Método colorimétrico para determinação de dióxido de nitrogênio atmosférico com preconcentração em coluna de c-18

An alternative analytical method for nitrogen dioxide (NO2) in atmosphere was developed. The collection of NO2 is performed by a Sep-Pack C-18 cartridge impregnated with 11% (v/v) of triethanolamine plus 3,6 % (v/v) of ethylene glycol plus 25 % (v/v) of acetone combined solution. When the impregnating is used, NO2 is collected with good repeatibility (CV = 3,3 %). The NO2 absorbed in the sampler was stripped from the sorbent with a methanol 5% (v/v) aqueous solution and was determined by colorimetry as nitrite by using the Griess-Saltzman reagent. The detection limit of 1,4 ppb for 60 min sampling at 0,5 L min-1 flow rate was obtained. Preparation and conditioning procedures for TEA-C-18 cartridge, sampling flow rate, absorption capacity and interference of other species are discussed.

A química do estanho no século 18, ou como uma consulta se transformou num projeto de pesquisa

An ominous suspicion arose in France in the second half of the 18th century, that household tin objects might be contaminated with arsenic. Charged with the task of studying and deciding the question, the chemists Pierre Bayen and Louis Charlard set up a comprehensive research project, which resulted in a book describing the whole enterprise. It is very gratifying to analyse this work today, for the many lights it sheds on the way chemistry was practised and reasoned at the time, and for the whiff of modernity we are presented with.

De cantico Israëlitarum ad Beerah, numer. XXI. 17. 18

Arkit: 1 arkintunnukseton lehti, A4 B1.

De vi vocabuli pneumatos, I Petr. III:18

Painovuosi nimekkeestä.

De petitione Naamanis Syri, II. Reg. cap. V. vers. 18

Invocatio: D.D.

Feoforbídeo (etoxi-purpurina-18) isolado de Gossypium mustelinum (Malvaceae)

The phaeophorbide ethyl ester named Purpurin-18 and the flavonoids quercetin and kaempferol were obtained by chromatographic procedures from the chloroform fraction of aerial parts of Gossypium mustelinum. The structure of these compound was determined by NMR, IR and mass spectra data analysis. This is the first occurrence of this compound in Angiosperm.

Työväen kokemusta tavoittamassa : : työväen historian ja perinteen tutkimuksen seuran kesäseminaari Työväki ja kokemus 18.-19.8.2008, Nurmijärvi

Ajankohtaista

Lähteneelle, op. 18 n:o 2

Ei vapaa, vapautuu 2027. Kosti Vehanen (1887-1957).

Gutenberg 18:1895

Gutenberg-lehti ilmestyi vuosina 1893-1915. Se oli perustettu ammattilehdeksi ja yhdyssiteeksi Suomen kirjanpainajille sekä äänenkannattajaksi Suomen kirjaltajaliitolle.

Gutenberg 18:1896

Gutenberg-lehti ilmestyi vuosina 1893-1915. Se oli perustettu ammattilehdeksi ja yhdyssiteeksi Suomen kirjanpainajille sekä äänenkannattajaksi Suomen kirjaltajaliitolle.