Heterogeneous hydride generation in a packed membrane cell

Summary Volatilization of arsenic, selenium and antimony for sample introduction in atomic absorption spectrometry has been performed by pumping an acidic sample through an anion exchanger in the tetrahydroborate (III) form packed as a bed in the liquid channel of a gas-liquid separation membrane cell. The hydrides generated in the heterogeneous reaction between bound tetrahydroborate (III) ions and the analytes are rapidly transferred with the aid of the concomitantly generated hydrogen gas through the gas-permeable membrane into the gas phase and swept to the spectrometer by an additional hydrogen gas flow. This instant transfer of the hydrides to the gas phase kinetically discriminates the reaction of the hydride with metal borides and metal colloids, whose formation by reaction with tetra-hydroborate (III) is slower than the hydride reaction. The susceptibility to interference by transition metal ions is thus markedly reduced, as compared with both batch hydride generation methods and a previously presented heterogeneous reaction scheme. The detection limits for arsenic, selenium, and antimony were 1.2, 3.7, and 10 g/l, respectively. The calibration graphs were linear from the detection limit up to 125 g/l for arsenic, 150 g/l for selenium, and 250 g/l for antimony. The relative standard deviations at concentration levels of 10 and 100 g/l were 1.8 and 0.7% for arsenic and 2.3 and 1.2% for selenium. Corresponding figures for 50 and 100 g/l antimony were 2.5 and 1.6%.     

Anwendung der Ringofenmethode zum Nachweis einiger Heteroelemente in organischen Verbindungen

Zusammenfassung Ein schnelles und einfaches Mikroverfahren zum Nachweis einiger Heteroatome organischer Verbindungen wurde entwickelt. Nach Aufschluß mit metallischem Kalium werden die entstehenden Ionen mit der Ringofenmethode getrennt und mit empfindlichen Reaktionen nachgewiesen. Nachweisgrenze: 0,5 bis 1g Stickstoff, 1 bis 2g Schwefel, 2 bis 3g Jod, 4 bis 5g Brom, 5 bis 10g Chlor in 0,5 bis 1 mg Einwaage.

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Summary A rapid and simple micromethod was developed for the detection of several hetero-elements in organic compounds. After breaking down the sample with metallic potassium, the resulting ions are separated by the ring oven method and detected by means of sensitive reagents. Detection limits: 0.5 to 1g nitrogen, 1 to 2g sulfur, 2 to 3g iodine, 4 to 5g bromine, 5 to 10g chlorine in samples weighing 0.5 to 1 mg.

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Résumé On a découvert un procédé à l'échelle micro, simple et rapide, pour rechercher certains hétéroéléments dans les composés organiques. Après mise en solution par le potassium métallique, on sépare les ions formés suivant la méthode du four annulaire et l'on effectue la recherche au moyen de réactions sensibles. Limite de dilution: 0,5 à 1g d'azote, 1 àg de soufre, 2 àg d'iode, 5 à 10g de chlore sur 0,5 à 1 mg de prise d'essai.

     

Mineral speciation of copper and zinc in flying ash from a thermal power plant

Summary We studied the mineral speciation of Cu, Zn and Hg in fly ash from a large thermal plant burning lignite. By applying various treatments carried out under different conditions and taking into account the solubility and physical properties (boiling and melting point, etc.) and the behaviour towards combustion of the different possible compounds, we concluded that the ash assayed contained 109.6, 114.4 and 14.30 g/g of zinc silicate, zinc oxide and/or zinc sulphide and metal zinc, respectively, as well as 24.5 g/g of copper silicate and 31.2 g/g of a mixture of copper oxide, sulphide and metal. The formation of these compounds in the combustion of lignite is discussed.     

Protonation of Os3(μ-H)(CO)9(μ3-σ,η2-C≡C-R) clusters (R=CMe2OH,C(Me)=CH2)

Protonation of triosmium clusters Os₃(-H)(CO)₉(₃-,²-CC-R) (R=CMe₂OH, C(Me)=CH₂) affords a cationic complex containing a six-electron propargyl ligand which has been detected for the first time.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1144–1145, June, 1993.     

Flame atomic absorption spectrometric determination of cadmium and copper in biological reference materials using on-line sorbent extraction preconcentration

Summary Cadmium and copper at the g/g to ng/g level in plant and animal tissue reference materials, and at the g/l level in urine were determined by flame atomic absorption spectrometry using on-line sorbent extraction preconcentration based on flow injection techniques. Bonded silica reversed phase sorbent with octadecyl functional groups (RP-C 18), packed in a 100 l column, was used to collect the diethylammonium-N,N-diethyldithiocarbamate (DDTC) complex formed on-line in the sample digests at low pH. Methanol was used to elute the analyte chelates directly into the nebulizer-burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased the sensitivity. A sampling frequency of 85/h could be obtained with a sample loading time of 30 s at a flow rate of 4.0 ml/min. The enrichment factor for both elements was 20 and the enhancement factors, including the effect of the organic solvent and with the flow spoiler removed, were 126 and 114 for cadmium and copper, respectively. The detection limits (3) were 0.15 g/l for cadmium and 0.2 g/l for copper. The precision was 2.3% and 1.4% r.s.d. for 10 g/l Cd and 45 g/l Cu, respectively (n=11). Results for the determination of cadmium and copper in various biological reference materials were typically in good agreement with certified values. Low recoveries were observed, however, for cadmium in samples containing high levels of copper and/or iron, such as bovine liver.On leave from Flow Injection Analysis Research Center, Institute of Applied Ecology, Academia Sinica, Shenyang, China     

Untersuchungen zur Bestimmung von Spurenelementen in Blutserum mit Hilfe der Totalreflexions-R?ntgenfluoreszenzanalyse

Summary The quantitative determination of trace elements in human blood serum by Total Reflection X-Ray Fluorescence Analysis (TXRF) is influenced by absorption- and reflection-effects caused by the organic (proteins) and inorganic (P, S, Na, K, Ca, Cl) matrices. To minimize these effects we have developed a sample preparation technique based on the decomposition of the organic matrix and followed by the separation of the trace elements from the organic matrix by ion-exchange. The described method enables the simultaneous determination of K (1584 g), Ca (666 g), Fe (22 g), Cu (9.6 g), Zn (8.8 g), Se (0.97 g), Sn (1.3 g), Pb (0.12 g) and Rb (1.6 g) (obtained values in parentheses).

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet     

Triiron and Triruthenium Carbonyl Clusters Bearing Bridging Long Chain Diphosphine and Capping Chalcogenido Ligands

Treatment of Ru₃(CO)₁₂ with dpphSe₂ (dpph = 1,6-bis(diphenylphosphino)hexane) in refluxing toluene in the presence of Me₃NO afforded two new compounds, Ru₃(CO)₇(-CO)(₃-Se)(-dpph) (1) and Ru₃(CO)₇(₃-Se)₂(-dpph) (2). A similar reaction of Ru₃(CO)₁₂ with dpppeSe₂ (dpppe = 1,5-bis(diphenylphosphino)pentane) gave exclusively Ru₃(CO)₇(₃-Se)₂(-dpppe) (3). Treatment of Ru₃(CO)₁₂ with dpphS₂ and dpppeS₂ at 110°C in the presence of Me₃NO afforded Ru₃(CO)₇(₃-S)₂(-dpph) (4) and Ru₃(CO)₇(₃-S)₂(-dpppe) (5), respectively. Reactions of Fe₃(CO)₁₂ with dpphSe₂ and dpppeSe₂, under identical conditions, afforded Fe₃(CO)₇(₃-Se)₂(-dpph) (6) and Fe₃(CO)₇(₃-Se)₂(-dpppe) (7), respectively. Compounds 1–7 were characterized spectroscopically and the molecular structures of compounds 1–4 were determined by single crystal X-ray crystallography. The core of 1 contains an equilateral triangle of ruthenium atoms with one capping selenium, one bridging dpph, one doubly bridging carbonyl and seven terminal carbonyl ligands. Complexes 2–4 have a square-pyramidal structure with two metal and two chalcogenide atoms alternating in the basal plane and the third metal atom at the apex of the pyramid, and belong to the family of well-known nido clusters with seven skeletal electron pairs.     

Bestimmung flüchtiger organischer Verbindungen in atmosphärischen Aerosolproben durch thermische Desorption und FID-Detektion

Zusammenfassung Staub- und Aerosolproben werden im Stickstoffstrom im Temperaturbereich 25–420° C einer temperaturprogrammierten thermischen Desorption unterworfen. Die flüchtigen organischen Komponenten werden mittels FID summarisch als volatile organic carbon (VOC) bestimmt. Die Eichung des Analysators erfolgt durch ein Aliphaten-Standardgemisch. Bei Probemengen von 50–100g Aerosol ist eine Bestimmung des VOC-Gehaltes mit einer Reproduzierbarkeit vons=3,5–7 rel.% möglich. Die Nachweisgrenze der Methode liegt für Aerosolproben bei 0,3g VOC.

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Determination of volatile organic components in atmospheric aerosol samples by thermal desorption and FID-detection

Summary Atmospheric dust and aerosol samples are treated in a nitrogen carrier gas stream at the temperature range 25–420° C by temperature programmed desorption. The volatile organic components are detected by FID. Calibration of the analyzer is carried out with a standard mixture of aliphatic hydrocarbons. The result is expressed as volatile organic carbon (VOC). The reproducibility of the method for aerosol samples (sample weight 50–100g) is in the range of 3,5–7% r. s. d. The detection limit of the method is 0,3g VOC.

     

Spectrophotometric method for phosphine residue determination in coriander

Spectrophotometric method for the determination of phosphine (PH₃) residues in coriander has been developed based on the reaction of phosphine with silver nitrate in 2% aqueous isopropanol. The yellow chromophore formed has an absorption maximum at 430 nm and the linear relation between the absorbances at 430 nm and the concentration of PH₃ is obeyed in the range of 0.02 to 0.17 g. The method is sensitive with a detection limit of 0.008 g and can be applied for determination of 0.02 g/g residue in coriander. Recovery of added PH₃ from a closed system ranges from 96 to 101%.     

Bulk acoustic wave sensor for the ion chromatographic determination of copper in human plasma

By using ion chromatography with series bulk acoustic wave detection, a method for the determination of copper in human blood plasma has been developed. The advantages of the good selectivity of ion chromatography and the highly sensitive response of SBAW have been combined to improve detection limit, accuracy and reproducibility. The detection limit (3) of the method to copper is 0.3 g/ml. The relative standard deviation for the determination of 1.0 g/ml of copper is 2.1% (n=7). For the IC analysis, the analytical column is a Shim-pack IC C1 column, and the mobile phase is 4.0 mM tartaric acid/2.0 mM ethylenediamine solution with pH 4.2. This system has been applied to the determination of Cu in blood plasma from healthy people or patients with renal failure.     

Synthesis,characterization and crystal structures of heterometallic trinuclear carbonyl sulfido clusters (η5-Cp)MoFeCo- (CO)8(μ3-S) and [(η5-Cp)Mo]2Fe(CO)7(μ3-S)

HFe2Co(CO)9(3-S) reacts with (5-Cp)Mo(CO)3Cl in refluxing THF to give heterometallic trinuclear clusters (5-Cp)MoFeCo(CO)8(3-S) and [(5-Cp)Mo]2Fe(CO)7-(3-S), which have been characterized by elemental analyses, i.r., 1H- and 13C-n.m.r. and X-ray crystal structure determination. An electrophilic addition–elimination sequence is proposed for their formation.     

An investigation of 3μm reverse-phase octadecylsilane packing materials for high-performance liquid chromatography

Summary The efficiency of high-performance liquid chromatography columns packed with 5 m and 3 m reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

Simultaneous determination of copper,mercury and lead by first-order derivative spectrophotometry using dithizone as reagent

A first-order derivative spectrophotometric method has been developed for the simultaneous determination of copper, mercury and lead at g/L levels using dithizone as reagent. The procedure involves the simultaneous extraction of these elements by dithizone in chloroform from weakly alkaline solutions. Linear calibration curves were obtained in the ranges 0.5–10 (Cu), 1–10 (Hg) and 1–10 (Pb) g present in 40 ml of aqueous phase with detection limits of 5 g/L (Cu) and 20 g/L (Hg and Pb). The R.S.D.s for 100 g/L of copper, mercury and lead were 2.5, 2.6 and 3.1% respectively, for 5 determinations. The method is applicable for the determination of copper and lead in marine sediment samples with good precision and accuracy.     

Indirect spectrophotometric determination of cyanide

A spectrophotometric method for cyanide based on its inhibition of the colour formation reaction between nickel(II) and 3-(4,5-dimethyl-2-thiazolylazo)-2,6-dihydroxybenzoic acid has been developed, and allows the determination of down to 0.1 g of cyanide. Most of the interferences can be avoided by displacement of the hydrogen cyanide using an arsine generator.     

Reactions of dodecacarbonyltriruthenium with α,β-unsaturated ketones. Crystal and molecular structures of two reaction products

The thermal reactions of Ru₃(CO)₁₂ with RCOCH=CHPh (R=Me, p-MeC₆H₄) in hydrocarbon solvents lead to the formation of a series of complexes, several of which have been isolated as individual compounds by chromatography. The dinuclear complex Ru₂(-H)(CO)₆(-MeCOCH=CPh) and the tetranuclear complex Ru₄(-H)(-CO)(CO)₇(p-MeC ₆H₄ COCH=CPh)(-p-MeC₆H₄COCH=CPh)(₄-p-MeC₆H₃COCH=CHPh) are characterized by an X-ray structural study. The structures of other reaction products are discussed on the basis of spectral data. The reactions are accompanied by reduction of the starting enones to the corresponding unsaturated ketones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1293, July, 1993.     

Quantitation of polychlorinated biphenyl (PCB)-residues after hydrodechlorination to biphenyl using liquid chromatography with UV-detection

Summary A method for the determination of polychlorinated biphenyls (PCB's) via the dechlorination to biphenyl by LiAlH₄ in dodecane has been developed. The use of a high pressure liquid Chromatograph, monitoring with an UV-detector at 248 nm and a 7 m Silicagel column with more than 5000 theoretical plates for biphenyl increased the sensitivity of the dechlorination method remarkably. It is now comparable in sensitivity to the perchloration methods, i.e. the detection limit is at 100 ng absolute for PCB's. Overall yields better than 90% have been obtained, when using standard solutions containing 0,1–20 g absolute of PCB Clophen A 30 or A 60.The DDT-group, chloro-naphthalines and polychloro-terphenyls can be determined simultaneously with the polychloro-biphenyls by the same procedure.

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Quantifizierung von Rückständen der polychlorierten Biphenyle (PCB) durch Hydrodechlorierung zum Biphenyl und Flüssig-Chromatographie mit UV-Detektion

Zusammenfassung Polychlor-biphenyle (PCB) lassen sich mit LiAlH₄ in Dodecan zum Biphenyl hydrodechlorieren. Das Biphenyl kann nach Hochdruckflüssig-Chromatographie (Säule: Merck Hibar, Si60, 7 m, Bodenzahl 5000, Länge 25 cm, Elutionsmittel: n-Heptan) mit UV-Detektion bei 248 nm bestimmt werden. Für die Derivatisierungsreaktion wurden bei Mengen von absolut 0,1–20 g PCB (Clophen A 30 oder A 60) Ausbeuten besser als 90% bestimmt. Die Nachweisgrenze für Derivatisierung, Trennung und Bestimmung liegt bei 100 g PCB absolut. Unter Berücksichtigung eines möglichen Aufgabevolumens von 100 l wird in der Gesamtheit die Nachweisstärke der Perchlorierung der PCB zum Decachlorbiphenyl erreicht.Unter gleichen Bedingungen ist die Bestimmung der DDT-Gruppe, der Chlor-naphthaline und der Polychlor-terphenyle über ihre Stammkohlenwasserstoffe möglich.

     

Semiquantitative estimation of the mycotoxins citrinin, Ochratoxin A, Aflatoxin M1 and penicillic acid on thin-layer chromatograms with a grey scale

Summary Spots of citrinin, ochratoxin A, aflatoxin M₁ and penicillic acid on thin-layer chromatograms can be semi-quantitatively estimated by using a grey scale, commonly used in photo laboratories. The detection limits are 0.01 g for citrinin, 0.006 g for ochratoxin A, 0.002 g for aflatoxin M₁ and 0.01 g for penicillic acid. Standard curves for these mycotoxins are given.

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Halbquantitative Bestimmung der Mycotoxine Citrinin, Ochratoxin A, Aflatoxin M₁ und Penicillinsäure auf Dünnschicht-Chromatogrammen mit Hilfe eines Graukeils

Zusammenfassung Mit Hilfe eines in Photolabors gebräuchlichen Graukeils können dünnschicht-chromatographische Flecke der obengenannten Mycotoxine halbquantitativ bestimmt werden. Die Nachweisgrenzen betragen 0,01 g für Citrinin, 0,006 g für Ochratoxin A, 0,002 g für Aflatoxin M₁ und 0,01 g für Penicillinsäure. Eichkurven werden angegeben.

     

Determination of heavy metals in sea water and in marine organisms by flameless atomic absorption spectrophotometry

Summary In natural waters, heavy metals such as Cd may be present in bound form. It is, therefore, important to consider chemical speciation, especially at low concentrations of the metal where a significant part can be bound by other trace constituents so tightly that it escapes several forms of its determination. It has been demonstrated that even the very strong complexant APDC is unable to leach out all of the heavy metal present in several coastal water samples from the German Bight.This paper describes a new micro method for the determination of total Cd in natural waters. First a small sample is dried in a polypropylene vial. Then the salt residue is heated to 90° C with a mixture of sulphuric and nitric acid for digestion of organic trace constituents (and oxidation of sulphides if present). After dilution subsamples are neutralized using an excess of NaHCO₃ buffer solution. Extraction results are then independent from the possible slight variations of pH. The extractant, a solution of APDC in CCl₄ is stable for weeks, and even the extract is stable for at least 16h. Precision is in the range of 7% at a concentration of 0.066 g Cd l^–1; the detection limit is below 0.002 g l^–1 and can be lowered, if necessary, by enlargement of the original sample. According to the sensitivity of the method the typical blank of 0.022 g Cd l^–1 is high, but it is rather constant (mean variation from the mean: 0.0024 g l^–1).Teil XI: Fresenius Z. Anal. Chem. 299, 206–207 (1979)     

Differential pulse polarographic determination of l-lactate with a soluble enzyme preparation

Summary An electrochemical method for the determination of l-lactic acid using the specific reaction of lactate oxidase, has been studied and applied to lactic acid beverage and yoghurt. The technique is reasonably rapid and simple to perform. The calibration curve is linear in the concentration range from 1.0 to 20 mol/l, the reproducibility (R.S.D.) at 10 mol/l l-lactic acid is 1.34% (n=6) and the detection limit is 0.29 mol/l (k=2). The method can possibly be used for monitoring l-lactate or l-lactic acid in food industries and clinical laboratories.