Ion chromatographic determination of selected ions in antarctic ice

Ion chromatography is used to measure the concentrations of chloride, nitrate, sulphate, ammonium and sodium ions at the μg l^?1 level in Antarctic ice and to investigate the occurrence of methanesulphonate, fluoride, formate, acetate and nitrite. Of the latter group of ions, only methanesulphonate was found in measurable concentrations.     

Ion chromatographic determination of common ions at ultratrace levels in Antarctic snow and ice

The simultaneous determination of major impurities present in Antarctic snow and ice at ng g^? (ppb) concentrations by ion chromatography is described. Calibration data are presented for ammonium, sodium, potassium, chloride, nitrate and sulphate ions. Special attention is paid to the different ways of removing field contamination from ice and snow cores and suitable equipment is described. The results provide evidence against the validity of published sets of concentration data for nitrogen-containing compounds (NO^?₃ and NH⁺₄ in Antarctic snow, and demonstrate a crucial contamination problem in the determination of ammonium ions.     

Analysis of snow from Antarctica: a critical approach to ion-chromatographic methods

Ion-chromatographic methods for anion and cation determination in snow samples from Antarctica are evaluated with regard to sensitivity and selectivity. An eluent-step change method is proposed to determine simultaneously mono- and divalent cations with detection limits lower than 1 g/L. Special attention is given to the determination of the ammonium ion at trace levels in the presence of high sodium concentrations and the problems of sample contamination by the laboratory environment are evaluated. Two alternative methods, one using isocratic and the other a gradient elution, are proposed for the determination of fluoride, acetate, formate and methanesulphonate ions. Both methods are discussed to evaluate their use in snow sample analysis.     

Effect of ammonium formate as ionizing additive in thermospray liquid chromatography-mass spectrometry for the determination of triazine,phenylurea and chlorinated phenoxyacetic acid herbicides

A comparison between the use of ammonium acetate and ammonium formate in thermospray liquid chromatography-mass spectrometry with positive and negative ion modes using ‘filament-on’ mode has been applied for the determination of simazine, atrazine, propazine, monuron, diuron, linuron, 2,4,-D, 2,4,5-T and silvex. By using ammonium formate, the positive ion mode showed for triazine and phenylurea herbicides [M + H]⁺ and [M + NH₄]⁺, respectively, and the formation of other adduct ions different from ammonium acetate. In the negative ion mode, chlorinated phenoxyacetic acid herbicides exhibited [M + acetate]^? or [M + formate]^?, depending on the ionizing additive. Applications are reported for the determination of triazine and chlorinated phenoxyacetic acid herbicides in spiked soil and water samples, respectively.     

Polychlorobiphenyls in Antarctica

The presence and the distribution of polychlorobiphenyls (PCBs) in Antarctic environmental components and the effect of the seasonal formation/melting process of pack ice on the pollution level of seawater were investigated. Seawater, marine, and lake sediment and soil samples were collected in a large area of the Ross Sea and Victoria Land during the 1988–1989, 1989–1990, 1990–1991, and 1991–1992 Italian expeditions. The results obtained highlighted a low and quite homogeneous PCB contamination of the studied area. Surface seawater samples from Gerlache Inlet and Wood Bay showed a typical PCB concentration of 130 pg/liter, and an increase after pack ice melting of about 30–40%. Marine sediment, lake sediment, and soil samples showed normalized mean PCB contents of 150, 240, and 130 (pg/g)/(m²/cm³), respectively.     

An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g Pb concentrations

Measurements of Pb isotope ratios in ice containing sub-pg g⁻¹ concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g⁻¹ and fg g⁻¹ concentrations in Polar ice, were also measured. The final blank amounted to 0.2 ± 0.2 pg of Pb with ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios of 1.16 ± 0.12 and 2.35 ± 0.16, respectively, 1.5 ± 0.4 pg of Ba and 0.6 ± 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only ∼5%, ∼14% and ∼0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g⁻¹, 0.3 pg g⁻¹ and 2.3 fg g⁻¹. Uncertainties in the Pb isotopic ratio measurements were degraded by only ∼0.2%.     

Multiple Regulation Effects of Ammonium Acetate on ZnO Growth Process in Chemical Bath Deposition

Chemical bath deposition method has been used to synthesize a variety of ZnO morphology structures. However, the specificity and interaction of acetate and ammonium ions with ZnO crystal during the growth process remain elusive. This study contributes to understand the roles of ammonium acetate on the growth mechanism of ZnO in Zn(NO₃)₂-HMTA system. The growth process indicates that the nucleation experienced Zn²⁺-layered basic zinc salts (LBZs)-ZnO process, while the self-assembled unit changed from urchin-shaped, rod-shaped to a fully coupled twin-shaped structure with increasing ammonium acetate concentration. Ammonium acetate dominates the growth process by combing the ligand-ligand interaction of acetate ions binding to the same Zn-rich (0001) polar surface and ammonium ions regulating hexamethylenetetramine (HMTA) hydrolysis. Relatively regular hexagonal wurtzite structure and a dissolve-renucleation-regrowth process which retains the twin-shaped template and renucleates at the same position are observed at ∼10 mM ammonium acetate. Photoelectrochemistry (PEC) measurements show that the uniform hexagonal ZnO rods (Y-10, the sample named as Y-x (x represents x mM ammonium acetate, herein, x is 10 mM)) have a maximum photocurrent density of 1.54 mA cm⁻² at 1.23 V (vs. RHE), much higher than that of the dumbbell-shaped ZnO rods (Y-50, 0.20 mA cm⁻²) at the same voltage. These results provide a further explanation of morphology regulation mechanisms on ZnO synthesis processes and pave the road for more practical applications.     

A new method based on low background instrumental neutron activation analysis for major,trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores

Dust found in polar ice core samples present extremely low concentrations, in addition the availability of such samples is usually strictly limited. For these reasons the chemical and physical analysis of polar ice cores is an analytical challenge. In this work a new method based on low background instrumental neutron activation analysis (LB-INAA) for the multi-elemental characterization of the insoluble fraction of dust from polar ice cores is presented. Thanks to an accurate selection of the most proper materials and procedures it was possible to reach unprecedented analytical performances, suitable for ice core analyses. The method was applied to Antarctic ice core samples. Five samples of atmospheric dust (μg size) from ice sections of the Antarctic Talos Dome ice core were prepared and analyzed. A set of 37 elements was quantified, spanning from all the major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) to trace ones, including 10 (La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu) of the 14 natural occurring lanthanides. The detection limits are in the range of 10⁻¹³–10⁻⁶ g, improving previous results of 1–3 orders of magnitude depending on the element; uncertainties lies between 4% and 60%.     

Speciation analysis of iodine and bromine at picogram-per-gram levels in polar ice

Iodine and bromine species participate in key atmospheric reactions including the formation of cloud condensation nuclei and ozone depletion. We present a novel method coupling a high-performance liquid chromatography with ion chromatography and inductively coupled plasma mass spectrometry, which allows the determination of iodine (I) and bromine (Br) species (IO ₃ ^? , I^?, Br^?, BrO ₃ ^? ) at the picogram-per-gram levels presents in Antarctic ice. Chromatographic separation was achieved using an IONPAC® AS16 Analytical Column with NaOH as eluent. Detection limits for I and Br species were 5 to 9 pg g^?1 with an uncertainty of less than 2.5% for all considered species. Inorganic iodine and bromine species have been determined in Antarctic ice core samples, with concentrations close to the detection limits for iodine species, and approximately 150 pg g^?1 for Br^?. Although iodate (IO ₃ ^? ) is the most abundant iodine species in the atmosphere, only the much rarer iodide (I^?) species was present in Antarctic Holocene ice. Bromine was found to be present in Antarctic ice as Br^?.     

Analysis of 5-methyltetrahydrofolate in human blood, serum and urine by on-line coupling of capillary isotachophoresis and zone electrophoresis

The predominant circulating folate coenzyme in plasma/serum, 5‐methyltetrahydrofolate (5‐MTHF) was determined in human blood, serum and urine using a method based on the hyphenation of capillary ITP and zone electrophoresis. Measurements were done with a commercially available instrument for capillary isotachophoresis equipped with a column‐switching system. The choice of electrolytes was limited by the instability of 5‐MTHF and volatility of electrolytes for the potential coupling of the instrumentation with MS detector. To get an insight into the separability of individual sample components in an isotachophoretic analysis, we constructed zone existence diagrams for isotachophoretic electrolyte systems having a leading electrolyte composed of acetate and ammonium of pH 4.5 and 7.0, hydrocarbonate and ammonium, pH 7.8, chloride and ammonium, pH 5.6, and chloride and creatinine, pH 5.0, with hydroxide ion as the terminator. For isotachophoretic preseparation, the non‐volatile leading electrolyte with good buffering capacity composed of 1×10⁻² M HCl and 2.5×10⁻² M creatinine, pH 5.0, and terminating electrolyte composed of 1×10⁻² M MES was selected as the most suitable. The optimum BGE for CZE analysis from the standpoint of analyte stability, separability and volatility for MS coupling was 1×10⁻² M acetate with 3.5×10⁻² M ammonium, pH 4.5. Using this combination of electrolytes, LODs reached with optical detection at 220 nm were 1.6×10⁻⁷ M in human blood, 1.1×10⁻⁷ M in human serum and 4.7×10⁻⁶ M in human urine. Estimated content of 5‐MTHF in blood and serum samples of women following oral daily administration of 0.8 mg of folic acid was 1.2×10⁻⁵ and 5.8×10⁻⁶ M, respectively.     

An evaluation of differential pulse anodic stripping voltammetry at a rotating glassy carbon electrode for the determination of cadmium,copper, lead and zinc in antarctic snow samples

A procedure is described for the determination without preconcentration of Cd, Cu, Pb and Zn in Antarctic snow, based on differential pulse anodic stripping voltammetry at a rotating glassy carbon electrode with in situ mercury plating. Thirty four surface snow samples from Adelaide Island in the Antarctic Peninsula demonstrate the scope of this method, and allow an assessment of local heavy metal sources such as the rock, the sea, and a manned base. The zinc data are affected by container contamination, but concentrations as low as 0.005, <0.02 and 0.05 ng g^-1 were measured for Cd, Cu and Pb, respectively.     

Hepatic butyltin concentrations in beluga whales (Delphinapterus leucas) from the St Lawrence Estuary and northern Quebec,Canada

Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg⁻¹ on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g⁻¹ for MBT and <0.2 ng Sn g⁻¹ for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT‐based antifoulants on small craft. Copyright © 2000 John Wiley & Sons, Ltd.     

Sulphur(IV) in rain water and antarctic ice by ion chromatography

Sulphur(IV) is quantified as the α-hydroxysulphonic acid, hydroxymethanesulphonate, which is stabilized in samples and standards by a stoichiometric excess of formaldehyde. The addition of 0.2% (v/v) formaldehyde to the very dilute eluent protects against oxidation of the adduct, which is eluted as a single symmetrical peak, completely resolved from ali other anions including methanesulphonate. The detection limit is 0.1 μg l^?1 S(IV). The method is applied in the analysis of Tasmanian rain water and Antarctic ice.     

Determination of traces of As,Cd, Cr,Hg, Mn,Ni, Sb,Se, Sn and Pb in human hair by triple quadrupole ICP-MS

With the wide range of metallic contaminants discharged in the environment, studying the human health requires a growing number of elements to be monitored in biological samples. Hair analysis has been suggested as a suitable tool for biomonitoring environmental and occupational exposure to toxic elements. This study describes a method for the determination of 10 trace elements in hair samples using ICP-QQQ-MS. Combining the power of the MS/MS high-energy Helium mode with the MS/MS O₂ mass-shift mode, the method offers great analytical performances with detection limits reaching 0.0014 µg g^?1 for As, 0.0016 µg g^?1 for Cd, 0.012 µg g^?1 for Cr, 0.0035 µg g^?1 for Hg, 0.0055 µg g^?1 for Mn, 0.10 µg g^?1 for Ni, 0.0012 µg g^?1 for Sb, 0.0083 µg g^?1 for Sn, 0.011 µg g^?1 for Se and Pb. The accuracy of the method was tested on a human hair ERM® certified reference material. Percent recoveries varied from 91.3% and 106.9% being always in the acceptance range of 90–110%. For all analysed elements, RSD% of repeatability ranged between 0.6% and 9.0% and those of intermediate precision did not exceed the limit of 20% being always lower than 10% (except for As). The proposed method was applied for the determination of trace elements in hair samples from 20 unexposed subjects. The geometric mean levels were as follows: Cr 0.28 µg g^?1, Mn 0.30 µg g^?1, Sn 1.04µg g^?1, Sb 0.07 µg g^?1, Hg 0.42 µg g^?1, As 0.02 µg g^?1, Cd 0.03 µg g^?1, Ni 0.51 µg g^?1, Se 0.45 µg g^?1 and Pb 1.83 µg g^?1. Element concentrations were in the same range with the reported data. The reported results may be useful for environmental exposure assessment or comparisons studies when establishing reference values of trace elements in exposed population.     

When High-Temperature Cesium Chemistry Meets Self-Templating: Metal Acetates as Building Blocks of Unusual Highly Porous Carbons

Self-templating is a facile strategy for synthesizing porous carbons by direct pyrolysis of organic metal salts. However, the method typically suffers from low yields (<4%) and limited specific surface areas (SSA<2000 m² g⁻¹) originating from low activity of metal cations (e.g., K⁺ or Na⁺) in promoting construction and activation of carbon frameworks. Here we use cesium acetate as the only precursor of oxo-carbons with large SSA of the order of 3000 m² g⁻¹, pore volume approaching 2 cm³ g⁻¹, tunable oxygen contents, and yields of up to 15 %. We unravel the role of Cs⁺ as an efficient promoter of framework formation, templating and etching agent, while acetates act as carbon/oxygen sources of carbonaceous frameworks. The oxo-carbons show record-high CO₂ uptake of 8.71 mmol g⁻¹ and an ultimate specific capacitance of 313 F g⁻¹ in the supercapacitor. This study helps to understand and rationally tailor the materials design by a still rare organic solid-state chemistry.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Mercury in atmospheric aerosols: A preliminary case study for the city of Krakow,Poland

The level of contamination by mercury associated with airborne particulate matter in Krakow was determined. Samples of PM10 were collected on quartz filters using low-volume samplers. The total particulate mercury (TPM) concentrations in collected samples were determined by mercury analyser MA-3000 (Nippon Instruments Corporation). The reported results include also data on the carbonaceous aerosol and inorganic ions concentrations during the reported sampling campaign. The average concentration of the Total Particulate Mercury (TPM) in Krakow (Poland) was 0.22 ng·m⁻³ (during the period from 22 February to 2 March) and 0.49 ng·m⁻³ (on 3 March). A marked correlation between TPM and elemental carbon (EC) as well as with Cl^– was found. No significant association of the TPM with NO₃^– and SO₄^2– could be shown. The dry deposition flux of mercury was calculated as an average over the sampling period and was 47.3 ng·m⁻²·d⁻¹.     

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

The effects of three additives—ammonium acetate, ammonium formate, and nicotinic acid—to the liquid chromatographic (LC) eluent and of the vaporizer temperature on the ion formation of N-methyl carbamate pesticides in thermospray (TSP) mass spectrometry was investigated by using filament- or discharge-assisted ionization. Nineteen carbamates and 12 of their known environmental degradation products were used as model compounds. The additives cause a strong reduction in the abundance of the characteristic fragment ions [M + H ? CH₃NCO]⁺ and [M ? H ? CH₃NCO]^? for some of the carbamates. The addition of nicotinic acid reduces the quasimolecular ion intensity and, in most cases, produces nicotinic acid adduct ions. The addition of ammonium acetate or ammonium formate increases the intensity of the quasimolecular ion and in most cases produces a base peak for the ammonium adduct ion. The combination of a suppression of fragmentation and an enhancement of quasimolecular ion formation produces an overall gain in sensitivity. As to more specific effects, the addition of the ammonium salts reduces the intensity of M^?? with the chlorinated carbamate barban and suppresses the formation of “odd” adduct ions in the TSP mass spectra of most other carbamates. Monitoring the intensity of the fragment and the quasimolecular ion signal as a function of the probe stem temperature, and the related probe tip temperature, proved to be an easy method to study the thermal degradation of the carbamates. This monitoring procedure showed that methiocarb and its sulfone already suffer from thermal degradation at a stem temperature of 90°C and that these compounds will therefore present problems in quantitation with LC/TSP mass spectrometry.     

A Carbocationic Triarylmethane-Based Porous Covalent Organic Network

A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m² g⁻¹ and pore size of 10.3 Å. The material has CO₂ uptake of 2.14 mmol g⁻¹ (0.5 bar), 2.7 mmol g⁻¹ (1 bar), and 6.8 mmol g⁻¹ (20 bar), the latter corresponding to 3 CO₂ molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10⁻⁷ S cm⁻¹, which increases to 5.26×10⁻⁴ S cm⁻¹ upon exposure to I₂ vapor. DFT calculations using periodic conditions support the findings.     

Determination of hydride forming elements (As,Sb, Se,Sn) and Hg in environmental reference materials as acid slurries by on-line hydride generation inductively coupled plasma mass spectrometry

A method for the determination of As, Hg, Sb, Se and Sn in environmental and in geological reference materials, as acidified slurries, by flow injection (FI) coupled to a hydride generation system (HG) and detection by inductively coupled plasma mass spectrometry (ICP-MS) is proposed. The HG unit has a gas liquid separator and a drying unit for the generated vapor. The slurries were prepared by two procedures. Approximately 50 mg of the reference material, ground to a particle size ≤50 μm, was mixed with acid solutions in an ultrasonic bath. In Procedure A, the medium was a hydrochloric acid solution while in Procedure B, the medium was aqua regia plus a hydrochloric acid solution. The conditions for the slurry formation and the instrumental parameters were optimized. Harsh conditions were used in the slurry preparation in order to reduce the hydride forming analytes to their lower oxidation states, As (III), Se(IV), Sb(III) and Sn(II), before reacting with sodium tetrahydroborate. To test the accuracy, 10 certified reference materials were analyzed (four sediments, three coals, one coal fly ash and two sewage sludges), with the analyte concentrations mostly in the μg g⁻¹ level. Good agreements with the certified values were obtained for Hg, Sb and Sn in the sediments using Procedure A and calibration against aqueous standard solutions. Using Procedure B, good results were obtained for Hg, Se and Sn in the sediment samples, for Se in the coal and coal fly ash samples and for Hg in the sewage sludge samples, also using external calibration with aqueous standard solutions. For As in sediments, coals and coal fly ash, Procedure B and the analyte addition calibration was required, indicating matrix effects. The relative standard deviations were lower than 5%, demonstrating a good precision for slurry analysis. The limits of quantification (10 times the standard deviation; n=10), in the samples, in ng g⁻¹, were: 20 for As, 60 for Hg, 80 for Sb, 200 for Se and 90 for Sn. The method requires small amounts of reagents and reduces contamination and losses.