Analytical capabilities of inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (ICP-oa-TOF-MS) for multi-element analysis of food and beverages.

Analytical capabilities of ICP-oa-TOF-MS for rapid, simultaneous and reliable determination of more than 50 major, trace and ultra-trace elements in different food and beverages samples (milk and dairy based products, cereals, meat, offal, sugar and sugar products, potatoes, fats, baby food samples, fruit juices, alcoholic beverages), following microwave closed vessel digestion of samples, were described. Under optimum instrumental conditions, and by using Rh as an internal standard and an external calibration method, ICP-oa-TOF-MS enables an accurate analysis, taking about one minute per a sample for all elements and isotopes of interest even for some elements such Zn, Ni, Cu, As or Co whose assay is more difficult when using conventional quadrupole instruments. In order to verify the accuracy and precision of the proposed method, 8 commercially available reference materials representing 3 major groups of food (milk and dairy based products, meat, cereals) were analysed, yielding results in agreement with certified values and the precision bellow 15%. In addition, accuracy was confirmed by spiked analytical recoveries study and accurate isotopic ratio determinations with the precision typically better than 5% with 5s data acquisition period, also for other elements of interest whose content was not certified and different sample matrices. Limits of detection (3σ) have varied from 0.04ngg(-1) for Th to 1630ngg(-1) for Ca.

Carbon microparticles as a physical carrier for ETV-ICP-MS.

In this study, carbon microparticles (CMs) as a physical carrier to enhance the analyte transport efficiency for inductively coupled plasma mass spectrometry connected with electrothermal vaporization (ETV-ICP-MS) are proposed. Carbon microparticles mixed with samples or calibration standard solutions were dosed as a slurry into the graphite furnace. The optimization of working conditions was done for the standard solution 0.5 µg L-1 of Au and Tl. The pyrolysis and vaporization temperatures were 500 and 2700 °C for Au and 400 and 1900 °C for Tl. The optimized CMs concentration was 1 g L-1 for Au and 2.5 g L-1 for Tl. For the quantification, external calibration standard solutions were used. The result obtained for Au in the digested CRM GBW 07601 (the informatory value 2.1 ±â€¯2 µg kg-1) was 2.2 ±â€¯0.1 µg kg-1. The result for Tl in the digested CRM BCR 679 (the certified value 3 ±â€¯0.3 µg kg-1) was 3.2 ±â€¯0.2 µg kg-1 and in the slurry 2.7 ±â€¯0.1 µg kg-1. The result for Tl in the CRM GBW 10052 (the certified value 57 ±â€¯11 µg kg-1) was 51 ±â€¯3 µg kg-1. The instrumental limits of detection were 0.016 ng L-1 for Au and 0.026 ng L-1 for Tl. The recoveries and repeatabilities measured on calibration standards were in the range 99-100% and 0.2-2.3% for Au and 100-111% and 2.9-6.7% for Tl.

The cryogenic grinding as the important homogenization step in analysis of inconsistent food samples.

Some homogenisation approaches have been investigated to make easier and overcome troublesome preparation of inconsistent food samples. Contents of Na, Ca, Mg, P, Fe, Mn and Zn in muesli, seed and instant food samples were determined by inductively coupled plasma optical emission spectrometry after their grinding with an agate mortar, a kitchen coffee grinder and a cryogenic mill. The efficiency of a grinding step was evaluated using RSDs and homogeneity factors (H-factor). For cryogenically grinded samples, RSDs were detected about 4% and H-factors on 10, what is acceptable for the analytical purpose. The results for grinding with an agate mortar as well as a coffee grinder were quite unsatisfactory (RSDs in tens percent). Differences between RSDs and H-factors for the procedures tested were detected to be statistically significant. Different element contents were observed in differently treated samples which is probably a result of an unevenly element distribution in inhomogeneous components forming sample.

An elemental analysis of conventionally, organically and self-grown carrots.

Conventionally-, organically- and self-grown carrots available across the Czech market were characterised based on their elemental, nitrate and dry matter content (218 samples, 20 parameters) in order to assess the quality of the carrots and address the question whether organic also means better. The results were compared with information describing the elemental composition of carrots published previously, recommended daily intakes, and legislative limits for contaminants in food. Significant differences in the amounts of Na, K, S, Al, Mn, Ni, As and Cd were observed between conventional and organic carrots. From the perspective of inter-element interactions, and the origin of these, a principal components analysis of the datasets found no significant differences between conventionally- and organically-grown carrots. For the consumer, it is valuable to know there are no differences between conventionally- and organically-grown carrots, and no potential harm arising from heavy metal contamination. Based on our data, carrots are an excellent source of potassium.

Elemental analysis of nutritional preparations by inductively coupled plasma mass and optical emission spectrometry.

This paper reports the development and using of ICP-MS and ICP-OES methods for determination of major, minor and trace elements in multivitamin preparations and dietary supplements and, based on results, their classification using multivariate statistical methods. The method was optimised and evaluated with the use of "in-house" reference material, commercial reference materials and spiked samples. Macroelements (Na, K, Ca, Mg, P), microelements (Cu, Fe, Mn, Zn, Se, Cr), toxic elements (As, Cd, Pb, Ni, V) and a whole series of other elements (e.g. REEs, Ti, Au, Pt, Pd, etc.) were detected with excellent limits of detection as well as other procedure parameters suitable for the purpose of the elemental analysis. As for physiologically significant elements, contents were found as follows (mgkg(-1)): Ca 560-196,000, Mg 308-70,300, Na 289-74,000, K from undetectable to 28,200, Cu 28-1460, P from undetectable to 217,000, Zn 2.1-25,000, Fe 115-39,400, Mn 28-1860, Cr 0.486-26.6, Mo 0.0418-9.88, and Se 0.395-161. It was found out, if compared with recommended daily intakes, that maximally 50% Ca, 37% Mg, 3% K, 20% P, 14% Na, 100% Cu, 160% Mn, 190% Fe, 120% Zn, 24% Cr, 29% Mo and 79% Se can be obtained from one dose. Extreme samples presenting a possible health risk (Ni content nearly 200mgkg(-1)) were indicated. Most of the remaining elements (e.g. REEs) were analysed in order to get reference values for nutritional preparation.

Quantitative LIBS analysis of vanadium in samples of hexagonal mesoporous silica catalysts.

The method for the analysis of vanadium in hexagonal mesoporous silica (V-HMS) catalysts using Laser Induced Breakdown Spectrometry (LIBS) was suggested. Commercially available LIBS spectrometer was calibrated with the aid of authentic V-HMS samples previously analyzed by ICP OES after microwave digestion. Deposition of the sample on the surface of adhesive tape was adopted as a sample preparation method. Strong matrix effect connected with the catalyst preparation technique (1st vanadium added in the process of HMS synthesis, 2nd already synthesised silica matrix was impregnated by vanadium) was observed. The concentration range of V in the set of nine calibration standards was 1.3-4.5% (w/w). Limit of detection was 0.13% (w/w) and it was calculated as a triple standard deviation from five replicated determinations of vanadium in the real sample with a very low vanadium concentration. Comparable results of LIBS and ED XRF were obtained if the same set of standards was used for calibration of both methods and vanadium was measured in the same type of real samples. LIBS calibration constructed using V-HMS-impregnated samples failed for measuring of V-HMS-synthesized samples. LIBS measurements seem to be strongly influenced with different chemical forms of vanadium in impregnated and synthesised samples. The combination of LIBS and ED XRF is able to provide new information about measured samples (in our case for example about procedure of catalyst preparation).

Overcoming interference from the alumina matrix on the determination of arsenic at 189 nanometers using electrothermal atomic absorption spectrometry.

A method is described enabling to eliminate the spectral interference from alumina matrix onto As determination at the wavelength 189 nm by electrothermal atomic absorption spectrometry with deuterium background correction. Matrix modification was performed by the addition of ammonium fluoride to protect the formation of aluminium oxide implicated in causing spectral interference and to increase volatility of alumina matrix via the formation of AlF(3). Pre-treating of the pyrolytic graphite platform with a solution of rhodium and citric acid has enabled to stabilize the analyte up to temperature of 1300 degrees C at which most of AlF(3) could be removed from the graphite furnace. The application of 2 microg of Rh+20 microg of citric acid+200 microg of NH(4)F has enabled an accurate and interference-free determination of As up to 40 microg of Al in the form of AlCl(3) as verified by analytical recoveries study and resulted in characteristic mass and LOD value in the original sample 15 pg and 50 ngg(-1), respectively (10-microL aliquots of sample).

Palladium-citric acid-ammonium fluoride as a matrix modifier for overcoming of interferences occurring during the direct determination of Sn in aqua regia extracts from environmental samples by D2-ETAAS.

When tin is to be determined in such a complex matrix like aqua regia extracts of environmental samples by electrothermal atomic absorption spectrometry (ETAAS), spectral interferences occur when deuterium-lamp (D(2)) background correction is used, even using high pyrolysis temperature of 1400 degrees C achieved with palladium with citric acid chemical modifier. We have found that the further addition of NH(4)F to palladium with citric acid chemical modifier is essential for overcoming the above-mentioned problems for which aluminium oxide is most probably responsible. It is supposed, that NH(4)F enables volatilization of the alumina matrix formed by hydrolysis from the chloride salt and interfering in a gas phase via the formation of AlF(3) which could be, in contrast to aluminium oxide, removed from the graphite furnace during the pyrolysis stage. Using the proposed chemical modifier, the direct and accurate determination of Sn in aqua regia extracts from rocks, soils and sediments is possible even when using matrix free standard solutions. This presumption was confirmed by the analysis of certified reference samples and by the comparison with inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS) method. Characteristic mass and LOD value for the original sample (10-microL aliquots of sample) was 17 pg and 0.055 microg g(-1), respectively.

Study of contamination sources in the process of cryogenic grinding.

The study of contamination effect during cryogenic grinding of pure cellulose was carried out. The optimisation of important parameters of the grinding process (pre-cooling time, grinding time, cooling time and number of cycles) was performed and the different sources of a possible contamination of samples (earlier processed sample, metal parts of grinding tool) were evaluated. The results of ICP-oa-TOF MS analysis after microwave digestion of cellulose samples were used in this study. Significant contamination of cellulose samples by Fe at the level 130 microg kg(-1) caused by wearing of steel stoppers and an impact bar was detected. Cross-contamination by Fe, Cr, Mn and Cu at the level 400, 200, 200 and 2100 microg kg(-1), respectively was caused by previous grinding of electro-waste sample. This cross-contamination was possible to be avoided by changing of a polycarbonate part of a grinding vessel.

Interference-free determination of thallium in aqua regia leaches from rocks, soils and sediments by D(2)-ETAAS method using mixed palladium-citric acid-lithium chemical modifier.

The mixture of palladium (chloride) with citric acid and lithium is proposed as a new chemical modifier for the elimination of interference occurred during the determination of Tl in aqua regia extracts from rocks, soils and sediments by electrothermal atomic absorption spectrometry using instrumentation with deuterium-lamp background correction (D(2)-ETAAS). Palladium was preferred to rhodium and platinum as to analyte stabilization, citric acid served as an effective reducing agent facilitating formation of Pd-Tl stable covalent bonds playing an important role in the analyte stabilization. Citric acid in addition helps to remove most of interfering chloride at low temperature. The further addition of Li increased significantly the robustness of chemical modifier against strongly interfering ZnCl2 matrix by binding free chlorine into a more stable LiCl molecule. In the presence of the proposed chemical modifier the temperature for the final step of pyrolysis was adjustable up to 1000 degrees C, without any noticeable loss of volatile Tl species and the interference of the rest chloride matrix was significantly reduced. The application of the modifier to direct determination of Tl in aqua regia extracts from rocks, soils and sediments has ensured the characteristic mass and LOD value for the original sample 13 pg and 0.043 microg g(-1), respectively (10-microL aliquots of sample) and has enabled the use of matrix-free standard solutions for attaining accurate analysis. The accuracy was verified by the analysis of certified reference samples and by the comparison of results with those found by an inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer (ICP-oa-TOFMS) method.

Determination of metal impurities in pure hydroxides and salts by inductively coupled plasma optical emission spectrometry.

A simple analytical method sufficient for the determination of Na, K, Ca, Mg, Al, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, V and Zn at mg kg(-1) levels in pure NaOH, KOH, NaCl and KCl using the optical emission spectrometry was developed. The results of direct determination with multi-elemental aqueous standards were compared with them obtained by the internal standardisation, by the standard addition methods and with the maximal allowable contents of above-mentioned elements in pure chemicals. The method was shown to be very sensitive and exhibits following limits of detection: Na 0.90, K 3.0, Ca 0.064, Mg 0.026, Al 0.43, B 0.13, Ba 0.015, Cd 0.023, Co 0.056, Cr 0.041, Cu 0.063, Fe 0.060, Li 0.017, Mn 0.035, Mo 0.19, Ni 0.055, Pb 0.39, Sr 0.030, V 0.065 and Zn 0.043 (all in mg kg(-1)). The method presents a satisfactory precision (relative standard deviation 4-11%), high analytical recoveries, linear responses of at least four orders of magnitude, accuracy and low contamination susceptibility.

Ammonium fluoride as a novel chemical modifier for the elimination of magnesium chloride interference on the determination of lead by graphite furnace atomic absorption spectrometry.

Ammonium fluoride was found to be very efficient modifier for the elimination of MgCl(2) interference on Pb determination. Ammonium fluoride probably converts strongly interfering volatile MgCl(2) to less volatile MgF(2) matrix that makes possible the release of Pb analyte at lower temperature, before the matrix starts to vaporize. It was observed likewise that NH(4)F removes the interferences mentioned, i.e. caused by MgCl(2) presence, much more effectively as compared with some modifiers, before now recommended for this purpose. The application of this modifier to the determination of Pb in 2% (m/v) MgCl(2) has ensured the characteristic mass and LOD value in the original sample of 12pg and 60ngg(-1), respectively (10mul aliquots of sample). Applying the modifier to standards and samples enables the use of matrix-free standard solutions for attaining accurate analysis as verified by recovery studies.

ED XRF analysis of precious metallic alloys with the use of combined FP method.

The "combined" FP method, which combines standardless FP method with empirical calibration, was applied to the analysis of Ir-Pt, Rh-Pt, Rh-Pd-Pt and Rh-Ir-Pt disk samples and Pt-Rh thermocouple wire. Four reference materials of binary Pt-Ir system, eight Pt-Rh systems, eight reference materials of ternary Pt-Ir-Rh system and 10 Pt-Rh-Pd systems were used for calibration of "combined" FP XRF method. Results of mentioned method agreed well with certified values, or ICP OES results respectively. For determination of elements, which were not present or certified in calibration standards (Ru in Rh-Pt-Pd disc and Fe in Pt-Rh thermocouple wire) the standardless FP method was used. This approach provides good results as well.