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A preconcentration technique by using Ni/NixB sorbent was developed for trace aluminium determination prior to the fluorimetric detection in dialysis solutions and water samples. the sorbent was synthesized by reducing sulphate salts of nickel with NaBH4 in an inert atmosphere. Characterization studies were executed with the aid of X-ray photoelectron spectroscopy analysis. To achieve best results, optimization studies were conducted. Sorption efficiencies for Al(III) at initial pH values between 3-10 were found to be quantitative. Adsorption rate was quite high and in 5 min sorption efficiencies reached 99%. the recovery of Al(III) was established to be quantitative (>95%) for sample volumes up to 250 mL. the sorption capacity for Al(III) was found to be 394 mg/g in batch studies. the sorption capacity obtained from batch studies was compatible with that obtained by isotherm studies. the method was applied to the preconcentration of Al(III) in haemodialysis solutions and various real water samples with satisfactory recoveries., Ege University Research FundEge University [2012 FEN 040]; Scientific and Technical Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK), We would like to thank Ege University Research Fund for the financial support of this study, Project no. 2012 FEN 040. Yasemin Islek Coskun also thanks to the Scientific and Technical Research Council of Turkey (TUBITAK) for the scholarship during this study.

Optical sensors based on UV-visible absorption, fluorescence, phosphorescence, chemiluminescence, surface plasmon resonance, and surface-enhanced Raman scattering techniques are widely used to detect trace levels of pesticides. Generally, molecularly imprinted polymers have been used as selective adsorbent and the recognition unit of the optical sensors in pesticide analysis. Due to the combination of the selectivity of the molecularly imprinted polymers with the sensitivity of the detection techniques, molecularly imprinted polymer-based optical sensors take an important place in pesticide analysis. This chapter aims to highlight the usage of different types of molecularly imprinted polymer-based optical sensors designed for the determination of pesticides. © 2021 Elsevier Inc.

In this study, magnetite-molecularly imprinted polymer has been used for the first time as selective adsorbent before the fluorimetric determination of carbendazim. Adsorption capacity of the magnetite-molecularly imprinted polymer was found to be 2.31±0.63mgg-1 (n=3). Limit of detection (LOD) and limit of quantification (LOQ) of the method were found to be 2.3 and 7.8μgL-1, respectively. Calibration graph was linear in the range of 10-1000μgL-1. Rapidity is an important advantage of the method where re-binding and recovery processes of carbendazim can be completed within an hour. The same imprinted polymer can be used for the determination of carbendazim without any capacity loss repeatedly for at least ten times. Proposed method has been successfully applied to determine carbendazim residues in apple and orange, where the recoveries of the spiked samples were found to be in the range of 95.7-103%. Characterization of the adsorbent and the effects of some potential interferences were also evaluated. With the reasonably high capacity and reusability of the adsorbent, dynamic calibration range, rapidity, simplicity, cost-effectiveness and with suitable LOD and LOQ, the proposed method is an ideal method for the determination of carbendazim.

Potteries are traditionally used for cooking and storing foods in Turkey, the Mediterranean, and Middle East regions. Leaching of inorganic arsenic into the traditional white bean dish cooked in pottery has been determined for the first time in the literature. Accuracy of this method was validated by the analysis of a certified reference material, commercially marketed standard solutions, and arsenic spiked solutions. Locally available potteries were examined for the leaching studies. Variation in the leachability of inorganic arsenic from the potteries by acetic acid versus the number of use was studied. The concentrations of arsenic leached by 4% acetic acid decreased by the usage number. The glazed potteries released arsenic at lower concentrations to leaching by acetic acid than the same group of nonglazed potteries. The concentrations of leached arsenic were relatively high in the white bean dish, where the leach of arsenic from the potteries to acetic acid was low. All of the potteries examined released inorganic arsenic to white bean dish in concentrations that exceed the daily BMDL 0.5 (210 μg/day). However, because the potteries are used only about once a month, direct application of the daily dietary intake limits is not appropriate. According to the weekly BMDL 0.5 , the estimated contribution from arsenic was in the range of 34–79% of BMDL 0.5 . The results of this study showed that the potteries are the potential sources of arsenic. Pottery oiling in ovens, which is another traditional procedure before using the potteries, reduced the leaching of arsenic to foods.

Arsenic in drinking water is a serious problem for human health. Since the toxicity of arsenic species As(III) and As(V) is different, it is important to determine the concentrations separately. Therefore, it is necessary to develop an accurate and sensitive method for the speciation of arsenic. It was intended with this work to determine the concentrations of arsenic species in water samples collected from Izmir, Manisa and nearby areas. A batch type hydride generation atomic absorption spectrometer was used. As(V) gave no signal under the optimal measurement conditions of As(III). A certified reference drinking water was analyzed by the method and the results showed excellent agreement with the reported values. The procedure was applied to 34 water samples. Eleven tap water, two spring water, 19 artesian well water and two thermal water samples were analyzed under the optimal conditions.

A new nickel/nickel boride-based nanosorbent which provides high sorption efficiency for tin(IV) was developed in this study. The sorbent capacity was found to be 26.33 ± 2.18 mg tin(IV)/g sorbent (n = 3). Tin(IV) can be determined by measuring the fluorescence signal of the tin(IV)–flavonol complex. Recovery of tin(IV) with 1 mol/L hydrochloric acid was found to be 98.70 ± 1.29 (n = 5). The limit of detection and the limit of quantification of the method were found to be 0.5 and 1.7 µg/L, respectively. The calibration graph was linear in the range of 4–80 µg/L. The adsorption type was determined by using the adsorption isotherms. Interference effects of several metal ions on tin(IV) determination were investigated and the tolerable concentration limits of these metal ions were determined. The nickel/nickel boride nanosorbent reduces the interference effects and improves the sensitivity and the selectivity of the method. With the aid of the novel nanosorbent, higher tolerable concentration limits ...

A novel adsorbent named Ni/NixB nanoparticles was synthesized for the preconcentration of both As(III) and As(V) from water samples. Both adsorbent preparation and adsorption procedure were optimized. The adsorption efficiencies for both As(III) and As(V) were higher than 99% when the initial pHs ranged from 4.0 to 10.0. The rate of the adsorption was high, and in the first 10 min, the adsorption efficiency reached 95%. Adsorbed As(III) and As(V) were recovered with high efficiencies from the adsorbent using 2 mol L−1 HCl. Under the optimal conditions, an enrichment factor of 50 was reached. Hundred-fold excess of Cd2+, Cu2+, Mg2+, Zn2+, K+, , , and ions did not affect the adsorption efficiencies of As(III) and As(V). The adsorption for both As(III) and As(V) obeyed the Freundlich and Langmuir isotherms. The maximum adsorption capacities calculated from the Langmuir isotherm were 2,500 mg g−1 for both species, and the adsorptions were favorable. The validation and the real sample application studi...

A novel adsorbent named nickel/nickel boride nanoparticles coated resin has been introduced for the removal of both As(III) and As(V) from water. Nickel/nickel boride nanoparticles were formed on Purolite C-100 resin successfully. Perlite, pumice, zeolite and silica gel were also tried as the support material. However, nickel/nickel boride nanoparticles on those materials were not stable. Optimal preparation conditions for nickel/nickel boride nanoparticles coated resin were established. In the batch method, initial pH did not significantly affect the arsenic removal efficiencies for As(III) and As (V) in the pH range 33-11.5. As(III) and As(V) were removed quantitatively from the solutions at all pHs. 15% and 10% decreases were observed for As (III) removal efficiency when the solution contained phosphate and silicate respectively. However, none of the ions studied showed significant effect on the As(V) removal efficiency. Isotherm studies indicate that the Langmuir model fits the experimental data better than the Freundlich model. The isotherms also showed that the adsorption is favorable. Maximum arsenic adsorption capacities were calculated as 23.4 mg/g and 17.8 mg/g for As(III) and As(V), respectively. The kinetics of the adsorption process were tested for the pseudo-first order and pseudo-second order and intra-particle diffusion models. The comparison among the models showed that the pseudo second-order model best described the adsorption kinetics. As(III) and As(V) could be desorbed from the adsorbent without any efficiency loose using a mixture containing NaCl and NaOH and, therefore, the adsorbent could be used several times. Ni/NixB-NPCR could reduce the concentration of both As(III) and As(V) below the maximum allowable concentration level (WHO limit, 10 mu g/L) from such high arsenic containing waters. (C) 2014 Elsevier B.V. All rights reserved.

WOS: 000382184900009, PubMed ID: 27506713, A selective matrix separation/enrichment method, utilizing a simple batch procedure with nickel/nickel boride (Ni/NixB) nanoparticles was proposed for the determination of inorganic mercury(II), Hg2+ and methyl mercury(I), CH3Hg+ in waters prior to cold vapor-atomic fluorescence spectrometry (CV-AFS). The Ni/NixB nanoparticles, were synthesized by the chemical reduction of Ni(II) to Ni/NixB. The novel adsorbent was selective to Hg2+ and CH3Hg+ species between pH values of 4 - 10. Both of the mercury species were recovered from the adsorbent using 1.0 mol L-1 hot HNO3 with high efficiency. It was observed that the adsorbent selectively removed Hg2+ and CH3Hg+ from the bulk solution in the presence of several competitor ions (As3+, Sb3+, Pb2+, Zn2+, Cu2+, Cd2+ and Fe3+) with >= 96% adsorption. The limit of detection (3 sigma above blank) was found to be 1.8 ng L-1 with a preconcentration factor of 20. The validation of the method was tested through spike recovery experiments with several water samples (tap and seawater) at mu g L-1 concentration levels, and all recovery values were found to vary between 95 and 105%., Ege University Research FundEge University [2008 Fen 054], The authors acknowledge financial support provided by the Ege University Research Fund, Project No: 2008 Fen 054.

The characterization of a new optical sensor membrane is described for the determination of Ni(II) based on the immobilization of the fluorescent thiazolo-triazol derivative in PVC matrix. This optode has a wide linear range of 1.0 × 10 −9 –4.4 × 10 −3 M at pH 6.0 for Ni(II) ions with the detection limit of 8.5 × 10 −10 M. The response of the optode membrane to Ni(II) is fully reversible and reveals a very good selectivity towards Ni(II) ion over a wide variety of other metal ions in solution. The membrane showed a good durability and short response time with no evidence of reagent leaching. The proposed optical sensor gives good results for applications in direct determination of Ni(II) in real samples that are satisfactorily comparable with corresponding data from flame atomic absorption spectrometry.

Studies have been carried out to clarify the mechanism of nickel interferences in the hydride generation atomic absorption spectrometric determination of arsenic and antimony. The most serious nickel interferences are observed when nickel/nickel boride nanoparticles are produced during NaBH 4 reduction. In this study these particles have been observed to have diameters of less than 40 nm and sorb As(III), As(V) and Sb(III) species rather than arsine and stibine generated as so far assumed. Bulk chemical composition and surface structure of these nanoparticles were studied and it was found that if the NaBH 4 reduction is carried out while passing nitrogen through the solution the black nanoparticles were composed of Ni 2 B and, if the reduction is carried out under air the black nanoparticles were found to consist of Ni 3 B or possibly a mixture of Ni(0) and Ni 2 B. Surface analysis studies with scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectrometry and X-ray diffraction analysis have shown that the particles have amorphous structure consisting of Ni(0), Ni 2 B, Ni 3 B and Ni(OH) 2 . However, sorption studies have shown that Ni(0) and Ni(OH) 2 do not sorb the analyte ions and arsine and stibine significantly.

The applicability of poly(acrylamide) grafted onto cross-linked poly(4-vinyl pyridine) (P4-VP-g-PAm) has been investigated for the separation, preconcentration and speciation of Hg(II) and MeHg(I). In batch experiments, Hg(II) was quantitatively retained (≥95%) in the pH range of 1.0-8.0, whereas the sorption of MeHg(I) was insignificant in the pH range of 1.0-2.0. Freundlich and Langmuir isotherm models were investigated in order to characterize the sorption, and the capacity of the sorbent was found to be 817 mg Hg(II) g(-1). The limit of detection (3δ above blank) was 2 ng L(-1). The sorbent has excellent selectivity for Hg(II) in the presence of Pb(II), Zn(II), Cu(II), Cd(II) and Fe(III) ions. The method was successfully applied to the determination of Hg(II) and MeHg(I) in seawater and estuarine water. The sorbent can remove Hg(II) at pH 2.0, and therefore makes the determination of MeHg(I) possible, even if the sample contains a high amount of Hg(II).

Removal of As(III) and As(V) species using ferric hydroxide supported on silica gel was studied. Laboratory reagent quality silica gel was used as to avoid uncertainties that may be caused by impurities. Ferric hydroxide precipitation was realized at various pH values and a relatively low pH 6.0 was chosen because, at this pH, the highest arsenic removal capacity and removal efficiency were obtained and clear supernatant solution was observed. It was also shown by arsenic speciation analysis at trace level that As(III) is adsorbed onto ferric hydroxide partly without oxidation to As(V); this has been a controversial point in the literature. The effects on arsenic removal of some parameters such as pH, flow rate and matrix ions were investigated. In the batch method, initial pH change of the solution did not significantly affect the arsenic removal efficiencies for As(III) and As(V) in the pH range of 3.1-9.7. This was attributed to the decreases of the initial pH values to around 5 at equilibrium. The column capacities of 1.32 mg As(III)/g sorbent and 1.21 mg As(V)/g sorbent were found for initial concentration of 1.00 mg/L arsenic. Batch capacities were 16.2 mg As(III)/g sorbent and 17.7 mg As(V)/g sorbent for initial arsenic concentration of 100 mg/L. The method was applied successfully to the removal of As(III) and As(V) from drinking water, geothermal water and mineral water.

A sensitive new optical sensor for Zn2+ is described. This optode is based on a novel Schiff base ligand, 2-(2-hydroxy-5-chloro)benzaldehyde-[4-(3-methyl-3-mesitylcyclobutyl)-1,3- thiazol-2yl]hydrazone, in plasticized polyvinyl chloride membrane. This sensing membrane is capable of determining Zn2+ with a high sensitivity and selectivity over a wide dynamic range between 5.0×10-7 to 1.0×10-4 mol L-1 at pH 6.0 with a lower detection limit of 2.2×10-7 mol L-1 (14.4 g L-1 . The sensor can readily be regenerated with 1.0 mol L-1 EDTA solution. In addition to high stability, the sensor shows a unique selectivity toward Zn2+ with respect to common metal cations. The sensor was successfully applied for the determination of zinc real samples. The results obtained for the determination of zinc ions in hair samples using the proposed method was found to be comparable with the well-established flame atomic absorption method

A highly sensitive and selective optical sensor for the determination of trace amounts of Cu 2+ based on fluorescence quenching has been developed. The sensing membrane was prepared by immobilization of a novel fluorescent Schiff base ligand 4-(1-phenyl-1-methylcyclobutane-3-yl)-2-(2-hydroxy-5-romobenzylidene)aminothiazole, on polyvinlyl chloride. The novel sensor, which has a linear range of 1.0 × 10 −8 – 5.7 × 10 −4 mol L −1 for Cu 2+ ions with a detection limit of 8.8 × 10 −9 mol L −1 (0.56 μg L −1 ), is fully reversible and the response time ( τ 90 ) was approximately 2.5 min. The optode was highly selective and can readily be regenerated by treatment with 10 −2 mol L −1 HCl. The accuracy of the proposed sensor was confirmed by analyzing standard reference materials of natural water and peach leaves. The sensor was successfully applied for the determination of copper in tap water and tea samples.

The application of the recently introduced ethylchloroformate derivatization method for the separation and determination of selenomethionine and selenocystein in selenium-enriched yeast and yeast-free tablets by means of a gas chromatography–mass spectrometry (GC–MS) system has been studied. The efficiency of three methods for the extraction of selenomethionine from the tablets were compared. Total selenium content of the same tablets were measured using inductively coupled plasma (ICP)-MS and it was found that in the selenized yeast tablets about 80% of the total selenium is present as selenomethionine. The results were in agreement with the values in the labels and with the literature. The accuracy of the total selenium analysis was controlled by the analysis of a reference material.

The interferences between arsenic and antimony on each other during the hydride generation atomic absorption spectrometry (HGAAS) determination of arsenic and antimony using a quartz tube atomizer (QTA) were examined. In order to eliminate or reduce such interferences by selective heat decomposition of arsine and stibine, a Pyrex adsorption U-tube trap containing glass wool was placed between the drying tube and the quartz tube atomizer. Although at 250 °C stibine decomposes and is held almost completely by the trap, arsine is also decomposed to an extent of 24% and, therefore, thermal decomposition is not useful to eliminate antimony interference on arsenic determination. The effect of coating the glass wool in the U-tube with antimony on the arsenic suppression of the antimony signal was studied. The results showed that the antimony coating in the U-tube could not hold arsenic effectively and its interference on the antimony signal could not be eliminated by this means. In the second part of the study, oxygen was supplied to the quartz tube atomizer during atomization in order to study the effect of supplying oxygen on the antimony signal and on the interference of arsenic in the antimony determination. Sensitivity was increased in the presence of oxygen and interferences of arsenic on antimony determination was decreased by about 10% when oxygen was supplied. It was also observed that the extent of interferences depended mainly on the interferent concentration rather than the analyte concentration.

Tea is one of the most popular beverages in the world. Thus, the chemical components in tea are of great interest, especially in relation to health. In this study, 12 tea samples (10 black, 1 white and 1 green) and 5 herbal tea samples were purchased from supermarkets in Izmir, Turkey. Sample preparation has been performed using wet and microwave digestion procedures. The elemental content (Fe, Zn, Cu, Mn, Ni, Na and K) in the digests and infusions has been analysed. Generally, elemental contents in tea leaves were found to be higher than those in tea infusions. The accuracy of the method was checked and confirmed by standard reference material analyses. The comparison of wet and microwave digestion has not shown significantly different results. Therefore, the microwave digestion procedure was preferred because it is less laborious. The elemental intake related to tea consumption has also been studied.

Azlactone molecules can be protonated in acidic media, and the process of protonation is irreversible due to ring opening in solutions. A new fully reversible pH sensor has been developed 4-(p-N,N-dimethylamino phenyl methylene)-2-phenyl-5-oxazolone (DPO), an azlactone derivative, embedded in a plasticized PVC polymer film. The sensor membrane is completely transparent and exhibits pH induced color change which is capable of measuring of pH in the range 1–7 and has a pKa value of 3.4. In agreement with crystal phase studies, DPO displays enhanced fluorescence emission quantum yield, Qf=0.52, and fluorescence emission lifetime, τ f =1.35 ns , in immobilized PVC film matrix, compared to Qf≅0.03 and τ f =0.02–0.03 ns in solutions. Stokes shift decreased to 46 nm in plasticized PVC film, with respect to Stokes shift of 81 nm in acetonitrile solution. Singlet energy, E s =60.4 kcal mol −1 , of DPO in PVC film, which is 1.1–1.4 kcal mol−1 lower with respect to solutions, is taken as evidence of lessened singlet–triplet crossings in excited state of DPO in immobilized phase, and result in enhanced fluorescence emissions.

Interferences of some metals in the determination of arsenic by hydride generation atomic absorption spectrometry utilizing a quartz tube atomizer were studied. The atomizers were coated under vacuum with Ni, Au, Pd and Cr. The arsenic signal was almost totally suppressed by all the metal coatings and thus the interferences from metal ions in the determination of arsenic were attributed both to the carry over of the reaction mixture, as well as interferences in the hydride formation step. Inter-element interferences by arsenic and antimony on each other in the atomizer of the same system were also studied. When arsine and stibine reach the atomizer at the same time they suppress each other’s signals. The interference of arsenic on antimony was eliminated by simply separating arsine, which elutes first, from stibine using a simple gas chromatographic column (GC column). However, even when arsine and stibine are separated using the GC column, antimony is deposited in the quartz tube atomizer at the temperatures the quartz tube attains when heated in the air–acetylene flame, suppressing the arsenic signal in subsequent experiments. Therefore, directing of stibine outside of the atomizer, after elution of arsine from the GC column, was suggested for arsenic determination.

Determination of the total amount of tin by molecular emission cavity analysis (MECA) after generation of stannane by means of reduction with sodium tetrahydroborate(III) and measuring the SnH emission within the flame-containing MECA cavity is described. The volatile hydrides of tin, germanium and arsenic were separated on a short gas chromatographic column. The calibration graph was linear over the range 5–250 ng Sn, and the detection limit ( S N = 21 ) was 5 ng Sn, and the relative standard deviation for the determination of 50 ng Sn was 2.8% (n = 8). The method was applied successfully to the determination of total tin in fish, canned soft drinks and sea sediment samples. Hydride generation recovery from soil sample solutions, however, was low.

The moss, Hypnum cupressiforme and bark of the pine, Pinus brutia have been used for passive monitoring of airborne heavy metal pollution by an iron-steel mill of an industrialised area of Izmir, Turkey. Six metals, lead (Pb), cadmium (Cd), zinc (Zn), chromium (Cr), manganese (Mn) and iron (Fe) have been monitored using atomic absorption spectrometry. Between 26.2.1992 and 13.8.1992 samples were taken on five occasions at a distance of 0.25, 1.0 and 2.5 km from the mill. The results show an accumulation of all six metals, with differences between the moss and bark samples and a decrease in concentration with distance from the mill. The arithmetic means of the measured heavy metal concentrations in the moss, Hypnum cupressiforme, were always much higher than those in the bark of the P. brutia, indicating that the moss H. cupressiforme is more suitable than the bark of P. brutia for use in monitoring heavy metal pollution. The results show that the study area, within 2.5 km from the iron-steel mill, is heavily polluted.

Glazed and non-glazed earthenware is traditionally and widely used in Turkey and most of the Mediterranean and the Middle East countries for cooking and conservation of foodstuff. Acid-leaching tests have been carried out to determine whether the use of glazed and non-glazed earthenware may constitute a human health hazard risk to the consumers. Earthenware was leached with 4% acetic acid and 1% citric acid solutions, and arsenic in the leachates was measured using hydride generation atomic absorption spectrometry. Arsenic concentrations in the leach solution of non-glazed potteries varied from 30.9 to 800 μg L⁻¹, while the glazed potteries varied generally from below the limit of detection (0.5 μg L⁻¹) to 30.6 μg L⁻¹, but in one poorly glazed series it reached to 110 μg L⁻¹. Therefore, the risk of arsenic poisoning by poorly glazed and non-glazed potteries is high enough to be of concern. It appears that this is the first study reporting arsenic release from earthenware into food.

A sensor membrane based on the fluorescence enhancement of a novel triazine-thione derivative, 4-ethyl-5-hydroxy-5,6-di-pyridin-2-yl-4,5-dihydro-2H-[1,2,4]triazine-3-thione, was capable of determining mercury(II) with high selectivity over the range 5.0 × 10−10 and 5.0 × 10−5 mol L−1 with a limit of detection of 1.8 × 10−10 mol L−1 (0.036 μg L−1). The sensor can be regenerated using 5% thiourea in 1.0 mol L−1 HCl solution. The sensor also displayed unique selectivity toward mercury(II) ion with respect to other common metal cations and was applied to the determination of mercury(II) in tap water and human hair samples. The accuracy of the results were comparable to those obtained by cold vapour atomic fluorescence spectrometry.

The use of an unmodified native sheep wool packed minicolumn for the online preconcentration of Hg(II) and methyl mercury species prior to the determination of mercury by atomic fluorescence spectrometry was investigated. Experimental conditions, such as pH, desorbing agents, volume of solution were optimized. 0.5 M thioglycolic acid was found to be a successful eluting agent for both mercury species. Breakthrough and total capacities were determined. The method is simple and rapidly applicable for the determination of Hg(II) and methyl mercury in tap water. The accuracy of the method was examined by the analysis of a peach leaves standard reference material. Recoveries of spiked mercury species in tap water were 105.8% for Hg(II) and 98.8% for methyl mercury. (C) 2008 Elsevier B.V. All rights reserved.

In recent years squarines received attention as fluorescent labels. Their very promising spectral properties such as long wavelength absorption and emission, high extinction coefficients and quantum yields could lead novel sensing technologies. In this work newly synthesized fluoroinophores named bis[4-N-(1-aza-4,7,10,13-tetraoxacyclopentadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-1 and 2 bis[4-N-(1-aza-4,7,10,13,16-pentaoxacyclooctadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-2 have been used for sodium and potassium sensing in plasticized PVC matrix. The squaraine derivatives exhibited fluorescence emission based optical responses to sodium and potassium with a detection limit of 1.10(-9) M. The sensor compositions exhibited wide response ranges between 10(-9) and 10(-5) M Na+ or K+, and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2-7.3. Throughout fiber optic based studies a relative signal change of 54-56% has been achieved. The azacrown dyes have the advantage that they can be excited with long wavelength light and, are, therefore, LED compatible. The cross sensitivity of azacrown-1 and -2 to Ba2+ Ca2+ and NH4+ were also tested in separate solutions. (C) 2002 Elsevier Science B.V. All rights reserved.

It is well known that one of the main materials, responsible for environmental pollution is coal, that is used in vast amounts in most countries. Coal utilization affects terrestrial, aquatic and atmospheric environments. Effects on the terrestrial environment include disruption of land, soil and their surfaces. Effects on aquatic environment include disruption of surface and underground aquatic systems, and the thermal, particulate and chemical contamination of waters. Effects on atmospheric environment include deterioration of air quality by particulate and gaseous emissions and modification of the climate. The latter effect becomes more serious when the combustion of coals proceed in an uncontrolled way. The various effects on air, land and water may result in damages to plant and animal life, damages to food resources and modification of the landscape.

Ammonium-, nitrite- and nitrate-nitrogen were determined by molecular emission cavity analysis using a cavity containing an entire flame. Ammonium-nitrogen was converted to ammonia by injection on to solid sodium hydroxide. The calibration graph was linear for 5–100 µg ml–1 of nitrogen when the ammonia generated was swept directly into the cavity and for 0.05–1.0 µg ml–1 of nitrogen when it was collected in a liquid nitrogen cold-trap. Concentrations of 1.5 and 0.01 µg ml–1 of nitrogen could be detected using the direct and cold-trap methods, respectively. Nitrite was determined after conversion to nitrogen monoxide by iodide. Nitrate was reduced to nitrite using a copperised cadmium column and then determined as nitrite. The calibration graphs for both anions were linear up to 7 µg ml–1 of nitrogen and 0.1 µg ml–1 of nitrogen could be detected. The methods were applied successfully to the determination of nitrite and nitrate in meat products, and nitrate-nitrogen in drinking water samples.

Arsenic (0.1–5 μg), antimony (1–40 μg), tin (0.5–10 μg) and germanium (0.2–10 μg) are determined simultaneously by reduction to their hydrides with sodium tetrahydroborate(III), followed by gas chromatographic separation on a column of 10% E-301 silicone gum rubber on Porapak Q, and measurement of the emissions at 490 nm in an oxygen/hydrogen flame within a cavity. Detection limits for 1-ml samples are 35 ng As, 400 ng Sb, 85 ng Sn and 100 ng Ge. A more sensitive determination of arsenic (0.05–3 μg) and antimony (0.1–5 μg) in binary mixtures is also described; the detection limits are 15 ng As and 40 ng Sb.

Molecular emission cavity analysis (MECA) is shown to be useful for selective detection of sulphur or phosphorus compounds at the nanogram level in g.l.c. effluents. Introduction of a small oxygen flow into the cavity allows many other elements (e.g. Si, As, Sb, N, C) to be detected. The detection of microgram amounts of silylated amino acids is possible by measuring their SiO emission in the cavity at 580 nm.

Selenium (0.02–2 ppm), after conversion to hydrogen selenide -with sodium tetrahydroborate, can be determined by molecular emission cavity analysis. The detection limit is 7 ng of selenium. The effects of 26 ions are reported. The depressive effects of arsenic and antimony can be removed by selective volatilisation, and the enhancing effects of tellurium and sulphite by addition of tellurium to standards and by oxidation to sulphate, respectively.