Development of a dispersive liquid-liquid microextraction method for spectrophotometric determination of barbituric acid in pharmaceutical formulation and biological samples

In this paper, a novel and simple method for the determination of trace amounts of barbituric acid in water and biological samples was developed by using dispersive liquid–liquid microextraction (DLLME) techniques combined with spectrophotometric analysis. The procedure is based on color reaction of barbituric acid with p-dimethylaminobenzaldehyde and extraction of the color product using the DLLME technique. Some important parameters such as reaction conditions and the type and volume of extraction and dispersive solvents as well as the extraction time were investigated and optimized in detail. Under the optimum conditions, the calibration graphs were linear over the range of 5.0 to 200 ng ml⁻¹ with limit of detection of 2.0 ng ml⁻¹. Relative standard deviation for five replicate determinations of barbituric acid at 50 ng ml⁻¹ concentration level was calculated to be 1.64%. Average recoveries for spiked samples were determined to be between 94% and 105%. The proposed method was applied for the determination of barbituric acid in pharmaceutical formulation and biological samples.     

Rapid determination of trace thiabendazole in apple juice utilizing dispersive liquid–liquid microextraction combined with fluorescence spectrophotometry

Food safety has become a large concern and prompts an urgent need for the development of rapid, simple and sensitive analytical methods that can monitor pesticide residues in foods. This study aimed to provide a method for quantitative determination of trace thiabendazole in apple juice. Due to its high sensitivity and selectivity, fluorescence spectrophotometry was utilized as a front end to dispersive liquid–liquid microextraction (DLLME). The experimental parameters that influenced the extraction were systematically investigated. Under optimum conditions, the whole procedure, including DLLME and analysis of one sample, was carried out within 5 min, and linearity was found in the 5–50 µg/L range with a correlation coefficient (r) of 0.9987. The limit of detection value was 2.2 µg/L. Good reproducibility was achieved based with a less than 4.5% relative standard deviation (RSD) for five replicates at different sample concentrations. This method was shown to be suitable for rapid and sensitive quantification of thiabendazole in apple juice. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of cobalt in water samples using solidified floating organic drop microextraction coupled with graphite furnace atomic absorption spectrometry

Abstract

A simple, rapid and inexpensive method of the solidified floating organic drop extraction (SFODME) technique coupled with graphite furnace atomic absorption spectrometry (GFAAS) has been developed for the determination of cobalt in water samples. 8-Hydroxyquinoline was used as a complex agent and 1-undecanol was used as the extraction solvent. The factors, including solvent types, solution pH, extractant volume and interfering ions, were investigated and optimised. Under the optimum conditions, the calibration graphs were linear in the range 0.05–10.0 ng mL^-1 cobalt, the limit of detection was 0.02 ng mL^-1, the limit of quantification was 0.05 ng mL^-1 and the relative standard deviation for 10 replicate measurements of 3 ng mL^-1 cobalt was 2.8%. The proposed method was successfully applied for the determination of cobalt in different water samples and the results were satisfactory.     

Use of cloud-point preconcentration for spectrophotometric determination of trace amounts of antimony in biological and environmental samples

This work presents a cloud-point extraction process using the micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological and environmental samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and 3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 4.5. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal reaction conditions and extraction were studied, and the analytical characteristics of the method (e.g., limits of detection and quantification, linear range, preconcentration, improvement factors) were obtained. Linearity for Sb(III) was obeyed in the range of 0.2–20 ng ml⁻¹. The detection and quantification limits for the determination of Sb(III) were 0.055 and 0.185 ng ml⁻¹, respectively. The method has a lower detection limit and wider linear range, inexpensive instrument, and low cost, and is more sensitive compared with most other methods. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma, urine, biological, and water samples.     

Cloud point extraction-flame atomic absorption spectrometry for pre-concentration and determination of trace amounts of silver ions in water samples

A cloud point extraction (CPE) method was used as a pre-concentration strategy prior to the determination of trace levels of silver in water by flame atomic absorption spectrometry (FAAS) The pre-concentration is based on the clouding phenomena of non-ionic surfactant, triton X-114, with Ag (I)/diethyldithiocarbamate (DDTC) complexes in which the latter is soluble in a micellar phase composed by the former. When the temperature increases above its cloud point, the Ag (I)/DDTC complexes are extracted into the surfactant-rich phase. The factors affecting the extraction efficiency including pH of the aqueous solution, concentration of the DDTC, amount of the surfactant, incubation temperature and time were investigated and optimized. Under the optimal experimental conditions, no interference was observed for the determination of 100 ng·mL⁻¹ Ag⁺ in the presence of various cations below their maximum concentrations allowed in this method, for instance, 50 μg·mL⁻¹ for both Zn²⁺ and Cu²⁺, 80 μg·mL⁻¹ for Pb²⁺, 1000 μg·mL⁻¹ for Mn²⁺, and 100 μg·mL⁻¹ for both Cd²⁺ and Ni²⁺. The calibration curve was linear in the range of 1–500 ng·mL⁻¹ with a limit of detection (LOD) at 0.3 ng·mL⁻¹. The developed method was successfully applied for the determination of trace levels of silver in water samples such as river water and tap water.     

Urinary excretion of lead and δ-aminolevulinic acid in workers occupationally exposed to tetraethyl lead

Forty-nine refinery workers and 50 motor mechanics were selected and examined for total lead (PbT), inorganic lead (PbI), and δ-aminolevulinic acid (ALA) in urine. The worker groups were exposed to tetraethyl lead (TEL) mainly by inhalation, but motor mechanics received additional exposure by skin because of hand cleansing with gasoline. The levels of urinary ALA (ALA-U) and urinary PbT (PbT-U) in refinery workers and motor mechanics were found to be significantly higher than the control group (p<0.05). The correlation between the ALA-U and PbT-U was found significant in both worker groups (p<0.001); however, relatively higher positive correlation was found between ALA-U and urinary inorganic lead (PbI-U) in TEL-exposed workers.     

Speciation of platinum in blood plasma and urine by micelle-mediated extraction and graphite furnace atomic absorption spectrometry

A highly sensitive and selective technique for the speciation of platinum by cloud point extraction prior to determination by graphite furnace atomic absorption spectrometry (GFAAS) was described. The separation of Pt(II) from Pt(IV) was performed in the presence of 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) as chelating agent and Triton X-114 as a non-ionic surfactant. The extraction of Pt(II)–HCPTS complex needs temperature higher than the cloud point temperature of Triton X-114 and pH = 7, while Pt(IV) remains in the aqueous phase. The Pt(II) in the surfactant phase was analyzed by GFAAS, and the concentration of Pt(IV) was calculated by subtraction of Pt(II) from total platinum which was directly determined by GFAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. An enrichment factor of 42 was obtained for the preconcentration of Pt(II) with 50 mL solution. Under the optimum experimental conditions, the calibration curve was linear up to 30 μg L^?1 with detection limit of 0.08 μg L^?1 and the relative standard deviation was 1.8%. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing different spiked samples (tap water, blood plasma and urine). The proposed method was applied to the speciation analysis of Pt in blood plasma and urine with satisfactory results.     

Determination of cadmium and lead levels in human blood of a general Czech population by GFAAS

The development of a method for the direct determination of cadmium (Cd) and lead (Pb) in blood samples by GFAAS, is described. Samples were properly diluted by a matrix modifier to enable measuring both analytes in one solution. For the determination of Cd, a matrix-matched, and for the determination of Pb, an aqueous calibration was used. The precision, accuracy, and detection limits of this method are presented. A method is applied to the investigation of Cd and Pb levels in a general Czech population, selected according to the WHO-MONICA project criteria. To avoid possible contaminations, samples were treated in a clean room class 100.     

Determination of lead content in medicinal plants by pre‐concentration flow injection analysis–flame atomic absorption spectrometry

Introduction – Although medicinal plants are widely used throughout the world, few studies have been carried out concerning the levels of heavy metal contaminants present. Such metals are highly toxic to living organisms even in low concentrations owing to their cumulative effect. The present paper describes the the development of a pre‐concentration flow injection analysis‐flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Objective – To develop a pre‐concentration flow injection analysis‐flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Methodology – A pre‐concentration flow system was coupled to a flame atomic absorption spectrometer. The plant samples were analysed after nitroperchloric digestion. The proposed system was optimised by evaluating the following parameters: nature, concentration and volume of the eluent solution, elution flow rate, elution efficiency, pre‐concentration flow rate and pre‐concentration time. Results – The proposed system exhibited good performance with high precision and repeatability (RSD ≤ 2.36%), excellent linearity (r = 0.9999), low sample consumption (10.5 mL per determination) and an analytical throughput of 55 samples/h. Lead concentrations ranged from 3.37 ± 0.25 to 7.03 ± 0.51 μg/g in dry material. This concentration interval is greater than that previously published in the literature. Conclusion – The inclusion of a pre‐concentration column in the flow manifold improved the sensitivity of the spectrometer. Thus, it was possible to determine the analyte at the ng/mL level in sample solutions of medicinal plants. This is a very important accomplishment, especially when the cumulative effect of heavy metals in living organisms is considered. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of trace cadmium in saliva samples using spray assisted droplet formation-liquid phase microextraction prior to the measurement by slotted quartz tube-flame atomic absorption spectrophotometry

BackgroundAn effective, green and rapid analytical strategy namely the simultaneous spray assisted droplet formation-liquid phase microextraction (S-SADF-LPME) method was developed for the determination of trace quantity of cadmium in saliva samples by using the slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS). By the developed method, external dispersive solvent usage for droplet formation was reduced to obtain a more environmental-friendly method.MethodsMethod consists of a simultaneous complexing and extraction step, which was based on spraying an extraction solvent containing a solid ligand into the aqueous sample solution, forming fine droplets without the use of dispersive solvent. The procedure was implemented using a customized, cost effective and portable spray apparatus to minimize the consumption of reagent, analysis time and operation steps. Thus, this methodology ensures better repeatability and accuracy while minimizing the relative errors caused by the experimental steps. Parameters including the buffer amount, extractant/ligand concentration, extraction solvent type, extraction/ligand solution volume, spraying number and vortex period were systemically optimized to lower the detection limit.ResultsUnder the optimal extraction conditions, 96.9-folds enhancement in the detection power of the traditional FAAS was achieved. The limit of detection and limit of quantification values of presented method were calculated to be 0.65 and 2.17 ng mL⁻¹, respectively. Accuracy and applicability of the optimized method was investigated by collecting saliva samples from smokers. Satisfactory percent recovery values wereachieved for cadmium with a low standard deviation in the acceptable range of 84.9–109.6 %.ConclusionThe developed dispersive solvent-free S-SADF-LPME technique presents a fast, simple, cost-effective and eco-friendly microextraction method based on the use of an easily accessible and functional spray apparatus.     

Application of Poly 1,8‐diaminonaphthalene/multiwalled carbon nanotubes‐COOH hybrid material as an efficient sorbent for trace determination of cadmium and lead ions in water samples

Poly 1,8‐diaminonaphthalene/multiwalled carbon nanotubes‐COOH hybrid material as an effective sorbents in solid phase extraction has been developed for the separation and preconcentration of Cd(II) and Pb(II) at trace levels in environmental water samples. The results indicate that the novel nanocomposite show a high affinity for these heavy metals due to the presence of several good extractive sites, which are introduced to the synthesized nanocomposite The maximum adsorption capacity of the synthesized sorbent for cadmium and lead ions was found to be 101.2 and 175.2 mg g^?1, respectively. The detection limits of this method were 0.09 and 0.7 ng ml^?1 for Cd(II) and Pb(II), respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Cloud point formation based on mixed micelle in the presence of electrolyte for extraction, preconcentration, and spectrophotometric determination of trace amounts of hydrazine in water and biological samples

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate and the nonionic surfactant Triton X-114 to extract hydrazine from aqueous solutions was investigated. The method is based on the condensation reaction of hydrazine with p-(dimethylamino)benzaldehyde, azine formation, and mixed micelle-mediated extraction of azine in the presence of NaCl electrolyte as an inducing phase separation. An azine product was concentrated in surfactant-rich phase after separation. The optimal extraction and reaction conditions (e.g., surfactant, reagent and electrolyte concentrations, and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.50-110ngml(-1) of hydrazine and the detection limit of the method is 0.08ngml(-1). The interference effect of some cations, anions, and organic compounds was also tested. The method was successfully applied to the determination of hydrazine in water and biological samples.     

The improvement of sensitivity in lead and cadmium determinations using flame atomic absorption spectrometry

Various designs of quartz tubes of the slotted tube atom trap were examined to improve the sensitivity of flame atomic absorption spectrophotometry. The studied designs include the diameter length and the length of the upper slot of quartz tubes. Tubes having a diameter of 5 and 6 mm and an upper slot length of 2.3 cm produce the best sensitivity—as high as 6- and 10-fold enhancement for lead (Pb) and cadmium (Cd), respectively. The limits of quantitation were found to be 35 and 4 ng ml⁻¹ for Pb and Cd, respectively, by the optimized method. The achieved technique was applied to determine the concentrations of Pb and Cd in cancerous (malign) and noncancerous (adenoma) human thyroid tissues.     

Determination of puerarin in biological samples and its application to a pharmacokinetic study by flow‐injection chemiluminescence

A simple and sensitive flow injection–chemiluminescence (FI–CL) method has been developed for the determination of puerarin, based on the fact that puerarin can greatly inhibit CL of the luminol–H₂O₂–haemoglobin system. The inhibition of CL intensity was linear to the logarithm of the concentration of puerarin in the range 0.08–10.0 μg/mL (r² = 0.9912). The limit of detection was 0.05 μg/mL (3σ) and the relative standard deviation (RSD) for 1.0 μg/mL (n = 11) of puerarin solution was 1.4%. Coupled with solid‐phase extraction (SPE) as the sample pretreatment, the determination of puerarin in biological samples and a preliminary pharmocokinetic study of puerarin in rats were performed. The recoveries for plasma and urine at three different concentrations were 89.2–110.0% and 91.4–104.8%, respectively. The pharmacokinetics of puerarin in plasma of rat coincides with the two‐compartment open model. The T_1/2α, T_1/2β, CL/F, V_Z/F, AUC_{(0 – t)}, MRT_{(0 – ∞)}, T_max and C_max were 0.77 ± 0.21 h, 7.55 ± 2.64 h, 2.43 ± 1.02 L/kg/h, 11.40 ± 3.45 L/kg, 56.67 ± 10.65 mg/h/L, 5.04 ± 2.78 h, 1.00 ± 0.35 h and 19.70 ± 4.67 μg/mL, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

湿式消解-石墨炉原子吸收光谱法测定金线莲铅、铜、镉含量

采用湿式消解法对金线莲药材进行处理,石墨炉原子吸收光谱法测定其铅(Pb)、铜(Cu)、镉(Cd)等重金属元素含量。结果表明,Pb、Cu、Cd 三种元素的原子化温度分别是2100、2200和1800 ℃,灰化温度分别是400、800和250 ℃。Pb、Cu、Cd三种元素的检出限分别为0.47、0.50、0.62 μg·L-1,其加标回收率在92.7%～94.0%之间,平均相对标准偏差为1.71%,说明仪器精密度良好,湿式消解-石墨炉原子吸收光谱法能有效测定金线莲药材中Pb、Cu、Cd含量。     

Problems in determination of skeletal lead burden in archaeological samples: an example from the First African Baptist Church population

Human bone lead content has been demonstrated to be related to socioeconomic status, occupation and other social and environmental correlates. Skeletal tissue samples from 135 individuals from an early nineteenth century Philadelphia cemetery (First African Baptist Church) were studied by electrothermal atomic absorption spectrometry and X-ray fluorescence for lead content. High bone lead levels led to investigation of possible diagenetic effects. These were investigated by several different approaches including distribution of lead within bone by X-ray fluorescence, histological preservation, soil lead concentration and acidity as well as location and depth of burial. Bone lead levels were very high in children, exceeding those of the adult population that were buried in the cemetery, and also those of present day adults. The antemortem age-related increase in bone lead, reported in other studies, was not evidenced in this population. Lead was evenly deposited in areas of taphonomic bone destruction. Synchrotron X-ray fluorescence studies revealed no consistent pattern of lead microdistribution within the bone. Our conclusions are that postmortem diagenesis of lead ion has penetrated these archaeological bones to a degree that makes their original bone lead content irretrievable by any known method. Increased bone porosity is most likely responsible for the very high levels of lead found in bones of newborns and children.     

Determination of subnanomolar concentrations of vanadium in environmental water samples using flow injection with luminol chemiluminescence detection

A flow injection chemiluminescence method is described for the determination of subnanomolar concentrations of vanadium in environmental water samples. The procedure is based on the oxidation of luminol in the presence of dissolved oxygen catalyzed by vanadium(IV). Vanadium(V) reduction and preconcentration of vanadium(IV) was carried out using in‐line silver reductor and 8‐hydroxyquinoline chelating columns at pH 3.15, respectively. The calibration graph for vanadium(IV) was linear in the concentration range of 0.025–10 µg/L with relative standard deviation in the range of 0.4–5.58%. The detection limit (3s blank) was 3.8 × 10^?3 µg/L without preconcentration; when the vanadium(IV) was preconcentrated with an 8‐HQ column for 1 min (2.0 mL of sample loaded), the detection limit of 5.1 × 10^?4 µg/L was achieved. One analytical cycle can be completed in 2.0 min. The analysis of certified reference materials (CASS‐4, NASS‐5 and SLRS‐4) by the proposed method showed good agreement with the certified values. The method was successfully applied to the determination of total dissolved vanadium in environmental water samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Micell-mediated extraction for the spectrophotometric determination of nitrite in water and biological samples based on its reaction with p-nitroaniline in the presence of diphenylamine

A cloud point extraction process using the nonionic surfactant Triton X-100 to extract nitrite from aqueous solution was investigated. The method is based on the color reaction of nitrite with p-nitroaniline in the presence of diphenylamine in acid media and micell-mediated extraction of an azo product. The optimal extraction and reaction conditions (e.g., acid concentration, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, molar absorptivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 2-40 ng ml(-1) of nitrite ion. The detection limit of the method is 0.87 ng ml(-1) of nitrite ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of nitrite in tap water, waste water, and human urine samples.     

Heavy metals and trace elements in scalp hair samples of children with severe autism spectrum disorder: A case-control study on Jordanian children

BackgroundElemental analysis has been increasingly used for biomonitoring heavy metals and trace elements.MethodsThis study monitored the levels of two heavy metals (Al and Pb), and seven trace elements (Macroelements Mg, K, P and Ca; Microelements Zn, Cu, Fe) in scalp hair of 57 children with severe autism spectrum disorder (ASD) and 50 age-matched controls, using Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES).ResultsCompared to controls, significantly higher levels of Al (p = 0.001), Pb (p = 0.001) and K (p = 0.021), with lower levels of Mg and Zn (p = 0.038) were observed for the ASD group. ASD boys had higher levels of Al (p = 0.001), Pb (p = 0.001) and K (p = 0.017) than control boys, while ASD girls had higher Pb levels (p = 0.005) than control girls. The ASD subgroup exposed to passive smokers had higher levels of Al (p = 0.033) and Pb (p = 0.001, and the ASD subgroup not exposed to passive smoke had higher levels of Al (p = 0.011), Pb (p = 0.001), K (p = 0.003); and lower levels of Mg (p = 0.011) than their controls. Other confounding factors and the correlation between these elements were also investigated.ConclusionThis data suggests that exposure to Al and Pb, increase intake of K, and decreased intake of magnesium and zinc, may contribute to ASD etiology.