Antonín Kaňa

The response of broccoli (Brassica oleracea convar. italica) varieties on foliar application of selenium: uptake, translocation, and speciation.

A model small-scale field experiment was set up to investigate selenium (Se) uptake by four different varieties of broccoli plants, as well as the effect of Se foliar application on the uptake of essential elements for plants calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P), sulfur (S), and zinc (Zn). Foliar application of sodium selenate (Na2SeO4) was carried out at two rates (25 and 50 g Se/ha), and an untreated control variant was included. Analyses of individual parts of broccoli were performed, whereby it was found that Se in the plant accumulates mainly in the flower heads and slightly less in the leaves, stems, and roots, regardless of the Se rate and broccoli variety. In most cases, there was a statistically significant increase of Se content in all parts of the plant, while there was no confirmed systematic influence of the addition of Se on the changing intake of other monitored elements. Selenization of broccoli leads to an effective increase in the Se content at a rate of 25 g/ha, whereas the higher rate did not result in a substantial increase of Se content compared to the lower rate in all varieties. Therefore, the rate of 25 g/ha can be recommended as effective to produce broccoli with an increased Se content suitable for consumption. Moreover, Se application resulted in an adequate increase of the main organic compounds of Se, such as selenocystine (SeCys2), selenomethionine (SeMet), and Se-methylselenocysteine (Se-MeSeCys).

The Response of Macro- and Micronutrient Nutrient Status and Biochemical Processes in Rats Fed on a Diet with Selenium-Enriched Defatted Rapeseed and/or Vitamin E Supplementation

The response of nutrient status and biochemical processes in (i) Wistar and (ii) spontaneously hypertensive (SHR) rats upon dietary intake of selenium- (Se-) enriched defatted rapeseed (DRS) and/or vitamin E fortification was examined to assess the health benefit of DRS in animal nutrition. Twenty-four individuals of each type of rat were used: The control group was fed with an untreated diet (Diet A). In Diets B and C, soybean meal was replaced with defatted DRS, which comprised 14% of the total diet. The selenized DRS application resulted in ~3-fold increase of Se content in the diet. Diet C was also fortified with the addition of vitamin E, increasing the natural content by 30%. The Se content of the blood and kidneys tended to increase in the DRS groups, where the changes were significant (P < 0.05) only in the case of SHR rats. The iodine (I) content and the proportion of iodide in rat livers indicated a lower transformation rate of iodide into organoiodine compounds compared to the control. Slight and ambiguous alterations in the antioxidative response of the rat were observed in the DRS groups, but the addition of vitamin E to the diet helped to moderate these effects.

Speciation analysis of selenium in human urine by liquid chromatography and inductively coupled plasma mass spectrometry for monitoring of selenium in body fluids

Abstract Speciation analysis of selenium metabolites in urine was performed using hyphenation of mixed ion-pair reversed-phase chromatography and inductively coupled plasma mass spectrometry. A chromatographic separation was performed with a C8 stationary phase and a mobile phase containing 2.5 mmol L−1 sodium butane-1-sulfonate, 8 mmol L−1 tetramethylammonium hydroxide, 4 mmol L−1 malonic acid, and 0.05% methanol, pH 3.0. Under this condition, the selenium species selenite, selenate, selenomethionine, selenoethionine, selenourea, trimethylselenonium, and Se-methylselenocysteine were successfully separated. Selenium determination was carried out by monitoring 80Se. The internal standard Ge was added into the mobile phase. The calibration was linear at least up to 100 μg L−1 Se for all species. The limit of detection was 0.4 μg L−1 Se. When higher (1400 W) ICP power was applied, the calibration based solely on selenate provided accurate results for all species. Stability tests revealed extremely short stability of selenite. After collection, the urine samples should be acidified to pH 3.0, stored below –5 °C, and analyzed before 12 h after collection. The method was used for the short-time (single capsule, one day observation, 5 persons) monitoring of the excretion of selenium after ingestion of Se-containing dietary supplements. When a formulation containing selenate was applied, almost 50% of Se was excreted during 24 h (mostly in the unchanged form of selenate) and the plasma Se remained unaltered. In the case of organically bound Se, only 8% of Se was lost by urination during 24 h as selenite, Se-methylselenocysteine, selenomethionine, and unknown species. Subsequently, a statistically significant increase of plasma Se was observed.

Analysis of iodine and its species in animal tissues

Abstract A method allowing the determination of the total iodine content and iodine species in samples of animal tissues using inductively coupled plasma mass spectrometry (ICP-MS) as an element-specific detector was developed. The total iodine content was determined after microwave digestion with 25% (w/w) water solution of tetramethylammonium hydroxide. The detection limit was 26.9 μg kg−1 I, and the accuracy of the determination was proven through the analysis of SRM “Non-Fat Milk Powder,” porcine liver, and Atlantic Cod muscle samples using standard addition methods. The extracts for the speciation analysis were prepared through sample dispersion in water using an Ultra-Turrax® T10. The extraction yields ranged from 46 to 84% for different types of tissues. The determination of the inorganic iodine species was performed using ion-exchange chromatography (PRP X100, mobile phase 100 mmol L−1 ammonium nitrate, pH 7.4) coupled to ICP-MS. A detection limit of 1.1 μg kg−1 I was obtained for both species. The organic iodine species were separated using size-exclusion chromatography (Superdex 75 column, mobile phase 20 mmol L−1 Tris–HCl, pH 7.5) and also detected using ICP-MS. Samples of porcine muscle, liver, kidney and thyroid gland, chicken muscle and liver and Atlantic Cod muscle were analyzed. The porcine thyroid gland and Atlantic Cod muscle samples were the richest in iodine (a more than 10× greater content of iodine than the other samples). With respect to the inorganic species, only iodide was found in the sample extracts. Conversely, many organic iodine species were found in the extracts.

Software Solution for Post-Column Isotope Dilution Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

The application of isotope dilution in high performance liquid chromatography (HPLC) and inductively-coupled plasma mass spectrometry (ICP-MS) represents an important tool for elemental speciation analysis. Currently commercially available software deals only with one type of HPLC-ID-ICP-MS measurement comprising an addition of isotope-enriched species into the sample before HPLC separation, that is, species-specific isotope dilution. However, there is another possibility: species-unspecific isotope dilution, which is, unfortunately, not easily employed by common software. In this method, the isotope enriched solution containing common inorganic compound of the analyzed element is added to the sample after HPLC separation. Here a novel software system addresses this problem. The most important features of the computer program include easy operation, data adjustment by smoothing, detector dead-time correction, mass discrimination correction, background correction, integration of peak area and ID enumeration, processing of multi-elemental analyses, a choice of various isotopes, and a database of isotope abundances. The reliability of the software was demonstrated by processing of artificial chromatographic data and real chromatograms of standard reference materials containing mercury species and mixtures of selenium species.

Transfer of thallium from rape seed to rape oil is negligible and oil is fit for human consumption

ABSTRACT Rape and other Brassicaceae family plants can accumulate appreciable amounts of thallium from the soil. Because some species of this family are common crops utilised as food for direct consumption or raw materials for food production, thallium can enter the food chain. A useful method for thallium determination is inductively coupled plasma mass spectrometry. The limit of detection (0.2 pg ml–1 Tl or 0.02 ng g–1 Tl, taking in the account dilution during sample decomposition) found in the current study was very low, and the method can be used for ultra-trace analysis. Possible transfer of thallium from rape seed to the rape oil was investigated in two ways. The balance of thallium in rape seed meal (content 140–200 ng g–1 Tl) and defatted rape seed meal indicated that thallium did not pass into the oil (p < 0.05). Moreover, the analyses of thallium in six kinds of edible rape seed oil and three kinds of margarines showed that the amount of thallium in rape seed oil is negligible.

The use of inductively coupled plasma mass spectrometry for the evaluation of the mobility of iodine in bentonite

Inductively coupled plasma mass spectrometry (ICP-MS) was used for investigating iodine in deep geological repository barriers. Major problems that can arise in the method application include different behaviours of individual iodine species, memory effects and strong non-spectral interferences owing to high salt content in samples. When proper conditions were applied (i.e. the addition of tetramethylammonium hydroxide, use of Ge as an internal standard, and spiking of iodate calibration solutions with sample matrix), ICP-MS provided accurate results, irrespective of the iodine speciation. The quantification limit of iodine determination in highly saline samples was 1.1 μg/L I. The calibration was linear at least within the range of 1–100 μg/L I. The analysis accuracy was verified by an analysis of a model sample of synthetic bentonite water and a 0.1 mol/L NaCl matrix that contained various iodine species (iodide, elemental iodine and iodate) and their mixtures, and recovery ranged from 97 to 101%. The analysis by ICP-MS coupled with liquid chromatography (LC) could also distinguish between the main iodine species of iodide and iodate. The detection limits were less than 2.0 μg/L I for both species. Both ICP-MS determination of the total iodine and the LC-ICP-MS speciation analysis were applied to a preliminary investigation of iodine diffusion through Czech bentonite from the Rokle deposit. No iodide speciation changes were observed during the diffusion experiment which was performed under atmospheric conditions.

Internal standardisation for arsenic and its species determination using inductively coupled plasma mass spectrometry

The signal of As measured by inductively coupled plasma mass spectrometry (ICP-MS) suffers from strong non-spectral interferences due to carbon and alkali metals. The accuracy of the determination of total As using ICP-MS and its species using anion-exchange chromatography coupled to ICP-MS was increased by using selenium as an internal standard. For chromatography, selenium was used in the form of a trimethylselenonium cation, which did not interact with the stationary phase and could be added directly to the mobile phase as the selenite was sufficient for total As determination. Selenium is able to correct non-spectral interferences caused by carbon or sodium up to concentrations of 3000 mg L-1 C and 35 mg L-1 Na, respectively, in the case of total As determination, and up to 3000 mg L-1 C and 3450 mg L-1 Na in the case of speciation analysis. Selenium as an internal standard was tested for the analysis of arsenobetaine in the DORM-2 standard reference material. The results were in good accordance with certified values regardless of NaCl spikes. Also, the results of total As determination in canned fish using a selenium internal standard were not affected by residual carbon in an imperfectly decomposed sample.

Analysis of Silver Nanoparticles Using Single-Particle Inductively Coupled Plasma – Mass Spectrometry (ICP-MS): Parameters Affecting the Quality of Results

ABSTRACT Single–particle analysis using inductively coupled plasma mass spectrometry offers a new tool for the characterisation of inorganic nanoparticles. Its development is connected with new generations of ultrafast spectrometers. This work is concerned with thorough investigation of parameters affecting the quality of the analysis of Ag nanoparticles, i.e., nanoparticle stability, transport efficiency and sensitivity of determination. The short-term stability of Ag nanoparticles in demineralised water can be prolonged to at least 7 h by the addition of 0.05% gelatin. The sensitivity was affected by plasma power and the nebuliser Ar flow. The transport efficiency decreased with increasing sample uptake, so a compromise between the efficiency and the total number of particles entering the spectrometer should be selected. The estimate of transport efficiency is distorted when more concentrated dispersions of nanoparticles are analysed because of the overlapping of signals of multiple nanoparticles. This effect was observed for dispersions of concentration greater than 1 × 106 mL−1 where an apparent decrease in transport efficiency from an initial value 7–8% to 1% was observed. The following parameters were found by method validation: concentration limit of detection of 97 mL−1, nanoparticle diameter limit of detection 15 nm, linearity from 20 to at least 100 nm and repeatability of 1.3%. After validation, the method was applied to determine Ag nanoparticles in river water from the Vltava in Prague. Nanoparticles with diameters of 32–114 nm were found, and their number concentration increased from 340 mL−1 to 1670 mL−1 as the stream of water passed through urban agglomeration.