Sequential injection fluorimetric determination of Sn in juices of canned fruits

The present work describes the development of a fast and robust sequential injection fluorimetric procedure for the determination of Sn in juices of canned fruits. The developed automatic methodology is based on the complexation of Sn with 8-hydroxyquinoline-5-sulfonic acid (HQSA) to form a fluorimetric product (λ_exc = 354 nm; λ_em = 510 nm). The influence of dimethylsulfoxide (DMSO) and cetylpyridinium bromide (CPB) on the sensitivity of the fluorimetric determination was evaluated.Linear calibration plots were obtained for Sn concentrations between 1 and 10 mg L⁻¹, with a detection limit of 0.38 mg L⁻¹. In each analytical cycle 0.006 mg of HQSA and 0.47 mg of CPB were consumed and 1.5 mL of effluent was generated.The developed methodology was applied to the determination of Sn in juices of canned fruits and the results complied with those furnished by an electrothermal atomic absorption spectrometry comparison procedure, with relative deviations lower than 5.2%.The automatic procedure exhibited good precision (R.S.D. < 1.4%) and the sampling rate was about 70 determinations per hour.     

An atomic absorption spectrophotometric method for the determination of trace amounts of zinc in canned juices after ion exchange separation

An atomic absorption spectrophotometric method is described for the determination of microgram quantities of zinc in canned juices. After sample digestion in concentrated nitric acid, the solution is evaporated till near dryness, and then a solution of 2 M HCl is added to form tetrachlorozincate (II) ion. This acid solution, containing the zinc complex is passed through an ion-exchange column (anion exchange resin, chloride form, which is preconditioned by passing 1 M HCl solution). Zinc is eluted from the column with 0.01 M HCl solution. After evaporation to dryness, the residue is dissolved in 1% (v/v) HNO3, and then atomized into an air-acetylene flame. The limit of detection of the method is 0.15 micrograms ml-1 Zn. The analytical aspects of the proposed method, including the standard addition technique are discussed.     

A turbidimetric micromethod for analysis of hydrazine

Summary A rapid turbidimetric micromethod of analysis of hydrazine concentrations down to about 10^–4 M has been described. It depends on oxidation with selenium dioxide in acid solution, yielding selenium in suspension,

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Zusammenfassung Eine schnelle turbidimetrische Mikromethode zur Bestimmung von Hydrazin in Konzentrationen bis herab zu 0,0001-m wurde beschrieben. Sie beruht auf der Oxydation mit Selendioxyd in saurer Lösung, wobei sich eine Suspension elementaren Selens bildet. Die Genauigkeit beträgt etwa 5%. Der Einfluß einiger organischer Hydroxylverbindungen auf das Verfahren wurde untersucht und erwies sich in den meisten Fällen als gering.

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Résumé On décrit une microméthode turbidimétrique rapide d'analyse de l'hydrazine pour des concentrations descendant jusqu'à environ 10^–4 M. Elle repose sur l'oxydation par l'anhydride sélénieux en solution acide, ce qui produit une suspension de sélénium et sa précision est à 5% près environ. On a étudié l'influence sur la méthode de quelques composés organiques hydroxylés et on l'a trouvée petite dans la plupart des cas.

     

A turbidimetric micromethod for analysis of tertiary butyl alcohol

Summary A rapid turbidimetric method for the analysis of very dilute aqueous solutions of tertiary butyl alcohol has been developed, using a mercuric sulphate/sulphuric acid reagent similar to the Denigés reagent. Concentrations as low as 1–6 mg/litre can be determined to within about 5% error.

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Zusammenfassung Eine schnelle turbidimetrische Methode zur Bestimmung sehr verdünnter, wäßriger Lösungen von tertiärem Butylalkohol wurde beschrieben. Sie beruht auf der Reaktion mit einer dem Reagens vonDenigés ähnlichen Quecksilber(II)-sulfat-Schwefelsäure-Lösung. Konzentrationen von 1 bis 6 mg/1 können mit einer Genauigkeit von etwa 5% bestimmt werden.

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Résumé L'auteur a mis au point une méthode turbidimétrique rapide pour l'analyse de solutions aqueuses très diluées d'alcool butylique tertiaire; à cette fin il emploie un réactif acide sulfurique-sulfate mercurique semblable à celui deDenigès. Dans ces conditions il est possible de déterminer des concentrations s'abaissant à 1–6 mg/litre avec une erreur inférieure à environ 5%.

     

A semiquantitative micromethod for the determination of barbiturates and doriden

A semiquantitative thin-layer chromatographic method is described for barbiturates and Doriden determinations from blood using micro volumes.     

A specific micromethod for the determination of phytic acid in biological material

A method for the quantitative determination of phytic acid in biological material is described. The method permits a determination of phytic acid in quantities below 0.1 mg even if the material contains closely related compounds includingmyo-inositol pentakisphosphate.

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Eine spezifische Mikromethode für die Bestimmung von Phytinsäure in biologischem Material

Zusammenfassung Es wird eine Methode zur quantitativen Bestimmung von Phytinsäure in biologischem Material beschrieben. Die Methode erlaubt die Bestimmung von Phytinsäure in Mengen von weniger als 0.1 mg, selbst wenn das Untersuchungsmaterial nahe verwandte Substanzen wie z. B.myo-Inositpentakisphosphat enthält.

     

Determination of lead in fresh and canned pineapple by isotope dilution mass spectrometry and isotope systematics

Pineapple stored in welded and soldered can was analysed for lead to assess the extent to which it is contaminated during processing and storage. To avoid contamination during analysis the samples were prepared in clean laboratory using ultra-clean procedures. The lead concentration was determined by isotope dilution mass spectrometry and the sources of lead were identified by their isotopic signature and quantified by isotope systematics. The results showed that the lead concentration in pineapple stored in the soldered cans (ca. 150 ng g^?1) was about 2.5 times that found in the welded cans and 60–80% of this lead was traced to the soldered joint using isotope systematics. The edible portion of a fresh pineapple contained < 0.85 ng g^?1 lead, showing that even pineapple in welded cans may be contaminated 80 times more than the natural level.     

Levels of mercury,cadmium, lead and other selected elements in canned tuna fish commercialised in Jordan

During 2010, the concentrations of mercury and eight other trace elements in 90 canned tuna samples commercialised in Jordan were determined using mercury analyser (Hydra C®) and the inductively coupled plasma-optical emission spectrometer (ICP-OES). The mean concentrations and ranges for elements analysed in mg?kg ^{? 1} (wet base) were as follows: total Hg (0.21; 0.06–0.57), Cd (0.06;?<?0.01–0.63), Pb (0.09; <0.04–0.24), total As (0.74; 0.11–1.56), Ni (0.51; 0.03–2.85), V (0.04; <0.03–0.1), Al (0.26; 0.08–1.63), Ba (0.13; 0.05–0.42) and Ag was not detected in any of the analysed samples (<0.02?mg?kg^?1). The data obtained in the present study compared well with data obtained from similar studies carried out in different parts of the world. Few samples had the mercury and cadmium levels slightly exceeding the Codex Committee on Food Additives and Contaminants draft guidelines. However, the estimated weekly intakes of these metals showed that there was no health risk associated with the consumption of the analysed canned tuna samples.     

分子印迹固相萃取检测罐装食品中双酚A

以双酚A为模板分子,3-氨基丙基乙氧基硅烷为功能单体,通过溶胶-凝胶反应合成双酚A分子印迹纳米硅胶微球。以印迹微球为固相萃取吸附剂,优化固相萃取条件,确定二氯甲烷为上样溶剂。固相萃取选择性实验表明,在双酚A及其结构类似物四溴双酚A、双酚C、壬基酚的混合物溶液中,印迹萃取柱对双酚A具有良好的选择性能,回收率达到90.7%。浓度为2.5和5μmol/L的加标罐装食品样品,经印迹萃取柱预处理,液相色谱检测得到回收率72%～84%,相对标准偏差2.9%～4.4%。     

A microfluidic "baby machine" for cell synchronization

Common techniques used to synchronize eukaryotic cells in the cell cycle often impose metabolic stress on the cells or physically select for size rather than age. To address these deficiencies, a minimally perturbing method known as the "baby machine" was developed previously. In the technique, suspension cells are attached to a membrane, and as the cells divide, the newborn cells are eluted to produce a synchronous population of cells in the G1 phase of the cell cycle. However, the existing "baby machine" is only suitable for cells which can be chemically attached to a surface. Here, we present a microfluidic "baby machine" in which cells are held onto a surface by pressure differences rather than chemical attachment. As a result, our method can in principle be used to synchronize a variety of cell types, including cells which may have weak or unknown surface attachment chemistries. We validate our microfluidic "baby machine" by using it to produce a synchronous population of newborn L1210 mouse lymphocytic leukemia cells in G1 phase.