PMID- 25318462
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20150528
LR  - 20160512
IS  - 1618-2650 (Electronic)
IS  - 1618-2642 (Linking)
VI  - 407
IP  - 11
DP  - 2015 Apr
TI  - Long-term stability monitoring of pH reference materials using primary pH method.
PG  - 3249-52
LID - 10.1007/s00216-014-8263-0 [doi]
AB  - This work presents the results from a series of stability studies for some 
      batches of different aqueous pH reference materials, packed in high-density 
      polyethylene (HDPE) bottles, taking primary pH measurements over long periods 
      (time lengths from 18.4 to 21.0 months). The results obtained over time for acid 
      and neutral buffer solutions (nominal pH values of 1.68, 4.00, and 6.86 at 
      25  degrees C), considering their uncertainties, were statistically similar, 
      demonstrating the high stability of these materials. On the other hand, for the 
      alkaline buffer solutions (nominal pH values of 9.18 and 10.01 at 25  degrees C), there 
      was a clear decrease in the results over time, with pH variation rates around 
      -8.5 x 10(-4) per month. The results showed that reference materials of the acid 
      and neutral buffer solutions can be easily provided with small uncertainty values 
      and long shelf lives in simple HDPE bottles closed under air atmosphere, whereas 
      reference materials of the alkaline buffer solutions must have more limited shelf 
      lives and higher uncertainty values (taking into account the pH decrease over 
      time) or must be provided in special packaging (such as ampoules) to prevent 
      carbon dioxide interference.
FAU - Gonzaga, Fabiano Barbieri
AU  - Gonzaga FB
AD  - Chemical Metrology Division, National Institute of Metrology, Quality and 
      Technology (INMETRO), Av. Nossa Senhora das Gracas, 50, Xerem, 25250-020, Duque 
      de Caxias, RJ, Brazil, fbgonzaga@inmetro.gov.br.
FAU - Dias, Julio Cesar
AU  - Dias JC
LA  - eng
PT  - Journal Article
DEP - 20141016
PL  - Germany
TA  - Anal Bioanal Chem
JT  - Analytical and bioanalytical chemistry
JID - 101134327
EDAT- 2014/10/17 06:00
MHDA- 2014/10/17 06:01
CRDT- 2014/10/17 06:00
PHST- 2014/09/02 00:00 [received]
PHST- 2014/10/08 00:00 [accepted]
PHST- 2014/10/03 00:00 [revised]
PHST- 2014/10/17 06:00 [entrez]
PHST- 2014/10/17 06:00 [pubmed]
PHST- 2014/10/17 06:01 [medline]
AID - 10.1007/s00216-014-8263-0 [doi]
PST - ppublish
SO  - Anal Bioanal Chem. 2015 Apr;407(11):3249-52. doi: 10.1007/s00216-014-8263-0. Epub 
      2014 Oct 16.