ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

Flow injection on-line sorption preconcentration of platinum in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed. The pyrrolidine dithiocarbamate complexes of either Pt⁴⁺ or Pt²⁺, formed in 0.7 mol L^–1 HNO₃, are on-line adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol. An enhancement factor of 112 and a detection limit (3 σ) of 10 ng L^–1 along with a sampling frequency of 21 h^–1 are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mL min^–1. The relative standard deviation is 2.5% for 0.4 μg L^–1 Pt. The method has been applied to the determination of platinum in blood samples. Received: 6 October 1997 / Revised: 26 November 1997 / Accepted: 3 December 1997     

Determination of bromine and iodine in biological and environmental materials using epithermal neutron activation analysis

Epithermal neutron activation analysis (ENAA) was applied to the determination of the contents of bromine and iodine in 40 biological and environmental standard reference materials and Chinese diets. Boron nitride (BN) for solid samples and BN+Cd for liquid samples were adopted as shield material. Irradiation was carried out in inner and outer irradiation sites in a Miniature Source Reactor (MNSR) for solid and liquid samples, respectively. The 443 keV photopeak of ¹²⁸I and the 616 keV photopeak of ⁸⁰Br were used. The precision of measurement (relative standard deviation) is 2∼6% for contents of iodine of more than 100 ng/g and 8∼12% in the 20∼100 ng/g range in solid samples, and 12∼18% at less than 100 ng/ml in liquid samples. For bromine, the precision of measurement is 2–8% for solid samples and lower than 13% for liquid samples. The detection limits under experimental conditions varied between 10∼30 ng/g, 55∼95 ng/g and 25∼68 ng/g for iodine and 50∼150 ng/g, 200∼450 ng/g and 100∼300 ng/g for bromine in ENAA with BN shield in inner irradiation sites, with Cd shield and BN+Cd shield in outer irradiation sites, respectively. Received: 13 June 1996 / Revised: 2 September 1996 / Accepted: 19 September 1996     

Indirect atomic absorption spectroscopic determination of SiO2 in copper composite coatings

A fast, sensitive and reliable method for the indirect atomic absorption determination of SiO₂ in copper composite coatings after extraction of silicomolybdic acid in a mixture of isobutyl methyl ketone and butanol (volume ratio 5 : 1) and measurement of the molybdenum absorbance in an air/acetylene flame is described. The experimental conditions are optimized for (i) prevention of the silicon polymerization during sample preparation and storage; (ii) for overcoming of the Cu(SiF₆) – complex formation and (iii) for quantitative extraction of the yellow complex into the organic phase for a wide silicon concentration range. The method permits the determination of 0.5–10 mg/g Si in copper. The analytical performance of the proposed method is compared with direct Si determination using ICP-AES. Received: 15 May 1997 / Revised: 19 September 1997 / Accepted: 25 September 1997     

Sensitive and simple determination of the vasodilator agent dipyridamole in pharmaceutical preparations by phosphorimetry

The applicability of heavy atom-induced room-temperature phosphorescence to pharmaceutical samples is demonstrated in this work. Thus a new, simple, rapid, and selective phosphorimetric method for dipyridamole determination is proposed. The phosphorescence signals are a consequence of intermolecular protection when analytes are exclusively in the presence of heavy atom salts and sodium sulfite as an oxygen scavenger to minimize RTP quenching. The determination was performed in 0.1 mol L^–1 thallium(I) nitrate and 8 mmol L^–1 sodium sulfite at a measurement temperature of 20 °C. The phosphorescence intensity was measured at 635 nm, with excitation at 305 nm. Phosphorescence was easily developed; a linear concentration range was obtained between 0 and 100 ng mL^–1 with a detection limit of 940 ng L^–1, an analytical sensitivity of 2.5 ng mL^–1, and a standard deviation of 2.7% at 60 ng mL^–1 concentration. The method has been successfully applied to the analysis of dipyridamole in a unique Spanish commercial formulation containing 100 ng mL^–1 per capsule. The recovery was 101.6% with 6.5% standard deviation of analytical measurement. The method using the standard addition methodology has been validated.     

Determination of vitamin B12 in pharmaceutical preparations by a highly sensitive fluorimetric method

A fluorimetric method for the determination of vitamin B₁₂ has been developed. The fluorescence emission was measured at λ_ex/λ_em275/305 nm in phosphate buffer solution (pH 7.0), and the experimental variables and possible interference were studied. The linear calibration range was 1.000 ng/mL to 100.0 ng/mL with a correlation coefficient of 0.9994 and a detection limit of 0.1 ng/mL. The method is rapid, simple and highly sensitive. It was used to determine vitamin B₁₂ in pharmaceutical preparations. The recovery was 96%–98% and the relative standard deviation was in the range of 1.8%–2.7%. The results agreed with those obtained by spectrophotometry. Received: 17 July 2000 / Revised: 4 September 2000 / Accepted: 7 September 2000     

Laser-induced fluorescence determination of thallium in sediments

A simple dissolution procedure is decribed for sediments to be analyzed for thallium by Laser-Excited Atomic Fluorescence Spectrometry (LEAFS). It simply uses a nitric – hydrofluoric acid mixture at room temperature (a “cold dissolution” procedure as opposed to the hot acid digestion) followed by a dilution with water (as opposed to the tedious steps of separation and preconcentration). Excellent accuracy (91–106% recoveries) and precision (4–10% relative standard deviation) were demonstrated by the use of five sediment reference materials of diverse origins. The detection limit was estimated to be 0.5 ng/g of thallium. Additionally, a hot plate digestion procedure, using an in-house designed semi-enclosed Teflon beaker, was also investigated; its analytical results agreed with certified values and confirmed the adequacy of the cold dissolution technique. The method is being applied to study the sediment – water interactions in lake environments. Received: 30 December 1996 / Revised: 20 March 1997 / Accepted: 30 March 1997     

Micellar-stabilized room-temperature phosphorimetric determination of the fungicide thiabendazole in canned pineapple samples

A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives a linear dynamic range of 23.8–500.0 ng mL^–1 and a detection limit of 23.8 ng mL^–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL^–1 thiabendazole. Received: 30 April 1997 / Revised: 18 July 1997 / Accepted: 23 July 1997     

Sampling and determination of gas phase divalent mercury in the air using a KCl coated denuder

KCl coated denuders were employed for the measurement of divalent mercury (Hg²⁺) species in the air. Laboratory tests show that gaseous Hg²⁺ can be collected by the denuder with an average efficiency of 98% and elemental Hg will pass through it freely. Hg²⁺ trapped in the denuder can be quantitatively extracted by 1 mol/L HCl and analyzed by the method of SnCl₂ reduction-CVAFS determination. Hg²⁺ concentrations of 0.04–0.15 ng m^–3 corresponding to about 2–9% of the total gaseous mercury in the ambient air were determined at several sampling locations. Received: 24 September 1996 / Revised: 14 January 1997 / Accepted: 18 January 1997     

Simultaneous Quantification of Sodium Ferulate, Salicylic Acid, Cinnarizine and Vitamin B1 in Human Plasma by LC Tandem MS Detection

A rapid and simple high performance liquid chromatographic method coupled with tandem mass spectrometry (LC–MS–MS) via electrospray ionization (ESI) has been developed and validated to separate and simultaneously quantify sodium ferulate (SF), salicylic acid (SA), cinnarizine (CIN) and vitamin B1 (VB1) in human plasma. Gemfibrozil (GEM) was used as the internal standard (IS) for SF and SA, whereas lomerizine (LOM) was used as the IS for CIN and VB1. The plasma samples were prepared by one-step protein precipitation followed by an isocratic elution with 10 mM ammonium acetate buffer (pH = 5.0): acetonitrile (35:65, v/v,) on an Agilent Zorbax SB-CN column (150 mm × 2.0 mm ID, 5 μm). The precursor and product ions of these drugs were monitored on a triple quadrupole mass spectrometer, operating in the selected reaction monitoring mode (SRM) with polarity switch, in the negative-ion mode for SF, SA and GEM, in the positive-ion mode for CIN, VB1 and LOM. The method was validated over the concentration range of 1.5–1,000 ng mL⁻¹ for SF, 20–5,000 ng mL⁻¹ for SA, 2–500 ng mL⁻¹ for CIN, 1–30 ng mL⁻¹ for VB1. The intra- and inter-batch precisions were less than 15% of the relative standard deviation. The recoveries for analytes and IS achieved from spiked plasma samples were consistent and reproducible. The validated LC–MS–MS method has been successfully applied to the pharmacokinetic study of sodium ferulate and aspirin capsule in healthy volunteers.     

Direct multiparametric determination of anions in soil samples by integrating on-line automated extraction/filtering with capillary electrophoresis

An integrated continuous flow-capillary electrophoresis for the determination of soluble anions in soil samples is presented. A filtration probe coupled with the flow system, which is located before the capillary electrophoresis instrument, was designed to simplify sample pretreatment and to perform clean-up of aqueous soil suspensions. Only the manual weighing of the samples is needed. The extraction process for soil samples was optimized. The clear filtrate containing the soluble anions from soil was then passed to the capillary electrophoresis equipment by a home-made programmable arm. Chloride, sulfate, nitrite and nitrate were determined in soil samples at μg g^–1 level and the results compared to manual reference methods. The precision expressed as relative standard deviation was in the range of ± 1.6 to ± 2.5% for the set of analytes determined. The procedure is up to 4 times faster than the competitive manual methods. Received: 29 July 1997 / Revised: 10 September 1997 / Accepted: 13 September 1997     

Determination of citric acid in soft drinks using flow injection with potentiometric detection

A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with copper (II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations of citric acid in the range of 1 × 10^–3 mol/L – 1 × 10^–2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0% to 101.0%. The system allows a sampling frequency of 60 samples/h. Received: 22 October 1998 / Revised: 14 December 1998 / Accepted: 16 December 1998     

Highly selective catalytic determination of ultra trace amounts of rhodium by linear sweep voltammetry

A highly selective and sensitive method is proposed for the determination of rhodium, based on the catalytic effect on the oxidation of Nile blue by periodate. The reaction rate is monitored by measuring the current of Nile blue at –0.37 V vs. Ag/AgCl reference electrode. The linear working range is 5 to 100 ng/mL with a limit of detection of 0.1 ng/mL. The interference effects of more than forty ions were studied. The method was used for the determination of Rh (III) in synthetic samples with satisfactory results. Received: 2 July 1997 / Revised: 23 September 1997 / Accepted: 24 September 1997     

A new validated high-performance liquid chromatographic method for the determination of EGIS-9933 in rat plasma

Summary A new highly sensitive high-performance liquid chromatographic (HPLC) procedure for determination of EGIS-9933 (a newly developed anxiolytic compound) in rat plasma is described. A gradient, elution method with UV detection at 270 nm has been developed using a mobile phase of a mixture of A: methanol:acetonitrile 1:9 and B:0.5% triethilamine in water, the pH of B was adjusted to 3 with phosphoric acid. Solid phase extraction (SPE) was used for the sample preparation. The calibration was linear in the 10–10000 ng mL⁻¹ concentration range. The limit of quantification was 10 ng mL⁻¹. The bioanalytical method was validated according to internationally accepted criteria for biological samples. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Development and Validation of LC–MS Method for the Determination of Hydroxyzine Hydrochloride in Human Plasma and Subsequent Application in a Bioequivalence Study

A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry method has been developed and validated for the determination of hydroxyzine hydrochloride in human plasma. Samples were separated using a Thermo Hypersil-HyPURITYC18 reversed-phase column (150 mm × 2.1 mm i.d., 5 μm). The mobile phase consisted of 50 mM ammonium acetate (pH 4.0)–methanol–acetonitrile (45:36:19, v/v). Hydroxyzine and its internal standard were measured by electrospray ion source in positive selective ion monitoring mode. The method was validated with a linear range of 1.56–200.0 ng mL⁻¹ and the lowest limit of quantification was 1.56 ng mL⁻¹ for hydroxyzine hydrochloride (r ²= 0.9991). The extraction efficiencies were about 70% and recoveries of the method were in the range of 93.5–104.4%. The intra-day relative standard deviation (RSD) was less than 8.0% and inter-day RSD was within 7.4%. QC samples were stable when kept at ambient temperature for 12 h at −20 °C for 30 days and after four freeze–thaw cycles. The method has been successfully applied to the evaluation of pharmacokinetics and bioequivalence of two hydroxyzine hydrochloride formulations in 12 healthy Chinese volunteers after an oral dose of 25 mg.     

FIA determination of pyruvate in serum based on direct chemiluminescence oxidation

Chemiluminescence was observed by mixing acidic potassium permanganate solution with pyruvate in the presence of quinine. A new simplified method for pyruvate determination based on this phenomenon was established. The chemiluminescence intensity is a linear function of the concentration of pyruvate in the range of 2 × 10^–6 to 1 × 10^–3 g/mL with a detection limit of 0.8 μg/mL and a relative standard deviation of less than 2.3%. The method has been successfully used to determine pyruvate in serum. Received: 3 April 1998 / Revised: 20 July 1998 / Accepted: 17 September 1998     

Determination of total iron in ground waters and multivitamin tablets using a solid-phase reactor with tiron immobilised on amberlite ion-exchange resin in a flow injection system

A method is described for the flow injection determination of total iron as Fe(III) using a solid-phase reactor containing disodium-1,2-dihydroxybenzene-3,5-disulphonate (tiron) as substrate. The iron(III) reacted with tiron to form a complex which absorbs strongly at 667 nm, where it was measured spectrophotometrically. The system has a linear range of 1 to 50 mg L^–1 with a detection limit of 0.67 mg L^–1. It is suitable for the determination of total iron in multivitamin tablets and iron-rich ground waters, with a relative standard deviation of better than 1.1%. The results obtained compared favourably with the certified values and a standard ICP-AES method. Received: 12 November 1997 / Revised: 9 March 1998 / Accepted: 15 March 1998     

Determination of copper in sulfide minerals by Zeeman electrothermal atomic absorption spectrometry

A method for the determination of copper in some sulfide minerals (lorandite, realgar, orpiment, marcasite, stibnite, galenite and sphalerite) by Zeeman electrothermal atomic absorption spectrometry is presented. After the dissolution of samples, copper was extracted with sodium diethyldithiocarbamate into different organic solvents (carbon tetrachloride, chloroform and methylisobutyl ketone) at pH 11.0–12.0. The procedure was verified by standard addition. The standard deviation (SD) for 0.5 ng Cu is 0.01 ng, the relative standard deviation ranges from 3.5 to 5.5% and the detection limit of the method, calculated as 3 SD of the blank, was found to be 0.05 μg · g^–1.     

Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS

A simple, rapid and reproducible method for the determination of some pesticide residues in water was developed using micro liquid-liquid extraction and gas chromatography - mass spectrometry with selected ion monitoring (GC/MS-SIM). The chlorinated insecticides α- and β-endosulfan and endosulfan-sulfate as well as the synthetic pyrethroids bifenthrin, permethrin, cypermethrin, fenvalerate and deltamethrin can be separated from a 500 mL sample water extracted with 0.5 mL of n-hexane containing anthracene-d₁₀ as internal standard without clean-up in only 13 min. The recovery efficiencies of the tested compounds yielded more than 93.0% at a fortification level of 5 ng mL^–1 and their relative standard deviations were between 1.9 and 11.7%. Detection limit of each compound ranged between 3 and 35 pg mL^–1. The method was applied to ground, sea and tap waters from Almería (Spain). The solubilities in water at 20° C were determined. Received: 21 March 1997 / Revised: 28 July 1997 / Accepted: 18 August 1997