Newsgroup: it.scienza.chimica
Titolo: ppm --> ug/L

Se di un metodo analitico mi si dice che ha la sensibilita' di 10 ppm,
esprimendola in ug/L che sensibilita' mi devo aspettare? 
Come si effettua la conversione?
Grazie 
B.

 ha scritto nel messaggio
news:3A080CB7...@maxidata.it...


 Considera che 1 ppm equivale ad 1 mg/l.
Attenzione che di solito l'unità ppm (parte per milione) sta per mg/kg
(se la si considera in volume, dovrebbe diventare mcl/l e non mg/l).
Quindi in un litro d'acqua, che pesa 1 kg (1 kg = 1 milione di mg) a 4°C
e 997 g a 25°C, 10 ppm sono effettivamente 10.000 mcg/l.
Ma non sarebbe così in un litro d'alcool etilico, che pesa 789 g a 20°C
(circa 8/10 il peso dell'analogo volume d'acqua).
Bye,
  -= Ginzo =-

> Considera che 1 ppm equilvale ad 1 mg/l.
in effetti bastava pensarci
1 g in un  g e' una parte su una 
1 g in un kg e' una parte su mille
1 mg in un kg e' una parte su un milione
1 ug in un kg e' una parte su un miliardo
Anche in italiano si sigla ppb?
Grazie ciao

 ha scritto nel messaggio
news:3A08BA3F...@flashnet.it...


 Anche in italiano si sigla ppb?
Certamente... proprio come te, visto che abitualmente
tu hai in attività un neurone su un bilione... ;-)))
Bye,
  -= Ginzo =-

 Anche in italiano si sigla ppb?
Aggiungo qualche referenza a supporto:
  [1] Biol Trace Elem Res 1989 Oct;22(1):9-15
 Gallium distribution in several human brain areas.
 Speziali M, Orvini E, Rizzio E, Giordano R, Zatta P, Favarato M, Perazzolo M
 CNR Centro di studio per la Radiochimica e l'Analisi per Attivazione,
 Universita di Pavia, Italy.
  Gallium is an element of increasing biological interest: It is involved
 in problems related to environmental pollution (Ga compounds are used in
 electronics industry) and to clinical treatments (Ga radionuclides are
 employed to detect neoplastic lesions). Moreover, since its chemical
 behavior is similar to that of aluminum, gallium could play a role in the
 health effects attributed to this element. Data on naturally occurring Ga
 levels in human samples from healthy subjects are scanty; regarding the
 brain, the only reliable values available in the literature were published
 by Hamilton in 1972/73. In this work, the gallium distribution in several
 human brain areas, evaluated by radiochemical neutron activation analysis
 (RNAA), was found to be dishomogeneous. The element concentration
 determined in dry samples was, in any case, lower than the ppb level.
                                                            ^^^
 PMID: 2484232, UI: 90334964
  [2] Boll Chim Farm 1992 May;131(5):193-8
 A gas-chromatographic determination of the ppb levels of volatile halogen-
 ated hydrocarbons in water for injections. ^^^
 Ziglio G, Beltramelli G, Montanari L, Cingolani E
 Istituto di Igiene, Universita di Milano, Italy.
  Some volatile halogenated hydrocarbons have been found in commercial large
 volume parenterals (LVPs) prepared from untreated or treated (disinfected)
 water. To monitor the presence of volatile halogenated hydrocarbons in
 the source water and also in the water for injections, a low cost and
 sufficiently simple procedure has been developed, specifically for the
 following components: 1,1,1 trichloroethane, 1,1,2 trichloroethylene,
 1,1,2,2 tetrachloroethylene, carbon tetrachloride, chloroform, dichloro-
 bromomethane and dibromochloromethane. A Head-space technique coupled with
 ECD-gaschromatography was used. The procedure is thoroughly discussed
 in the article, including the results of a ring test for a preliminary
 validation of this method.
 PMID: 1445685, UI: 93075493
  [3] Chemosphere 1998 Dec;37(14-15):2873-84
 Volatile halocarbons in a drinking water supply system: forecasting
 contamination values and estimating health risk.
 Crosta GF, Dotti M
 DISAT, Universita degli Studi, Milano, IT. 
giov...@alpha.disat.unimi.it
  The network, which supplies drinking water to the city of Milan, has a
 number of sampling points, where the concentrations of several contaminants
 are periodically measured. From the time series of total volatile halocarbon
 (VHC) concentration values (in the ppb range) autoregressive models can be
 obtained for each sampling point.  ^^^   A suitable figure of merit is
 minimized, which depends on the backcast error and on the model order.
 The best model is then applied to predicting concentration one time step
 e.g., one year, forward. The experimental data pertain to the years 1981
 to 1992. Predicted values are compared with the measured ones. The results
 obtained in 1991 contributed to avert a major emergency situation in Milan.
 Population exposure and the related health risk, based on the proportional
 dosage-response model, were also estimated. The excess casualty figure for
 Milan was computed. The method and the procedures described herewith may
 be used by public authorities to manage drinking water resources, whenever
 detailed models of the aquifer and of the network are not applicable.
 PMID: 9839405, UI: 99056784
Invece pPB è un plasmidio:
  [4] Gene 1998 Feb 16;208(1):37-42
 Two aberrant mercury resistance transposons in the Pseudomonas stutzeri
 plasmid pPB.
         ^^^
 Reniero D, Mozzon E, Galli E, Barbieri P
 Dipartimento di Genetica e di Biologia dei Microrganismi, Universita degli
 Studi di Milano, via Celoria 26, 20133, Milan, Italy.
  The two mer operons of the Pseudomonas stutzeri OX plasmid pPB and their
 flanking regions have been sequenced and found to be part of two aberrant
 transposons. The narrow spectrum mer operon is almost identical to that
 of Tn501, but is associated with the remnants of Tn5053 tni genes rather
 than the Tn501 transposition module. The broad spectrum mer operon shows
 an overall homology with that of Tn5053, but differs from it in the presence
 of a merB gene, absent in Tn5053, and a merC gene instead of a merF.
 The pPB broad spectrum mer operon is associated with an incomplete
 Tn5053-like transposition module and with the Tn501 tnp genes, which are
 proximal, respectively, to the end and to the beginning of the mer operon.
 A hypothesis about pPB evolution is presented.
 PMID: 9479042, UI: 98148002
Bye,
  -= Ginzo =-

   -= Ginzo =-
Ho capito ho capito, sono sinonimo di "molto poco". :-)
Aho' quando c'e' da scherzare tutti a dare la baia, invece a spiegarmi
come e perche' non e' vero che l' ICP-EAS e' migliore dell' AAS, nessuno
che si degni.
Nessuno di voi usa la spettrometria di emissione atomica al plasma in
matrici biologiche?  
Tanto l'anno prossimo l' AA col fornetto e l'effetto Zeeman (no pun,
please) mi arriva veramente, allora si' che ci divertiamo.
Ciao!

 please) mi arriva veramente, allora si' che ci divertiamo.
Sta' attento, che con Zeman finisci in panchina... ;-)
Bye,
  -= Ginzo =-

 dal sito della Varian (si leggono con Adobe Acrobat):
Ti ringrazio, buona parte di questa pur ottima roba l'avevo gia' trovata
anch'io, adesso chiedevo pareri di umani con esperienza diretta delle
due metodiche.  
Ciao
B.