The application of Westcott Formalism k0 NAA method to estimate short and medium lived elements in some Ghanaian herbal medicines complemented by AAS

The epithermal neutron shape factor, α of the inner and outer irradiation sites of the Ghana Research Reactor-1 (GHARR-1) was determined obtaining results of 0.105 for the inner (Channel 1) Irradiation site and 0.020 for the outer (channel 6) irradiation site. The neutron temperatures for the inner and outer irradiation sites were 27 °C and 20 °C, respectively. The α values used in Westcott Formalism k₀ INAA was applied to determine multi elements in 13 Ghanaian herbal medicines used by the Centre for Scientific Research into Plant Medicine (CSRPM) for the management of various diseases complemented by Atomic Absorption Spectrometry. They are namely Mist. Antiaris, Mist. Enterica, Mist. Morazia, Mist. Nibima, Mist. Modium, Mist. Ninger, Mist Sodenia, Mist. Tonica, Chardicca Powder, Fefe Powder, Olax Powder, Sirrapac powder and Lippia Tea. Concentrations of Al, As, Br, K, Cl, Cu, Mg, Mn, Na and V were determined by short and medium irradiations at a thermal neutron flux of 5×10¹¹ ncm⁻² s⁻¹. Fe, Cr, Pb, Co, Ni, Sn, Ca, Ba, Li and Sb were determined using Atomic Absorption Spectrometry (AAS). Ba, Cu, Li and V were present at trace levels whereas Al, Cl, Na, Ca were present at major levels. K, Br, Mg, Mn, Co, Ni, Fe and Sb were also present at minor levels. Arsenic was not detected in all samples. Standard Reference material, IAEA-V-10 Hay Powder was simultaneously analysed with samples. The precision and accuracy of the method using real samples and standard reference materials were evaluated and within ±10% of the reported value. Multivariate analytical techniques, such as cluster analysis (Q-mode and R-mode CA) and principal component analysis (PCA)/factor analysis (FA), have been applied to evaluate the chemical variations in the herbal medicine dataset. All the 13 samples may be grouped into 2 statistically significant clusters (liquid based and powdered herbal medicines), reflecting the different chemical compositions. R-mode CA and PCA suggest common sources for Co, Mg, Fe, Ca, Cr, Ni, Sn, Li and Sb and Na, V, Cl, Mn, Al, Br and K. The PCA/FA identified 3 dominant factors as responsible for the data structure, explaining 84.5% of the total variance in the dataset.     

Fractionation metallothionein-like proteins in mussels with on line metal detection by high performance liquid chromatography-inductively coupled plasma-optical emission spectrometry

A rapid method for the determination of Al, Ba, Cu, Fe, Mn, Sr and Zn binding metallothionein-like proteins (MLPs) in mussels (Mytilus galloprovincialis) by inductively coupled plasma-optical emission spectrometry was developed. The method uses a short column (8 mm × 75 mm) anion exchange high performance liquid chromatography (HPLC) with inductively coupled plasma-optical emission spectrometric (ICP-OES) detection. Working in isocratic mode (75 mM Tris-HCl at pH 7.4, flow rate at 0.8 ml min⁻¹), two major MLPs isoforms (MLP-1 and MLP-2) can be separated in ten minutes. The distribution of basal metals binding MLPs was assessed by on line HPLC and ICP-OES, while the basal contents of metals binding MLPs were obtained after off line HPLC and ICP-OES (collection of the two major fractions and multi-element determination by ICP-OES). The calculated LODs were 81, 6, 10, 13, 30, 9 and 123 ng g⁻¹ for Al, Ba, Cu, Fe, Mn, Sr and Zn binding MLP-1 and MLP-2, respectively. The repeatability of the over-all method (five different mussel cytosols prepared from the same mussel sample and subjected to the off line HPLC-ICP-OES procedure twice) was from 11.2 for Cu to 16.2% for Zn. The method was finally applied to different raft mussels from Ría de Arousa estuary in order to know basal levels of elements binding MLPs.     

Multivariate optimization by exploratory analysis applied to the determination of microelements in fruit juice by inductively coupled plasma optical emission spectrometry

A method for the direct determination (without sample pre-digestion) of microelements in fruit juice by inductively coupled plasma optical emission spectrometry has been developed. The method has been optimized by a 2³ factorial design, which evaluated the plasma conditions (nebulization gas flow rate, applied power, and sample flow rate). A 1:1 diluted juice sample with 2% HNO₃ (Tetra Packed, peach flavor) and spiked with 0.5 mg L^− 1 of Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, and Zn was employed in the optimization. The results of the factorial design were evaluated by exploratory analysis (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) to determine the optimum analytical conditions for all elements. Central point condition differentiation (0.75 L min^− 1, 1.3 kW, and 1.25 mL min^− 1) was observed for both methods, Principal Component Analysis and Hierarchical Cluster Analysis, with higher analytical signal values, suggesting that these are the optimal analytical conditions. F and t-student tests were used to compare the slopes of the calibration curves for aqueous and matrix-matched standards. No significant differences were observed at 95% confidence level. The correlation coefficient was higher than 0.99 for all the elements evaluated. The limits of quantification were: Al 253, Cu 3.6, Fe 84, Mn 0.4, Zn 71, Ni 67, Cd 69, Pb 129, Sn 206, Cr 79, Co 24, and Ba 2.1 µg L^− 1. The spiking experiments with fruit juice samples resulted in recoveries between 80 and 120%, except for Co and Sn. Al, Cd, Pb, Sn and Cr could not be quantified in any of the samples investigated. The method was applied to the determination of several elements in fruit juice samples commercialized in Brazil.     

Foam Separation of Stannous Ion from Aqueous Solution

Sn(II) was removed from solution using various foam separation techniques. It was found that Sn(II) could be effectively removed by adsorbing colloid flotation using either Fe(OH)₃ or Al(OH)₃ as the adsorbing colloid. Over 99% of the Sn(II) was removed from a solution initially containing 50 ppm Sn(II).     

Determination of Trace Elements in Dendrobium Officinale Cultivated in Various Conditions

Dendrobium officinale is an important medicinal plant in traditional Chinese medicine. The consumption of D. officinale has increased rapidly in recent years due to the health awareness among Chinese people. The present study aimed to determine trace elements levels in 42 D. officinale samples and to utilize the elemental data for identifying the cultivation technique. Eighteen trace elements (B, V, Cr, As, Mn, Fe, Mo, Cu, Zn, Se, Sr, Sn, Ti, Al, Co, As Pb, Cd, and Bi) were determined by inductively coupled plasma–mass spectrometry. Of the 11 essential elements, the mean concentrations ranged from 30.6?µg?kg^?1 (Mo) in D. officinale with greenhouse cultivation to 161?mg?kg^?1 (Fe) in D. officinale with rock cultivation, and the contributions of Mn may exceed the dietary reference intake value by the uptake of 20?g of D. officinale. Of the seven toxic elements, the mean concentrations ranged from 3.29?µg?kg^?1 (Bi) in the D. officinale with greenhouse cultivation to 342?mg?kg^?1 (Al) in the D. officinale with rock cultivation, and the contributions of Al may exceed the provisional tolerable daily intake value by the uptake of 20?g of D. officinale. The concentrations of seven metals (Bi, Pb, Fe, Al, Cr, As, and Mo) were utilized to identify the cultivation technique of the analyzed D. officinale samples through linear discriminant analysis.     

Sediment Assessment of the Pchelina Reservoir,Bulgaria

The temporal dynamics of anthropogenic impacts on the Pchelina Reservoir is assessed based on chemical element analysis of three sediment cores at a depth of about 100–130 cm below the surface water. The ¹³⁷Cs activity is measured to identify the layers corresponding to the 1986 Chernobyl accident. The obtained dating of sediment cores gives an average sedimentation rate of 0.44 cm/year in the Pchelina Reservoir. The elements’ depth profiles (Ti, Mn, Fe, Zn, Cr, Ni, Cu, Mo, Sn, Sb, Pb, Co, Cd, Ce, Tl, Bi, Gd, La, Th and U_nat) outline the Struma River as the main anthropogenic source for Pchelina Reservoir sediments. The principal component analysis reveals two groups of chemical elements connected with the anthropogenic impacts. The first group of chemical elements (Mn, Fe, Cr, Ni, Cu, Mo, Sn, Sb and Co) has increasing time trends in the Struma sediment core and no trend or decreasing ones at the Pchelina sampling core. The behavior of these elements is determined by the change of the profile of the industry in the Pernik town during the 1990s. The second group of elements (Zn, Pb, Cd, Bi and U_nat) has increasing time trends in Struma and Pchelina sediment cores. The increased concentrations of these elements during the whole investigated period have led to moderate enrichments for Pb and U_nat, and significant enrichments for Zn and Cd at the Pchelina sampling site. The moderately contaminated, according to the geoaccumulation indexes, Pchelina Reservoir surface sediment samples have low ecotoxicity.     

Isotope dilution analysis mass spectrometry for the routine measurement of butyltin compounds in marine environmental and biological samples

The highly qualified primary method of species-specific isotope dilution analysis has been employed in this work to evaluate for the first time the levels of butyltin compounds in the estuary of the river Eo (Northwest Spain) where there is, since many years, a high oyster farming activity. A spike solution containing mono-, di- and tributyltin enriched in ¹¹⁹Sn allowed the simultaneous determination of the three compounds in different marine environmental and biological samples collected in this area (seawater samples, sediments and biological tissues of four different marine species). The results obtained in this work showed toxic TBT levels for many marine species in 45% of the seawater samples analyzed whereas significant organotin concentrations were found to be obtained only in one of the sediments analyzed. On the other hand, TBT levels ranging from 20 to almost 200 ng g^− 1 (dry weight) were obtained in the different biological tissues analyzed demonstrating the bioaccumulation of organotin compounds in certain marine species.     

Characterization of estuarine sediments by near infrared diffuse reflectance spectroscopy

It has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63 μm grid. Spectra were scanned from 833 to 2976 nm, averaging 36 scans per spectrum at a resolution of 8 cm⁻¹, using chromatographic glass vials of 9.5 mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NIR spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area. pH, redox potential (Eh), carbon (C), nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3 mg g⁻¹ for H. Prediction errors for pH and Eh were 0.15 units and 37 mV, respectively, thus indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknown samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400 ng g⁻¹ Cd and 100 μg g⁻¹ Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes.     

Neue Zinn‐reiche Stannide der Systeme AII‐Al‐Sn (AII = Ca,Sr, Ba)

New Tin‐rich Stannides of the Systems A^II‐Al‐Sn (A^II = Ca, Sr, Ba) Four new tin‐rich intermetallics of the ternary systems Ca/Sr/Ba‐Al‐Sn were synthesized from stoichiometric amounts of the elements at maximum temperatures of 1200 °C. Their crystal structures, representing two new types, have been determined using single crystal x‐ray diffraction. Close to the 1:1 composition, the structures of the two isotypic compounds A₁₈[Al₄(Al/Sn)₂Sn₄][Sn₄][Sn]₂ (overall composition A₉M₈; A = Sr/Ba, tetragonal, space group P4/mbm, a = 1325.9(1)/1378.6(1), c = 1272.8(2)/1305.4(1) pm, Z = 4, R1 = 0.0430/0.0293) contain three different anionic Sn/Al building units: Isolated Sn atoms (motif I) coordinated by the alkaline earth cations only (comparable to Ca₂Sn), linear Sn chains (II), which are comparable to the anions in trielides related to the W₅Si₃ structure type and finally octahedral clusters [Al₄M₂Sn₄] (III), composed of four Al atoms forming the center plane, two statistically occupied Al/Sn atoms at the apexes and four exohedral Sn attached to Al. Close to the AM₂ composition, two isotypic tin‐rich intermetallics A₉[Al₃Sn₂][(Sn/Al)₄]Sn₆ (overall composition A₉M₁₅; A = Ca/Sr; space group C2/m, a = 2175.2(1)/2231.0(2), b = 1210.8(1)/1247.0(1), c = 1007.4(1)/1042.0(2) pm, β = 103.38(1)/103.42(1)°, Z = 2, R1 = 0.0541/0.0378) are formed. Their structure is best described as a complex three‐dimensional network, that can be considered to consist of the building units of the binary border phases too, i.e. linear zig‐zag chains of Sn (motif I) like in CaSn, ladders of four‐bonded Sn/Al atoms (II) like in SrAl₂ and trigonal‐bipyramidal clusters [Al₃Sn₂] (III) also present in Ba₃Al₅. Despite the complex structures, some statistically occupied Al/Sn positions and the small disorder of one building unit, the bonding in both structure types can be interpreted using the Zintl concept and Wade's electron counting rules when taking partial Sn‐Sn bonds into account.     

Peculiarities of Chemical Binding in Anhydrous Lead(II) and Tin(II) Hexacyanoferrates(II,III)

The electronic structure and chemical binding of anhydrous lead and tin hexacyanoferrates(II,III) Pb₂Fe(CN)₆, Pb_1.5Fe(CN)₆, and Sn₂Fe(CN)₆ were studied by the linear muffm-tin orbital (tight binding approximation) and extended Hückel theory methods. The general tendencies of variation for the stability of the Pb–N, Sn–N, Fe–C, and C–N bonds were determined for Pb₂Fe(CN)₆, Pb_1.5Fe(CN)₆, and Sn₂Fe(CN)₆ crystals. Peculiarities of Pb(Sn)–N chemical interactions in the structure of the phases have been found.     

Synthesis and structural characterization of the type‐I clathrates K8AlxSn46–x and Rb8AlxSn46–x (x ≃ 6.4–9.7)

Exploratory studies in the systems A–Al–Sn (A = K and Rb) yielded the clathrates K₈Al_xSn_46–x (potassium aluminium stannide) and Rb₈Al_xSn_46–x (rubidium aluminium stannide), both with the cubic type‐I structure (space group Pmn, No. 223; a ? 12.0 Å). The Al:Sn ratio is close to the idealized A₈Al₈Sn₃₈ composition and it is shown that it can be varied slightly, in the range of ca ±1.5, depending on the experimental conditions. Both the (Sn,Al)₂₀ and the (Sn,Al)₂₄ cages in the structure are fully occupied by the guest alkali metal atoms, i.e. K or Rb. The A₈Al₈Sn₃₈ formula has a valence electron count that obeys the valence rules and represents an intrinsic semiconductor, while the experimentally determined compositions A₈Al_8±xSn_38?x suggest the synthesized materials to be nearly charge‐balanced Zintl phases, i.e. they are likely to behave as heavily doped p‐ or n‐type semiconductors.     

Measurement of butyltin contamination of water and sediment in Osaka Bay,Japan

The concentration of tributyltin (TBT) in surface water from Osaka Bay ranged from 0.023 to 0.061 µg l⁻¹ in 1989 and from not detected (ND) to 0.059 µg l⁻¹ in 1990 while the proportion of TBT as a percentage of the total butyltins (BTs) was more than 40%. The concentration of TBT was also surveyed in the Port of Osaka and the Yodo River basin. TBT levels were highest in the estuary (the Port of Osaka), followed by sea areas (Osaka Bay) and rivers (Yodo River basin). A fairly high correlation coefficient between TBT concentration and salinity in water from the estuary and the sea areas was observed. This result shows that the TBT in the estuary water is diluted by seawater. Generally, the TBT concentrations in the water columns were distributed uniformly and the composition of the BTs was also constant. TBT was detected in sediment from Osaka Bay in the range from ND to 0.023 mg kg⁻¹ dry weight with a high ratio of monobutyltin (MBT) to the total BTs. TBT in sediment core was also measured; its concentration decreased with core depth. It was estimated from these measurements that the release of TBT into Osaka Bay began in the 1960s. Copyright © 1998 John Wiley & Sons, Ltd.     

Investigation of the Property Constants of Both Al and Cu Complexes with Picramine Ca and Using Competition Coordination for the Selective Determination of Trace Amounts of Cu

The reactions between Cu(II) and picramine CA (PCA) and Al(III) and PCA were both sensitive at pH 7. The competition coordination between Cu and the Al–PCA complex was applied to the selective determination of Cu (CCSD) by the spectral correction technique. Results have shown that the complexes formed at pH 7 are Al₂(PCA) and Cu(PCA)₃, their cumulative stability constants are 4.43 × 10⁵ and 2.08 × 10¹⁵, respectively, and their real molar absorptivities are 5.78 × 10³ at 650 nm and 3.19 × 10⁴at 530 nm. At the analysis of the samples, the relative standard deviation (RSD) was 5.0% and the recovery rate of Cu was between 94 and 108%.     

Antifungal evaluation of cholic acid and its derivatives on Candida albicans by microcalorimetry and chemometrics

In the last few years, several fungus infections caused by multidrug-resistant pathogenic agents have got tremendous emergence and prevalence. Screening for novel antifungal agents is in great demand, but traditional microbiological techniques are far from sufficient to meet that requirement. In this study, a non-invasive and non-destructive microcalorimetric method was performed to investigate the antifungal activities of cholic acid (CA) and its derivatives, glycocholic acid (GCA) and taurocholic acid (TCA) on the multiplying and non-multiplying metabolism of Candida albicans. Then, the heat-flow power-time curves of C. albicans growth affected by different concentrations of CA, GCA and TCA were studied by similarity analysis (SA), the quantitative thermokinetic parameters from these curves were analyzed by multivariate analysis of variance (MANOVA) and principal component analysis (PCA). By comparing the values of two main parameters, P₂ (the heat-flow output power of the highest peak) and Q₂ (the heat output of the second exponential growth phase) of C. albicans, it could be found that CA had the strongest antifungal activity among the three steroid compounds, which might be used as a potential antifungal agent in the future. This study provided a useful method and idea of microcalorimetry with chemometrics to efficiently evaluate the antifungal activities of bile acid derivatives, giving some references for screening out new antifungal agents.However, it has to be stressed that all these experiments are carried out in vitro and they still require clinical validation.     

Determination of heavy metals by inductively coupled plasma-optical emission spectrometry in fish from the Piracicaba River in Southern Brazil

A total of 202 fish, representing 16 species, were collected during 2008 (March–October) in the Tanquan region of the Piracicaba River using nets. Flesh samples were collected and analyzed, using inductively coupled plasma-optical emission spectroscopy for Al, As, Cd, Co Cr, Cu, Mn, Mo, Ni, Pb, Se, Sn, Sr, and Zn. The results showed that the flesh of these fish all contained extremely high levels of Al and Sr, and moderately high levels of Cr, As, Zn, Ni, Mn and Pb. The metals were higher in these fish during rainy season, with fish collected during the months of March and October being the highest. In addition, the accumulation of metals was species-dependent. Cascudos (Hypostomus punctatus) and piranhas (Serrasalmus spilopleura) exhibited high levels of almost all of the metals, while curimbata (Prochilodus lineatus) had moderate levels. A few species, including pacu (Piaractus mesopotamicus) and dourado (Salminus maxillosus), had very low levels of most metals. The results show that the Piracicaba River Basin is widely contaminated with high levels of many toxic heavy metals, and that human consumption of some fish species is a human health concern.     

Development of a fast analytical tool to identify oil spillages employing infrared spectral indexes and pattern recognition techniques

A fast analytical tool based on attenuated total reflectance mid-IR spectrometry is presented to evaluate the origin of spilled hydrocarbons and to monitor their fate on the environment. Ten spectral band ratios are employed in univariate and multivariate studies (principal components analysis, cluster analysis, density functions - potential curves - and Kohonen self organizing maps). Two indexes monitor typical photooxidation processes, five are related to aromatic characteristics and three study aliphatic and branched chains. The case study considered here comprises 45 samples taken on beaches (from 2002 to 2005) after the Prestige carrier accident off the Galician coast and 104 samples corresponding to weathering studies deployed for the Prestige's fuel, four typical crude oils and a fuel oil. The univariate studies yield insightful views on the gross chemical evolution whereas the multivariate studies allow for simple and straightforward elucidations on whether the unknown samples match the Prestige's fuel. Besides, a good differentiation on the weathering patterns of light and heavy products is obtained.     

Partial least squares X-ray fluorescence determination of trace elements in sediments from the estuary of Nerbioi-Ibaizabal River

The feasibility of partial least squares (PLS) regression modeling of X-ray fluorescence (XRF) spectra of estuarine sediments has been evaluated as a tool for rapid trace element content monitoring. Multivariate PLS calibration models were developed to predict the concentration of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected from different locations across the estuary of the Nerbioi-Ibaizabal River (Metropolitan Bilbao, Bay of Biscay, Basque Country). The study was carried out on a set of 116 sediment samples, previously lyophilized and sieved with a particle size lower than 63 μm. Sample reference data were obtained by inductively coupled plasma mass spectrometry. 34 samples were selected for building PLS models through a hierarchical cluster analysis. The remaining 82 samples were used as a test set to validate the models. Results obtained in the present study involved relative root mean square errors of prediction varying from 21%, for the determination of Pb at hundreds μg g⁻¹ level, up to 87%, for Ni determination at little tens μg g⁻¹ level. An average prediction error of ±37% for the 14 elements under study was obtained, being in all cases mean differences between predicted and reference results of the same order than the standard deviation of three replicates from a same sample. Residual predictive deviation values obtained ranged from 1.1 to 3.9.     

The Use of Transplanted Venerupis Decussata to Evaluate the Pollution of Heavy Metals and Tributyltin in Marinas

Abstract

Live specimens of the clam Venerupis decussata were suspended in seawater of the Mazagon Marina, located in a heavy metal polluted area at the mouth of Huelva Estuary (SW Spain), Clams were preserved in plastic cages and subsamples were recovered every 5 days over a period of 40 days. Water from the marina was sampled every two days during the time course of the experiment. Clams and water were analyzed for metals and organotins. Results showed the accumulation of Mn, Cu, Fe, V, Zn and tributyltin in the bivalves reaching an equilibrium with the surrounding water. Bioconcentration factors ranged from 10² (for V) to 4×10³ (for Cu). Clams also accumulated Al and Pb but a steady state was not reached. A first-order kinetic model was applied to the data and results indicated that rates of accumulation differed in relation to clam size class. Clam mortality increased during the experiment and was total after 42 days which was attributed to the high concentration of Cu in seawater.     

Bestimmung von Zinnspuren in Lebensmitteln

Zusammenfassung Die vorgeschlagene Methode der Zinnbestimmung in Lebensmitteln beruht auf der selektiven Extraktion von Sn(IV) als Brilliant-grünhexabromostannat mit Äthylacetat. Das aus salzsaurem Medium extrahierte Ionenassoziat ist schwach gefärbt. Es wird in einen Quercetinkomplex umgesetzt und danach bei 440 nm photometriert. Fe(III), Cu(II), Cd, Pb(II), Hg(II), Al, Co, Bi, Ni und Cr(III) stören nicht. Das Beersche Gesetz ist zwischen 1 und 40g Sn erfüllt. Der Variationskoeffizient ist bein=30 und einer Zuverlässigkeit von 95% etwa gleich 7%. Die Methode ist durch große Genauigkeit und Empfindlichkeit gekennzeichnet. Man kann 1 ppm Sn in Nahrungsmitteln bestimmen.

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Determination of traces of tin in foodstuffs

Summary The method suggested is based on selective extraction of Sn(IV) as brilliant green-hexabromostannate with ethyl acetate. The ion associate, which is extracted from HCl medium, is weakly colored. It is converted into a pentahydroxyflavone complex and afterwards analysed photometrically at 440 nm. There is no disturbance by Fe(III), Cu(II), Cd, Pb(II), Hg(II), Al, Co, Bi, Ni, or Cr(III). Beer's law is fulfilled between 1 and 40g. With a confidence limit of 95% andn=30, the coefficient of variation is 7%. The method is characterized by great accuracy and sensitivity. 1 ppm Sn can be determined in foodstuffs.

     

Spatial and seasonal behaviour of organotin compounds in protected subtropical estuarine ecosystems in Okinawa,Japan

The spatial and temporal behaviours of the organotin compounds (OTCs) (butyl- and phenyltin) were investigated in the Manko and Okukubi protected estuarine ecosystems on Okinawa Island, Japan from February to October 2006. Butyltin compounds (BTCs) were frequently detected in all seasons, while phenyltin (PhTs) were found in winter and early spring. In Manko estuary, the total mean concentrations of BTCs and PhTs were 22.78?±?30.85, (mean?±?SD, n?=?53) and 0.08?±?0.27?ng(Sn)?L^?1, respectively. In Okukubi estuary, BTCs and PhTs were 12.58?±?23.96 and 0.47?±?1.67 (n?=?55) ng(Sn)?L^?1, respectively. The Manko sediments can be classified as lightly contaminated, while the Okukubi sediments were uncontaminated with tributyltin (TBT). The mean levels of TBT shown in Manko estuary exceeded the threshold level and represent an ecotoxicological risk to sensitive aquatic life. Generally, the present study reports the occurrence and continuous input of OTCs in the protected estuaries, even 16 years after legal restriction of TBT usage in coastal waters was implemented by the Japanese Environmental Authorities.