Characterization of a total diet reference material (ARC/CL HDP) for contents of essential and toxic elements

Summary A total diet reference material (RM) was prepared by employing material leftover from a nationwide Finnish hospital diet study. The material was carefully homogenized using Ti-blades, freeze-dried, rehomogenized with Ti-blades, passed through a 2 mm nylon sieve and carefully mixed in large glass cylinders. Homogeneity of the material divided into 20 g samples in polyethylene bottles was tested by taking ten 0.5 g samples from the beginning and end of the bottling line and analyzing them for Zn and Mg. The homogeneity was within 1.0% for both Zn and Mg. An interlaboratory comparison study involving reliable reference laboratories that employed a total of seven methods based on independent analytical principles was conducted on the contents of 14 mineral elements. After the exclusion of outliers the recommended concentrations (on a dry weight basis) expressed as the medians±95% confidence limits were established as follows: Ca=2.86±0.124 mg/g, Mg=785±25 g/g, K=9.42±0.30 mg/g, Na=7.87±0.57 mg/g, Fe=30.4±0.9 g/g, Mn=12.9±0.58 g/g, Zn=28.9±1.3 g/g, Cu=3.18±0.19 g/g, Mo=262±35 ng/g, Ni=271±38 ng/g, Se=181±17 ng/g, Pb=43±8 ng/g, Cd=21±3 ng/g and Hg=6.6±3.6 ng/g. All of the above recommended concentration ranges, except that for Ni, fell into category A, i.e. values recommended with a high degree of confidence according to the certification criteria established by Pszonicki.     

Selenium, chromium and zinc content of proposed SRM 1846 infant formula

A proposed infant formula SRM 1846 has been analyzed for zinc, selenium and chromium by isotope dilution mass spectrometry (IDMS). The precision of the IDMS methods has been sufficient to allow the estimation of the sample homogeneity with respect to these three analytes. Overall means of 60.9±0.9 g Zn/g (mean±standard deviation) and 76.1±1.9 ng Se/g have been found for 30 determinations. Values for chromium content have been found to depend on the sample preparation method, suggesting possible contamination. Accurary of the zinc, chromium and selenium values has been verified using a certified reference material, SRM 1549 Non-Fat Milk Powder.     

Development and application of a simple routine method for the determination of selenium in serum by octopole reaction system ICPMS

The aim of the study was to develop an inductively coupled plasma mass spectrometry (ICPMS) method for robust and simple routine determination of selenium in serum. Polyatomic interferences on ⁷⁶Se, ⁷⁷Se, and ⁷⁸Se were removed by applying an octopole reaction system ICPMS with the reaction cell pressurized with H₂ gas. We developed a novel simple optimization routine for the H₂ gas flow based on a signal-to-noise ratio (SNR) calculation of the selenium signal measured in a single selenium standard. The optimum H₂ flow was 2.9 mL min^–1. The selenium content in serum was determined after a 50-fold dilution with 0.16 M HNO₃ and quantified by using addition calibration and gallium as an internal standard. The method detection limit was 0.10 g L^–1 for ⁷⁶Se and ⁷⁸Se and 0.13 g L^–1 for ⁷⁷Se. Human serum samples from a case-control study investigating if selenium was associated with risk of colorectal adenoma were analyzed. The average selenium concentration for the control group (n=768) was 137.1 g L^–1 and the range was 73.4–305.5 g L^–1. The within-batch repeatability (a batch is ten samples) estimated from 182 replicate analyses was 6.3% coefficient of variation (CV), whereas the between-batch repeatability was 7.4% CV estimated from 361 replicates between batches. The method accuracy was evaluated by analysis of a human serum certified reference material (Seronorm Serum level II, Sero A/S, Norway). There was a fairly good agreement between the measured average of 145±3 g L^–1 (n=36) and the certified value of 136±9 g L^–1. In addition the method was successfully applied for analysis of zinc serum concentrations without further optimization. For the Seronorm certified reference material a value of 911±75 g L^–1 (n=31) for zinc was obtained, which corresponds well to the certified zinc value of 920±60 g L^–1.     

Inductively coupled plasma mass spectrometry for stable isotope tracer investigations

Inductively coupled plasma mass spectrometry (ICP-MS) has now been developed for application to stable isotope tracer investigations of several minerals/trace elements. Use of this method for such purposes requires an understanding of a number of fundamental issues: analytical chemistry performance of the method of isotopic analysis, relationship of the level of enriched isotope administered to the subject with background level of the isotope already present, the issues of cost, and finally the specific details of the biological issues to be explored.In this paper, a brief discussion of these issues is presented. As an example, the discussion is presented in relation to selected aspects of metabolism of selenium, employing the three stable isotopes⁷⁴Se,⁷⁷Se, and⁸²Se in the rat as the biological model.Analytical performance of hydride generation/ICP-MS is discussed for the required analyses of selenium isotopes. It is shown that for solutions containing 10 ng/ml Se of natural isotopic composition, optimized signal/background ratios greater than 40/1 can be obtained, resulting in worst-case detection limits (ng Se) of 2 (⁷⁴Se), and 0.6 (^77,82Se). The precision and accuracy of isotope ratio measurements for the method used routinely in biological studies is 1%. The accuracy of the method for quantitative isotopic analysis is compared with hydride generation/atomic absorption spectrophotometry (HG/AAS). The following results are given (g Se/g or ml; mean + 1 SD,n = 3–5; first HG/ICP-MS, second HG/AAS): SRM 1577a [bovine liver] 0.697 ± 0.002 versus 0.69 ± 0.01; human blood plasma 0.098 ± 0.001 versus 0.135 ± 0.008; human red cells 0.211 ± 0.002 versus 0.216 ± 0.012; and human urine 0.0473 ± 0.0003 versus 0.0489 ± 0.0003.An experiment is described with the rat to show the feasibility of the method for studies of selenium metabolism. Rats were placed on Se-free diet for eight weeks, given their Se requirements in the drinking water in the form of⁷⁶SeO ₃ ^2– and a single-day (day 3) replacement of their water with that containing highly enriched⁷⁴SeO ₃ ^2– . Isotopic analysis of carcass and selected organs revealed a high degree of isotopic enrichment with respect to⁷⁴Se during the entire eight weeks of the experiment, indicating the feasibility of this approach for detailed investigations of selenium metabolism in the rat.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Bestimmung von Fe, Co, Cu, Zn, Se, Rb und Cs in NBS-Ochsenleber, Blutplasma und Erythrocyten durch INAA und AAS

Zusammenfassung Der Gehalt von Fe, Co, Cu, Zn, Se, Rb und Cs wurde in Blutplasma und in Erythrocyten von sechs Normalpersonen mittels der instrumentellen Neutronenaktivierungsanalyse und der flammenlosen Absorptionsspektrometrie (Cu) bestimmt. Zur Überprüfung der Richtigkeit wurde der NBS-Standard 1577, Ochsenleber, verwendet. Die erhaltenen Resultate für Elemente mit höheren Gehalten (Fe, Cu, Zn) liegen weitgehend im Bereich der bisher veröffentlichten Daten. Bei Elementen mit kleineren Gehalten (Co, Se, Rb, Cs) liegen unsere Werte in dem unteren Bereich oder darunter. Für diese Elemente wurden in Blutplasma und in Erythrocyten (hier bezogen auf Trockenmasse) die folgenden Mittelwerte ermittelt: Für Co 0,22 ±0,14 ng/ml, 0,59±0,23 ng/g, für Se 103±18 ng/ml, 401±29 ng/g, für Rb 167±36 ng/ml, 12,1±2,5 g/g und für Cs 0,88±0,18 ng/ml, 13,0±5,7 ng/g.

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Determination of Fe, Co, Cu, Zn, Se, Rb and Cs in NBS Bovine Liver, blood plasma and erythrocytes by INAA and AAS

Summary The content of the above elements has been determined in blood plasma and in erythrocytes of six normal persons by instrumental neutron activation analysis and flameless atomic absorption spectrometry (Cu). The over-all accuracy of these techniques was checked by using the NBS standard 1577, Bovine Liver. The results obtained for elements of higher content (Fe, Cu, Zn) are essentially in the range of other published data. However, our results for elements occurring with lower contents (Co, Se, Rb, Cs) are in agreement with the lowest values of the published data and in some cases they are even significantly below these. For these elements, the following contents have been determined in blood plasma and in erythrocytes (here related to dry weight): for Co 0.22±0.14 ng/ml and 0.59±0.23 ng/g, for Se 103±18 ng/ml and 401±29 ng/g, for Rb 167 ±36 ng/ml and 12.1±2.5 g/g and for Cs 0.88 ±0.18 ng/ml and 13.0±5.7 ng/g, respectively.

Diese Arbeit wurde durch die Deutsche Forschungsgemeinschaft gefördert.Dem Kernforschungszentrum danken wir für den Erlaß der Bestrahlungskosten.Herrn Dr. med. K. Spenger sind wir für die Mitwirkung bei der Blutentnahme und für wertvolle Diskussion dankbar.     

Beitr?ge zur Ultramikro- und Spurenanalyse organischer Stoffe

Zusammenfassung Zur elementaranalytischen Bestimmung von Selen in schwerflüchtigen, löslichen organischen Verbindungen verbrennt man 1–10 g Substanz nach Lösungsteilung in der Sauerstoffflasche. Das in Natronlauge und Wasserstoffperoxid absorbierte Selen wird in einer Entwicklungsapparatur im Stickstoffstrom mit unterphosphoriger Säure in Selenwasserstoff übergeführt, der in Natronlauge absorbiert wird. Das Selen wird unmittelbar in der Absorptionsvorlage mit Bleiacetatlösung bipotentiometrisch titriert. Das Verfahren, das nur durch Kationen gestört wird, die schwerlösliche Selenide bilden, erlaubt 1 g Selen mit einer Standardabweichung von ±18 ng zu bestimmen.

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Summary For the determination of selenium in non-volatile soluble organic compounds 1–10 g of the substance are measured by taking an aliquot of a solution of known Se concentration; the substance is burnt in an oxygen flask and the selenium is absorbed in 0,003 N alkaline solution. Hypophosphoric acid reduces the absorbed selenium to hydrogen selenide, which is titrated bipotentiometrically with a 10^–4 M solution of lead acetate. 1 g of selenium can be determined with a standard deviation of ±18 ng of selenium. Only cations forming sparingly soluble selenides cause interferences.

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VII. Mitteilung: List, W. H., u. G. Tölg: diese Z. 226, 127 (1967).

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Der Deutschen Forschungsgemeinschaft, Bad Godesberg, sowie dem Verband der Chemischen Industrie e.V., Düsseldorf, danken wir für Unterstützungen.     

Determination of total arsenic in serum and packed cellsof patients with renal insufficiency

In order to investigate the arsenic level in serum and packed cells of patients with renal insufficiency, total arsenic (As) concentrations were determined with hydride generation atomic absorption spectrometry (HGAAS) in serum (S) and packed cells (PC) of 31 non-dialyzed patients. The accuracy of the method was tested by the analysis of arsenic in 3 certified reference materials. Patients showed a three-fold increase of arsenic concentrations in serum and a two-fold increase of arsenic in packed cells compared with controls. Patients (n=10) with higher serum creatinine (>2.0 mg/dL), urea (>0.70 g/L) and urinary protein (mean ±SD: 1.12±0.82 g/L) showed higher arsenic concentrations (5.8±3.3 g/L in serum and 18.0±16.7 g/kg in packed cells) compared with those with lower creatinine (<1.6 mg/dL), urea (<0.6 g/L) and urinary protein (mean ±SD: 0.27±0.82 g/L) (n=16, serum arsenic 1.2±1.2 g/L, packed cells arsenic 2.6±1.9 g/kg). The significant differences (both p<0.001) in S and PC-arsenic levels of patients in group I and II implies a relationship between the arsenic level and the degree of chronic renal insufficiency.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday     

Determination of cadmium in biological samples by inductively coupled plasma atomic emission spectrometry after extraction with 1,5-bis[phenyl-(2-pyridyl)methylene]-thiocarbonohydrazide

A systematic study was made of the optimum conditions for cadmium determination in biological samples by ICP-AES after extraction of the metal into methyl isobutyl ketone containing 1,5-bis[phenyl-(2-pyridyl)methylene]-thiocarbonohydrazide. The maximum volume ratio of aqueous to organic phase was 30 1 for a single-stage extraction of 99–100% of the metal ion. The detection limit was 0.3 ng/ml cadmium, and the calibration was linear from 0.4 to at least 150 ng/ml. No interferences from the elements commonly found in biological materials were observed. A precision of 2.5% (P = 0.05) at the 2 ng/ml level of the metal was achieved. The accuracy of the method was demonstrated by analysis of three standard reference materials, giving concentrations of 1.90 ± 0.43, 27.1 ± 1.4 and 2.63 ± 0.38 /g of cadmium, compared with the certified values of 2.20 ± 0.10, 26.3 ± 2.1, and 2.71 ± 0.15 g/g, respectively.     

Comparison of selenium content in human hair from different individuals in different countries,by76Se(n,γ)77mSe reaction

Samples of hair from 370 subjects were analysed by neutron activation. The samples were taken from residents of nine different countries: Japan, France, Ivory Coast, Brasil, Paraguay, Canary Islands, Papua New Guinea, Italy and New Zealand. The selenium determination was made using the⁷⁶Se(n,)^77mSe reaction.It was found that the average selenium concentration in the hair of Japanese subjects, both those living in Japan and those living in foreign countries was higher (total average: 0.59±0.14 mg/kg) than those of subjects from other countries (total average: 0.42±0.13 mg/kg).Our results from the determination of the selenium concentration in the hair of individuals from different countries show significant differences between different countries, nevertheless, the selenium content in human hair was small amounts. Since this is likely due to differences in diet. This method was able to analyze quickly for many samples.     

Determination of Mg,Al, P,Cu and Mn in biological fluids by neutron activation analysis

Thermal and epithermal neutron activation analysis has been applied to determine the concentrations of magnesium, aluminium, phosphorus, copper and manganese in two biological fluids: blood serum and market milk. Both epithermal neutron irradiation and radiochemical separation (a chromatographic column of HAP) were used to get rid of the interferences from 24-Na. Strongly acidic solutions of the irradiated samples were passed through the columns of HAP, where sodium was completely adsorbed while, Al, Cu, Mg and Mn were eluted with an efficiency of 99±1%. Since both Al and P were determined through the formation of²⁸Al (2.24 min) thermal and epithermal neutron activation have been applied in order to determine the contribution of each radionuclide to²⁸Al activity. The determination of Mg, Al and P in milk samples was done instrumentally, whereas in the case of blood serum with higher concentration of Na, a radiochemical separation is essential in both cases. The concentrations of Al, Cu, Mg, Mn and P in blood serum and market milk were found to be 0.24±0.02 and 1.85±0.09 g Al/ml, 1.35±0.04 and 0.068±0.005 g Cu/ml, 22.9±1 and 98.9±8.6 g Mg/ml, 22±3 and 16±2 ng Mn/ml and 167±13 and 865±32 g P/ml, respectively.     

Method for the determination of thorium and uranium in urine by ICP-MS

ICP-MS (inductively coupled plasma mass spectrometry) is shown as a very sensitive method for quantitative determination of Th and U concentration and excretion analysis in urine without any sample pretreatment. The current standard method for incorporation monitoring applies alpha-spectrometry, a very tedious and time consuming technique. ICP-MS offers an attractive alternative for monitoring of thorium and uranium body burdens in occupationally exposed subjects and also larger groups of the general population. A limit of determination of 0.5 ng/L in aqueous solutions and 1 ng/L in urine samples for both elements was achieved, with a precision of about ± 10% in the concentration range of appr. 10 ng/L. Due to the lack of a suitable reference material, the accuracy of the method was tested by comparing some of the results with those obtained by -spectrometry, especially for U. There was a sufficient agreement on both results.     

Analysis of trace elements distributed in blood

Summary For the analysis of trace elements distributed in blood, a combination of centrifugation, ultrafiltration and electrophoresis is proposed. A preparative (<- 200 mg protein) isotachophoretic system with an improved elution technique, working under physiological pH-conditions, was developed to localize the trace elements in definite protein fractions.The method was examined for beryllium, a toxic trace element with unknown physiological behaviour, in human and guinea pig blood in normal concentrations (about 1 ng/g), and after adding beryllium in vitro in the concentration range 10–100 ng/g, and in guinea pig blood with increased concentrations by inhalation. The corpuscular part of all samples contained 17–33% of the total Be, the low molecular serum fraction (MW <10000) showed 2–10% Be. 60–73% was found in serum proteins, localized at two immunologically identified fractions: the prealbumins and the -globulins. The Be distribution between the two protein regions depends on the absolute Be concentration in blood. The distribution was identical for in vivo- and in vitro-samples.All Be analyses were carried out by an optimized electrothermal AAS method with a detection limit of 0.01 ng/g and a standard deviation of s _r =±4% (10 ng/g, n=10) after isolating the Be from the matrix and s _r =±7% (10 ng/g, n=10) for direct aliquot injection of isotachophoretic fractions into the graphite furnace for AAS-determination.

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Analyse der Verteilung von Spurenelementen in BlutBestimmung von Berylliumkonzentrationen >- 0,01 ng/g in menschlichen und tierischen Blutkomponenten durch präparative Elektrophorese und flammenlose Atomabsorptions-Spektrometrie

Zusammenfassung Ein analytischer Verfahrensverbund aus Zentrifugation, Ultrafiltration und Elektrophorese ermöglicht die differenzierte Aufklärung der Verteilung von Spurenelementen in Blut. Die Zuordnung der Elementspuren zu definierten Serumfraktionen wurde nach Entwicklung eines präparativen (>-200 mg Protein) Isotachophoresesystems mit physiologischem Trenn-pH und einer speziellen Elutionseinrichtung zugänglich, wobei die native Konformation der Proteine in den getrennten Fraktionen erhalten bleibt.Die Methode wurde für Beryllium ausgearbeitet, dessen physiologisches Verhalten weitgehend unbekannt ist. Untersucht wurden Human- und Meerschweinchenblut mit Berylliumspuren in der Allgegenwartskonzentration (ca. 1 ng/g), Human- und Meerschweinchenblut mit in vitro-Berylliumzugaben (10–100 ng/g) und Meerschweinchenblut, dessen Be-Gehalt durch Inhalation von Be-Aerosol im Bereich 10–100 ng/g erhöht war. 17–33% des Gesamtberylliums wurden übereinstimmend bei allen Proben im Korpuskulärteil lokalisiert, 2–10% in den niedermolekularen (MG <10000) Serumfraktionen und 60–73% in den Serumproteinen. Zwei Proteinbereiche dienen als Trägersubstanzen von Beryllium: die Präalbumine und die -Globuline. Das allgegenwärtige Beryllium (<- 1 ng/g) befindet sich zu 8% im Präalbumin und zu 60% im -Globulin. Bei erhöhten Be-Gehalten (10–100 ng/g) kehrt sich der Verteilungsgrad um. Die Be-Verteilung war bei den in vivo- und in vitro-Proben identisch.Die Bestimmung des Berylliums in den Proteinfraktionen erfolgte sehr nachweisstark (>- 0,01 ng/g) durch FAAS mit einer relativen Standardabweichung von s _r =±4% (10 ng/g, n=10) nach Abtrennung des Berylliums von der Matrix und s _r =±7% (10 ng/g, n=10) bei direkter Vorgabe von 10 l-Aliquots der isotachophoretischen Fraktionen in das Graphitrohr.

     

Trace and minor elements in four commercial honey brands

Instrumental neutron activation analysis was used to measure the concentrations of 24 elements in four honey brands commercially available in Austin, Texas (USA). The measured elements (and concentration) were: As, (<30 ng/g); Ba, (<2 g/g); Br, (0.24–0.49 g/g); Ce, (<20 ng/g); Co, (9–180 ng/g); Cr, (37–64 ng/g); Cs, (<3–45 ng/g); Fe, (<4–15.9 g/g); Hf, (<3 ng/g); Hg, (1 ng/g); K, (91–230 g/g); La, (<4 ng/g); Na, (20.3–25.3 g/g); Ni, (0.39–0.77 g/g); Rb, (68–340 ng/g); Sb, (13–61 ng/g); Sc, (<0.3–200 ng/g); Se, (<20 ng/g); Sm, (<9 ng/g); Sr, (<2 ng/g); Th, (<4 ng/g); U, (<30 ng/g); Zn, (3.36–4.61 g/g); and Zr, (<0.5–0.84 g/g). The results obtained were compared to the concentration of the same elements in honey produced or commercially available in Turkey, Mexico, El-Salvador, China, Czechoslovakia and Yugoslavia.     

Use of INAA,PGAA, and RNAA to determine 30 elements for certification of an SRM: Tomato Leaves, 157a

Analyses for certification have been made for the determination of 30 elements in the National Institute of Standards and Technology (NIST) Tomato Leaves renewal reference material, SRM 1573a. Three of the analytical techniques used were instrumental neutron activation analysis (INAA), radiochemical neutron activation analysis (RNAA), and prompt gamma activation analysis (PGAA). These techniques provided data on 19 elements by INAA, 10 elements by PGAA, and 7 elements by RNAA, with some overlap between techniques. For example, INAA was able to obtain overall analytical uncerainties (at the 95% confidence level) averaging ±2.2% for major and minor constituents (Ca, Mg, K), ±3.3% for constituents from 1 to 1000 g/g (Na, Fe, Al, Mn, Ba, Zn, Rb, La, Cr), and ±6.4% for elements between 10 and 1000 ng/g (Co, V, Se, Th, Sc, Sb), using sample dry weights of approximately 150 mg. These analyses represent the most extensive use to date of nuclear analytical techniques in the certification of a trace element SRM at NIST.     

Determination of propanil in rice, potatoes and water by HPLC

Summary A simple and specific quantitative HPLC method for the analysis of propanil residues in rice, potatoes and water is described. The method is based on simple extraction steps, column clean-up, HPLC separation using a reversed phase column (RP-C18) and UV-detection. With this analytical system, propanil residues can be detected at the 5 ng/g level in rice and potatoes and at the 1 ng/ml level in water. Recovery rate in the range of 0.005–1 g/g is 87.3±6.9% in rice and 85.4±8.2% in potatoes and in the range of 0.001–10 g/ml 95.2±13% in water.

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Bestimmung von Propanil in Reis, Kartoffeln und Wasser durch HPLC

Zusammenfassung Eine einfache HPLC-Methode zur quantitativen Trennung und zum Nachweis der Propanilrückstände in Reis, Kartoffeln und Wasser wird beschrieben, mit der noch Mengen im ppb-Bereich erfaßbar sind. Das Verfahren besteht aus einem Extraktionsschritt, Aufreinigung auf einer Kieselgelsäule, der Trennung der Rückstände auf einer Umkehrphase (RP-C18) und der UV-Detektion. Die Methode gestattet im Bereich von 0,005–1 g/g eine Wiederfindungsrate von 87,3±6,9% in Reis, von 85,4±8,2% in Kartoffeln und im Bereich von 0,001–10 g/ml eine Wiederfindungsrate von 95,2±13% in Wasser.

     

Interaction of β-Cyclodextrin with Unsaturated and Saturated Straight Chain Fatty Acid Anions Studied by Phenolphthalein Displacement

The interaction of -cyclodextrin (-CD) with palmitoleate, linolenate, caprinate and caprylate was studied by the displacement of phenolphthalein (PHP) from the -CD cavity. Absorbance values of -CD–PHP solutions at 550 nm in 0.020 mol L-1 Na2CO3 buffer, pH 10.5, at 21.0 ± 0.5 °C, increased as the fatty acid anion was added. The concentration range of fatty acid anion used was 0.390–32.1 × 10-4 mol L-1 in the study of palmitoleate and linolenate, 1.92–80.0 × 10-4 mol L-1 in the study of caprinate and 0.770–32.0 × 10-3mol L-1 in the study of caprylate. Concentrations of -CD and PHP were 1.00 × 10-3 mol L-1 and 1.00–3.00 × 10-4 mol L-1 respectively. Data were fitted by nonlinear regression to a two step complexation model. Complex formation constants thus determined for the 1 : 1 and 1 : 2, fatty acid anion : -CD complex were: (1.2 ± 0.2) × 104 and (2.9 ± 0.2) × 102 mol-1 L for palmitoleate, (9.3 ± 0.9) × 103 and (1.1 ± 0.1) × 102 mol-1 L for linolenate, (4.1 ± 0.2) × 103 and 81 ± 8 mol-1 L for caprinate, and (5.2 ± 0.7) × 102 and 27 ± 5 mol-1 L for caprylate respectively. The PHP–-CD complex was also evaluated as a spectrophotometric sensor for the determination of olive oil acidity.     

Zur Verteilung von Dotierungsstoffen in Selengleichrichterplatten

Zusammenfassung Zur schichtweisen Analyse von Tellurmengen im ppm-Bereich in Selengleichrichterplatten wird das Selen mit wäßriger Alkalicyanidlösung in etwa 1 starken Schichten von diesen abgelöst. Für die Abtrennung der darin befindlichen Tellurspuren eignet sich die gemeinsame reduzierende Fällung durch Hydrazindichlorid mit Selen als Spurenfänger. Die quantitative Analyse des Tellurs erfolgt in Gegenwart eines maximal 10⁵fachen Selenüberschusses mit Hilfe der durch Chrom katalysierten Redoxreaktion zwischen Tellur(IV) und Tri-1, 10-eisen(III)-phenanthrolin (Ferriin). 20 Proben können in 2 Tagen analysiert werden. Es betragen die Standardabweichung im Bereich von 3–50 g Tellur etwa 0,6 g, der Streubereich für 99%ige Sicherheit ±42% resp. ±12%, die Erfassungsgrenze 1,5 g in 25 ml und die Grenzkonzentration 0,06 g/ml. Ein Beispiel für die Tellurverteilung in einer Selengleichrichterplatte ist wiedergegeben.

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On the distribution of doping elements in selenium rectifier cellsII. Method for the determination of the distribution of tellurium in selenium rectifier cells

The dissolution of the selenium in ca. 1 layers is realised by aqueous solutions of alkali cyanides. The separation of the ppm amounts of tellurium from this solution is possible in acid medium by a reducing coprecipitation of the traces of tellurium by hydrazine dichloride with selenium as trace catcher. In the presence of an excess up to 10⁵ of selenium tellurium is determined quantitatively by means of the Cr-catalysed redox reaction between tellur(IV) and tri-1,10-phenanthroline-iron(III) (ferriin). 20 samples can be completed in 2 days. The standard deviation in the range from 3 g to 50 g is about 0.6 g; the limit of error for 99% security is ±42%, respectively ±12%; the limit of detection is 1.5 g tellurium in 25 ml according to 0.06 g/ml. An example for the distribution of tellurium in a selenium rectifier cell is given.

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I. Mitteilung: D. Baresel u. K. Jaetsch: diese Z. 249, 234 (1970).

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Jetzt: Robert Bosch GmbH, Forschungsinstitut Berlin.

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Der Fa. Siemens AG danken wir für die Genehmigung zur Veröffentlichung der Ergebnisse, Herrn Dr. Iwantscheff und Herrn Ernst im Forschungszentrum der Siemens-Schuckert-Werke in Erlangen sowie Herrn Dr. Eggert im Schaltwerk Berlin für die anregenden Diskussionen.     

Beitr?ge zur Ultramikro- und Spurenanalyse organischer Stoffe

Zusammenfassung Für die Bestimmung von Jodmengen <1 g in schwerflüchtigen organischen Substanzen wurden 3 Verfahren entwickelt.Durch argentometrische Zweiphasentitration mit Dithizon als Indicator ließ sich 1 g J mit einer Standardabweichung von ±4 ng bestimmen. Der Vorteil dieses Verfahrens liegt in seiner einfachen und schnellen Durchführung. Etwa die gleiche Empfindlichkeit weist die etwas umständlichere jodometrische Titration mit amperometrischer Endpunktsanzeige auf. Mit 0,0001 n Lösungen wurden 129,4 ng Jodid (Standardabweichung ±2,3 ng) und mit 0,001 n Lösungen 1,90₁ g (Standardabweichung ±21 ng) bestimmt. Nicht ganz so genau ist die photometrische Jodbestimmung über das Kristallviolett-jodchlorid (Standardabweichung ±8 ng).Mit Hilfe dieser 3 Verfahren konnte gezeigt werden, daß die Verbrennung in der Sauerstoffflasche mittels Papierträger auch mit Substanzmengen kleiner als 1 g störungsfrei verläuft. Für schlecht verbrennbare Substanzen wird ein Zusatz von Pikrinsäure zur Erhöhung der Verbrennungstemperatur empfohlen.Der absolute Fehler, der sich durch die Aufschlußmethode ergab, war kleiner als 2 ng.

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Summary Three methods were developed for the determination of amounts <1 g of iodine in not easily volatile organic substances.The argentometric titration in a two-phase system with diphenylthiocarbazone permitted the determination of 1 g of I with a standard deviation of ±4 ng. The advantage of this method lies in its simple and rapid manipulation. Nearly the same sensitivity is obtained by a little more complicated iodometric titration with amperometric indication. 129,4 ng of iodide can be determined with a standard deviation of ±2,3 ng, when using 0,0001 n solutions, and 1,90 g of I^– with a standard deviation of 21 ng using 0,001 n solutions.A standard deviation of ±8 ng is obtained for the photometric determination of iodine by the crystal violet-iodine chloride method.These three procedures described above show that the combustion in the oxygen flask can be carried out even with amounts smaller than one microgram without any interference. Addition of picric acid to the paper holding the substance is recommended to increase the combustion temperature and to burn completely less easily combustible compounds. The absolute error resulting from this digestion method is less than 2 ng.

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I. Mitteilung: Tölg, G.: diese Z. 194, 20 (1963).

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Herrn Prof. Dr. R. Bock und Herrn Prof. Dr. F. Strassmann danken wir für die Möglichkeit zur Durchführung dieser Arbeit. Der Deutschen Forschungsgemeinschaft sei für ein Habilitandenstipendium gedankt.     

Negative thermal ionization mass spectrometry of selenium part 4. Selenium trace determination in sediments and related samples

Summary Selenium traces have been determined in different sediments (estuarine, river, lake), sandy soil and sewage sludge with isotope dilution mass spectrometry (IDMS). Negative selenium atomic ions are formed in a double-filament thermal ion source. The use of a silica gel technique for ionization improves the mass spectrometric sensitivity by a factor of 40 compared with the technique previously applied. An enriched⁸²Se spike is used for the isotope dilution process. The samples are decomposed with a mixture of conc. HNO₃ and conc. HE After decomposition selenium is separated by the formation of SeH₂ in a hydride generation system which is normally applied for atomic absorption spectrometry. The IDMS results for three standard reference sediments agree well with the certified values. In the case of three other standard reference materials, which are not certified for selenium up to now, the IDMS analyses were able to improve the selenium data given for information or as indicative values. The precision of the IDMS method in the concentration range of 0.2–3.5 g/g lies between 0.8 % and 4.1 %. The detection limit is 6 ng/g. A comparison with several other methods shows that IDMS is one of the very few analytical methods which produces accurate selenium results even at concentration levels of 0.2 g/g and less in sediments and related samples of environmental interest.

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Negative Thermionen-Massenspektrometrie von Selen Teil 4. Selenspurenbestimmung in Sedimenten und vergleichbaren Proben

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Dedicated to Prof. Dr. G. Tblg on the occasion of his 60th birthday     

Measurement of naltrexone in rat brain regions and serum by high performance liquid chromatography with electrochemical detection

Summary A method is described for the determination of naltrex-one in discrete rat brain regions and serum. Separation and quantitation are performed by reversed-phase high-performance liquid chromatography with electrochemical detection. The drug gave a linear response over the range of 12.5–100ng for either 1.0ml for cerebellar homogenate or 25l for serum (1.25–10ng on column). Recoveries of naltrexone, added to the homogenate or serum, were 94±7 and 86±6%, respectively, when compared with naltrexone dissolved in water. The mean between-run relative standard deviations were 5.8 and 6.8% for cerebellar homogenate and serum, respectively, over the concentration range studied. The within-run relative standard deviations for cerebellar homogenate (12.5ng/ml) or serum (12.5ng/25l) were 7.7%. The application of the method to an in vivo animal experiment is demonstrated.