Anion Exchange-Adsorption on Low Capacity Anion Exchangers: Separation of Organic Acids,Amino Acids,Small Chain Peptides

Abstract

The variables that influence the retention of organic analyte anions on a macroporous, high surface area polystyrenedivinyl-benzene copolymer that is chemically modified by attaching tetraalkylammonium groups to the copolymer surface are identified and studied as a function of anion exchange capacity. A combined adsorption-anion exchange retention of the organic analyte anion is possible providing the analyte has both a hydrophophic center and an anionic charge site. As the column anion exchange capacity (0 to 173 μeq of anion exchange sites/column was studied) increases, analyte retention due to adsorption decreases and retention due to anion exchange increases. The factors influencing organic analyte anion retention by adsorption are low anion exchange capacity and mobile phase solvent composition, type of organic modifier, and pH for analytes that are weak organic acids. For anion exchange the major factors are a high anion exchange     

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO₄. The relative standard deviation (10 replicate analyses) at the 10 μg l^?1 of chromium (VI) and 10 μg l^?1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l^?1 and 0.033 μg l^?1, respectively.     

Solid-Phase Extraction,Clean-pp and Liquid Chromatography for Routine Multiresidue Analysis of Neutral and Acidic pesticides In Natural Waters in One Run

Abstract

Solid-phase extraction using C₁₈ silica cartridges, liquid chromatography analysis and UV diode array detection were investigated for the routine trace-level determination of neutral pesticides over a wide range of polarity. Detection limits below the 0.1 μg/1 range were easily obtained in drinking water. If neutral and acidic pesticides over a wide range of polarity have to be determined in the same run, samples have to be acidified to obtain good recoveries of extraction. The effect of the sample matrix was studied and detection limits in the 0.1 μg/1 range were obtained in drinking water except for the more polar ones which are in the interfering peak of humic and fulvic acids. For surface water, a clean-up step using a Florisil cartridge has to be included in the procedure that allows detection limits in the range 0.05–0.3 μg/1.     

Simultaneous determination of sulfite, sulfate, and hydroxymethanesulfonate in atmospheric waters by ion-pair HPLC technique

A reversed-phase ion-pair HPLC with indirect photometric detection for the simultaneous determination of sulfite, sulfate, hydroxymethanesulfonate (HMS), and other inorganic anions in atmospheric water has been developed. Separations were accomplished in less than 10 min in a cetylpyridinium-coated C₁₈ column with 0.5 mM potassium hydrogen phthalate-0.015% triethanolamine-3% methanol at pH 7.9 as mobile phase. Quantitation was carried out by the peak area method, with detection limits in the pmol range. UV light absorption responses were linear over a wide concentration range from several hundred μmoles to the detection limits of each anion. The application of the method provides a rapid and efficient technique for the quantitative determination of sulfur and other inorganic species in atmospheric liquids.     

Analytical applications of laser moding caused by intracavity absorption

A continuous CO₂ laser with a reflecting mirror can operate at several wavelengths simultaneously. If an organic vapor is introduced into a separate cavity in the laser optical path, the laser will sometimes mode rapidly causing some lasing lines to diminish to zero and others to become enhanced; this has been observed even for very low amounts (10^-5 g) of organic gases. Laser intercavity absorption spectroscopy depends on overlap of a vibrational—rotational line of a sample with a laser transition line. The absorption by the sample greatly affects the laser wavetrain at that particular wavelength and interferes with the lasing action. The technique is not based on Beer's law, and the detection limits observed are orders of magnitude better than those of conventional infrared absorption spectroscopy. Two laser systems were used and various organic gases were studied. When a totally reflecting mirror which permitted free moding was used, the detection limits found were 0.14 μg, 0.95 μg and 0.60 μg for vinyl chloride, propylene, and ethylene, respectively. When a grating was used as the rear cavity optics restricting the wavelengths of the laser lines, the detection limits were 140 μg, 94 μg, 63 μg and 0.26 μg for vinyl chloride, propylene. ethylene and ethyl chloride, respectively.     

The Determination of a New Trifluorinated Quinolone,Fleroxacin, Its N-Demethyl,and N-Oxide Metabolites in Plasma and Urine by High Performance Liquid Chromatography with Fluorescence Detection

Abstract

A liquid chromatographic method is described for the determination of the new fluoroquinolone Ro 23–6240 and its N-demethyl and N-oxide metabolites in plasma and urine. The three substances were extracted from aqueous solution with dichloromethane/isopropanol containing sodium dodecyl sulphate. After evaporation and reconstitution, samples were analysed on a reversed-phase column using ion pair chromatography and fluorescence detection. The limit of quantification was 10–20 ng/ml (RSD 4%) using a 0.5 ml plasma sample, and the inter assay precision was 3–10% over the concentration range 50 ng/ml to 20 μg/ml. Recovery from plasma was 81% (RSD 10%) over the range 10 ng/ml to 5 μg/ml. The method has been applied successfully to the analysis of several thousand samples from human pharmacokinetic studies. Care has to be taken to avoid exposure of samples to direct sunlight, and the use of opaque vessels for sample storage and handling is recommended.     

Ion Chromatographic Determination of Phosphorus in Eight U.S.G.S. Standard Rocks

Abstract

A method is described for the analysis of phosphorus in geological samples involving the decomposition of the sample with hydrofluoric acid in a quartz tube and the measurement of phosphate ion concentration using an ion chromatograph (Dionex 10) with an anion separator column (Wescan anion 269-001). The detection limit is between 0.05-0.5% P₂O₅ in the original sample. Multiple analyses of eight U.S.G.S. standard rocks yielded a relative standard deviation range between 2.37-16.67%. In excess of 15 samples can be analyzed in an 8 hour day.     

Simultaneous determination of trace level bromate and chlorinated haloacetic acids in bottled drinking water by ion chromatography

A convenient and sensitive method for the simultaneous determination of trace level of bromate and chlorinated haloacetic acids in bottled drinking water with ion chromatography is presented. With a high capacity anion-exchange column and 11.5 mmol/l Na₂CO₃ eluent, all the 16 analytes could be separated in one injection within 31 min. By employing a microwave based evaporation technique, the bottled drinking water sample could be concentrated tenfold in 10 min. The recoveries of the compounds ranged from 90.6 to 107.2%. With a 500 μl large volume injection and high performance anion Atlas electrolytic suppressor, the detection limits were 0.06, 0.08, 0.06, 0.14 and 0.85 μg/l for BrO₃⁻, ClO₃⁻, monoacetic acid, dichloroacetic acid and trichloroacetic acid, respectively.     

Direct determination of Cu,Mn, Pb,and Zn in beer by thermospray flame furnace atomic absorption spectrometry

In this work, thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was employed for Cu, Mn, Pb, and Zn determination in beer without any sample digestion. The system was optimized and calibration was based on the analyte addition technique. A sample volume of 300 μl was introduced into the hot Ni tube at a flow-rate of 0.4 ml min⁻¹ using 0.14 mol l⁻¹ nitric acid solution or air as carrier. Different Brazilian beers were directly analyzed after ultrasonic degasification. Results were compared with those obtained by graphite furnace atomic absorption spectrometry (GFAAS). The detection limits obtained for Cu, Mn, Pb, and Zn in aqueous solution were 2.2, 18, 1.6, and 0.9 μg l⁻¹, respectively. The relative standard deviations varied from 2.7% to 7.3% (n=8) for solutions containing the analytes in the 25–50 μg l⁻¹ range. The concentration ranges obtained for analytes in beer samples were: Cu: 38.0–155 μg l⁻¹; Mn: 110–348 μg l⁻¹, Pb: 13.0–32.9 μg l⁻¹, and Zn: 52.7–226 μg l⁻¹. Results obtained by TS-FF-AAS and GFAAS were in agreement at a 95% confidence level. The proposed method is fast and simple, since sample digestion is not required and sensitivity can be improved without using expensive devices. The TS-FF-AAS presented suitable sensitivity for determination of Cu, Mn, Pb, and Zn in the quality control of a brewery.     

Optimisation of a Flow Injection System with a Piezoelectric Quartz Crystal Detector for the Determination of Inorganic Mercury

ABSTRACT

A new method combining flow injection methodology with quartz crystal microbalance (QCM) detection is proposed for inorganic mercury analysis. A modified simplex method is used in order to maximise the observed analytical signals (crystal frequency decrease). Six parameters were optimised: the concentration of the acidic carrier solution, the lengths of the sample loop and mixing coil, and the flow rates of the sample carrier, the reductant stream (SnCl₂), and the carrier of the mercury vapour (N₂). An increase of 18% in the signal of the centroid of the calibration line was achieved, as well as an increase in the sensitivity from 290 Hz μg^? to 313 Hz μg^?. Following the proposed procedure, detection limits of 47 μg L^? of inorganic mercury were found for sample volumes of 0.5 mL.     

dual stage preconcentration system for flame atomic absorption spectrometry using flow injection on-line ion-exchange followed by solvent extraction

A dual stage preconcentration system based on flow injection on-line ion-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger is incorporated into the FI manifold. The analyte is retained on the column by time-based sample loading and eluted by 1 mol/L HNO₃. The eluate is subsequently merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK). Lead is extracted on-line into IBMK as the ion-pair formed between the iodoplumbate anion and tetrabutylammonium cation. The organic phase is separated from the aqueous phase by a gravity phase separator. 50 μL of concentrate is introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 is achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The precision (relative standard deviation) is 2.4% at 10 μg/L level and the detection limit is 0.3 μg/L (3 σ). The method was successfully applied to the determination of lead in water samples.     

A Direct and Sensitive Method for the Determination of Salicylamide in Microplasma Samples by High-Performance Liquid Chromatography Using Fluorescence Detection

Abstract

A quantitative analysis of salicylamide in microplasma volumes by high-performance 1iquid chromatography using fluorescence detection is reported. The procedure is extremely simple and very rapid, involving the direct introduction of the plasma sample on the HPLC column. The assay procedure is linear over the concentration range studied, 0–100 ng/ml with correlation coefficient for the linear regression, r = 0.998. This assay procedure enables the detection of salicylamide as low as 5.0 ng/ml in plasma, using sample volume of 100 μl.     

Monitoring Airborne Particulate Mass by Beta Absorption

Abstract

A prototype airborne particulate mass monitor, using the principle of beta radiation absorption, has been fabricated and evaluated on airborne particulate matter. A detection sensitivity of 80 μg/cm² was attained. A series of samples were collected, and a comparison made between the gravimetric and beta absorption results obtained on each sample. This study demonstrated the feasibility of fabricating a fully automated system for the collection and analysis of airborne particulate mass, using the principle of beta absorption attenuation.     

阴离子交换-积分脉冲安培检测法分离测定氨基酸注射液中的氨基酸和葡萄糖

 用阴离子交换 积分脉冲安培检测法测定了氨基酸注射液中 1 7种氨基酸和葡萄糖。研究了氨基酸和葡萄糖在阴离子交换中的保留行为。采用了优化的水、NaOH和NaAc三元梯度淋洗条件。在优化的梯度淋洗条件和积分脉冲安培检测条件下 ,氨基酸和葡萄糖的检出限为 0 3pmol～ 1 0 3pmol,线性范围约为 2个数量级。样品加标回收率为 88 3 %～ 1 0 4 6 %。方法简单、灵敏、准确。     

Tetradecyldimethylbenzylammonium thiocyanate adsorbent supported on naphthalene for the preconcentration and determination of cobalt in aluminium alloys and steels using atomic absorption spectrometry

A solid ion-pair material produced from tetradecyldimethylbenzylammonium chloride (TDBA) and ammonium thiocyanate on naphthalene provides a simple, rapid and selective technique of preconcentrating cobalt from up to 200 ml of aqueous solution. Cobalt reacts with sodium 1-nitroso-2-naphthol-3,6-disulphonate (nitroso-R salt) to form a brown, water-soluble chelate anion. The chelate anion forms a water-insoluble Co-nitroso-R salt-TDBA complex on naphthalene packed in a column and trace cobalt is quantitatively retained on the naphthalene in the pH range 2.7–11.0 at a flow-rate of 2 ml min^?1. The solid mass is stripped from the column with 5 ml of dimethylformamide (DMF) and cobalt is measured by atomic absorption spectrometry (AAS) at 241 nm. The calibration graph is linear over the concentration range 0.5–15μg Co in 5 ml of dimethylformamide solution. Seven replicate determinations of 9 μg of cobalt gave a mean absorbance of 0.095 with a relative standard deviation of 1.7%. The sensitivity for 1% absorption was 0.0834μg ml^?1 (0.240 μg ml^?1 for direct AAS on the aqueous solution). The proposed method was utilized for the determination of cobalt in standard aluminium alloys and steel samples.     

Microdetermination of Trace Cobalt In Water By Direct Polyurethane From Thin-Layer Spectrophotometry

Abstract

Traces of cobalt in water sample are preconcentrated into a white thin-layer of a parallelpiped polyurethane foam, by the sorption of its thiocyanate complex from acidic medium.

The cobalt thiocyanate complex possesses a blue colour in the foam matrix which has a maximum absorption at 625 nm. the absorbance of the Dlue species is mesured directly in the foam matrix at 680 625 and 540 nm. with different media in the measuring cell. the net absorbance at 625 nm is calculated using a multiwavelength program, where the value of the blank is subtracted. Beer's law is obeyed in the concentration range 0.025-2.0 μg per dl with a detection limit of 25 μg per dl for a 100 ml sample volume. the method is specific for cobalt     

Identification and quantitative analysis of nitrogen-containing polycyclic aromatic hydrocarbons in sediments

An integrated analytical methodology has been developed for determining nitrogen-containing polycyclic aromatic hydrocarbons, which enables quantitation of individual contaminants as low as 1 μg/kg in sediment samples. A cross-sectional profile from the Hamilton Harbour sediment samples was analyzed for azaarenes. These contaminants were separated by Soxhlet extraction, and pH adjustment allowed their isolation from different classes of neutral and acidic components. Separation and identification of the organic bases in each sample were achieved by using open tubular column gas chromatography with thermionic detection and HRGC-mass spectrometry. Organic bases present in the samples included mostly azaarenes such as acridines, benzacridines, azafluorene, benzoquinolines, azapyrenes, etc. Quantitation and environmental significance of these compounds are discussed. Recoveries of individual azaarenes at two different levels were evaluated. Data presented indicate that detection limits of this method are between 1 and 10 μg/kg. Recovery azaarenes from bottom sediment samples at concentration levels between 1 to 100 μg/kg is 81 ± 17%.     

A Stability-Indicating Liquid Chromatographic Method for the Analysis of Erythromycin in Stored Biological Fluids Using Amperometric Detection

Abstract

A simple, sensitive and reliable high-performance liquid chromatographic procedure has been developed for the determination of erythromycin in human serum and urine using amperometric detection. A solid-phase extraction procedure was used followed by chromatography on a reverse-phase column. The mean recovery of erythromycin from serum and urine was 80%. Calibration plots for erythromycin base in serum and urine were linear over the ranges 0.25–5.0 μg/ml and 1.25–25.0 μg/ml respectively, with a sensitivity limit of 0.1 μg/ml.

This method allows both erythromycin and its principle degradation product, anhydroerythromycin, to be determined during a period of sample storage at 4°C and ?15°C. The method is sufficiently sensitive and precise and is thus highly suited for use in both pharmacokinetic and stability studies.     

Rapid and simple chromatographic separation of V(V) and V(IV) using KH-phthalate and their determination by flame atomic absorption spectrometry

A method was developed for the chromatographic separation of V(V) and V(IV) based on the different sorption forces of these vanadium species in C18 columns in presence of KH-phthalate. The vanadium species were detected with a flame atomic absorption spectrometer with acetylene/N₂O flame. The detection limits (3σ) of V(V) and V(IV) were 0.18 μg/mL and 0.15 μg/mL, respectively. The relative standard deviations (N = 5) are 4.2% and 3.4% for 20–20 μg/mL V(V) and V(IV), respectively. The sampling frequency is 75/h. Because of the special interaction occurring between phthalate and V(IV) on the C18 column and the acetylene/N₂O flame atomic absorption detection, practically no interferences can be detected even in large inorganic matrix.     

Multi-element characterization of high-purity titanium dioxide by neutron activation analysis

A radiochemical neutron activation analysis method for the determination of 34 elements in titanium dioxide has been developed. For the assay of indicator radionuclides with short and with long half-lives, the radiochemical separation was performed by anion exchange on a Dowex 1 × 8 column and by combination of cation and anion exchange on a Dowex 50W × 8 and a Dowex 1 × 8 column from HF- and HF/NH₄F-medium, respectively. With both separation modes, a selective removal of the matrix-produced radionuclides ⁴⁶Sc, ⁴⁷Sc and ⁴⁸Sc was achieved. A selective extraction of copper with dithizone from 15 mol/L HF enabled counting the intensive but unspecific 511-keV rays of ⁶⁴Cu for the determination of Cu. The limits of detection achieved were between 0.004 ng/g for Sm and 0.8 μg/g for Sn (via ¹²⁵Sb). The elements La, Mn and Th were determined by instrumental neutron activation analysis only. These techniques were applied to the analysis of two titanium dioxide samples of different purity grade. The results and limits of detection are compared with those of other methods.