Analysis of the fusariotoxins zearalenone and vomitoxin (deoxynivalenol) in human foods and animal feeds by high-performance liquid chromatography (HPLC)

Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C ₁₈ ¹ column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses.     

Simultaneous determination of neodymium and erbium in rare earth mixture with 5,7-dibromo-8-hydroxyquinoline and TX-100 by third-derivative spectrophotometry

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 5,7-dibromo-8-hydroxyquinoline in the presence of octylphenol poly(ethyleneglycol)ether have been studied by normal and third-derivative spectrophotometry. The proposed method is free of interference of other rare earths. The calibration graphs were linear up to 18 g/ml of neodymium and 21 g/ml of erbium (in the final solution). The derivative molar absorptivities are 395 l.mol^–1.cm^–1 for neodymium and 3421.mol^–1.cm^–1 for erbium. The corresponding values of Sandell's sensitivity were 0.36 and 0.49 g.cm^–1, respectively. The relative standard deviations evaluated from ten independent determinations of 2.5 g/ml of neodymium and erbium are 1.5 and 3.8% for neodymium and 1.8 and 4.1% for erbium in absence and presence of 70 g of lanthanum, respectively. The detection limits (signal to noise ratio=2) are 0.23 g/ml for neodymium and 0.30 g/ml for erbium. The method has been used for the determination of neodymium and erbium in mixed rare earths with satisfactory results.     

Comparison of various semiempirical MO LCAO methods

In an orthogonalized basis, the diagonal element F of the Fock operator, for a number of semiempirical MO LCAO methods, can be represented by a trinomial which is quadratic with respect to the Mulliken charge. The coefficients differ for different methods, depending on the manner in which the interelectronic interaction is taken into account. From a study, in general form, of the influence of change in the coefficients of the trinomial F on the bond order matrix, an explanation has been given for certain familiar calculation results: the equalization of the -charges on going from the Hückel method to the more advanced techniques, and the decrease in the covalent character of metal-ligand bonds when allowance is made for the interelectronic interaction in the calculations for complexes.In conclusion, we wish to thank V. D. Sutula and L. I. Chernyavskii for much valuable discussion.     

Preparation of spherical,mixed SiO2/TiO2 particles by the sol technique

Preparation of silica, titania and mixed silica/titania particles has been studied. The region for formation of monodisperse SiO₂ particles in the phase diagram tetraethyl orthosilicate (TEOS)-ethanol-H₂O was studied as a function of NH₃ concentration at room temperature. Titania particles could be prepared at lowered temperatures and concentration of ammonia up to 0.01 M. The size of SiO₂ particles was 0.03–1 m whereas TiO₂ particles were size range 0.5–0.8 m. Mixed SiO₂/TiO₂ particles were prepared from prehydrolyzed TEOS/EtOH solutions by adding tetraethyl orthotitanate (TEOT). This was accomplished at 3°C and slightly alkaline solutions. The final particle size of the mixed particles was about 0.3 m.     

A technique for capillary joining in capillary electrophoresis

Summary Aspects of cracking and joining capillaries have been investigated. Capillary coupling was achieved using various methods. The most successful used hydrofluoric acid-etched capillaries to form male and female ends which were then joined together. This type of joint was used to connect sections of capillary of similar and different internal diameters with minimal loss in resolution, peak width and number of theoretical plates. (Uridine and hypoxanthine was used as a test mixture). For hypoxanthine on a 50 m/50 m etched joined capillary 10 cm from the detector window the number of theoretical plates was 96.6% of that for hypoxanthine on an unbroken capillary. Following the relative success of capillary joining, a coupled capillary flowcell (50 m/200 m) was produced and evaluated.     

Separation of linear gramicidins using carbon dioxide-containing mobile phases

Packed-column supercritical-fluid chromatography (pSFC) is presented as a novel method for separating and analyzing gramicidin samples. By use of methanol-modified carbon dioxide as a mobile phase the pentadecapeptides gramicidin A (gA), gramicidin B (gB), and gramicidin C (gC) are readily separated and eluted from a PRP-1 poly(styrene–divinylbenzene) column. Although optimum separation conditions are typically achieved near a column temperature of 40°C, a column pressure of 11 MPa, and 30% methanol modifier, pressure and modifier gradients around these values are also found to improve the overall separation time. Measurements indicate that the mobile phase solubility of gramicidin under these conditions is 5.0±0.4 g mL^–1. Collection of individual peaks during chromatography achieved analytical-scale isolation of 2 g refined gC from 20 g injected gramicidin D. Further, supercritical-fluid extraction of 200 g gramicidin D from a Chromosorb 102 support packed into the vessel produced 57 g gA in 90% purity. The results establish that carbon dioxide-based mobile phases can be successfully used for the separation of individual gramicidin species.     

A simple separation of bismuth radionuclides in a carrier-free form from lead thick targets

A simple preparation of radionuclides of bismuth from lead thick targets bombarded by deuterons or protons consists in precipitation of solid lead nitrate in nitric acid /a minimum radiobismuth yield 98%/, coprecipitation of bismuth with lanthanum hydroxide and chromatographic isolation of carrier-free bismuth on a cation exchanger. The total yield of radiobismuth separation was not less than 85%. On bombardment with 20 MeV deuterons the yield is 20 Ci²⁰⁵Bi/Ah and 200 Ci²⁰⁶Bi/Ah. Mass distribution coefficients for bismuth were determined on the cation exchanger OSTION LG KS 0803 in dependence on the concentration of hydrochloric acid and nitric acid.     

Landolt-Reaktionen auf „Chlorgrundlage“ und ihre Anwendung zum Nachweis und zur Bestimmung katalytisch wirkender Spurenelemente. I

Zusammenfassung Gemische aus Ascorbinsäure, Hydrazin oder Zinn(II)-chlorid mit sauren, Chlorat und Chlorid enthaltenden Lösungen reagieren nach Art der bekannten Landolt-Reaktion unter Chlorausscheidung, die sich mit o-Tolidin indizieren läßt. Die Reaktion wird von Vanadin(V), Eisen(III) oder Osmium(VIII) katalysiert. Auf dieser Grundlage lassen sich diese Elemente sowohl chronometrisch wie auch mit Hilfe der Simultan-komparationsmethode bestimmen. Die Nachweisgrenzen liegen bei 0,1g V, 0,3g Fe bzw. 0,1g Os. Die Arbeitsvorschrift für die Analyse im Konzentrationsbereich 1 bis 10g/5 ml wird angegeben. Der relative Fehler bei der Simultankomparationsmethode liegt innerhalb 2%. Der Einfluß fremder Ionen wurde untersucht.

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Summary Mixtures of ascorbic acid, hydrazine or tin(II) chloride react with solutions containing acids, chlorate and chloride in accord with the familiar Landolt reaction, with liberation of chlorine. The latter can be detected witho-tolidine. The reaction is catalyzed by vanadium(V), iron(III) or osmium(VIII). On the basis of this behavior, it is possible to determine these elements chronometrically and also with the aid of the simultaneous comparation method. The detection limits are 0.1g V, 0.3g Fe, or 0.1g Os. The working directions are given for the analysis in the concentration range from 1 to 10g/5 ml. The relative error in the simultaneous comparation method is within 2%. The influence of foreign ions was studied.

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Résumé Les mélanges d'acide ascorbique, d'hydrazine ou de chlorure d'étain-II avec des solutions acides contenant chlorate et chlorure réagissent suivant la réaction bien connue de Landolt avec libération de chlore mis en évidence par l'o-tolidine. La réaction est catalysée par le vanadium-V, le fer-III ou l'osmium-VIII. Sur ce principe, on peut doser ces éléments aussi bien par chronométrie que par la méthode de comparaison simultanée. Les limites de dilution se situent à 0,1g V, 0,3g Fe ou 0,1g Os. On indique le mode opératoire de l'analyse dans le domaine de concentration de 1 à 10g/5 ml. L'erreur relative pour la méthode de comparaison simultanée est inférieure à 2%. On a étudié l'influence des ions étrangers.

     

Cathode erosion on copper electrodes in steam,hydrogen, and oxygen plasmas

Experimental data are presented for cathode erosion rates on copper cathodes (or magnetically rotated arcs in steam, and mixtures of steam, hydrogen, and oxygen with argon. Measurements were also made of the arc voltage and velocity. The erosion rates for steam and oxygen plasmas were significantly lower than those .16r argon and hydrogen. Pure steam and 10% oxygen in argon gave erosion rates of 2.3 and 6.1 g/ C respectively while pure argon and 70% hydrogen in argon gave rates of 14.8 and 13.0 g/C respectively. Erosion rates decreased with increasing are velocities. The variation of arc velocity with operating conditions is described in terms of both aerodynamic and surface drag on the arc and arc root respectively.     

Determination of boron in river water with flameless atomic absorption spectrometry (graphite furnace technique)

Summary A simple and rapid procedure is described for the determination of boron in water using flameless atomic absorption spectrometry. A Ca/Mg solution is added before measurement. The method is suitable for boron concentrations up to 250 g/l. The mean standard deviation is 6±4 g/l.

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Bestimmung von Bor in Flußwasser mittels flammenloser Atomabsorptions-Spektrometrie (Graphitrohrtechnik)

Zusammenfassung Eine schnelle und einfache Methode zur Bestimmung von Bor im Wasser mittels flammenloser AAS wird beschrieben. Die Messung erfolgt nach Zugabe einer Ca/Mg-Lösung. Die Methode ist geeignet für Borkonzentrationen bis 250 g/l. Die mittlere Standardabweichung beträgt 6±4 g/l.

     

Differential pulse adsorptive stripping voltammetric determination of nickel and cobalt in high purity aluminium

A sensitive method for the simultaneous determination of trace amounts of nickel and cobalt in pure aluminium has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the dimethyl glyoxime (DMG) complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.1 mol/l ammonia buffer, pH 9.0, containing ammonium citrate and 5×10^–4 mol/l DMG has been used. The determination limit obtained has been as low as 0.5 g/g for Ni and 0.2 g/g for Co (using about 100 mg sample) with a relative standard deviation of 13% and 22%, respectively.     

Modified method for filling micro-HPLC-columns

Summary A new method is introduced for packing micro-columns with an ID (inner diameter) of 320 m. The advantage of this method is the extraordinary economy of the packing material employed and the high reliability in production. The theoretical plate height ranges from 7 to 8 m for 3 m particles.     

Determination of minor element concentrations in reference materials

It has been shown, for a Pb isotopic reference material and for natural Cd, that total evaporation with integrating mass spectrometric measurement allows the determination of isotope ratios of these elements with sufficient accuracy and reproducibility. It is possible to use the method in carefully selected cases for IDA-TIMS measurements without the application of bias factors derived from isotopic reference material measurements. IDA-TIMS measurements were used for the determination of Cd (40–400 g/g) in polyethylene and Cd (10 g/g), Pb (500 g/g), Ga (150 g/g) and Zn (2000 g/g) in the Al alloy AlCuMg2. Relative standard deviations (n=5) were between 1.2% to 2.4% in the first case and 0.3% for Cd, 0.4% for Ga, 0.14% for Pb, 0.6% for Zn in the second. Deviations from the certified values were between 0.8% and 1.4% in the first case. The four concentration values contributed to the AlCuMg2 certification measurements but deviated from the finally certified values as follows: Cd+1.0%, Ga–1.6%, Pb–0.9% and Zn+10%.     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

Flow injection flame atomic spectrometric determination of iron, calcium, magnesium, sodium and potassium in ceramic materials by using a variable-volume injector

Summary A series of different ceramic materials, such as porcelain, feldspar, kaolin, varnish, clay and stoneware have been analyzed. Iron, calcium and magnesium have been determined in these materials by flame atomic absorption and sodium and potassium by flame emission. The use of a variable-volume injector enables one to carry out these analyses in a flow system (after fusion of samples with lithium metaborate) and does not require different dilutions for the determination of each type of sample considered, nor the use of different flow injection manifolds. The developed procedure provides a limit of detection of 100 g/l for Na, 70 g/l for Ca, 50 g/l for both Fe and K and 8 g/l for Mg. The coefficient of variation obtained for the absorbance measurement is of the order of 0.5–2%. A series of 17 real samples were analyzed by the proposed procedure and the obtained results turned out to be comparable to those found by batch analysis.     

Binuclear Osmium μ-Oxocarboxylate Complexes [Os2(μ-O)(μ-O2CR)2Cl4L2] (R = CH3, CCl3; L = PPh3, AsPh3) and Their Electrochemical Behavior in Dichloromethane

Cyclic voltammetry and galvanostatic coulometry techniques were used to determine how the redox properties of osmium binuclear -oxocarboxylates [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PPh₃ and R = CH₃; L = AsPh₃) are influenced by the nature of the bridging carboxylate ligand RCOO^– and ligand L. It was shown that all compounds in solution of dichloromethane undergo two single-electron reduction processes. The data obtained were compared with the DFT calculations of the electronic structure of the model complexes [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PH₃ and R = CH₃; L = AsH₃).     

Partition coefficients of ω-phenylalkanols between water and sodium deoxycholate micelles

The partition coefficient of -phenylalkanols [C₆H₅(CH₂)_mpOH, m _p =3–6] between water and micelles of sodium deoxycholate (NaDC) has been determined by a differential spectroscopic method at 25°C. The linear dependence of thestandard free energy change of transfer calculated from the partition coefficient on the alkyl chain length of the alkanols (m _p 4) yields the standard free energy change per methylene group [G^o(CH₂)]. G^o(CH₂) value for the present system, –3.21 kJ-mol ^–1 is larger in magnitude than that for sodium dodecylsulfate (SDS)--phenylalkanol system, –2.40 kJ-mol ^–1 . The result indicates that the alkyl chain of -phenylalkanols has higher affinity to NaDC micelles than to SDS micelles although the molecular structure of NaDC is more rigid and bulkier than that of SDS and the aggregation number of micelles of the former is much smaller than that of micelles of the latter. On the basis of the linear relation between the effect of added -phenylalkanols on the critical micelle concentration of NaDC (–dC_cmc/dC_a) and the partition coefficient, it is found that the degree of ionization of NaDC micelles is not influenced by solubilization of -phenylalkanols into the micelles.     

Bestimmung von Chlorid in konzentrierten S?uren durch inverse Polarographie am h?ngenden Quecksilbertropfen

Zusammenfassung Chlorid im ppm-Bereich wird in konzentrierter Phosphorsäure, Schwefelsäure und Perchlorsäure mit der inversen Polarographie am hängenden Quecksilbertropfen bestimmt. Das Elektrolysepotential gegen eine Silber-Silberchloridelektrode beträgt +0,3 Volt. Bei diesem Potential ist es nicht erforderlich, den Sauerstoff in den Probelösungen durch Stickstoff oder Wasserstoff zu entfernen. Die relative Standardabweichung des Verfahrens ist bei 0,5, 2 und 5 g Chlorid/ml 2%. Unter den angegebenen Bedingungen ist die Nachweisgrenze 0,1 g/ml; sie läßt sich noch mit Sicherheit auf 0,01 g/ml herabsetzen. Bromid und Jodid stören die Bestimmung. In konzentrierter Salpetersäure gelang bis jetzt die Chloridbestimmung noch nicht. Untersuchungen darüber sind zur Zeit im Gange.

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Summary Chloride can be determined in the ppm range in concentrated phosphoric, sulphuric, and perchloric acids by inverse polarography with the hanging mercury drop. The electrolysis potential vs. Ag-AgCl electrode is +0.3 volt. At this potential removal of oxygen from the sample solution by nitrogen or hydrogen is not necessary. The relative standard deviation for concentrations of 0.5, 2 and 5 g of chloride/ml has been found to be 2%. The limit of detection is 0.1 g/ml on the conditions described, but is believed to be improvable to 0.01 g/ml. Interferences are caused by bromide and iodide. The determination of chloride in concentrated nitric acid has been not successful so far, but further investigations are going on.