Assessment of trace aluminium content in parenteral solutions by combined cloud point preconcentration-flow injection inductively coupled plasma optical emission spectrometry

A micelle-mediated phase separation without added chelating agents to preconcentrate trace levels of aluminium in parenteral solutions as a prior step to its determination by flow injection inductively coupled plasma optical emission spectrometry has been developed. The enrichment step is based on the cloud point extraction of aluminium with the non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5). The chemical variables affecting the sensitivity of the extractive-spectrometric procedure were studied in detail. After optimization, a preconcentration factor of 200 and a %E higher than 99.9 were achieved. The detection limit (DL) value of aluminium for the preconcentration of 50 ml of parenteral solution was 0.25 microgl(-1). The calibration graph using the preconcentration system for aluminium was linear with a correlation coefficient of 0.9997 at levels near the DLs up to at least 200 microgl(-1). The developed hyphenated assay, which thoroughly satisfies the typical requirements for pharmaceutical control processes, is appropriate to monitor the aluminium concentration in parenteral nutrition.     

A method for the quantification of low concentration sulfamethazine residues in milk based on molecularly imprinted clean-up and surface preconcentration at a Nafion-modified glassy carbon electrode

An electrochemical method for the determination of sulfamethazine at a low concentration level (25 microgl(-1)) in milk is reported. The method involves sample clean-up and selective preconcentration of sulfamethazine with a molecularly imprinted polymer (MIP), and a further electrode surface preconcentration of the analyte at a Nafion-coated glassy carbon electrode (GCE). Square wave (SW) oxidative voltammetry of accumulated sulfamethazine was employed for its quantification. Sulfamethazine electrode preconcentration was carried out in 0.1 moll(-1) Britton-Robinson buffer of pH 1.5, and by applying 5 min of accumulation at open circuit. A linear calibration graph was obtained for sulfamethazine at the Nafion-modified GCE over the 1.0x10(-8) to 1.0x10(-6)moll(-1) concentration range, with a detection limit of 6.8x10(-9)moll(-1) (1.9 microgl(-1)). This detection limit is remarkably better than those reported previously in the literature using electroanalytical techniques. Although the detection limit achieved was sufficient to allow the direct determination of sulfamethazine at the concentration level required in milk, a sample clean-up was shown to be necessary to obtain analytically useful SW voltammograms. This was accomplished by processing the deproteinized milk through a cartridge containing a molecularly imprinted polymer for sulfamethazine, also allowing a selective preconcentration of the analyte. Elution of the analyte from the MIP cartridges was carried out with 2 ml of a (9:1) MeOH:acetic acid mixture. Determination of sulfamethazine in milk samples was accomplished by interpolation into a calibration graph constructed with sulfamethazine standard solutions which were subjected to the same procedure than the deproteinized milk samples. Results obtained for five samples, spiked at the 25 microgl(-1) level, showed a mean recovery of (100+/-3)%.     

Simultaneous determination of dysprosium and iron in urine by capillary zone electrophoresis coupled to cloud point extraction

Automated preconcentration strategies are needed when analyzing metals in real samples by capillary electrophoresis (CE) with UV detection. The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) associated with CE for simultaneously determining dysprosium and iron at ppb levels in urine is presented and evaluated for the first time. The preconcentration step is mediated by micelles of the non-ionic surfactant polyethyleneglycol-mono-p-nonylphenylether (PONPE 7.5) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. The micellar system containing the complex was loaded into the FIA manifold at a flow rate of 8 mlmin(-1), and the surfactant rich-phase was retained in a microcolumn packed with cotton, at pH 9.2. The surfactant-rich phase was eluted with 50 microl acetonitrile directly into the CE sample vial, allowing to reach an enrichment factor of 200-fold for a 10 ml sample urine. The type and composition of the background electrolytes (BGE) were investigated with respect to separation selectivity, reproducibility and stability. A BGE of 20mM sodium tetraborate buffer containing 13% acetonitrile, pH 9.0 was found to be optimal for the separation of metal chelates. Detection was performed at 585 nm. An enhancement factor of 200 was obtained for the preconcentration of 10 ml of sample solution. The detection limits for the preconcentration of 10 ml of urine were 0.20 microgl(-1) for Dy, and. 0.48 microgl(-1) for Fe. The calibration graphs using the preconcentration system were linear with a correlation coefficient of 0.9989 (Dy) and 0.9976 (Fe) at levels near the detection limits up to at least 500 microgl(-1). The method was successfully applied to the determination of dysprosium and iron in urine for monitoring the elimination of dysprosium-based pharmaceuticals.     

ET-AAS determination of aluminium in dialysis concentrates after continuous flow solvent extraction

Conditions of a continuous flow extraction (CFE) of aluminium acetylacetonate in acetylacetone and aluminium 8-hydroxyquinolinate into methylisobutylketone (lengths of reaction and extraction coils, flow rates of aqueous and organic phases and their flow rate ratio, pH of aqueous phase, lengths of coils for transport of aqueous and organic phases and effect of salts) were studied. The analytical signal of the aluminium chelates present in the organic phase was measured at 309.3 nm using atomic absorption spectrometry with electrothermal atomization (ET-AAS) at the flow rate ratio F aq/F org=3 for aqueous and organic phases. The five points calibration curves were linear (R2 0.9973 and 0.9987) up to 21 microgl(-1) Al with the limits of detection of 0.3 microgl(-1) and the recovery 100+/-2% and precision of 3% at 2-10-fold dilution of the dialysis concentrates. The acetylacetonate method was applied to the determination of aluminium in real dialysis concentrates. Aluminium in concentrations 5-6 microgl(-1) (R.S.D.s 5-10% in real samples) were found and the results were in the very good agreement with those obtained by an ET-AAS using preconcentration of Al(III) on a Spheron-Salicyl chelating sorbent (absolute and relative differences were under 0.4 microgl(-1) and 8.2%, respectively).     

On-line preconcentration and determination of chromium in parenteral solutions by flow injection-flame atomic absorption spectrometry

An on-line chromium preconcentration and determination system implemented with flame atomic absorption spectrometry (FAAS) associated to flow injection (FI) was studied. For the retention of chromium, 4-(2-Thiazolylazo)-resorcinol (TAR) and Amberlite XAD-16 were used, at pH 5.0. The Cr-TAR complex was removed from the micro-column with ethanol. An enrichment factor of 50 was obtained for the preconcentration of 50 ml of sample solution. The detection limit value for the preconcentration of 50 ml of aqueous solution of Cr was 20 ng l(-1). The precision for ten replicate determinations at the 5 microg l(-1) Cr levels was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for chromium was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 microg l(-1). The method was successfully applied to the determination of chromium in parenteral solution samples.     

Determination of cobalt in urine by FI-ICP-AES with online preconcentration

A method for the preconcentration and determination of cobalt in human urine samples was developed. The online preconcentration and determination were attained using inductively coupled plasma atomic emission spectromety (ICP-AES) coupled to a flow injection (FI) method. Cobalt was retained on an Amberlite XAD-7 resin as cobalt-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex at pH 9.5. Cobalt was removed from the microcolumn with perchloric acid. A sensitivity enhancement factor of 90 was obtained with respect to cobalt determination by ICP-AES without preconcentration. The value of detection limit for the preconcentration method proposed was 25 ng/L. The precision for 10 replicate determinations at the 5 mg/L (mean +/- SD, 5.1 +/- 0.14) Co level was 2.7% relative standard deviation, calculated from the peak heights obtained. The calibration graph preconcentration method for cobalt was linear with a correlation coefficient of 0.9994 from approximately 0.25 mg/L up to at least 100 mg/L. The method was successfully applied to the determination of cobalt in human urine samples.     

Stripping voltammetric determination of indapamide in serum at castor oil-based carbon paste electrodes

The diuretic drug indapamide has been characterized voltammetrically at carbon paste electrodes by means of cyclic and differential pulse voltammetry. An adsorptive stripping method at carbon paste electrode modified with castor oil for trace determination of indapamide was described. A study of the variation of the peak current with solution variables such as pH, ionic strength, concentration of indapamide, possible interference, and instrumental variables such as scan rate, pulse amplitude, preconcentration time, accumulation potential, paste composition has resulted in the optimization of the oxidation signal for analytical purposes. By anodic stripping differential pulse voltammetry, the calibration plot was linear in the range 5 x 10(-8) x 10(-7) M with a detection limit of 5 x 10(-9) M at carbon paste electrode modified with castor oil in pH 4.0. The preconcentration medium-exchange approach was utilized for selective determination of indapamide in spiked serum. A detection limit of 15 ng ml(-1) was obtained for dilute serum sample after 3 min accumulation and medium-exchange procedure.     

微波消解-ICP-OES法检测湘产朱砂中重金属的含量

目的建立微波消解-电感耦合等离子体原子发射光谱法（ICP-OES）检测湘产朱砂中Cd、Cr、Cu、Pb的含量,为矿物药的重金属检测提供参考。方法通过对比湿法消解,优选出微波消解作为朱砂样品的前处理方法,结合电感耦合等离子体发射光谱法（ICP-OES）的分析手段,对湖南产的11批朱砂样品中重金属含量进行检测。结果方法的线性相关系数为0.999 8～1.000 0,检出限为0.18～5.54μg·L^-1,RSD为0.55%～3.20%,回收率为84.30%～108.36%,经方法学验证适合同时测定朱砂中Cd、Cr、Cu、Pb的含量。结论该方法简便、准确,可同时检测朱砂中重金属Cd、Cr、Cu、Pb的含量。     

A study of the determination of the hypertensive drug captopril by square wave cathodic adsorptive stripping voltammetry

In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction current was related to the CPL concentration in the sample. The chemical and instrumental parameters affecting the response were investigated and optimized for the CPL determination. The calibration curve was linear from 0.5 to 180 microg l(-1) of CPL (depending on the preconcentration time), the limit of detection at a S/N ratio of 3 was 0.5 microg l(-1) with 300 s of preconcentration and the relative standard deviation was 3.2% at the 20 microg l(-1) level (with 120 s of preconcentration, n=8). The method was applied to the determination of CPL in two pharmaceutical formulations with recoveries of 97.9 and 98.8%. Finally, the potential for applying the proposed method to the determination of CPL in biological media is briefly discussed.     

微波消解-电感耦合等离子体原子发射光谱法测定全血中的镧

目的评估多效防护乳中镧(La)的透皮安全性,建立微波消解-电感耦合等离子体发射光谱(ICP-OES)法测定大鼠全血中镧的分析方法。方法全血样品经微波消解后,采用电感耦合等离子发射光谱仪分析,以333.749 nm为分析谱线,对大鼠全血中的La进行含量测定。结果该方法的标准曲线相关性良好(r>0.9994),方法检出限为0.0025μg/ml,定量限为0.0077μg/ml,精密度<3%,回收率在94.9%~102.0%之间。结论基于微波消解的ICP-OES方法稳定可靠,可为镧元素的含量测定和给药安全性研究提供重要依据。     

Separation and preconcentration system based on microextraction with ionic liquid for determination of copper in water and food samples by stopped-flow injection spectrofluorimetry

In this work, an efficient in situ solvent formation microextraction (ISFME) was combined with stopped-flow injection spectrofluorimetry (SFIS) for the determination of copper. In the proposed approach, thiamine was oxidized with copper(II) to form hydrophobic and highly fluorescent thiochrome (TC), which was subsequently extracted into ionic liquid as an extractant phase. A small amount of an ion-pairing agent (NaPF₆) was added to the sample solution containing a water-miscible ionic liquid ([Hmim][BF₄]) to obtain a hydrophobic ionic liquid ([Hmim][PF₆]), which acted as the extraction phase. After centrifuging, phase separation was performed and the enriched analyte was determined by SFIS. ISFME is an efficient method for separation and preconcentration of metal ions from aqueous solutions with a high ionic strength. Variables affecting the analytical performance were studied and optimized. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.024 μg L⁻¹ and a relative standard deviation (RSD) of 2.1%. The accuracy of the combined methodology was evaluated by recovery experiments and by analyzing certified reference material (GBW 07605 Tea). Finally, the proposed method was successfully applied to copper determination in water and food samples.     

Enhancement of an analytical method for the determination of squalene in anthrax vaccine adsorbed formulations

Specific lots of anthrax vaccine adsorbed administered to members of the U.S. Armed Forces have been alleged to contain squalene, a chemical purported to be associated with illnesses of Gulf War veterans. A method of enhanced sensitivity for determining squalene in anthrax vaccine adsorbed using high-performance liquid chromatography with photodiode array detection has been developed, validated, and applied to 44 bottles of 38 lots of anthrax vaccine. In 43 bottles of 37 lots, no squalene was detected within a detection limit of 1ng/0.5ml dose (2 parts-per-billion). One lot, FAV008, was found to contain trace amounts of squalene at 7, 9, and 1microgl(-1), levels considerably below normal human plasma levels (290microgl(-1)). The overall results of this investigation provide direct evidence for the absence of squalene in nearly all of anthrax vaccine preparations tested.     

Column solid phase extraction of iron(III), copper(II), manganese(II) and lead(II) ions food and water samples on multi-walled carbon nanotubes

A column solid phase extraction method for preconcentration of Fe(III), Cu(II), Mn(II) and Pb(II) on multi-walled carbon nanotubes (MWNTs) has been established. The adsorption was achieved quantitatively on carbon nanotube at pH 9.0, then the retained analyte contents on the column were quantitatively eluted with 1 M HNO₃ in acetone. The effects of analytical parameters including pH of the solution, eluent type, sample volume, flow rates of eluent, matrix ions, etc. were investigated for optimization of the presented procedure. The preconcentration factor was calculated as 20. The detection limits for the understudy analyte ions were found in the range of 3.5 μg/L (Mn)–8.0 μg/L (Pb). The validation of the presented procedure was checked by the analysis of TMDA 54.4 fortified lake water and HR-1 River Sediment certified reference materials. The method was applied to the determination of analyte ions in environmental samples.     

UV-spectrophotometry and square wave voltammetry at nafion-modified carbon-paste electrode for the determination of doxazosin in urine and formulations

By using several electrochemical techniques, the study of electroanalytical behaviour of antihipertensive Doxazosin at Nafion modified carbon paste electrode (NMCPE) has been carried out. The voltammetric peak is very pH dependent, reaching the maximum i(p) at pH 6.8 (Ep -0.17 V), the reduction process being quasi-reversible and fundamentally controlled by adsorption. A method based on the control of adsorptive preconcentration of the Doxazosin on the NMCPE, before its voltammetric determination, is proposed. The detection limit reached using square wave voltammetry (SWV) as redissolution technique was 2.33x10(-11) M and the variation coefficient at 2x10(-9) M level was 3.54%. A spectrophotometric study of Doxazosin has also been made and two waves at 244 and 329 nm (pH 1.7), were obtained. The wave at 329 nm changes its height and position with the pH, allowing the pKa determination (6.94+/-0.21) using different methods. The obtained detection limit was 0.5x10(-6) M, and the variation coefficient at 1.5x10(-5) M level was 0.99%. The UV spectrophotometric method is sufficiently accurate and precise to be applied in the Carduran tablets assay, while the voltammetric method (AdS-SWV) can in addition be used to determine the drug at trace level in human urine samples with good recoveries.     

电感耦合等离子体发射光谱法(ICP-OES)测定枸橼酸托法替布中钯、铑残留量

目的建立枸橼酸托法替布中钯、铑残留量的测定方法。方法样品用浓硫酸碳化,加浓硝酸及高氯酸消解后,采用电感耦合等离子体发射光谱法(ICP-OES)测定钯、铑元素含量。结果各元素线性关系良好,相关系数(r)均大于0.999,钯和铑的方法检出限为分别为0.10 mg·kg^-1和0.25 mg·kg^-1,加标回收率在88.9%~104.1%之间,相对标准偏差RSD为1.3%~4.3%(n=12)。结论该方法准确、可靠,可用于枸橼酸托法替布中钯、铑的残留量的测定。     

电感耦合等离子体发射光谱法测定右旋糖酐铁中8种重金属元素及光谱干扰的校正

目的 建立用电感耦合等离子体发射光谱法（ICP-OES）测定右旋糖酐铁中铅、镉、砷、汞、钴、钒、硒、钼8种重金属元素含量的分析方法。方法 通过检测波长考察,仪器参数优化,应用干扰元素校正法（IEC）校正光谱干扰,测定8种重金属元素的量。结果 应用IEC法校正光谱干扰,回收率在88.7%～101.3%之间,方法准确度良好,各待测元素线性关系良好,相关系数均大于0.999,检出限为0.12～7.26 ng/mL,定量限为0.40～23.96 ng/mL,方法精密度良好（RSD<3.5%,n=6）。结论 应用IEC法进行光谱校正后的结果明显优于未加校正的常规法测定结果。建立的方法准确、灵敏、迅速,可用于右旋糖酐铁中8种重金属元素含量的测定。     

A novel preconcentration procedure using cloud point extraction for determination of lead,cobalt and copper in water and food samples using flame atomic absorption spectrometry

In this work, a new cloud point extraction (CPE) procedure was developed for the separation and preconcentration of lead(II), cobalt(II), and copper(II) in various water and food samples. Complexes of metal ions with 1-Phenylthiosemicarbazide (1-PTSC) were extracted into the surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114) from samples. After phase separation, the enriched analytes were determined by flame atomic absorption spectrometry (FAAS). Factors affecting cloud point extraction, such as pH, reagent and surfactant concentrations, temperature, and incubation time were evaluated and optimized. The interference effect of some cations and anions was also studied. After optimization of the CPE conditions, the preconcentration factor of 25 and the limits of detection (L.O.D.) obtained for lead(II), cobalt(II), and copper(II) based on three sigma (n = 20) were 3.42, 1.00, and 0.67 μg L⁻¹, respectively. The method presented precision (R.S.D.) between 1.7% and 4.8% (n = 7). The presented preconcentration procedure was applied to the determination of metal ions in reference standard materials (SRM 1515 Apple leaves and GBW 07605 Tea) and some real samples including tap water, spring water, sea water, canned fish, black tea, green tea, tomato sauce and honey.     

Indirect fibre‐optic colorimetric determination of ascorbic acid using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol and cloud point extraction

A new method has been developed for the indirect determination of ascorbic acid (AA) in commercial syrup preparations based on cloud point extraction (CPE) separation and preconcentration, and determination by molecular absorption spectrometry. The colorimetric method was based on the reduction of Fe(III) to Fe(II) and complexation of Fe(II) with 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol (Br‐PADAP), followed by its extraction into Triton X‐114. Selectivity of the method was increased with the use of EDTA as a masking agent. The absorbance was measured at 742 nm. Various influencing factors on the separation and preconcentration of AA have been investigated systematically, and the optimized operation conditions were established. The proposed method allows the determination of AA in the range 5–200 µg L^?1 with a relative standard deviation of 3.0%. The detection limit was found to be 0.9 µg L^?1 for AA. This method has been applied to the determination of ascorbic acid in commercial pharmaceutical preparations. Copyright © 2011 John Wiley & Sons, Ltd.     

Voltammetric determination of fenbendazole in veterinarian formulations

A versatile voltammetric method for quantitative determination of fenbendazole (FBZ) in commercial tablets has been proposed, where direct dissolution of tablets is carried out in 0.1 mol l(-1) tetrabutylamoniun tetrafluorborate containing dimethylformamide solutions. Linear sweep (LSV), square wave (SWV) and differential pulse (DPV) voltammetry techniques were applied to study FBZ at a glassy carbon electrode, exhibiting a well defined irreversible oxidation peak at 1.15 V vs. SCE. This methodology allows a precise quantitative determination of FBZ presenting detection limits of 5.2 x 10(-5) (LSV), 5.0 x 10(-6) (DPV) and 5.0 x 10(-5) mol l(-1) (SWV).