Brazilian Journal of Analytical Chemistry - BRJAC - Brazilian Journal ...

edua r d o sidinei ch av e s, Ju l i a n o ca rva l h o ra m o s , Kl a i a n i bez Fo n ta n a, sa m u e l mo d o l o n, a n d ad i l s o n Jo s é cu rt i u s
Ta b l e ii. na an d k C o n C e n T r a T i o n s (a v e r a g e ± C o n f i d e n C e
i n T e r v a l, n=3) in r a w gl y C e r i n samples, a, C a n d e, d i l u T e d
w iT h 30% v/v n-pr o p a n o l in wa T e r or aC i d digesTed in a
m iC r o w a v e ov e n.
sa m p l e na (m g g -1 ) k (m g g -1 )
aCid digesTed di l u T e d aCid digesTed di l u T e d
30% v/v 30% v/v
n-p r o p a n o l n-p r o p a n o l
A 17 ± 2 19 ± 3 0.08 ± 0.01 < 0.08
C 0.33 ± 0.06 0.36 ± 0.03 30 ± 2 29 ± 6
E 0.69 ± 0.05 0.70 ± 0.03 30 ± 6 27 ± 3
3.5 an a l y T i C a l ap pl iC a T i on
Raw glycerin samples were produced by alkaline
catalysis using Na and K hydroxides. Four of the six
analyzed samples were obtained by transterification
of residual vegetable frying oil of unknown origin
and two samples were produced from industrialized
soy bean oils. The raw glycerin samples were
analyzed following the proposed procedure, that is,
sample dilution in 30% v/v n-propanol, calibration in
this same medium and detection by FAES, using Cs as
ionization suppressor. The Na and K concentrations
obtained are shown in Table III.
Ta b l e iii. na an d k C o n C e n T r a T i o n s (a v e r a g e ± C o n f i d e n C e
i n T e r v a l; n=3) in r a w gl y C e r i n samples ob T a i n e d fr o m
biodiesel pr o d u C T i o n us i n g naoh o r koh a s Ca T a l y s T s.
sa m p l e na (m g g -1 ) k (m g g -1 )
A 19 ± 3 < 0.08
B 0.48 ± 0.06 33 ± 2
C 0.36 ± 0.03 29 ± 6
D 16 ± 1 < 0.08
E 0.70 ± 0.03 27 ± 3
F 10 ± 1 92 ± 7
The two metal concentrations show great variations
in the different samples. The Na concentrations
varied from 0.7 mg g -1 to 16.3 mg g -1 . For K, the
lowest concentrations were below the quantification
limit, but above the detection limit. The highest K
concentration was 92.4 mg g -1 . The relatively high
concentrations of Na and K in sample F, may be due
to the material used, residual oil from frying. For the
other samples, the catalyst used in the biodiesel production,
if sodium or potassium hydroxide, seems to
control the residual Na or K concentrations in the raw
glycerin, even for the ones produced from frying oils.
It is clear that samples A and D were produced using
sodium hydroxide, while samples B, C and E used
potassium hydroxide in their production. The high K
concentration in sample F indicates that potassium
hydroxide was used for producing this sample, even
if the Na concentration is also relatively high, probably
due to the frying oil used as raw material.
4. co n c l u s I o n s
The determination and control of residual Na and K
concentrations in glycerin is very important to allow
its application as a component of different products.
The proposed analytical procedure, which requires a
simple sample dilution in 30% v/v n-propanol prior to
determination by FAES, using calibration standards
solutions prepared in the same medium, is easy, accurate
and requires common non-expensive instrumentation.
The procedure can be easily applied to
routine analysis of raw glycerin.
AcK n o w l e d g e m e n t s
The authors are thankful to Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq,
Brazil) for financial support. Chaves, Curtius and Ramos
have felloships from CNPq. The authors thank
the Universidade do Sul de Santa Catarina (UNISUL)
for supplying the samples.
ref e re n c e s
1. Geris, R.N.; dos Santos, A.C.; Amaral, B.A.; Maia, I.S.;
Castro, V.D.; Carvalho, J.R.M. Quim. Nova, 2007, 30,
1369.
2. Agarwal, A.K.; Prog. Energy. Combus. Sci. 2007, 33,
233.
3. Ramadhas, A.S.; Jayaraj, S.; Muraleedharan, C.; Renew.
Energy, 2004, 29, 727.
4. Xie, W.; Huang, X.; Catal. Lett. 2006, 107, 53.
5. Felizardo, P.; M.J.N. Correia,; Raposo, I.; Mendes, J.F.;
Berkemeier, R.; Bordado, J.M.; Waste Manag. 2006.26,
487.
6. Pinto, A.C.; Guarieiro, L.L.N.; Rezende, M.J.C.; Ribeiro,
N.M.; Torres, E.A.; Lopes, W.A.; Pereira, P.A.P.; de Andrade,
J.B.; J. Braz. Chem. Soc. 2005, 16, 1313.
7. De Souza, R.M., Master Thesis, Pontifica Universidade
Católica do Rio de Janeiro, Brazil, 2003.
8. Agência Nacional do Petróleo, Gás Natural e Biocombustíveis
(ANP), Resolução ANP Nº 7, DE 19.3.2008
- DOU 20.3.2008. http://nxt.anp.gov.br/nxt/gateway.
dll/leg/resolucoes_anp/2008/mar%C3%A7o/ranp%
207%20-%202008.xml, acessed in July, 2010.
9. Agência Nacional do Petróleo, Gás Natural e Biocombustíveis
(ANP), LEI Nº 11.097, DE 13.1.2005 - DOU
14.1.2005. http://nxt.anp.gov.br/NXT/gateway.dll/leg/
leis/2005/lei%2011.097%20-%202005.xml, accessed
in semptember 2010.
10. Salvador Á. F.; Machado A. S.; Santos, E. P.; Rede
Brasileira de Tecnologia de Biodiesel, Brasília, 2006.
http://www.biodiesel.gov.br/docs/congressso2006/Co-
58 Br J Anal Chem