O. Yavuz Ataman

Chemical composition of precipitation near an industrial area at Izmir, Turkey

Abstract Wet and dry deposition samples were collected near an industrial area on the Aegean coast of Turkey. Concentrations of major ions (Cl − , SO 4 2− , NO 3 , H + , Na + , K + , Cat 2+ Mg 2+ and NH 4 + were determined. The pH of the precipitation, calculated from the volume weighted H+ concentration, was found to be 5.6, indicating extensive neutralization of the acidity in the rain. Neutralization was found to be a local process. The main base responsible for the neutralization of acidity was NH 3 from fertilizer used in the region. The CaCO 3 from resuspended soil accounts for 16% of the neutralized acidity. The annual wet deposition of ions was determined by two parameters, namely the precipitation amount and concentrations of ions in the precipitation. Precipitation amount accounted for approximately 70% of the annual wet deposition of ions in the Menemen region, whereas concentrations of ions in precipitation had only a minor influence. Although concentrations decrease with precipitation amount due to dilution in heavy rain, precipitation amount is not the only factor affecting concentrations of ions in precipitation. The main source of ions in wet deposition is the emissions from nearby industries. However, airborne NH 4 NO 3 and (NH 4 ) 2 SO 4 fertilizer particles may also contribute to observed concentrations of SO 2 2− and NO 3 − in rainwater. Dry deposition of most of the ions was higher than their annual wet deposition.

Pre-concentration of some trace metals from sea water on a mercapto-modified silica gel

Silica modified by the addition of mercapto chelating groups has been developed for the pre-concentration of trace metals from natural waters. This material removes cadmium, copper, lead and zinc from aqueous solution and can be employed for the pre-concentration of these metals by both column and batch techniques. Under column and batch conditions recoveries larger than 95% were common. For batch extractions of cadmium, zinc, copper and lead from sea water, recoveries of 91 ± 5, 98 ± 4, 97 ± 4 and 96 ± 5%, respectively, were obtained.

Selective pre-concentration of selenite from aqueous samples using mercapto-silica

Silica gel modified with 3-mercaptopropyl-trimethoxysilane was used for the selective separation and pre-concentration of selenite (Se(IV)) from aqueous solutions containing Se(IV) and selenate (Se(VI)). Over a wide range of acidity, from 2 mol l(-1) HCl to pH 9.00, Se(IV) was taken up by the mercaptopropyl-silica with nearly 100% efficiency; Se(VI) however was unretained. Se(IV) content was determined by hydride generation atomic absorption spectrometry (HGAAS), following batch release of the selenium from the pre-concentration medium by acidic periodate. The overall pre-concentration efficiency, including both take-up and elution, in the range of 89-106%. The method was applied to spiked seawater samples containing as low as 800 ng l(-1) Se in selenite form. This solid-phase extraction system offers several major advantages over conventional solvent extraction procedures. It firstly exhibits high selectivity for Se(IV) over Se(VI). Using the solid-phase media, pre-concentration of Se(IV) in dilute water samples can be carried out in the field, stabilizing the selenite-selenium in a convenient form for transport and storage. In addition, selenium stored on silica is derived solely from Se(IV) overcoming problems of selenium redox speciation changes and loss during storage.

A novel silica trap for lead determination by hydride generation atomic absorption spectrometry

Abstract A novel silica trap for lead determination at concentration levels of ng/l was developed using hydride-generation atomic absorption spectrometry. The device consists of a 7.0-cm silica tubing which is externally heated to a desired temperature. The lead hydride vapor is generated by a conventional hydride-generation flow system. The trap is placed between the gas–liquid separator and silica T-tube; the device traps analyte species at 500 °C and releases them when heated further to 750 °C. The overall efficiency is 49%. The presence of hydrogen gas is required for revolatilization; O 2 gas must also be present. The analytical plot is linear up to 2.0 ng/ml for a collection period of 60 s. The response is also linear with respect to increasing collection periods up to 4 min. For 60-s trapping, the detection limit is 19 ng/l.

Determination of bismuth using on-line preconcentration by trapping on resistively heated W coil and hydride generation atomic absorption spectrometry

A novel analytical system was developed to trap and preconcentrate bismuth from the vapour phase stream. Bismuthine formed by sodium tetrahydroborate reduction was trapped on a tungsten coil previously heated to 270 °C. The analyte species were re-volatilised by increasing the coil temperature to 1200 °C and then transported to an externally heated silica T-tube by using a mixture of argon and hydrogen as the carrier gas. The base width of the transient signal was less than 0.5 s. The reproducibility of the analytical signal was influenced by the rate of heating of the tungsten coil at the releasing stage. The precision of the analytical system was found to be 5.8% RSD (n = 13) for 0.010 ng ml−1 Bi when peak height was used. Due to sharp signals, peak area readings gave higher RSD values but they could be used for quantitation. The relationship between the analytical signal and the sample volume was found to be linear between 0.5 ml and 60 ml when using 0.100 ng ml−1 Bi. When the sample volume was increased to 25 ml, the blank values became significant. The calibration plot for an 18 ml sampling volume was linear between 0.030 and 0.500 ng ml−1 Bi. A limit of detection of 0.0027 ng ml−1 (3s) was obtained with 18 ml of sample volume. The concentration limit of detection achieved was comparable with or better than those obtained by techniques such as ICP-MS and HG-ETAAS. When the distance between the trap and atomiser was increased to 200 cm, a 72% and 24% decrease was observed in the peak height and peak area, respectively. In order to validate the accuracy of the method, two geological standard reference materials and one certified water standard reference material were analysed and the results were found to be in good agreement with the certified values at the 95% confidence level.

Determination of boron in hazelnut (Corylus avellana L.) varieties by inductively coupled plasma optical emission spectrometry and spectrophotometry

Boron content of 16 Turkish hazelnut (Corylus avellana L.) cultivars were determined by using inductively coupled plasma optical emission spectrometry (ICP-OES) and Azomethine H. spectrophotometric method. The results varied between 13.8 and 22.2 mg/kg. No significant difference was observed between the results by the two methods (P > 0.05). However, the difference among boron content of hazelnut varieties was found to be significantly important (P < 0.01). The highest boron content was in Mincane (20–22.2 mg/kg). Results revealed that the Turkish hazelnut is a good natural source of boron.

Determination and interference studies of bismuth by tungsten trap hydride generation atomic absorption spectrometry

The determination of bismuth requires sufficiently sensitive procedures for detection at the microg L(-1) level or lower. W-coil was used for on-line trapping of volatile bismuth species using HGAAS (hydride generation atomic absorption spectrometry); atom trapping using a W-coil consists of three steps. Initially BiH(3) gas is formed by hydride generation procedure. The analyte species in vapor form are transported through the W-coil trap held at 289 degrees C where trapping takes place. Following the preconcentration step, the W-coil is heated to 1348 degrees C; analyte species are released and transported to flame-heated quartz atom cell where the atomic signal is formed. In our study, interferences have been investigated in detail during Bi determination by hydride generation, both with and without trap in the same HGAAS system. Interferent/analyte (mass/mass) ratio was kept at 1, 10 and 100. Experiments were designed for carrier solutions having 1.0M HNO(3). Interferents such as Fe, Mn, Zn, Ni, Cu, As, Se, Cd, Pb, Au, Na, Mg, Ca, chloride, sulfate and phosphate were examined. The calibration plot for an 8.0 mL sampling volume was linear between 0.10 microg L(-1) and 10.0 microg L(-1) of Bi. The detection limit (3s/m) was 25 ng L(-1). The enhancement factor for the characteristic concentration (C(o)) was found to be 21 when compared with the regular system without trap, by using peak height values. The validation of the procedure was performed by the analysis of the certified water reference material and the result was found to be in good agreement with the certified values at the 95% confidence level.

Stibine preconcentration in a quartz trap with subsequent atomization in the quartz multiatomizer for atomic absorption spectrometry

A preliminary evaluation of a simple (bare) quartz tube trap for collection of SbH3 and for volatilization of trapped analyte with subsequent atomization in a multiple microflame quartz tube atomizer (multiatomizer) for atomic absorption spectrometry is presented. The influence of relevant experimental parameters on the collection/volatilization efficiency was investigated. The parameters studied were: collection temperature and time, volatilization temperature and flow rates of air and hydrogen for the volatilization. Under optimized conditions, the collection/volatilization efficiency was 65%. For the collection time of 120 s (sample volume of 8 ml), the detection limit was 3.9 pg ml−1, and the analytical plot was linear up to 1.25 ng ml−1. Possible ways of improving the performance of the set-up as well as the collection/volatilization efficiency are suggested.

Cold vapour generation and on-line trapping of cadmium species on quartz surface prior to detection by atomic absorption spectrometry

A quartz trap for on-line preconcentration of Cd species was designed. The cold vapour generation technique was used for the generation of Cd species. The trapping medium was formed by external heating of the inlet arm of a quartz T-tube. The generated analyte species were trapped on a quartz surface heated to the collection temperature, 350 °C, and the collected species were revolatilized when the trap was heated further to revolatilization temperature, 1000 °C, and hydrogen gas was introduced in the trapping medium. Two-level fractional factorial design and central composite design were used to optimize generation conditions in the flow injection mode. The results of the fractional factorial design demonstrated that the factors and their interactions were statistically significant. Three factors, length of reaction coil, carrier HCl concentration and NaBH4 concentration, were considered to be the most significant parameters in the optimization and their optimum values were found to be 30 cm, 0.3 M and 3% (m/v), respectively. Sea-water (BCR), tomato leaves (NIST 1573a) and oyster tissue (NIST 1566b) standard reference materials were analyzed to assess the accuracy of the proposed method. For a collection period of 3.0 min, i.e., 6.0 ml sample volume, the 3σ limit of detection was 1.8 pg ml−1; the enhancement factor for LOD was found to be 90 as compared with FI-HGAAS. The sample throughput rate was 12 h−1.

Novel traps and atomization techniques for flame AAS

The analytical performance of three trap systems for flame AAS were evaluated for determination of Cd and Pb in waters. In addition to a water-cooled U-shaped silica trap, two other novel traps, namely, a water-cooled U-shaped silica trap combined with a slotted silica tube and a slotted silica tube trap were used. Flame alteration and organic solvent aspiration techniques were two atomization techniques introduced in this work. The slotted silica tube trap with either flame alteration or organic solvent aspiration was found to be the most sensitive, effective and simplest device. For a collection period of 2.0 min, sensitivity enhancements, compared to flame AAS, were 137 and 90 folds for Cd and Pb, respectively, using the slotted silica tube trap and organic solvent aspiration technique.