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Analytical and Bioanalytical Chemistry (v.377, #1)

Once you get there or think you have....mentoring to pass on the torch by John Fetzer (pp. 1-2).

2003 European Winter Conference on Plasma Spectrochemistry by Klaus G. Heumann (pp. 3-5).

Benefits of high resolution IC–ICP–MS for the routine analysis of inorganic and organic arsenic species in food products of marine and terrestrial origin by Ute Kohlmeyer; Eckard Jantzen; Jürgen Kuballa; Sandra Jakubik (pp. 6-13).

A recently developed and validated method for simultaneous determination of 17 inorganic and organic arsenic compounds in marine biota has been successfully applied to routine analysis of different food products, including fish, shellfish, edible algae, rice, and other types of grain. During one year, approximately 250 food samples were analyzed, mostly fish and rice. Long-term stability and robustness of the system was observed and reproducible results for certified reference materials were ensured by means of control charts. The separation was performed by ion-pair chromatography on an anion-exchange column to separate anionic, neutral, and cationic arsenic species in one chromatographic run. Hyphenation to ICP–MS allowed element-specific and sensitive detection of the different arsenic species with a detection limit as low as 8 ng As L⁻¹in the sample extract, which is equivalent to 2 ng As g⁻¹ in the original sample. Special emphasis was laid on the analysis of marine algae and rice samples. These food types can contain elevated levels of the very toxic inorganic arsenic species (up to 90% in rice) and therefore are the focus of interest in the food industry. In marine algae, inorganic arsenic was mainly present as arsenate whereas in rice arsenite predominated.

Keywords: IC–ICP–MS; Arsenic; Speciation; Food; Rice; Algae

Speciation of arsenic in water, sediment, and plants of the Moira watershed, Canada, using HPLC coupled to high resolution ICP–MS by Jian Zheng; Holger Hintelmann; Brian Dimock; Mark Stephen Dzurko (pp. 14-24).

High-performance liquid chromatography (HPLC) coupled with high-resolution sector field ICP–MS was applied to the speciation of arsenic in environmental samples collected from the Moira watershed, Ontario, Canada. Arsenic contamination in Moira River and Moira Lake from historic gold mine operations is of increasing environmental concern to the local community. In this study, the current arsenic contamination status in water, sediment, and plants was investigated. Elevated levels of arsenic in the surface water of up to 75 ng mL⁻¹ in Moira River and 50 ng mL⁻¹ in Moira Lake were detected, 98% of which was present as arsenate. High concentrations of arsenic (>300 ng mL⁻¹), mainly present as arsenite, were detected in sediment porewaters. A sediment profile of As from the West basin of Moira Lake showed lower As concentrations compared with data from the 1990s. An optimized extraction procedure using a phosphoric acid–ascorbic acid mixture demonstrated that an unknown "As-complex" which may consist of As, sulfide and organic matter is potentially responsible for the release of arsenite from the sediment to the overlying water column. Arsenic concentrations in plant samples ranged from 2.6 to 117 mg kg⁻¹, dry weight. Accumulation of arsenic was observed in submerged plants collected from Moira River and Moira Lake. Only a small part of the arsenic (6.3–16.1%) in the plants was extractable with methanol-water (9:1), and most of this arsenic (70–93%) was inorganic arsenic. A variety of organic arsenic compounds, including simple methylated compounds (methylarsonic acid and dimethylarsinic acid), trimethylarsine oxide, and tetramethylarsonium cation were detected at trace levels. No arsenobetaine and arsenocholine was found in any plant sample. An unknown compound, most probably an arsenosugar was detected in the two submerged plants, coontail ( Ceratophyllum demersum) and long-stemmed waterwort ( Elatine triandra). These submerged plants are constantly exposed to high arsenic concentrations in the surrounding water. Apparently, they are able to grow in this environment without invoking the same biochemical defence known from marine algae to detoxify inorganic arsenic. The detoxification mechanism of these plants remains unknown.

Keywords: Arsenic speciation; Water; Sediment; Plants; HPLC–ICP–SFMS

The potential of arsenic speciation in molluscs for environmental monitoring by Csilla Sörös; Erzsébet Tünde Bodó; Péter Fodor; Roberto Morabito (pp. 25-31).

This paper reports the assessment of total arsenic and six arsenic species (As(III), As(V), MMA, DMA, AsBet, AsCol) as contaminants of mussel samples collected around the island of Sardinia and in the Gulf of Venice. The samples were analysed using cation- and anion-exchange HPLC-HG-AFS for speciation and ICP-AES for the total As determination. To ensure the robustness of the routine analytical method, the technique was validated using a candidate reference material, BCR-710, and good agreement was obtained. It was recognised that higher total arsenic concentration in mussels does not necessarily result in higher toxicity of mussel samples.

Keywords: Arsenic speciation; Routine analysis; Biological monitoring; Mussels

Preparation, homogeneity and stability studies of a candidate LRM for Se speciation by Erzsébet Tünde Bodó; Zsolt Stefánka; Ildikó Ipolyi; Csilla Sörös; Mihály Dernovics; Péter Fodor (pp. 32-38).

A laboratory reference material (LRM) was prepared from Brazil nuts (Bertholletia excelsa) for quality control (QC) purposes of selenium speciation. The preparation of this LRM led through the usual operation steps applied during routine reference material production from biota samples—preparation of the raw material, homogenisation, storage design, checking of homogeneity, microbiological status and possible irradiation effects, and monitoring the species stability vs time at different storage temperatures. The selenium speciation studies to check species stability were carried out on a HPLC–UV–HG–AFS measurement set-up. Special attention was paid to the correct identification of selenium species by applying independent HPLC separation techniques (ion-pairing and anion-exchange chromatography). The concentration of selenomethionine (SeMet) and total Se content were quantified (79.9 µg g⁻¹ (calculated as Se) and 82.9 µg g⁻¹, respectively). The homogeneity and stability of this candidate reference material passed the relevant tests recommended by Bureau Communautaire de Référence (BCR).

Keywords: Selenium speciation; Laboratory reference material; Selenomethionine

Continuous measurement of metals in flue gas using ICP-OES by P. J. Clarkson; D. J. Poole; C. K. Ryu; V. N. Sharifi; J. Swithenbank; H.-J. Waarlo; D. Ardelt; H. Falk (pp. 39-47).

A system capable of continuously measuring a range of metallic elements in the effluent gas from incinerators and other similar industrial processes, and providing on-line results has been developed. With a state-of-the-art mobile laboratory measurements were taken from a UK municipal solid waste incinerator. The detection system used was an ICP-OES, with a modified torch to allow the introduction of flue gas directly into the plasma. Metals that were investigated were Ni, Hg, V, Al, Na, Ca, Cu, Sn, Pb, Sb, As, Cd and Tl, with limits of detection in the range 0.0004 mg m⁻³ to 0.1 mg m⁻³ being calculated. Emission measurements produced data that showed that the MSWI plants emission were significantly lower than the emission limits specified in EC 2000/76/EC.

Keywords: Flue gas; Continuous emission monitoring; ICP-OES; Metals; On-line analysis

On-line monitoring of a frontal chromatographic separation using inductively coupled plasma atomic emission spectroscopy by U. Wenzel; H. Vijgen; W. Ullrich (pp. 48-57).

A test array is described employing a destructive analytical technique for the long-term monitoring of an industrial-scale separation process. As an example, we chose frontal chromatography as the separation and ICP/AES as the analytical method. The feed solution of the process was conveyed by a process pump via the separation unit to a sample station, where a small portion was diverted and transported by a roller pump into the spectrometer. We equipped our array with different loops for operating the process, calibrating the instrument and verifying the calibration. We obtained identical results for the different loops by absorbing the pulsation of the process pump and arranging for identical suction lines of the spectrometer pump. Based on the results, we redesigned the sample station for a technical application using only commercially available parts.

Keywords: Frontal chromatography; Atomic emission spectroscopy; Process monitoring

Determination of thorium and light rare-earth elements in soil water and its high molecular mass organic fractions by inductively coupled plasma mass spectrometry and on-line-coupled size-exclusion chromatography by Evelton A. Casartelli; Norbert Miekeley (pp. 58-64).

Inductively coupled plasma mass spectrometry (ICP–MS) has been used for the determination of thorium and light rare-earth elements (LREEs) in soil and soil water samples from a mineral deposit (Morro do Ferro, Minas Gerais, Brazil). Size-exclusion chromatography (SEC) on-line coupled to ICP–MS and UV-detection was applied to verify possible association/complexation of these elements with organic matter in soil water separated by a centrifugation technique. Concentrations of DOC in soil waters are in the range of 10 to 500 mg L⁻¹ and correlate with the organic carbon content of the soil (r=0.950; p<0.001). Concentrations of 30 to 40 μg L⁻¹ for the LREEs (La, Ce, Nd) and up to 14 μg L⁻¹ for Th were measured in soil waters of highest DOC content. SEC chromatograms of these waters showed the association of elements with different nominal high-molecular-mass ranges, characteristic of soil humic and fulvic acids: >10,000 Da, with a retention time of about 10 min; 7000 to 8000 Da with retention times of 13 to 15 min; and 2000 to 4000 Da with retention times around 23 min. Elemental peaks associated with dissolved organic matter below 1000 Da were not observed, suggesting that complexation with simple plant organic acids or inorganic ligands is of minor importance in the environment studied in this work.

Keywords: Inductively coupled plasma mass spectrometry; Size-exclusion chromatography; Humic compounds; Thorium and rare earth elements in soil water; Natural analogues for transuranium elements

High-throughput microwave-digestion procedures to monitor neurotoxic elements in body fluids by means of inductively coupled plasma mass spectrometry by B. Bocca; A. Alimonti; G. Forte; F. Petrucci; C. Pirola; O. Senofonte; N. Violante (pp. 65-70).

for urine, digestion with nitric acid at atmospheric pressure in plastic vials;for serum, digestion with nitric acid at atmospheric pressure in glass vessels; andfor whole blood, digestion under pressure in quartz tubes. Because of the levels of the procedural blanks, Bi was not measurable at the concentrations expected in human fluids, and Al was accurately detectable in whole blood only.

Keywords: Neuro-toxic elements; Sample pretreatment; Microwave digestion; ICP–MS; Biological fluids; Urine; Serum; Blood

Analysis of additive metals in fuel and emission aerosols of diesel vehicles with and without particle traps by Andrea Ulrich; Adrian Wichser (pp. 71-81).

Fuel additives used in particle traps have to comply with environmental directives and should not support the formation of additional toxic substances. The emission of metal additives from diesel engines with downstream particle traps has been studied. Aspects of the optimisation of sampling procedure, sample preparation and analysis are described. Exemplary results in form of a mass balance calculation are presented. The results demonstrate the high retention rate of the studied filter system but also possible deposition of additive metals in the engine.

Keywords: Particle trap; Vehicle emission; Diesel; Aerosol; Inductively coupled plasma mass spectrometry; ICP-MS; Inductively coupled plasma emission spectrometry; ICP-OES; Microwave digestion

An unusual systematic behaviour of detection limits for elements from ⁵⁵Cs to ⁷³Ta by Surendra P. Verma; E. Santoyo (pp. 82-84).

A representative database for detection limits for all elements from ⁵⁵Cs to ⁷³Ta reveals that these limits are governed by a systematic zigzag pattern, according to which the odd atomic number elements have systematically lower detection limits than the even atomic number neighbour elements. This is true even when the actual detection limits vary by several orders of magnitude. We propose that such a systematic pattern be used as a requisite analytical criterion to evaluate the detection limit data, and any departure from this pattern be looked on with caution to check the analytical technique for any interference or matrix effect problems.

Keywords: Detection limit; ICP-MS; Lanthanides; Rare-earth elements; Trace elements

Condensation reaction in the bandpass reaction cell improves sensitivity for uranium, thorium, neodymium and praseodymium measurements by Vladimir Vais; Chunsheng Li; Jack Cornett (pp. 85-88).

Condensation reactions in the bandpass reaction cell or dynamic reaction cell (DRC) were used for the determination of actinides and lanthanides such as uranium, thorium, neodymium and praseodymium. These elements react with oxygen reagent gas in the dynamic reaction cell of the ELAN DRC II instrument to give mono- and/or dioxo cationic species (UO₂ ⁺, ThO⁺, NdO⁺ and PrO⁺, respectively). Increasing the oxygen flow rate in the dynamic reaction cell leads to the rapid decrease of the singly charged metal ions accompanied by the fast increase in the intensity of the oxide ion. This phenomenon is used to improve considerably the sensitivity of ICP-MS instruments equipped with a dynamic reaction cell for actinides and lanthanides. Estimated detection limits (EDL) obtained in this work for uranium, thorium, neodymium-144 and praseodymium are 0.022, 1.0, 0.045, and 0.10 ng L⁻¹, respectively.The detection limit for uranium measured in the standard (vented) mode of an ELAN DRC II was found to be 0.22 ng L⁻¹, which is an order of magnitude higher compared to the pressurized mode.

Keywords: Uranium; Thorium; Neodymium; Praseodymium; ICP-MS; Dynamic reaction cell; Collisional focussing; Gas-phase condensation reactions

'Decoking' of a 'coked' zeolite catalyst in a glow discharge by M. A. Khan; A. A. Al-Jalal; I. A. Bakhtiari (pp. 89-96).

'Decoking' of a 'coked' zeolite catalyst in a glow discharge in oxygen is investigated. The 'decoking' process involves reactions of atomic oxygen (O atoms) with 'coke' and yields gases such as CO, CO₂ as well as other gaseous products that could be easily pumped out.Three different modes of discharge were investigated including a static mode, a flowing-gas mode, and a periodic-purge mode where the oxygen and other gaseous products of the discharge were replaced by fresh O₂gas after short but regular intervals of time. In some cases, additional heating was also used to provide base temperatures of the order of 100 °C to facilitate penetration of oxygen atoms into the inner layers and cages of the zeolite catalyst.This paper presents some results of spectroscopic analytical techniques used to monitor the atomization of oxygen, oxidation of 'coke', and to confirm the process of 'decoking'. More specifically, radiation emission on the 3 s ⁵S– 3p ⁵P transitions of O around 777.2–777.5 nm were selected for monitoring the atomization of O₂. On the other hand, X-ray photo-electron spectroscopy (XPS) was used to determine the amount of residual carbon and extent of 'decoking'. Furthermore, evolution of CO and CO₂ gases as a function of time was systematically monitored in real time. For CO, the 451.1 nm band head belonging to the B 1 Σ - A 1 Π bands of the Angstrom system of the CO spectrum was used, while for CO₂, the band head at 353.4 nm belonging to the CO₂ ⁺ spectrum was used. The rates of evolution of CO and CO₂ were related to the rate of 'decoking' of the catalyst. It is noted that in the periodic-purge mode, about 63% of the total yield of CO from a given sample of the catalyst appears in the first 3-min exposure to discharge whereas it takes up to 15 min to remove nearly 94% of the removable carbon under our experimental conditions.

Keywords: Catalyst Regeneration; Oxidation of 'coke'; Glow Discharge; XPS Spectroscopy; CO and CO₂monitoring using visible region spectroscopy

An uncertainty budget for trace analysis by isotope-dilution ICP-MS with proper consideration of correlation by J. Moser; W. Wegscheider; T. Meisel; N. Fellner (pp. 97-110).

Isotope-dilution mass spectrometry (IDMS) is considered to be a method without significant correction factors. It is also believed that this method is well understood. But unfortunately a large number of different uncertainty budgets have been published that consider different correction factors. These differences lead to conflicting combined uncertainties especially in trace analysis. It is described how the known correction factors must be considered in the uncertainty budget of values determined by IDMS combined with ICP-MS (ICP-IDMS). The corrections applied are dead time, background, interference, mass discrimination, blank correction and air buoyancy.IDMS measurements consist always of a series of isotope abundance ratio measurements and can be done according to different measurement protocols. Because the measurement protocols of IDMS are often rather sophisticated, correlations of influence quantities are difficult to identify. Therefore the measurement protocol has to be carefully considered in the specification of the measurand and a strategy is presented to properly account for these correlations. This will be exemplified for the estimation of mass fractions of platinum group elements (PGEs) and Re in the geological reference material UB-N (from CRPG-CNRS, Nancy in France) with ICP-IDMS. The PGEs with more than one isotope and the element Re are measured with on-line cation-exchange chromatography coupled to a quadrupole ICP-MS. All contents are below 10 µg kg⁻¹. Only osmium is separated from the matrix by direct sparging of OsO₄ into the plasma. This leads to transient signals for all PGEs and Re. It is possible to estimate the combined uncertainties and keep them favourably small despite the low contents, the transient signals and the sophisticated correction model.

Keywords: Correlation; ICP-MS; Isotope dilution; Measurement uncertainty; Uncertainty propagation; Platinum group elements (PGE); Rhenium (Re)

Evaluation of the combined measurement uncertainty in isotope dilution by MC-ICP-MS by G. Fortunato; S. Wunderli (pp. 111-116).

The combination of metrological weighing, the measurement of isotope amount ratios by a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) and the use of high-purity reference materials are the cornerstones to achieve improved results for the amount content of lead in wine by the reversed isotope dilution technique. Isotope dilution mass spectrometry (IDMS) and reversed IDMS have the potential to be a so-called primary method, with which close comparability and well-stated combined measurement uncertainties can be obtained.This work describes the detailed uncertainty budget determination using the ISO-GUM approach. The traces of lead in wine were separated from the matrix by ion exchange chromatography after HNO₃/H₂O₂ microwave digestion. The thallium isotope amount ratio (n(²⁰⁵Tl)/n(²⁰³Tl)) was used to correct for mass discrimination using an exponential model approach. The corrected lead isotope amount ratio n(²⁰⁶Pb)/n(²⁰⁸Pb) for the isotopic standard SRM 981 measured in our laboratory was compared with ratio values considered to be the least uncertain. The result has been compared in a so-called pilot study "lead in wine" organised by the CCQM (Comité Consultatif pour la Quantité de Matière, BIPM, Paris; the highest measurement authority for analytical chemical measurements). k(Pb)=1.329×10⁻¹⁰mol g⁻¹ (amount content of lead in wine) U[k(Pb)]=1.0×10⁻¹²mol g⁻¹ (expanded uncertainty U=k×u c, k=2) The uncertainty of the main influence parameter of the combined measurement uncertainty was determined to be the isotope amount ratio R _206,B of the blend between the enriched spike and the sample.

Keywords: Isotope dilution; Measurement uncertainty; Lead; Multicollector inductively coupled plasma mass spectrometry; Isotope amount ratio; ISO-GUM

Validation of multi-element isotope dilution ICPMS for the analysis of basalts by M. Willbold; K. P. Jochum; I. Raczek; M. A. Amini; B. Stoll; A. W. Hofmann (pp. 117-125).

In this study we have validated a newly developed multi-element isotope dilution (ID) ICPMS method for the simultaneous analysis of up to 12 trace elements in geological samples. By evaluating the analytical uncertainty of individual components using certified reference materials we have quantified the overall analytical uncertainty of the multi-element ID ICPMS method at 1–2%. Individual components include sampling/weighing, purity of reagents, purity of spike solutions, calibration of spikes, determination of isotopic ratios, instrumental sources of error, correction of mass discrimination effect, values of constants, and operator bias. We have used the ID-determined trace elements for internal standardization to improve indirectly the analysis of 14 other (mainly mono-isotopic trace elements) by external calibration. The overall analytical uncertainty for those data is about 2–3%.In addition, we have analyzed USGS and MPI-DING geological reference materials (BHVO-1, BHVO-2, KL2-G, ML3B-G) to quantify the overall bias of the measurement procedure. Trace element analysis of geological reference materials yielded results that agree mostly within about 2–3% relative to the reference values. Since these results match the conclusions obtained by the investigation of the overall analytical uncertainty, we take this as a measure for the validity of multi-element ID ICPMS.

Keywords: Multi-element; Isotope dilution; ICPMS; Geological reference material; Analytical uncertainty; Method validation

Multi-element trace determinations in pure alkaline earth fluoride powders by high-resolution ICP-MS using wet-chemical sample preparation and laser ablation by Markus Tibi; Klaus G. Heumann (pp. 126-131).

Four alternative analytical procedures for the determination of ten important trace impurities (Mg, Cr, Fe, Cu, Zn, Sr, Zr, Cd, Ba, and Pb) in pure alkaline earth fluoride powders were applied using high-resolution inductively coupled plasma mass spectrometry (ICP-MS). Two procedures are based on a wet-chemical microwave digestion with boric acid and quantification by the standard addition technique and isotope dilution mass spectrometry (IDMS), respectively. In addition, analyses are also performed by laser ablation as a direct solid sampling technique applying matrix-matched external calibration as well as isotope dilution of the powdered sample. For most elements good agreement between the different methods is found. Detection limits for laser ablation vary between 0.05 ng g⁻¹ for Zr and 20 ng g⁻¹ for Mg. They are about one to two orders of magnitude lower than those of the wet-chemical procedures, which is mainly due to the high dilution factor during the sample preparation step. Advantages and restrictions of the different analytical procedures are discussed with respect to their routine applicability. Due to its relatively high accuracy, low detection limits, and time-efficiency LA-ICP-IDMS is the preferred choice if no standard reference materials are available.

Keywords: Inductively coupled plasma mass spectrometry; Alkaline earth fluoride samples; Laser ablation; Boric acid decomposition; Standard addition; Isotope dilution; Mass spectrometry

Determination of sulfur and selected trace elements in metallothionein-like proteins using capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry with an octopole reaction cell by Daniel Pröfrock; Peter Leonhard; Andreas Prange (pp. 132-139).

The determination of sulfur in biologically relevant samples such as metalloproteins is described. The analytical methodology used is based on robust on-line coupling between capillary electrophoresis (CE) and octopole reaction cell inductively-coupled plasma mass spectrometry (ORC–ICP–MS). Polyatomic ions that form in the plasma and interfere with the determination of S at mass 32 are minimised by addition of xenon to the collision cell. The method has been applied to the separation and simultaneous element-specific detection of sulfur, cadmium, copper, and zinc in commercially available metallothionein preparations (MT) and metallothionein-like proteins (MLP) extracted from liver samples of bream (Abramis brama L.) caught in the river Elbe, Germany. Instrumental detection limits have been calculated according to the German standard procedure DIN 32645 for the determination of sulfur and some simultaneously measured trace elements in aqueous solution. For sulfur detection limits down to 1.3 μg L⁻¹ (³⁴S) and 3.2 μg L⁻¹ (³²S) were derived. For the other trace elements determined simultaneously detection limits ranging from 300 ng L⁻¹ (⁵⁸Ni) to 500 ng L⁻¹ (⁶⁶Zn, ⁵⁵Mn) were achieved. For quantification of sulfur and cadmium in a commercially available MT preparation under hyphenated conditions the use of external calibration is suggested. Finally, the need for proper sample-preparation technique will be discussed.

Keywords: Inductively coupled plasma mass spectrometry; Capillary electrophoresis; Hyphenation; Collision cell; Metallothionein; Speciation; Biomolecules

Comparison of GC–ICP–MS and HPLC–ICP–MS for species-specific isotope dilution analysis of tributyltin in sediment after accelerated solvent extraction by Raimund Wahlen; Céline Wolff-Briche (pp. 140-148).

This study describes a direct comparison of GC and HPLC hyphenated to ICP–MS determination of tributyltin (TBT) in sediment by species-specific isotope dilution analysis (SS-IDMS). The certified reference sediment PACS-2 (NRC, Canada) and a candidate reference sediment (P-18/HIPA-1) were extracted using an accelerated solvent extraction (ASE) procedure. For comparison of GC and LC methods an older bottle of PACS-2 was used, whilst a fresh bottle was taken for demonstration of the accuracy of the methods. The data obtained show good agreement between both methods for both the PACS-2 sediment (LC–ICP–IDMS 828±87 ng g⁻¹ TBT as Sn, GC–ICP–IDMS 848±39 ng g⁻¹ TBT as Sn) and the P-18/ HIPA-1 sediment (LC–ICP–IDMS 78.0±9.7 ng g⁻¹ TBT as Sn, GC–ICP–IDMS 79.2±3.8 ng g⁻¹ TBT as Sn). The analysis by GC–ICP–IDMS offers a greater signal-to-noise ratio and hence a superior detection limit of 0.03 pg TBT as Sn, in the sediment extracts compared to HPLC–ICP–IDMS (3 pg TBT as Sn). A comparison of the uncertainties associated with both methods indicates superior precision of the GC approach. This is related to the better reproducibility of the peak integration, which affects the isotope ratio measurements used for IDMS. The accuracy of the ASE method combined with HPLC–ICP–IDMS was demonstrated during the international interlaboratory comparison P-18 organised by the Comité Consultatif pour la Quantité de Matière (CCQM). The results obtained by GC–ICP–IDMS for a newly opened bottle of PACS-2 were 1087±77 ng g⁻¹ Sn for DBT and 876±51 ng g⁻¹ Sn for TBT (expanded uncertainties with a coverage factor of 2), which are in good agreement with the certified values of 1090±150 ng g⁻¹ Sn and 980±130 ng g⁻¹ Sn, respectively.

Keywords: Organotin; Sediment; Species-specific IDMS; GC–ICP–MS; HPLC–ICP–MS; Accelerated solvent extraction.

Possible interferences of mercury sulfur compounds with ethylated and methylated mercury species using HPLC-ICP-MS by R.-D. Wilken; F. Nitschke; R. Falter (pp. 149-153).

The HPLC-ICP-MS coupling technique is able to separate and detect methyl, ethyl and inorganic mercury isotopes specifically. An identification of ethyl mercury(+) is not possible when the widely used sodium tetraethylborate derivatisation method in combination with GC-AFS/AAS or ICP-MS techniques is performed because it contains ethyl groups.An unidentified compound with the same retention time as ethyl mercury was found in the HPLC chromatograms of industrial sewage samples and humic-rich soils of microcosm experiments after applying water vapour distillation. We also observed such unidentified peaks in samples of heavily contaminated sites in Eastern Germany, separated by HPLC fractionation only. In the experiments described, different mercury sulfur adducts were synthesised and tested for their retention times in the HPLC-ICP-MS system. It was found that the compound CH₃–S–Hg⁺ showed the same retention time as the ethyl mercury standard. It is therefore possible that ethyl mercury detected in chromatography by comparison of the retention time could also be due to an adduct of a sulfur compound and a mercury species. CH₃–S–Hg⁺should be tested in other chromatographic mercury speciation methods for this effect.This work can also be regarded as a contribution to the discussion of artificially occurring methyl mercury in sediments during sample preparation.

Keywords: Mercury; Speciation; Ethyl mercury; Methyl mercury; Microcosm; HPLC-ICP-MS

Determination of the ratio of calcium to phosphorus in foodstuffs by dynamic reaction cell inductively coupled plasma mass spectrometry by Min-Chuan Wu; Shiuh-Jen Jiang; Tai-Sung Hsi (pp. 154-158).

An inductively coupled plasma mass spectrometer (ICP–MS) equipped with a dynamic reaction cell (DRC) was used for the determination of Ca and P in foodstuffs. In this study, two different reaction gases, CH₄ and O₂, were introduced successively through the different channels to alleviate different interferences in the same analysis run. The effect of the operating conditions of the DRC system was studied to get the best signal-to-noise ratio for each element. The interfering ⁴⁰Ar⁺ at m/z 40 was reduced in intensity by up to five orders of magnitude by using 1.0 mL min⁻¹ CH₄ as reaction cell gas in the DRC. On the other hand, by using O₂ as the reaction gas, ³¹P⁺ was converted to ³¹P¹⁶O⁺ that could be detected at m/z 47 where there was less interference. The limits of detection for Ca and P were 0.2 ng mL⁻¹ and 0.3 ng mL⁻¹, respectively. This method was used to determine the concentrations of Ca and P and the ratio of Ca to P in NIST SRM 1549 non-fat milk powder and NIST RM 8345 whole milk powder reference materials and an infant milk powder and an infant cereal-rice sample purchased locally. The results for the reference samples agreed satisfactorily with the reference values. The accuracy of the determination was better than 4.1 and 0.9% for Ca and P, respectively. The results for infant milk powder and infant cereal were also found to be in good agreement with the value on the bottle label. Precision (RSD) between sample replicates was better than 4.8% for all the determinations.

Keywords: Inductively coupled plasma mass spectrometry; Dynamic reaction cell; Calcium; Phosphorus; Foodstuffs

Electrospray ionization mass spectrometry of ionic liquids and determination of their solubility in water by Z. B. Alfassi; R. E. Huie; B. L. Milman; P. Neta (pp. 159-164).

Electrospray ionization mass spectrometry is used to detect both the cations (C⁺) and the anions (A⁻) of ionic liquids (CA). In this study, the ionic liquids are diluted with aqueous methanol before injection. In addition to the main peaks of the parent ions, fragmentation products are observed upon increasing the cone voltage, whereas aggregates of the parent ion with one or more ionic liquid molecules (e.g., C(CA)_n ⁺, A(CA)_n ⁻) are observed upon decreasing the cone voltage. The ions of several ionic liquids in a mixture are also detected and the ratios of their concentrations estimated. A method is developed to determine quantitatively the concentration of an ionic liquid in solution by using the cation and anion of another ionic liquid as internal standards. By using this method, the solubilities in water at room temperature (22±1 °C) of three typical hydrophobic ionic liquids have been determined: 0.70±0.08 g L⁻¹ for methyltributylammonium bis(trifluoromethylsulfonyl)imide (MeBu₃NNTf₂), 6.0±0.5 g L⁻¹ for butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyrNTf₂), and 18.6±0.7 g L⁻¹ for 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF₆).

Keywords: Ionic liquids; Electrospray; Mass spectrometry; Solubility

Method development for the determination of iron in milligram amounts of rice plants (Oryza sativa L.) from cultivation experiments using graphite furnace atomic absorption spectrometry by Márcia M. Silva; Maria Goreti R. Vale; Isabel C. Ferreira Damin; Bernhard Welz; Marcos Mandaji; Janette P. Fett (pp. 165-172).

The amount of sample that is available for analysis in laboratory plant cultivation experiments is usually very limited. Highly sensitive analytical techniques are therefore required, even for elements that are present in the plants at mg g⁻¹ concentrations, and graphite furnace atomic absorption spectrometry (GFAAS) was chosen in this work because of its micro-sampling capability, and its relatively simple operation. Four micro-methods were investigated for the determination of iron in roots and leaves of rice plants: i) a micro-digestion with nitric and hydrochloric acids, ii) a slurry procedure using tetramethylammonium hydroxide (TMAH) tissue solubilizer, iii) a slurry prepared in 1.4 mol L⁻¹ nitric acid, and treated in an ultrasonic bath, and iv) the direct analysis of solid samples. The micro-digestion was suffering from high blank values and contamination problems, so that it could not be recommended for routine purposes. The TMAH method exhibited poor precision and occasional low recoveries, particularly for real samples. Direct solid sampling analysis gave results similar to those obtained with the slurry technique with ultrasonic agitation for the determination of iron in certified reference materials with iron content up to about 100 μg g⁻¹, but was too sensitive for the investigated rice plants, which had an iron content up to several mg g⁻¹. The slurry technique with ultrasonic treatment of the samples, suspended in dilute nitric acid, was finally adopted as the method of choice.The method was then applied for the determination of iron in the leaves and in different compartments of the roots of two rice cultivars, one sensitive to iron toxicity, an important nutritional disorder, and the other one resistant to iron toxicity. The results suggest that the higher resistance to iron toxicity of the second cultivar is due to a smaller uptake of iron from the soil, resulting in lower iron levels in all compartments of the plant.

Keywords: Graphite furnace atomic absorption spectrometry; Microsampling; Solid sample analysis; Slurry sampling; Iron toxicity; Rice plants

Freezing curve-based monitoring to quickly evaluate the viability of biological materials subject to freezing or thermal injury by Jing Liu; Yi-Xin Zhou (pp. 173-181).

This paper is aimed at investigating the roles of freezing dynamics of a liquid droplet to characterize the properties of the material. In particular, freezing curve-based monitoring was proposed to quickly evaluate the viability of biological materials subject to freezing, re-warming, or other kinds of injury, which is an extremely important issue in practices such as cryobiology, hyperthermia, or freshness evaluation of bio-samples. An integrated micro analysis device was fabricated which is simple in structure and cheap to make. Preliminary freezing results demonstrated that minor changes in a biological material due to freezing or warming injury might result in a significant deviation of its freezing curve from that of the intact biomaterials. Several potential thermal indexes to quantify the material features were pointed out. Further, experiments were performed on some freezing and thawing processes of small amount of water on a cooling surface to test the effects of droplet sizes, measurement sites, cooling strength, and cooling geometry, etc., on the freezing responses of a water droplet. Their implementation in developing a new micro analysis system were suggested. This freezing curve-based monitoring method may open a new strategy for the evaluation of biomaterials subject to destruction in diverse fields.

Keywords: Viability evaluation; Biological material; Freezing injury; Thermal injury; Freezing curve-based monitoring; Biological chip; Micro analysis system; Material characterization; Microscale heat transfer

Miniaturized dynamic liquid–liquid extraction of organophosphate triesters from blood plasma using the hollow fibre-based XT-tube extractor by Ove B. Jonsson; Ulrika L. Nilsson (pp. 182-188).

A miniaturized liquid–liquid extractor for bioanalytical sample preparation is described. The extractor consists of a polypropylene hollow fibre mounted inside polytetrafluoroethylene (PTFE) tubing by means of a cross (X) connector and a tee (T) connector. All parts are commercially available, inexpensive, and easily assembled. The aqueous sample, injected into a carrier flow, is pumped along the outside of the fibre and the organic phase, which also wets the pores of the hollow fibre wall, is pumped inside. Eight organophosphate triester (OPE) plasticisers/flame retardants were extracted from 50 µL spiked blood plasma that had been mixed with 50 µL formic acid to denature plasma proteins. The organic phase was a mixture of hexane and methyl tert-butyl ether (MTBE). A high concentration of formic acid in the sample and of MTBE in the organic phase had positive effects on the recovery of some OPE. When investigating the recovery as a function of extraction time it was found that the extraction reached a maximum after 10 min, at a flow-rate of 15 µL min⁻¹. Recoveries varied between 40 and 80% with RSD around 4% for most compounds. The whole 150-µL extract was injected into a GC–MS system equipped with a programmed-temperature vaporization (PTV) injector. With the MS in selected-ion monitoring (SIM) mode, the LOD for triphenyl phosphate and 2-ethylhexyl diphenyl phosphate were 0.3 and 0.2 ng mL⁻¹, respectively. More than 40 plasma extractions were performed with the same fibre without any detectable change in extraction efficiency.

Keywords: Microporous membrane liquid–liquid extraction; Hollow fibre; Plasma sample clean-up; Organophosphate triesters

Determination of ATP via the photochemical generation of hydrogen peroxide using flow injection luminol chemiluminescence detection by Tomás Pérez-Ruiz; Carmen Martínez-Lozano; Virginia Tomás; Jesús Martín (pp. 189-194).

The determination of ATP using the coupling between a photochemical reaction and a chemiluminescence reaction in a flow injection (FI) system is described. The method is based on the reaction of glucose with ATP catalyzed by hexokinase and Mg²⁺ ions. The glucose that is not consumed by ATP is subsequently photooxidized using 9,10-anthraquinone-2,6-disulfonate as a sensitizer. The hydrogen peroxide produced in the photochemical reaction is monitored through the chemiluminescence reaction with luminol catalyzed by hematine. There is a linear relationship between the decrease in the chemiluminescence response and the ATP concentration at a constant concentration of glucose. Under the optimum conditions, the calibration graph is linear in the range 0.20–50.5 mg L⁻¹ with a throughput of 25 samples per hour and relative standard deviations between ±0.62 and ±1.42%. The limit of detection is 0.07 mg L⁻¹. The method was used for the determination of ATP in pharmaceuticals, milk, and soils.

Keywords: ATP; 9,10-Anthraquinone-2,6-disulfonate; Photochemical reaction; Flow injection; Chemiluminescence detection

Study of the impact of penetrant characteristics upon diffusion into Teflon membranes to further assess the performance of an ATR/FTIR sensor by B. Murphy; P. Kirwan; P. McLoughlin (pp. 195-202).

In order to critically assess the performance and measuring dynamics of an attenuated total reflectance (ATR)/Fourier transform infrared (FTIR) sensor based on polymer preconcentration the impact of penetrant properties upon diffusion into the enrichment membrane must be characterised. Teflon AF2400, a highly amorphous and robust polymer not previously used in this role, was chosen as the enrichment membrane and various environmentally significant chlorinated hydrocarbon and alcohol species selected as analytes. Analyses were performed on aqueous solutions running in continuous flow configuration. Diffusion coefficients, calculated through regression of experimental data with simulated Fickian diffusion curves, were employed as the primary indicator of diffusion behaviour. Penetrant size and shape were both demonstrated to exhibit a substantial impact upon diffusion behaviour. Significant multi-component effects were observed for the simultaneous detection of two analytes. The results presented highlight the necessity for full characterisation of the observed effects prior to the development of a sensing technology for real applications.

Keywords: Diffusion behaviour; Penetrant characteristics; Mathematical simulation; Teflon AF polymer membrane; Mid-infrared spectroscopy; Attenuated total reflectance

Highly sensitive determination of ectoine and other compatible solutes by anion-exchange chromatography and pulsed amperometric detection by Volker Riis; Thomas Maskow; Wolfgang Babel (pp. 203-207).

In saline media prokaryotes compensate for the osmotic pressure of the surrounding medium by producing osmolytes. Although these osmolytes or osmoprotectors have quite diverse structures, most of them can be determined by anion-exchange chromatography combined with integrated pulsed amperometric detection. This technique offers the advantages of very high sensitivity and new opportunities to determine ectoine and 5-hydroxyectoine—two important osmolytes —after hydrolytic cleavage of the pyrimidine ring. It can even be used to screen bacterial colonies on agar for compatible solutes. Furthermore, it allows amino acids and osmolytes of this type to be determined without derivatization. To test the method we applied it to two halotolerant bacterial strains: Stenotrophomonas rhizophila DSM 14405^T and Halomonas elongata DSM 2581^T. The first strain produced trehalose and glucosylglycerol, and the second ectoine, as the main osmotic counterweight. The relationship between the content of these osmolytes in the bacterial biomass and the external salinity is described.

Keywords: Compatible solutes; Ectoine; Amino acids; Carbohydrates; Anion-exchange chromatography; Pulsed amperometric detection; Microorganisms

Separation and determination of the antitumor drug piritrexim by molecularly imprinted microspheres in high-performance liquid chromatography by Jia-Ping Lai; Xi-Wen He; Feng Chen (pp. 208-213).

Molecularly imprinted microspheres were synthesised using the antitumor drug piritrexim (PTX) as a template molecule by aqueous microsuspension polymerisation and were used as a high-performance liquid chromatographic stationary phase. The molecularly imprinted column exhibited strong retention behaviour to the template molecule. The influences of pH of the buffer and the ratio of methanol to buffer on the retention behaviour were investigated in detail. Results indicated that the baseline separation of PTX, trimetrexate (TMX), trimethoprim (TMP) and sulfamethazine (SMZ) was achieved when the pH value of the acetate buffer was above pH 3.5 and the ratio of methanol to the buffer was 6:4 (v/v). A gradient elution programme was employed to enhance the separation, which led to an improvement in sensitivity and a reduction in determination errors. The method developed was used to analyse urine samples supplemented with PTX. The recoveries of 5 μg mL⁻¹ PTX in the urine sample were 99.1±3.0% and 93.3±2.8% at the beginning and 24 h later, respectively.

Keywords: Molecularly imprinted microspheres; Aqueous microsuspension polymerisation; Chromatographic stationary phase; Piritrexim; Trimetrexate

A simple method for automated pretreatment of usable chromatographic profiles in pattern-recognition procedures: application to HPAEC–PAD chromatograms of honeys by Christophe B. Y. Cordella; Julio S. L. T. Militão; Daniel Cabrol-Bass (pp. 214-219).

In this article a simple method for automated pretreatment of chromatograms is presented. The resulting data matrix can be used as input for multivariate statistical analysis. Application of this method to high-performance anion-exchange chromatography–pulsed amperometric detection (HPAEC–PAD) chromatograms of honeys before canonical discriminant analysis results in very good performance in the data reduction with regard to the preservation of the original information content of the data. This pretreatment of the chromatogram allows for the use of all the peaks corresponding to the sugars present in the sample. This results in a high-quality discrimination between honeys of various types. A versatile program has been developed to apply this method. This serves as a starting point for software suited for food characterization and adulteration detection by semi-automatic pattern recognition applied to chromatographic analysis.

Keywords: Chromatographic profiles; Chromatogram pretreatment; Pattern-recognition procedures; Multivariate statistical analysis; Discriminant canonical analysis; High-performance anion-exchange chromatography–pulsed amperometric detection (HPAEC–PAD); Honey

An ELISA-based approach to optimize elution conditions for obtaining hapten-specific antibodies by K. V. Singh; Jasdeep Kaur; Manoj Raje; Grish C. Varshney; C. Raman Suri (pp. 220-224).

The correct choice of the elution conditions to break an affinity interaction is important for the successful purification of biomolecules. The optimal elution buffer liberates the bound substance in a minimum volume and maintains the activity of the purified material. The present study demonstrates an enzyme-linked immunosorbent assay (ELISA)-based approach for selection of specific elution conditions for eluting antibodies against a small molecule (atrazine) from pooled sera. Six different elution conditions were tried for the removal of antibodies from the complex. Large-scale purification of anti-atrazine antibodies from the sera was done with a hapten-specific column using an amino-terminal crosslinked agarose gel. Efficacy in terms of total amount of recovery and binding affinities of eluted antibodies from the column were further investigated by ELISA. Results indicate that the ELISA-based elution approach is ideal for the selection of suitable elution buffer that can subsequently be utilized for affinity purification applications.

Keywords: Affi-gel 102; Affinity purification; Antibody; ELISA; Hapten

2004 Winter Conference on Plasma Spectrochemistry (pp. 225-225).

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Analytical and Bioanalytical Chemistry (v.377, #1)