment impregnated with extraction solvent as the LPME sampling probe, which was connected to a microsyringe pre-filled with derivatizing agents, and it was immersed into sample solution for extraction. After extraction, the extracting solution was subjected to derivatization reaction that was performed inside the syringe barrel followed by GC-ECD analysis. Under optimal conditions, the best extraction efficiency was obtained using sampling probe (2.0 cm hollow fiber) impregnated with 1-octanol immersed into water sample (5.0 mL, adjusted pH below 1.0) and stirring (1,250 rpm) for 10 min at 70 °C and diisopropylcarbodiimide (2 μL) and 1,1,1,3,3,3-hexafluoro-2-propanol (1 μL) were the derivatizing agents used. The detection limits of 3 ng mL^?1 for cis- and trans-Cl₂CA, 2 ng mL^?1 for cis-Br₂CA, 6 ng mL^?1 for 4-F-3-PBA, and 0.6 ng mL^?1 for 3-PBA and 2-PBA. The method showed good linearity (R ² = 0.973?0.998), repeatability from 4.0 to 13 % (n = 5), recovery from 79.2 to 95.7 %, and enrichment factors ranged between 109 and 159 for target analytes spiked in water samples. The proposed method and conventional methods were compared. Results suggested that the proposed HF-LPME-ISD/GC-ECD method was a rapid, simple, inexpensive, and eco-friendly technique for the analysis of metabolites of pyrethroids.     

Two Minute Separation of the cis- and trans-Isomers of Vitamin K1 without Heptane, Chlorinated Solvents, or Acetonitrile

Resolution of the cis-, trans-isomers of vitamin K₁ (phylloquinone) is important in nutritional analysis since only the trans-isomer is biologically active, while artificial vitamin K₁ may contain significant amounts of the inactive cis-isomer. The cis-, trans-isomers of vitamin K₁ were separated, with a resolution of 3.4, using pure carbon dioxide (CO₂) as the mobile phase, with a run time ≈6 min, on a 4.6 × 150 mm, 3.5 μm RX-Sil bare silica column, using supercritical fluid chromatography (SFC). With 2.5 % ethyl acetate in CO₂, R_s = 2.77, with a run time <4 min. On a 3 × 100 mm, 1.8 μm RX-Sil column R_s remained at 2.69, with a run time just over 2 min. This is the first report on the apparent separation of these isomers by SFC, and is up to 3–5 times faster than separations using high performance liquid chromatography (HPLC) in the literature. Unlike most HPLC separations, no dichloromethane, acetonitrile, or hexane/heptane was used. The CO₂ was beverage grade, at 1/20th to 1/50th the cost of the replaced organics, is recycled, and is considered “green”.     

Reactions of platinum complexes with 4,7-phenanthroline: crystal structures of mono- and binuclear platinum(II) complexes containing 4,7-phenanthroline

The reaction of a mixture of cis and trans-[PtCl₂(SMe₂)₂] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl₂(SMe₂)(4,7-phen)] (1) and trans-[Pt₂Cl₄(SMe₂)₂(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, ¹H, ¹³C{¹H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr₂(SMe₂)₂] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr₂(SMe₂)(4,7-phen)] (3) and trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)].C₆H₆ reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr₂(SMe₂) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products.     

Determination of Bromate in Bottled Drinking Water from Saudi Arabian Markets by HPLC/ICP-MS

The determination of bromate BrO₃ ^? in 50 different bottled drinking water samples collected from Saudi Arabian markets has been investigated using liquid chromatography inductively coupled plasma mass spectrometry (HPLC/ICP-MS). For analysis, samples were injected directly without any further pretreatment or dilution, using only a 50 μL injection volume. The method showed: detection limit of 0.5 μg/L, limit of quantification of 1.0 μg/L, 1.0 ? 200.0 μg/L linearity range (r² = 0.9998), relative standard deviation (%RSD) for reproducibility (inter-day precision) values of 14% and 4% for low and high concentration levels (10,100 μg/L), respectively. The results obtained for bromate showed that 30% of the samples are acceptable as US EPA standards (10 μg/L), 40% of the samples are acceptable as Gulf (Saudi Arabia) standards (25 μg/L), and almost 60% of the samples exceed the allowable limits for bromate in bottled drinking water.     

HPLC column-switching technique for sample preparation and fluorescence determination of propranolol in urine using fused-core columns in both dimensions

A new and fast high-performance liquid chromatography (HPLC) column-switching method using fused-core columns in both dimensions for sample preconcentration and determination of propranolol in human urine has been developed. On-line sample pretreatment and propranolol preconcentration were performed on an Ascentis Express RP-C-18 guard column (5?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water (5:95, v/v) at a flow rate of 2.0 mL min^?1 and at a temperature of 50 °C. Valve switch from pretreatment column to analytical column was set at 4.0 min in a back-flush mode. Separation of propranolol from other endogenous urine compounds was achieved on the fused-core column Ascentis Express RP-Amide (100?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water solution of 0.5 % triethylamine, pH adjusted to 4.5 by means of glacial acetic acid (25:75, v/v), at a flow rate of 1.0 mL min^?1 and at a temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 229/338 nm. A volume of 1,500 μL of filtered urine sample solution was injected directly into the column-switching HPLC system. The total analysis time including on-line sample pretreatment was less than 8 min. The experimentally determined limit of detection of the method was found to be 0.015 ng mL^?1.

Volatile Pd–Pb and Cu–Pb heterometallic complexes: structure,properties, and trans-to-cis isomerization under cocrystallization of Pd and Cu β-diketonates with Pb hexafluoroacetylacetonate

Preparation of volatile heterometallic precursors is a significant step on the way to advanced multicomponent materials. Study of molecular transformations in solution upon precursor synthesis is of importance to optimize the preparation of the stable solid product of desired composition. Two new volatile heterobimetallic complexes, cis-PdL₂*Pb(hfa)₂ and cis-CuL₂*Pb(hfa)₂, were obtained (L = 2-methoxy-2,6,6-trimethylheptane-3,5-dionate, hfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) under cocrystallization of trans-bis-beta-diketonates of Pd(II) and Cu(II) with Pb(hfa)₂ from organic solvents. Crystals of these compounds are built of discrete bimetallic molecules where transition metal complex isomerized from trans-to-cis form. Complexation followed by isomerization was studied by solution NMR. The bimetallic molecular species were formed early in solution. Enthalpy and activation energy of isomerization were estimated to be 49 and 93 kJ mol^?1, respectively. A new synthesis technique of Pd(II) beta-diketonates which is distinguished by simplicity and selectivity as well as the crystal structure of trans-PdL₂ is described. Volatility of all obtained compounds was confirmed by thermogravimetric analysis and fractional sublimation in vacuum; Pd-containing heterobimetallic complex appeared to be more volatile than both the initial monometallic complexes and Cu-containing complex.     

Generic Automated Fluorimetric Assay for the Quality Control of Gamma Aminobutyric Acid-Analogue Anti-Epileptic Drugs Using Sequential Injection

The first sequential injection assay for the generic determination of gabapentin and pregabalin is reported. The analytes react with o-phthalaldehyde in the presence of N-acetylcysteine as a nucleophilic reagent in alkaline medium under flow conditions to form highly fluorescent derivatives. The effect of the main instrumental and chemical variables on the assay was examined. The proposed method was validated for both analytes in terms of linearity, detection, and quantitation limits (c _L  = 160 μg L^?1, c _Q  = 480 μg L^?1 for gabapentin, and c _L  = 70 μg L^?1, c _Q  = 210 μg L^?1 for pregabalin), precision (s _r  < 1.0% in both cases), selectivity, and accuracy. The applicability of the assay was demonstrated by successfully analyzing commercially available formulations. The experimental percent recoveries were in the range of 97.9–102.0% for gabapentin and 98.3–102.3% for pregabalin.     

NMR and kinetic studies of the interactions of [Au(cis-DACH)Cl2]Cl and [Au(cis-DACH)2]Cl3 with potassium cyanide in aqueous solution

The interactions of [Au(cis-DACH)Cl₂]Cl and [Au(cis-DACH)₂]Cl₃ [where cis-DACH is cis-1,2-diaminocyclohexane] with enriched KCN were carried out in CD₃OD and D₂O, respectively. The reaction pathways of these complexes were studied by ¹H, ¹³C, ¹⁵N NMR, UV spectrophotometry, and electrochemistry. The kinetic data for the reaction of cyanide with [Au(cis-DACH)₂]Cl₃ are k = 18 M^?1s^?1, ?H^≠ = 11 kJ M^?1, ?S^≠ = ?185 JK^?1 M^?1, and E_a = 13 kJ M^?1 with square wave voltammetric (SWV) peak +1.35 V, whereas the kinetic data for the reaction of cyanide ion with [Au(cis-DACH)Cl₂]Cl are k = 148 M^?1s^?1, ?H^≠ = 39 kJM^?1, ?S^≠ = ?80 JK^-1 M^?1, and E_a = 42 kJM^?1 along with SWV peak +0.82 V, indicating much higher reactivity of [Au(cis-DACH)Cl₂]Cl toward cyanide than [Au(cis-DACH)₂]Cl₃. The interaction of these complexes with potassium cyanide resulted in an unstable [Au(¹³CN)₄]^? species which readily underwent reductive elimination reaction to generate [Au(¹³CN)₂]^? and cyanogen.     

A new phenylimidorhenium(V) compound containing the 2-[(2-hydroxyethylimino)methyl]phenol Schiff-base ligand: experimental and theoretical aspects

Reaction of equimolar trans-[Re(NPh)(PPh₃)₂Cl₃] with H₂L, a 1?:?1 Schiff-base condensate of salicylaldehyde and ethanolamine, in chloroform gives trans-[Re(NPh)(HL)(PPh₃)Cl₂] (1a) in good yield. 1a has been characterized by C, H, and N microanalyses, FTIR and UV–vis spectra. The X-ray crystal structure of 1a reveals that it is an octahedral trans-Cl,Cl phenylimidorhenium(V) complex. The rhenium center has an ‘N₂OCl₂P’ coordination sphere. 1a crystallizes in the monoclinic space group P2₁/c with a = 11.2391(5), b = 16.4848(7), c = 16.3761(8) Å, V = 3034.0(2) ų and Z = 4. The electrochemical aspects of 1a have been studied. Electrochemical studies of 1a in dichloromethane show a quasi-reversible Re(V) to Re(VI) oxidation at 1.128 V versus Ag/AgCl. This redox potential reasonably matches the calculated redox potential, 1.186 V versus Ag/AgCl. Geometry optimization of the trans-Cl,Cl 1a vis-à-vis its cis analog, cis-Cl,Cl 1b, have been performed at the level of density functional theory (DFT). It is revealed that 1a is more stable than 1b by 21.6 kcal per mole of energy in the gas phase.     

Comparison of HPLC Versus HPTLC-Densitometry for the Quantification of Chromone Glucosides in Saposhnikoviae divaricatae Radix

A HPLC and a HPTLC-densitometric method were developed for the quantification of prim-O-glucosylcimifugin and 4′-O-β-d-glucosyl-5-O-methylvisamminol the major chromone glucosides in the roots of Saposhnikovia divaricata. The validation of both methods resulted in comparable parameters regarding stability, specificity, linearity, robustness, precision and recovery, whereas complementary advantages were obtained concerning LOD and LOQ. The HPTLC-based densitometry revealed a lower LOD (1.11 versus 4.37 μg mL⁻¹ in HPLC) and LOQ (3.36 versus 13.24 μg mL⁻¹ in HPLC) for prim-O-glucosylcimifugin, whereas the HPLC resulted in a lower LOD (1.00 versus 4.10 μg mL⁻¹ in HPTLC-densitometry) and LOQ (3.04 versus 12.46 μg mL⁻¹ in HPTLC-densitometry) for 4′-O-β-d-glucosyl-5-O-methylvisamminol. Both methods revealed nearly matching contents of the chromones after analysis of different commercially available batches of Saposhnikoviae divaricatae radix with a total content for both chromone glycosides in the range from 0.31 ± 0.011 to 0.56 ± 0.021 % determined by HPLC and between 0.34 ± 0.011 and 0.61 ± 0.009 % determined by HPTLC. The plant material cultivated in Germany showed a very similar content and ratio of both chromone glucosides in comparison to the standard batches originating from China.

     

Development and Validation of an HPLC–UV Method for the Determination of Insulin in Rat Plasma: Application to Pharmacokinetic Study

A simple, sensitive high performance liquid chromatographic method with UV detection was developed and validated for determination of insulin in rat plasma, using methyl paraben as an internal standard. Insulin was extracted from plasma by a liquid–liquid extraction with a mixture of dichloromethane and n-hexane (1:1, v/v) followed by an acidic back extraction. Chromatographic separation was achieved isocratically with a Phenomenex® C₁₈ analytical column (150 × 4.6 mm ID, 5 μm) at ambient room temperature. The calibration curves were linear within a concentration range of 0.7–8.4 μg mL^?1 (r ² = 0.9994). The inter-day and intra-day accuracy and precision were ≤3.33 and ≤5.55%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.35 and 0.7 μg mL^?1. The average recovery was 87.86% for insulin and 83.52% for methyl paraben. Insulin containing plasma samples were stable at ?20 °C for 7 days. Validated HPLC method was successfully applied to a pharmacokinetic study of insulin in streptozotocin induced diabetic rats.     

Antimicrobial and antiparasitic activities of three algae from the northwest coast of Algeria

The objective of this study was to investigate the biological activities of Algerian algae, Sargassum vulgare, Cladostephus hirsutus and Rissoella verruculosa. Antimicrobial activity of the crude extracts and their fractions was assessed using the disc diffusion assay, the minimum inhibitory concentration and the minimum bactericidal concentration. Antiparasitic activity was studied in vitro against the blood stream forms of Trypanosoma brucei brucei and the intraerythrocytic stages of Plasmodium falciparum. Ethyl acetate (EA) fractions of the three tested algae showed more potent antimicrobial activity against S. aureus (7–14.5 mm) and B. cereus (7–10.75 mm), MIC values ranged from 0.9375 to 7.5 mg mL^?1 and MBC values > 15 mg mL^?1. Concerning the antiparasitic activity, EA factions of S. vulgare (IC₅₀ = 9.3 μg mL^?1) and R. verruculosa (IC₅₀ = 11.0 μg mL^?1) were found to be more effective against T. brucei brucei, whereas the three EA fractions were little active against P. falciparum.     

Lanthanide-Organic Frameworks with Flexible Triacid Ligand: Structural Variation Under Different Reaction Conditions

Three metal-organic frameworks (MOFs) [La(bta)(H₂O)]_n (1), [La(bta)(H₂O)₂·H₂O]_n (2) and [Er(bta)(H₂O)₂·H₂O]_n (3) with different structures were synthesized by reactions of 1,3,5-benzenetriacetic acid (H₃bta) with the corresponding lanthanide salts under different conditions. X-ray diffraction analyses reveal that complexes 1 and 2 have the same metal atom and ligand but different structures. In 1, each bta^3 ?  adopts cis, cis, cis conformation and acts as a μ₆-bridge linking six lanthanum atoms to form a 2D framework; while in 2, the bta^3 ?  has cis, trans, trans conformation and serves as a μ₅-bridging ligand, which results in a 3D channel-like structure. In the case of 3, each bta^3 ?  also adopts cis, trans, trans conformation but acts as a μ₄-bridge linking four erbium atoms to form a 3D channel-like framework. The results imply that the reaction conditions have great impact on the structure of MOFs, and the flexible triacid ligand H₃bta is versatile and can adopt different conformations in the formation of MOFs. The magnetic property of complex 3 was investigated in the temperature range of 1.8–300 K.     

Development of dynamic headspace-liquid phase microextraction method performed in a home-made extraction vessel for extraction and preconcentration of 1,4-dioxane from shampoo

In the present study, a new, simple, rapid, and environmentally friendly headspace-liquid phase microextraction method followed by gas chromatography–flame ionization detection has been developed for the extraction/preconcentration and determination of 1,4-dioxane from shampoo. The developed procedure is performed in a home-made extraction vessel, connected to a glass vial containing sample and extraction solvent. In this method, an aliquot weight of shampoo is mixed with a binary mixture of n-hexane and dichloromethane (50:50, v/v) as the extractant and the target analyte is extracted during a liquid–liquid extraction procedure. Then a home-made extraction vessel containing a few microliters of a collection/extraction solvent is contacted to a glass vial containing the organic phase obtained from the previous step. By heating 1,4-dioxane is vaporized and enriched in a μL volume of the collection/extraction solvent. Then an aliquot volume of the collected phase is injected into the separation system. The effect of several factors which may influence performance of the method, including kind and volume of the extraction solvents used in both steps, extraction temperature, extraction time, and salt addition were evaluated. Under the optimum extraction conditions, limits of detection and quantification for the target analyte were obtained 0.52 and 1.73 μg kg^?1, respectively. Enrichment factor and extraction recovery were 333 and 89 %, respectively. The method precision was evaluated at a concentration of 25 μg kg^?1 and relative standard deviation was less than 6.9 % for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method has been successfully applied in analysis of 1,4-dioxane in different shampoo samples.     

Validated LC Method for Simultaneous Analysis of Tramadol Hydrochloride and Aceclofenac in a Commercial Tablet

This paper describes development and validation of a high-performance liquid chromatographic method for simultaneous analysis of tramadol hydrochloride (TR) and aceclofenac (AC) in a tablet formulation. When the combination formulation was subjected to ICH-recommended stress conditions, adequate separation of TR, AC, and the degradation products formed was achieved on a C₁₈ column with 65:35 (v/v) 0.01 M ammonium acetate buffer, pH 6.5—acetonitrile as mobile phase at a flow rate of 1 mL min⁻¹. UV detection was performed at 270 nm. The method was validated for specificity, linearity, LOD and LOQ, precision, accuracy, and robustness. The method was specific against placebo interference and also during forced degradation. The linearity of the method was investigated in the concentration ranges 15–60 μg mL⁻¹ (r = 0.9999) for TR and 40–160 μg mL⁻¹ (r = 0.9999) for AC. Accuracy was between 98.87 and 99.32% for TR and between 98.81 and 99.49% for AC. Because degradation products were well separated from the parent compounds, the method was stability-indicating.