Uğur Şahin

Spectrophotometric determination of molybdenum in steel samples utilizing selective sorbent extraction on Amberlite XAD-8 resin

Abstract A preconcentration procedure, using a short column filled with Amberlite XAD-8, is proposed for the Spectrophotometric determination of traces of molybdenum. Molybdenum as a Mo(V)- thyiocyanate complex is sorbed strongly on the resin and is easily eluted with acetone. The molybdenum complex in the effluent can be determined spectrophotometrically at 462.0 nm. The influence of several ions, as interferents, was discussed. The procedure was applied to the determination of molybdenum in steel with satisfactory results (recovery ≥ 95%; relative error ≤ 3%; relative standard deviation ≤ 5% in the concentration range of 0.006–0.024%; IUPAC detection limit, 60 μg l −1 in solution).

An on-line preconcentration/separation system for the determination of bismuth in environmental samples by FAAS

An on-line preconcentration procedure for the determination of bismuth by flame atomic absorption spectrometry (FAAS) has been described. Lewatit TP-207 chelating resin, including iminodiacetate group, packed in a minicolumn was used as adsorbent material. Bi(III) was sorbed on the chelating resin, from which it could be eluted with 3 mol L(-1) HNO(3) and then introduced directly to the nebulizer-burner system of FAAS. Best preconcentration conditions were established by testing different resin quantities, acidity of sample, types of eluent, sample and eluent solution volumes, adsorption and elution flow rates, and effect of interfering ions. The detection limit of the method was 2.75 microg L(-1) while the relative standard deviation was 3.0% for 0.4 microg mL(-1) Bi(III) concentration. The developed method has been applied successfully to the determination of bismuth in pharmaceutical cream, standard reference materials and various natural water samples with satisfactory results.

Development of a new on-line system for the sequential speciation and determination of chromium species in various samples using a combination of chelating and ion exchange resins

A new on-line flow injection (FI) procedure for the sequential separation, preconcentration and speciation of Cr(III)/Cr(VI) species in different matrices is described based on the combining of solid phase extraction and flame atomic absorption spectrometry (FAAS). Poly 2-(5-methylisoxazol)methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinyl-benzene and Dowex 21K resins were used as chelating and ion-exchange materials for the separation/preconcentration of Cr(III) and Cr(VI) ions, respectively. Trace amounts of chromium retained on the resins were eluted sequentially with HNO3 and then introduced directly to the nebulizer-burner system of FAAS. The optimum conditions such as pH of the sample solution, amount of the resin, volume of the sample and interfering ions, which are effective on the quantitative recovery of the analytes, were investigated for sequential determination of Cr(III) and Cr(VI) ions. The preconcentration factors were found to be 48 and 30 for Cr(III) and Cr(VI), and the detection limits corresponding to three times the standard deviation of the blank (3s/b) were 0.05 and 0.3 µg L(-1), respectively. The method was verified by analyzing a certified reference material. The proposed method was applied to the determination based on the speciation of chromium in various real samples with satisfactory results.

An automated on-line minicolumn preconcentration cold vapour atomic absorption spectrometer: Application to determination of cadmium in water samples

A method was developed for on-line solid phase preconcentration and cold vapour atomic absorption spectrometric determination of Cd(II) in aqueous samples. Lewatit Monoplus TP207 iminodiacetate chelating resin was used for the separation and preconcentration of Cd(II) ions at pH 4.0. The whole system was labmade. The influence of analytical parameters such as concentration of eluent and sodium tetrahydroborate solution, flow rate of eluent, sample, and Ar, and matrix ions were investigated. A preconcentration factor of 20 and a detection limit (3s(b)) of 2.1ngL(-1), along with a sampling frequency of 28h(-1) were achieved with 1.4min of sample loading time and with 2.8mL sample consumption. The relative standard deviation (R.S.D.) was 2.5% for 0.05μgL(-1) Cd(II) level. The developed method was used for Cd(II) analysis in water samples. The certified reference material (LGC6019) experimental results are in good agreement with the certified value.

On-line determination of palladium by flame atomic absorption spectrometry coupled with a separation/preconcentration minicolumn containing a new sorbent

A method was developed for the on-line determination of palladium in complex matrices with flame atomic absorption spectrometry (FAAS) using Amberlite XAD-16 resin functionalized with 2-[2-(5-thiol-1,3,4-thiadiazolyl)]-azonaphthol (TTAN) reagent. Optimum experimental conditions such as pH of sample, type of eluent, amount of resin, volumes of sample and eluent solution, flow rates of sample and eluent, and effect of interfering ions were established. A 0.1 mol L−1 thiourea solution in 0.5 mol L−1 HCl was used as the eluent and subsequently transportation the analyte ions into the nebulizer–burner system for atomization. The synthesized chelating resin material showed excellent chemical and mechanical resistance, fast adsorption kinetics permitting the use of high sample flow rates without significant losses of retention efficiency. The detection limit of the method was 1.5 µg L−1 while the relative standard deviation (RSD%) was 2.4% at 0.1 mg L−1 Pd(II) level. The developed method was successfully applied to the determination of palladium in the catalytic converter and water samples.

An automated solid phase extraction coupled with electrothermal atomic absorption spectrometric determination of Pb(II) in high salt content samples.

A novel Pb(II) analysis in dialysis concentrates and seawater samples has been developed with on-line separation and preconcentration system coupled with electrothermal atomic absorption spectrometer (FI-ETAAS). Lewatit Monoplus TP207 imminodiacetat chelating resin was used for separation and preconcentration of Pb(II) ions at pH 4.0. The influence of the analytical parameters such as type of eluent, flow rate of eluent and sample, eluent volume and matrix ions were investigated. W-Rh coated furnace was used as the atomization site. A preconcentration factor of 14 and a detection limit (3s/b) of 12 ng L(-1), along with the sampling frequency of 21 h(-1) were achieved with a 170 s sample loading time and with 2.8 mL sample consumption. The relative standard deviation (RSD) was 1.6% for 1 μg L(-1) Pb(II) level. The developed method was used for Pb(II) analysis in dialysis concentrates and seawater samples. The certified reference material (CRM403) experimental results are in good agreement with the certified value.

On-line solid-phase separation/preconcentration for the determination of copper in urine by flame atomic absorption spectrometry

A new on-line separation/preconcentration system was developed for the determination of Cu(II) ions by flame atomic absorption spectrometry in urine samples. A newly synthesized chelating resin, by anchoring eriochrome blue black R reagent to Amberlite XAD-16 resin, was used as a packing material for the selective separation/preconcentration of Cu(II) ions. The influence of the parameters on the determination of Cu(II) ions such as pH of sample solution, amount of the resin, eluent type, interfering ions and flow variables was studied. The detection limit of the method was 1.0 μg L(-1) while precision was 2.3% (n=15) at 50 μg L(-1) Cu(II) level. The adsorption capacity of the resin was 217 μg g(-1) Cu(II). The accuracy of the method was proven using TMDA-64 standard lake water and synthetic urine sample. The developed method has been applied successfully to the determination of copper in urine with satisfactory results.

Real-Time Monitoring of Indigo Concentrations in the Dyebath with a Laser Diode Spectrometer

A laser diode absorption spectrometer is coupled with a continuous dilution system for real-time monitoring of indigo dyeing of denim yarn. The reduced form of indigo in the dyebath is continuously pumped by a peristaltic pump into a mixing cuvette, where it is diluted by a factor of 80 with aerated water and oxidized into its stable form. This solution is then pumped into the sampling cell of the laser diode spectrometer for absorption measurements. Monochromatic radiation emitted from the laser diode at 635 nm is used to measure indigo absorption at the shoulder of a broad absorption peak. A linear calibration curve is obtained in a concentration range between 10 and 150 mg/L with a linear regression coefficient of r2 = 0.9993, which corresponds to indigo concentrations in the dyebath covering the range between 0.8-12 g/L. This range exceeds indigo concentrations typically used in industry, which range between 1-3 g/L. The reproduc ibility of measurements is 0.5%. In this technique, there is no interference due to sulfur compounds present in the dyebath, which is a problem with electrochemical titration methods commonly used for indigo determinations.

DLLME-spectrophotometric determination of glyphosate residue in legumes

A new separation and pre-concentration method for spectrophotometric determination of glyphosate herbicide was developed. Glyphosate was converted into dithiocarbamic acid with CS2, followed by copper in the presence of ammonia to promote complex formation. This complex was collected in a CH2Cl2 organic drop and absorbance measured at 435nm. The analytical parameters, such as the amount of NH3, Cu(II) and CS2, type of extraction solutions, and the ratio of dispersive and organic liquids were optimized. The calibration curve was linear in the range 0.5-10mgl-1. The limits of detection and quantification were calculated from 3s to 10s criterions as 0.21mgl-1 and 0.70mgl-1, respectively. The developed method was applied to legume samples with the satisfactory recovery values of 98±4-102±3%.

Determination of 3,5 – dimethylpyrazolium glyceroborate nitrification inhibitor in nitrogen fertilizer samples: HPLC-DAD method development and validation for 3,5 – dimethylpyrazole

3,5 - Dimethylpyrazolium glyceroborate is a nitrification inhibitor (a member of pyrazole derivatives) used for the fixation of nitrogen into the soil. In this study, an HPLC-DAD method was developed and validated for determination of 3,5 - dimethylpyrazole in order to determine 3,5 - dimethylpyrazolium glyceroborate in fertilizer samples. For method development, analytical parameters like type of eluent solution and column filling material and device parameters like eluent flow rate, column oven temperature and measurement wavelength were all optimized. For method validation, implementations were performed for linearity, limit of detection (LOD), limit of quantification (LOQ), specificity, stability, intra- and inter-day precision and accuracy. The developed and validated method was used for inhibitor detection in nitrogenous fertilizers. Sample analyses were performed with 95.6-103.3% recovery rates and 0-4.61% relative errors.