Solid-phase fluorescence determination of gallium(III) with morin and lumogallion immobilized on cellulose matrices

It has been demonstrated that the fluorometric test determination of gallium(III) can be performed with morin and lumogallion immobilized on thin-layer cellulose matrices. Test procedures have been developed for the determination of Ga(III) in the range 0.5–90 mg/L by the length of fluorescence zone on a test strip sealed into a polymer film (after its contact with the test solution) in the ranges 0.001–1 and 0.01–1 mg/L with the visual detection of the fluorescence of the indicator matrix with morin and lumogallion, respectively (after passing 100 and 20 mL of a test solution through it), and in the range 0.0001–0.1 mg/L by detecting the fluorescence with a portable fluorimeter.     

Laser ablation-atomic fluorescence approach for the determination of mercury

A method for the determination of mercury in solid samples using laser ablation coupled with atomic fluorescence spectroscopy has been developed. An Nd-YAG laser was used for ablation and the vaporised and atomised material was rapidly led to an atomic fluorescence detector, where excitation and emission took place. The experimental approach was applied to the assessment of different procedures as sensitive as possible for implementing standard addition methods. Calibration curves were recorded using the prepared standards, which exhibited linear ranges between 0.5–100 μg/g, with excellent regression coefficients in all instances (0.9907). The precision, expressed as RSD %, was 3 and 4% for contents of 1 and 30 μg/g, respectively, in the same pellet; and 7 and 12% for the same contents and different type of pellets. The method has been applied to the determination of mercury in CRM of sewage sediment and a sludge sample with a known amount of mercury determined by an interlaboratory study. The results obtained show good agreement with those expected. Received: 21 December 1998 / Revised: 12 April 1999 / Accepted: 14 April 1999     

A simple method for the determination of glyphosate residues in soil by capillary gas chromatography with nitrogen phosphorus

A simple method was developed to determine the residues of glyphosate, N-(phosphonomethyl)glycine, in soil. The residues were extracted from soil matrices with 2 M NH₄OH, derivatized by trifluoroacetic anhydride and trifluoroethanol, and, then, determined by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). The results were further confirmed by gas chromatography-mass spectrometry (GC-MS). The limit of detection was estimated to be 9 × 10⁻¹² g, and the minimum determination concentration of glyphosate in the samples was 0.01 mg/kg. The ranges for the average recoveries and relative standard deviation (RSD) of the method were 84.4–94.0% and 8.1–13.7%, respectively, in agreement with the directives for method validation in residue analysis. The proposed method was successfully employed for the determination of glyphosate residue levels and dissipation retes in the soil from an apple orchard. The text was submitted by the authors in English.     

Determination of diagnostical markers of urolithiasis by capillary electrophoresis

Methods of the electrophoretic determination of the main markers of urolithiasis, i.e., inorganic cations, ammonium, potassium, sodium, magnesium, and calcium; inorganic anions, chloride, sulfate, and phosphate; and organic acid anions, urate, citrate and oxalate, and creatinine in 24-hour collection urine with spectrophotometric detection were developed. The detection limits of analytes ranged form 0.25–1.0 μg/mL. The precision and accuracy were 2–5% and 97–101.5%, respectively. In dependence on the analyte. The developed procedures were used in the analysis of 156 urine samples. Normal ranges were preliminarily determined on a group of healthy donors.     

Indirect spectrophotometric determination of gentamicin and vancomycin antibiotics based on their oxidation by potassium permanganate

Four simple, accurate, sensitive and economical procedures (A–D) for the estimation of gentamicin sulphate and vancomycin hydrochloride, both in pure form and in pharmaceutical formulations have been developed. The methods are based on the oxidation of the studied drugs by a known excess of potassium permanganate in sulphuric acid medium and subsequent determination of unreacted oxidant by reacting it with amaranth dye (method A), acid orange II (method B), indigocarmine (method C) and methylene blue (method D), in the same acid medium at a suitable λ_max=521, 485, 610 and 664 nm, respectively. The reacted oxidant corresponds to the drug content. Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 4–8, 3–8, 4–9 and 5–9 μg ml⁻¹ with gentamicin and 4–8, 1.5–4, 1.5–4 and 3.5–5.5 μg ml⁻¹ with vancomycin for methods A, B, C, and D, respectively. The molar absorptivity, sandell sensitivity, detection and quantification limits were calculated. The stoichiometric ratios for the cited drugs were studied. The optimum reaction conditions and other analytical parameters were evaluated. The influence of the substance commonly employed as excipients with these drugs were studied. The proposed methods were applied to the determination of these drugs in pharmaceutical formulations. The results have demonstrated that the methods are equally accurate and reproducible as the official methods.     

An integrated reaction-retention and spectrophotometric detection flow system for the determination of nickel

An integrated flow-through photometric sensor for the determination of nickel in real samples of various origins has been developed. The sensor is based on the reaction of Ni(II) with 1-(2-pyridylazo)-2-naphthol (PAN) immobilized on a cationic resin which was placed in a flow-cell using a spectrophotometer tuned at 566 nm as detector. The Ni(II) ion from the sample injected into the carrrier stream (pH = 5.0) of a monochannel continuous flow system reacts with the immobilized chromogenic reagent to form a red chelate which remains on the active solid support and generates the analytical signal. When this reached its maximum value the Ni(II)-PAN chelate was destroyed using 1 M H₂SO₄ as eluents, leaving the sorbed PAN untouched. The response of the sensor was linear in the three concentration ranges assayed: 0.3–4.0, 0.1–1.6 and 0.05–0.8 μg mL^–1 for sample volumes of 100, 400 and 800 μL, respectively, and the R.S.D.(%) (n = 10) were 1.80(100 μL), 3.04(400 μL) and 2.29(800 μL). The sensor showed an excellent selectivity which could also be increased with a simple on-line modification to avoid interference from copper. It was applied to a variety of real samples with very good results in all cases. Received: 15 April 1998 / Revised: 29 June 1998 / Accepted: 3 July 1998     

Capillary-electrophoretic determination of zinc and cadmium ions in aqueous solutions with ion-exchange preconcentration

An approach to choosing analyte preconcentration conditions for the subsequent capillary electrophoresis (CE) analysis of the concentrate was substantiated using the simultaneous determination of zinc(II) and cadmium(II) trace concentrations as an example. A CE procedure was developed for the determination of Zn and Cd with the following characteristics: The time of the analysis, including analyte preconcentration from a 50-mL sample, was 30 min. The analytical ranges were 0.01–0.2 mg/L for cadmium(II) and 0.005–0.1 mg/L for zinc(II).     

Application of classical versus bayesian statistical control charts to on-line radiological monitoring

False positive and false negative incidence rates of radiological monitoring data from classical and Bayesian statistical process control chart techniques are compared. The on-line monitoring for illicit radioactive material with no false positives or false negatives is the goal of homeland security monitoring, but is unrealistic. However, statistical fluctuations in the detector signal, short detection times, large source to detector distances, and shielding effects make distinguishing between a radiation source and natural background particularly difficult. Experimental time series data were collected using a 1″ × 1″ LaCl₃(Ce) based scintillation detector (Scionix, Orlando, FL) under various simulated conditions. Experimental parameters include radionuclide (gamma-ray) energy, activity, density thickness (source to detector distance and shielding), time, and temperature. All statistical algorithms were developed using MATLAB™. The Shewhart (3-σ) control chart and the cumulative sum (CUSUM) control chart are the classical procedures adopted, while the Bayesian technique is the Shiryayev–Roberts (S–R) control chart. The Shiryayev–Roberts method was the best method for controlling the number of false positive detects, followed by the CUSUM method. However, The Shiryayev–Roberts method, used without modification, resulted in one of the highest false negative incidence rates independent of the signal strength. Modification of The Shiryayev–Roberts statistical analysis method reduced the number of false negatives, but resulted in an increase in the false positive incidence rate.     

Simultaneous stepwise injection-photometric determination of nitrite and nitrate ions in aqueous media

A procedure for the stepwise injection-photometric determination of nitrite and nitrate ions has been developed. The procedure employs their subsequent determination by the reaction of colored azo compound formation after the reduction of nitrate ions into nitrite ions on a cadmium reducer. The analytical ranges for nitrite and nitrate ions are 2–15 and 5–50 mg/L (sample volume 2 mL, analysis time 14 min).     

Simultaneous HPLC Analysis of Olmesartan and Hydrochlorothiazide in Combined Tablets and in vitro Dissolution Studies

A simple, rapid and reproducible HPLC method was developed and validated for the simultaneous determination of olmesartan (OLM) medoxomil and hydrochlorothiazide (HCT) in combined tablets. Chromatography was carried out on a 4.6 mm I.D × 200 mm, 5 μm cyano column with methanol–10 mM phosphoric acid containing 0.1% triethylamine (pH 2.5, 50:50 v/v) at a flow rate of 1.0 mL min⁻¹ and UV detector was set at 260 nm. Valsartan (VAL) was used as internal standard (IS). A linear response was observed in the range of 0.2–6 μg mL⁻¹ (r ² = 0.9998) for OLM and 0.1–4 μg mL⁻¹ (r ² = 0.9999) for HCT, respectively. The method showed good recoveries (99.56% for OLM and 99.48% for HCT) and the relative standard deviation (RSD) values for intra- and inter-day precision were 0.70–1.59 and 0.80–2.00% for OLM and 1.20–1.37 and 1.63–1.93% for HCT, respectively. The developed method was applied successfully for quality control assay of OLM and HCT in combined tablets and in vitro dissolution studies.     

Development of a voltammetric procedure for assay of thebaine at a multi-walled carbon nanotubes electrode: quantification and electrochemical studies

The study of electrochemical behavior and determination of thebaine (THEB), an opiate alkaloid, is described on a multi-walled carbon nanotube (MWCNT) modified glassy carbon electrode by adsorptive stripping voltammetry and electrochemical impedance spectroscopy. The results indicated that MWCNT electrodes remarkably enhance electrocatalytic activity toward the oxidation of THEB in a wide pH range of 2.0–10.0, and it shows two irreversible and diffusion-controlled anodic peaks. Then, a sensitive, simple, and time-saving cyclic voltammetric procedure was developed for the analysis of THEB in human urine samples. Under optimized conditions, the oxidation peak has two linear dynamic ranges of 1.0–80.0 and 100.0–600.0 μM, with detection limit of 0.23 μM and a precision of <4% (relative standard deviation for eight analysis).     

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%.      

LC Method for the Determination of NPC1161, Primaquine and their Metabolites in Various Biological Systems

NPC1161 is an 8-aminoquinoline anti-malarial analog, which has a favorable toxicity profile relative to primaquine and other 8-aminoquinolines. High-performance liquid chromatographic method was developed for the determination of NPC1161, primaquine and their metabolites in biological samples in order to facilitate metabolic and pharmacokinetic studies. The method includes extraction of the unchanged drugs and their metabolites from the biological samples. Separation was achieved by reversed-phase chromatography on a C18 column with water–acetonitrile both containing 0.025% trifluoroacetic acid as the mobile phase. Recoveries of NPC1161 and its metabolites were greater than 60% in various biological samples tested. No interference with the components of the biological material was observed. The detector response was linear with concentrations of NPC1161 and its metabolites (desalkyl NPC1161 and carboxy NPC1161) in the ranges from 0.5 to 80.0, 0.4–60.0 and 0.4–70.0 μg mL⁻¹, respectively. A mass spectrometry coupled with electrospray ionization (ESI) interface method is described for the identification of NPC1161 and its metabolites in biological samples. This method involved the use of the [M + H]⁺ions of NPC1161, C3 analog (internal std. for the assay), desalkyl NPC1161 and carboxy NPC1161 at m/z 434, 406, 349 and 449 in the positive ion mode with extractive ion monitoring (EIM). This method will have an important application in pharmacokinetic studies of NPC1161 and in understanding the mechanism of metabolism of this novel 8-aminoquinoline analog in more detail.     

Determination of paralytic shellfish poisoning toxins in cultured microalgae by high-performance liquid chromatography with fluorescence detection

A novel method for the determination of paralytic shellfish poisoning (PSP) toxins using high-performance liquid chromatography with fluorescence detection was developed. The fluorescent derivates of neosaxitoxin (neoSTX), saxitoxin (STX), gonyautoxins 1 and 4 (GTX1+4), and gonyautoxins 2 and 3 (GTX2+3) were separated on a μBondapak NH₂ column (300 mm × 3.9 mm, 10 μm) using water and acetate buffer (pH 6.5) as the mobile phase (1.00 mL min⁻¹) in gradient mode with fluorescence detection at 390 nm (excitation at 330 nm). The linear ranges of neoSTX, STX, GTX1+4 and GTX2+3 were 3.31–331, 0.952–95.2, 3.78–378 and 0.124–12.4 ng mL⁻¹, respectively. The detection limits of neoSTX, STX, GTX1+4 and GTX2+3 were 1.10, 0.32, 1.26 and 0.041 ng mL⁻¹, respectively. The method was successfully applied to the determination of PSP toxins in microalgae. The recoveries ranged from 88±2% to 107±4% and the relative standard deviations were 0.16% to 4.4%. The procedure is also environmentally friendly because no organic solvent is used in the mobile phase.     

GC-FID optimization and validation for determination of 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine and methamphetamine in ecstasy tablets

A methodology for the determination of 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and methamphetamine (MA) in seized tablets using gas chromatography with a flame ionization detector (GC-FID) is described. The chromatographic conditions, i.e. gas flow rates and temperatures for the column, injector and detector were optimized. The optimum chromatographic conditions were as follows: a CP-SIL 24 CB WCOT fused silica capillary column (30 m × 0.32 mm I.D., 0.25 μm film thickness), N₂ carrier gas flowing at 2.6 mL/min, injector temperature at 290°C and detector temperature at 300°C. The oven temperature was ramped from 80°C at a rate of 20°C/min to final temperature of 270°C (1 min). All analytes were well separated within 7 min with an analysis time of 10.5 min. Calibration curves were linear over the concentration ranges of 3.125–200 μg/mL for MDMA and 6.25–200 μg/mL for MDA and MA (r > 0.990). The intra- and inter-day precisions for determining all analytes were 2.32–10.38% RSD and 1.15–9.77% RSD, respectively. The intra- and inter-day accuracies ranged from −19.79 to +17.51% DEV and −6.84 to +5.2% DEV, respectively. The lower limits of quantification (LLOQs) were 3.125 μg/mL for MDMA and 6.25 μg/mL for MDA and MA. All analytes were stable at room temperature during 24 h but significant loss occurred after 2-month storage at −20°C. The method was shown to be useful for determining the purity of MDMA in seized tablets.     

An LC Ion-Pairing Method for the Determination of Fe(II) in Ferrous Bisglycinate Pharmaceutical Formulation

A reversed-phase ion-pairing liquid chromatographic method was developed and validated for the assay of Fe(II) in ferrous bisglycinate (Fe-bis-gly) capsules using 4-(2-pyridylazo) resorcinol reagent. The analysis was carried out using a Gemini RP-18 (150 mm × 4.6 mm I.D., particle size 5 μm) analytical column; the mobile phase consisted of a mixture of acetonitrile–water (28:72 v/v) containing 1 mM tetrabutylammonium hydrogensulfate and 1% phosphate buffer (pH 8.0). The flow rate was 1.0 mL min⁻¹ and the detection was achieved with a photodiode array (PDA) detector at 706 nm. The specificity of the method was proved using stress conditions and evaluated using a PDA detector. The data validation showed that the method is specific, fast, accurate, and reproducible for the determination of Fe-bis-gly in dosage form. The response was linear over a range of 1.0–2.6 μg mL⁻¹ (r = 0.9999). The accuracy of the method ranged from 98.02 to 102.75%. The RSD values for intra- and inter-day precision studies were below 1.3 and 1.1%, respectively. There was no interference of the excipients on the determination of the active pharmaceutical ingredient.     

Determination of Organophosphorus Pesticides in Soybean Oil, Peanut Oil and Sesame Oil by Low-Temperature Extraction and GC-FPD

A low-temperature clean-up method for residue determination was developed and validated for 14 organophosphorus pesticides in soybean oil, peanut oil and sesame oil by gas chromatography with flame photometric detector (GC-FPD). A different matrix influenced the response and retention time of pesticides. Hence matrix-matched calibration standards were used to counteract the matrix effect. The pesticide responses in blank samples of soybean oil, peanut oil and sesame oil were within the linear range of 0.02–1 mg kg⁻¹ and the correlation coefficients were higher than 0.9989. Average recoveries obtained from different oil samples at three fortified levels were higher than 50% with relative standard deviations (RSDs) of less than 15%. The limit of detections (LODs) of studied pesticides ranged from 2 to 5 μg kg⁻¹. Thirty-nine commercial samples were analyzed, and the results were confirmed by gas chromatography–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode.     

Ultra-trace analysis of pesticides by solid-phase extraction of surface water with carbopack B cartridges, combined with large-volume injection in gas chromatography

Summary A method has been developed for determination of twenty-four polar pesticides—nine organophosphorus pesticides, thirteen organonitrogen compounds, and two triazine degradation products—in surface water. It entails extraction of the target pesticides from 1-L water samples by solid-phase extraction (SPE), then gas chromatography (GC) with large-volume (40 μL) injection. Filtered surface water, from the St Lawrence River in Canada and the River Loire and its tributaries in France, was extracted on cartridges filled with 500 mg Carbopack B (120–400 mesh). Analysis was performed by gas chromatography with a thermionic specific detector (GC-TSD) and a mass spectrometric (MS) detector. Overall percentage recoveries were satisfactory (>70%) for all target pesticides, with precision below 10%. Detection limits were between 0.5 and 4 ng L⁻¹.     

Flavonol Derivatives for Determination of Cr(III) and W(VI)

 Simple, rapid, sensitive and selective methods for the determination of Cr(III) and W(VI) with flavonol derivatives in the presence of surface-active agents are proposed. In the pH ranges 3.4–4.2 and 1.9–2.5, the molar absorptivities of Cr(III)-morin-emulsifier S (EFA) and W(VI)-morin-polyvinylpyrrolidone (PVP) systems are 1.13×10⁵ and 2.13×10⁴ L mol⁻¹ cm⁻¹ at 435 and 415 nm, respectively. The Cr(III)-quercetin-PVP and W(VI)-quercetin-cetylpyridinium bromide (CPB) systems are formed in the pH ranges 4–4.6 and 2.2–2.8 with molar absorptivities 1.02×10⁵ and 9.02×10⁴ L. mol⁻¹ cm⁻¹ at 441 and 419 nm, respectively. The linear dynamic ranges for the determination of Cr(III) and W(VI) with morin in the presence of EFA and PVP are 0.03–0.46 and 0.71–8.1 μg mL⁻¹, respectively. The corresponding ranges with quercetin are 0.04–0.54 and 0.14–2.1 μg mL⁻¹ of Cr(III) and W(VI), respectively. The r.s.d (n = 10) for the determination of 0.25 and 3.7 μg mL⁻¹ of Cr(III) and W(VI) with morin and their detection limits are 0.88 and 0.99% and 0.016 and 0.63 μg mL⁻¹, respectively. Using quercetin, the r.s.d (n = 10) for 0.22 and 1.2 μg mL⁻¹ of Cr(III) and W(VI) and their detection limits are 0.92 and 0.91% and 0.015 and 0.08 μg mL⁻¹, respectively. The critical evaluation of the proposed methods is performed by statistical analysis of the experimental data. The proposed methods are applied to determine Cr in steel, non-ferrous alloys, wastewater and mud filtrate and to the determination of W in steel. Received March 8, 1999. Revision January 21, 2000.     

Simultaneous analysis of three catecholamines by a kinetic procedure: comparison of prediction performance of several different multivariate calibrations

A rapid kinetic method for the simultaneous determination of levodopa, dopamine, and dobutamine was examined and developed. It was based on a consecutive reaction of a reduction of Cu(II) to Cu(I) by catecholamines, followed by the complexation of Cu(I) with neocuproine to form a yellow product in an acetic acid-acetate buffer. Spectrophotometric data were recorded at 453 nm (wavelength at the yellow complex absorption maximum) for 300 s. Linear calibrations were obtained in the concentration ranges of (0.08–1.44) × 10⁻⁵ mol L⁻¹, (0.08–1.44) × 10⁻⁵ mol L⁻¹, and (0.16–1.44) × 10⁻⁵ mol L⁻¹ for levodopa, dopamine, and dobutamine, respectively. A variety of multivariate calibration models was developed for simultaneous analysis of the three analytes; while most models produced satisfactory prediction results for synthetic samples, the hybrid linear analysis method was arguably the best-performing (relative prediction error, RPET = 6.6 %). The proposed method was applied to an analysis of spiked rabbit serum samples and the results showed good agreement with the high performance liquid chromatography measurements.