Ionic liquid promoted synthesis of bis(indolyl) methanes

1-benzyl-3-methyl imidazolium hydrogen sulphate [bnmim][HSO₄] was found to be an effective catalyst for the condensation reaction of indoles and derivatives with benzaldehydes in microwave irradiation with lower reaction time and higher yields to give bis(indolyl) methanes.      

Properties of naproxen ion-selective electrodes

Naproxen membrane electrodes based on different plasticizers and the quaternary ammonium salts (QASs) dimethyldidecylammonium bromide, methyltrioctylammonium chloride, or tetraoctylammonium chloride, were prepared. The following basic parameters were investigated for the optimal electrode: measurement range (10⁻⁴ − 10⁻¹ mol L⁻¹), slope of the linear range of the calibration curve (−58.3 mV decade⁻¹), limit of detection (6.0 × 10⁻⁵ mol L⁻¹), lifetime (2.5 months), dependence of the electrode potential on pH (5.5 − 9.0), reproducibility of potential (1.2 mV) and selectivity coefficients in relation to selected organic and inorganic anions. The electrode was utilized for determination of naproxen in tablets by the calibration curve method and the standard addition method.      

Determination of penicillin V potassium in pharmaceuticals and spiked human urine by chemiluminescence

A simple and selective method for penicillin V potassium (PVK) determination by chemiluminescence (CL) was developed. Oxidation of PVK by alkaline hydrogen peroxide produces CL, which is greatly enhanced by N, N-dimethyl formamide (DMF) and N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). Optimum conditions were established using luminometry. There is a linear relationship between the chemiluminescent peak height and the amount of PVK within the range 0.5–129.5 mg L⁻¹, with a detection limit of 0.2 mg L⁻¹. The coefficient of variation was 1.2% for 40 mg L⁻¹ PVK solution (n = 7). The method is very simple, has high sensitivity and good selectivity, and is usable for process control. It was successfully utilized for the determination of PVK in pharmaceuticals and spiked human urine.      

Removal of Pb and Cd from aqueous media and fish liver using novel polyurethane foam functionalized with pyrazolone as a new metal ion collector

In the present paper, an off-line preconcentration procedure for the determination of cadmium and lead by flame atomic absorption spectrometry (FAAS) is proposed. Polyurethane foam (PUF) functionalized with o-aminophenol (o-AP) followed by Pyrazolone (Pyr) packed in a minicolumn was used as a sorbent material. The metals were retained on the modified PUF, from which it could be eluted and effectively preconcentrated. The detection limits were 0.072 and 0.016 μg L⁻¹ for Pb and Cd respectively. Enrichment factors were 250 and 319 for lead and cadmium respectively. The procedure has been applied successfully to metal determination in water samples, fish liver and reference material.      

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

Spatial trends of petroleum hydrocarbons in water and sediments

Seasonal changes in petroleum hydrocarbons in water and streambed sediment from selected oil-related areas of Ondo State, Nigeria have been examined using gravimetric and infrared methods. The highest and lowest total petroleum hydrocarbon concentrations (TPH) in water (sediments in brackets) gravimetrically were 3.49 mg L⁻¹ (199.3) mg kg⁻¹ and 0.003 mg L⁻¹ (81.0) mg kg⁻¹ while the concentrations found by IR were 24.0 mg L⁻¹ (135.0 mg kg⁻¹) and 14.0 mg L⁻¹ (33.0 mg kg⁻¹) respectively. The two seasons were positively correlated (α = 0.01) by both methods. The TPH level was well correlated with the sediment organic carbon (OC) during both seasons. The characteristic carbonyl (C=O) vibrations at 1650 cm⁻¹ and 1700 cm⁻¹ indicate oxidation of the oil residue. The study recommends further investigation into the type of organics present to evaluate their toxicity and appropriate remediation.      

Proposal for a mercury isolation procedure using cold vapor method in combination with voltammetric determination using a rotating gold electrode

The optimal process of pre-treatment and activation of gold rotating disc electrode (AuRDE) before voltammetric determination of mercury is proposed. This treatment encompasses polishing of the electrode surface, electrochemical cycling, and activation. This procedure both increases determination sensitivity as well as improves determination reproducibility. The detection limit on the working electrode achieved using this approach amounted to 8.26·10⁻¹⁰ mol L⁻¹for direct mercury determination in water solution (applying 200 s running accumulation). The procedure of the quantitative mercury isolation from complicated sample matrix was developed as well. It provides better selectivity and significant increase of sensitivity of mercury determination. In case of mercury isolation from one liter of water the detection limit is 6.23·10⁻¹¹ mol L⁻¹ (analyzing a greater sample volume the determined concentration could be lower).      

Estimation of platinum in environmental water samples with solid phase extraction technique using inductively coupled plasma mass spectrometry

A solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectromA solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectrometry (ICP-MS) was developed. The method was based on retention of platinum in a sample on silica gel modified with aminepropyl groups. The retention of platinum(IV) from the sample solution and the recovery of platinum with 1.0 mol L⁻¹ thiourea solution were quantitative. The relative standard deviation (RSD) was calculated as 5% (n = 7) at the 10 ng L⁻¹ level. The enrichment factor was found to be (50-fold) for 250 mL of water sample. Under optimum conditions, the method detection limit (MDL) was found to be 1 ng L⁻¹ for platinum in water matrices. Recoveries of Pt from spike addition to atmospheric water samples were quantitative (80–95%). The present method was used for the determination of platinum in precipitation, throughfall and runoff water samples.      

Ionic liquid promoted Diels-Alder Reaction between anthrone and maleimides

Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]⁺[Cl]⁻, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.      

Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L⁻¹) and low detection limit (0.03 μg L⁻¹), which makes it suitable for determination of PCP in water samples.      

Influence of EDTA,carboxylic acids,amino- and hydroxocarboxylic acids and monosaccharides on the generation of arsines in hydride generation atomic absorption spectrometry

The influence of EDTA, carboxylic acids, amino-and hydroxocarboxylic acids, monosaccharides and humic substances on the generation of arsines in hydride generation atomic absorption spectrometry (HGAAS) was investigated. EDTA (0.02 mol L⁻¹), ascorbic acid (0.02 mol L⁻¹) and glucose or fructose (0.2 mol L⁻¹) are useful additives for levelling sensitivities for As(III), monomethylarsonate (MMA) and dimethylarsinate (DMA). The presence of glycine, malonic, tartaric acids, BICIN and soil humin extracts leads to differences in analytical signal response between these arsenic species. An analytical application to the determination of the sum of As(III), monomethylarsonate (MMA) and dimethylarsinate (DMA) as well as the sum of toxicologically relevant hydride forming arsenic fraction As(III) + As(V) + MMA + DMA in EDTA soil/sediment extracts using continuous flow HGAAS was demonstrated. The limit of detection was 0.2 mg kg⁻¹ As. Within-day and between-day precision were in the range 3–7% and 4–10%, respectively, for arsenic contents of 0.7–25 mg kg⁻¹, with recoveries 95–103%.      

Preliminary results of a quick,simple method of detecting antimony in water samples

Preliminary results of development of a direct and fast method of determination of antimony in samples of tap water using GFAAS are presented. The found levels of antimony were lower than permitted for human consumption. A mixture of Pd and Mg(NO₃)₂ (concentrations in the injected solution: 8.6 μg mL⁻¹ and 5.8 μg mL⁻¹ respectively) was used as the chemical modifier. The pyrolysis and atomization temperatures were 1000 and 1700°C, respectively and the mean analytical recovery 98.2%.      

Indirect determination of lutetium by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode

Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA. Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically, resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL⁻¹ lutetium could be detected after a 2 min deposition.      

Hollow fibre liquid phase microextraction of parabens

A hollow fibre liquid phase microextraction for gas chromatographic determination of some p-hydroxybenzoic acid esters has been developed. Chlorobenzene containing tetradecane as internal standard was used for the extraction. Optimized extraction was carried out at room temperature for 40 min in the presence of 0.4 g mL⁻¹ NaCl in the sample solution. Calibration was linear up to 30 mg L⁻¹. Correlation coefficients were 0.996–0.998. Enrichment factors were 21, 95 and 154, and detection limits were 0.20, 0.03 and 0.01 μg mL⁻¹ for methylparaben, ethylparaben and propylparaben, respectively. Reproducibility was acceptable with relative standard deviations up to 11.7%. The technique was tested for water and urine analysis.      

Use of an immiscible diluent in ionic liquid / ion pair LC for the assay of an injectable analgesic

Injectable solutions used in treatment of intense pain are based on combinations of active ingredients such as metamizole sodium (MTZ), pitofenone hydrochloride (PTF) and fenpiverine bromide (FPB). The simultaneous chromatographic assay of such combinations poses difficulties due to their structural variety, highly polar character, and wide concentration ranges (500 mg mL⁻¹ for MTZ, 2 mg mL⁻¹ for PTF and 0.02 mg mL⁻¹ for FPB). Fast hydrolysis of MTZ on aqueous dilution causes additional problems due to impurity (MTC) formation. Sodium hexane sulphonate (10 mM) was used as ion pairing agent for PTF, FPB and MTC in a mobile phase consisting of 48/52 (v/v) methanol and aqueous 0.2% triethylamine at pH=3. The ionic liquid 1-butyl-1-methyl-pyrrolidinium tetrafluoroborate (10 mM) was used as mobile phase additive to preserve the MTZ peak symmetry. The minor active ingredient FPB was selectively extracted into 1-octanol by ion pair formation with picric acid. A 20 μL aliquot of the organic layer was directly injected into the column.      

Determination of diclofenac in pharmaceuticals and urine samples using a membrane sensor based on the ion associate of diclofenac with Rhodamine B

The potentiometric response characteristics of a diclofenac selective electrode, based on ion association in different plasticizers, were compared. The sensitivity, working range, detection limit and selectivity of membrane sensors demonstrated significant dependence on the type of plasticizers. The potentiometric unit presented a linear response toward diclofenac concentrations between 1 × 10⁻⁵ − 5 × 10⁻² mol L⁻¹, with slopes of approximately 60 mV dec⁻¹, and exhibited a response time of 3 s. The potentiometric analysis of sodium diclofenac in pharmaceutical formulations was perfomed by the membrane electrode proposed and compared with the results of potentiometric titration given by the Pharmacopoeia of Ukraine.      

Preparation and utilization of a molecularly imprinted polymer for solid phase extraction of tramadol

In this paper, a highly selective molecularly imprinted polymer (MIP) for tramadol hydrochloride, a drug used to treat moderate to severe pain, was prepared and its use as solid-phase extraction (SPE) sorbent was demonstrated. The molecularly imprinted solid-phase extraction procedure followed by high performance liquid chromatography with ultraviolet detector (MISPE-HPLC) was developed for selective extraction and determination of tramadol in human plasma and urine. The optimal conditions for molecularly imprinted solid-phase extraction (MISPE) consisted of conditioning with 1 mL methanol and 1 mL of deionized water at neutral pH, loading of tramadol sample (50 μg L⁻¹) at pH 7.5, washing using 1 mL acetone and elution with 3 × 1 mL of 10% (v/v) acetic acid in methanol. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of tramadol. Results from the HPLC analyses showed that the calibration curve of tramadol (using MIP from human plasma and urine) is linear in the ranges of 6–100 and 3–120 μg L⁻¹ with good precisions (1.9% and 2.9% for 5.0 μg L⁻¹), respectively. The recoveries for plasma and urine samples were higher than 81%.      

Cloud point extraction-preconcentration and flame atomic absorption spectrometric determination of low levels of zinc in water and blood serum samples

A simple, sensitive and selective flotation method is described for the preconcentration and atomic absorption spectrometric determination of zinc ion in water and blood samples. At a solution pH of 5.2, 4-(2-pyridylazo-resorcinol) and Triton X-114 were used as hydrophobic ligand and non-ionic surfactant, respectively. The chemical variables affecting the preconcentration process were optimized. Under the optimized experimental conditions, the selective preconcentration and determination of as low zinc concentration as 6.5 μg L⁻¹ can be made. The proposed method was successfully applied to the preconcentration and low-level determination of zinc in different water and blood serum samples.      

Solid-state linear polarized IR-spectroscopy of croconic and rhodizonic acids

The applications of linear-polarized IR-spectroscopy to oriented colloid suspensions in a nematic host are demonstrated with croconic and rhodizonic acids. The experimental IR vibrational assignments of the solid-state of both neutral compounds are presented. Assignments are supported by theoretical quantum chemical calculations and vibrational analysis at the DFT level of theoretical approximation with the 6-311++G^** basis set.      

Properties of ibuprofen ion-selective electrodes based on the ion pair complex of tetraoctylammonium cation

Ibuprofen membrane electrodes based on different plasticizers: diisobutyl phthalate (DIBP), o-nitrophenyloctyl ether (o-NPOE), dioctyl sebacate (DOS) and tetraoctylammonium 2-(4-isobutylphenyl)propionate were prepared. All electrodes show: a near Nernstian slope of characteristic (58.3–60.9 mV decade⁻¹) in the measurement range (10⁻⁴–10⁻¹ mol L⁻¹), limit of detection (5.0×10⁻⁵ mol L⁻¹), really long lifetime (12 months), dependence of the electrode potential on pH (5.5–9.0), reproducibility of potential (0.6–1.2 mV) and selectivity coefficients in relation to some organic and inorganic anions. The electrodes were applied for the determination of ibuprofen in tablets by the calibration curve method and the standard addition method.