Journal of Analytical Sciences, Methods and Instrumentation, 2011, 1, 31-36
doi:10.4236/jasmi.2011.12005 Published Online December 2011 (http://www.SciRP.org/journal/jasmi)
31
Determination of Di-n-Butyl Phosphate in Organic
Streams of FBTR Mixed Carbide Fuel Reprocessing
Solution by Gas Chromatographic Technique
P. Velavendan, S. Ganesh, N. K. Pandey, U. Kamachi Mudali, R. Natarajan
Reprocessing Group, Indira Gandhi centre for Atomic Research, Kalpakkam, India.
Received September 20th, 2011; revised October 25th, 2011; accepted November 16th, 2011.
ABSTRACT
The present work describes the amount of Di-n-butyl phosphate (DBP) produced when PUREX solvent (30% tri-n-butyl
phosphate (TBP) mixed with 70% hydrocarbon diluent) is exposed to intensive radiolytic and chemical attack during
the separation of uranium and plutonium from fission products of FBTR mixed carbide fuel reprocessing solution. DBP
is the major degradation product of Tri-n-butyl phosphate (TBP). Amount of DBP formed in the lean organic streams of
different fuel burn-up FBTR carbide fuel reprocessing solutions were analyzed by Gas Chromatographic technique. The
method is based on the preparation of diazo methane and conversion of non-volatile Di-n-butyl phosphate in to volatile
and stable derivatives by the action of diazomethane and then determined by Gas Chromatography (GC). A calibration
graph was made for DBP over a concentration in the range from 200 to 1800 ppm with correlation coefficient of
0.99587 and RSD 1.2%. The degraded 30% TBP-NPH solvent loaded with heavy metal ions like uranium was analyzed
after repeated use and results are compared with standard ion chromatographic technique. A column comparison study
to select of proper gas chromatographic column for the separation of DBP from other components in a single aliquot of
injection is also examined.
Keywords: Gas Chromatography, Flame Ionization Detector, Diazomethane, Di-n-Butyl Phosphate, PUREX Process,
Degradation of TBP, Lean Organic Streams, Carbide Fuel
1. Introduction
Tributylphosphate (TBP) is the most popular reagent in
liquid-liquid extraction. Di-n-butyl phosphate (DBP) is
one of the degradation products of Tri-n-butyl phosphate
(TBP) ((C4H9O)3P = O), used in the well known PUREX
(Plutonium Uranium Refining by Extraction) process [1]
for the separation of uranium and plutonium from fission
products in nuclear fuel reprocessing. During the solvent
extraction process the solvent TBP undergoes degrada-
tion by hydrolysis and radiolysis yielding mainly Di
-n-butyl phosphate (DBP) ((C4H9O)2P = O-(OH)), to a
lesser extent monobutylphosphate (MBP) ((C4H9O)P = O-
(OH)2), phosphoric acid and butanol [2]. The DBP com-
plexes with Zr, Pu and other metal ions [3] which leads
to loss of heavy metals to lean organic stream. Hence the
quality of PUREX solvent is generally measured in terms
of the concentration of DBP. Various analytical methods
were reported in the literature for the determination of DBP.
Bocek et al. [4] have used high-speed Isotachophoresis, a
form of capillary electrophoresis with conductivity detec-
tion, to analyze TBP for its degradation products in solu-
tions containing nitrates and nitrites. Muller et al. [5] have
determined trace amounts of DBP and TBP in nuclear
fuel reprocessing solutions by Liquid Chromatography [6]
while Wilkinson and Williams [7] determined DBP and
MBP by direct titration of irradiated TBP samples. The
latter method fails in presence of nitric acid. Krishna-
murthy and Sampathkumar [8] have used titrimetry to
determine DBP and MBP as degradation products in the
two component TBP-nitric acid system. Grant et al. [9]
have performed the separation and measurement of TBP,
DBP and MBP by Ion-pair Chromatography with refrac-
tive index detection. Infra Red Spectroscopy is used [10]
for determination of DBP concentration in the solvent
based on the P=O absorption at 1230 cm–1 with a poor
detection limit due to interferences from the TBP. Tech-
niques [11] of ionization at atmospheric pressure, i.e., elec-
trospray (ESI) or atmospheric pressure chemical ionization
(APCI) with Mass Spectrometry (MS) have been used

Determination of Di-n-Butyl Phosphate in Organic Streams of FBTR Mixed Carbide Fuel Reprocessing Solution by
32
Gas Chromatographic Technique
for the direct quantification of MBP and DBP in a TBP
matrix, without any prior separation. Recently use of
ligand-sensitized Fluorescence Spectroscopy [12] is re-
ported for the determination of DBP in TBP/dodecane
solutions with Tb3+ as the fluorescent. This method is suit-
able for the determination of DBP over the concentration
of 0.1% - 10% DBP in TBP. Among the various methods
of analysis, application of chromatographic methods has
gained wider acceptance owing to their high sensitivity
and greater resolving power [13] Gas Chromatography
(GC) is the most widely used technique for the determi-
nation of DBP, mainly in the organic phase. Hardy et al.
[14] showed that DBP could be analyzed by gas chroma-
tography of the corresponding methyl esters formed by
reaction with diazomethane. Brignocchi et al. [15] devel-
oped the gas chromatographic method of Hardy [16,17]
into a quantitative procedure for the determination of
DBP and MBP in various organic streams [18,19]. Ex-
perimental details and results obtained by this method are
described in this paper
2. Experimental
2.1. Reagents
Tri-n-butyl phosphate (Merck) and Di-n-butyl phosphate
(Fluka). All other chemicals used were of AR or GR grade.
Diazomethane was prepared immediately before use
from a precursor in the laboratory fume hood and stored
in refrigerator. The precursor used in the present study is
N-methyl-N-nitroso-p-toluenesulfonamide (Diazald)
2.2. Instrumentation
A Shimadzu Gas chromatograph model 14 B equipped
with a Flame Ionization Detector (FID) was used to de-
tect the eluted components. Metrhom IC Net 2.3 software
is used for data acquisition. A stainless steel column of 4
meters long and 1/8’’ dia packed with 10% XE-60 was used
for the separation of components. Nitrogen gas with a flow
rate of 30ml/min was used as carrier gas. Hydrogen gas
and zero air with a flow rate of 30 and 300ml/min were
respectively used to generate flame. Column, Injector and
detector temperatures were 230˚C, 260˚C and 260˚C re-
spectively.
3. Gas Chromatographic Condition
Gas chromatograph: Shimadzu GC model 14 B
Analytical Column: Stainless steel packed column
Liquid phase: 10% XE-60
Nature of the column: Polar
Length: 4 meters
Diameter: 1/8”
Solid: Anakrom-ABS
Mesh range: 60/80
Maximum column
operating temperature: 250˚C
Column temperature : 230˚C
Injector temperature: 260˚C
Detector temperature: 260˚C
Fuel gas: Hydrogen
Supporting gas: Zero air
Carrier gas: Nitrogen
Carrier gas flow rate: 30 ml/min
Hydrogen gas flow rate: 30 ml/min
Zero Air flow rate: 300 ml/min
Detector: Flame Ionization Detector
Detector range: 2
Detector polarity: 1
Analytical mode: Isothermal
Injection volume: 5 μL
Run time: 15 min
Quantitation: Peak area
3.1. Preparation of Diazomethane
Diazomethane (CH2N2) is the most common methylat-
ing reagent for carboxylic acid and has found wide ap-
plication in the methylation of phenols, enols, and hetero-
atoms such as nitrogen and sulfur. Diazomethane is easy
to prepare and use. It is prepared immediately before use
from a precursor, after addition of base. The precursor used
in the present study is N-methyl-N-nitroso-p-toluenesul-
fonamide.
Preparation and handling of diazomethane requires
special precautions because it is a highly explosive gas at
room temperature. Diazomethane gas may explode vio-
lently even if it is diluted with nitrogen (OSHA, US De-
partment of Labor). Contact with sharp or rough surfaces,
or heat may cause diazomethane to explode. Diazome-
thane is a severe pulmonary irritant and causes coughing,
fever, fulminating pneumonia, and death on humans. High
velocity ventilation in the working area involving diazo-
methane is needed to guarantee minimum exposure to
diazomethane. Diazomethane was prepared by the use of
specially designed glassware kit (Aldrich Diazald Appa-
ratus) in order to avoid accidental explosion of CH2N2
with sharp or rough surfaces. A safety shield was placed
in the highly ventilated reaction hood to provide maxi-
mum isolation from exposure to diazomethane and pos-
sible explosion. The receiving flask was surrounded by a
NaCl-ice bath (33% NaCl by weight) giving a cool envi-
ronment at about –20˚C because diazomethane is a gas at

Determination of Di-n-Butyl Phosphate in Organic Streams of FBTR Mixed Carbide Fuel Reprocessing Solution by 33
Gas Chromatographic Technique
room temperature and liquifies at –23˚C (density 1.45),
and freezes at –145˚C. Ethanol (10 ml) was added into
KOH solution in the reaction flask, which was prepared
by dissolving potassium hydroxide (5 g) in water (8 ml).
The solution of Diazald (5.0 g Diazald in 45 ml ether)
was added in the reaction flask, and was heated to 65˚C.
The rate of addition of Diazald solution was approxi-
mately the rate of distillation. Some extra ether was ad-
ded in the reaction flask after the Diazald solution was used
up in order to trap the entire diazomethane in the receiv-
ing flask. The reaction was terminated when the distillate
become colorless. The strength of diazomethane was de-
termined Spectrophotometrically at 410 nm where its ex-
tinction coefficient, ε, is 7.2.
3.2. Procedure
Stock solution of DBP was prepared in n-dodecane and
from this stock solution various concentration of DBP was
diluted in n-dodecane and treated with diazomethane so-
lution which was prepared immediately before use from
a precursor. Solution was warmed at 60˚C using a water
bath. The ether and the excess diazomethane were evapo-
rated by the flow of nitrogen gas through the solution.
After the conversion of DBP into its methyl ester, solu-
tion was injected into Gas chromatograph using Hamilton
microliter syringe.




4922493 2
22
C H OPOOHCHNCH OPOOCHN 
DBP Diazomethane MDBP
Radioactive lean organic solutions of various burn-up
of FBTR mixed carbide fuel reprocessing solution was
washed with 2N sulphuric acid to remove any heavy me-
tal ions and then subsequently treated with diazomethane
before injection in to Gas chromatograph.
In another experiment degraded solvent of repeatedly
used 30% TBP-NPH phase loaded with 70 g/L concen-
tration of uranium was analyzed for its DBP content by
this procedure. 3 ml of organic phase was equilibrated
twice with 0.01 M nitric acid and subsequently washed
twice with 2N sulphuric acid to remove heavy metals.
Then 0.25 ml of organic phase was taken in a 5 ml stan-
dard flask and made up to the mark with n-dodecane.
From this 0.2 ml of aliquot was taken in a 15 ml centri-
fuge tube and followed the above procedure to determine
the concentration of DBP.
3.3. Studies on the Selection of Gas
Chromatographic Column for
DBP Separation
Studies were carried out to find best gas chromatographic
column for the separation of DBP from hydrocarbon
peaks (C10 to C14) and TBP in a single aliquot of inject-
tion. Columns of different stationary phases SE-30 and
XE-60 were taken for studies. Detailed column parame-
ters were described in Table 1
4. Results and Discussion
Diazomethane is an ideal derivatization reagent. The reac-
tion is fast, the yield is high, side reactions are minimal,
the by-product is nitrogen gas and reaction conditions are
very mild. Diazomethane is a yellow gas so the progress
of the reaction can be easily is followed. The reaction for
the conversion of DBP to methyl ester is outlined below:
Table 1. Comparison of Column parameters used for the
separation of DBP from other components.
Properties of Column XE-60 SE-30
Material S.S packed column S.S packed column
Liquid phase 10% XE-60 10% SE-30
Nature Polar Non-Polar
Length 4 meters 4 meters
Diameter 1/8” 1/8”
Solid Anakrom-ABS ChW/HP
Mesh range 60/80 60/80
Maximum
Temperature 250˚C 300˚C
Column temperature 230˚C 230˚C
Injector temperature 260˚C 260˚C
Detector temperature 260˚C 260˚C
Fuel gas Hydrogen Hydrogen
Supporting gas Zero air Zero air
Carrier gas Nitrogen Nitrogen
Carrier Gas flow rate 30 ml/min 30 ml/min
Hydrogen gas flow rate 30 ml/min 30 ml/min
Zero Air flow rate 300 ml/min 300 ml/min
Detector FID FID
Detector range 2 2
Detector polarity 1 1
Analytical mode Isothermal Isothermal
Injection volume 5 μL 5 μL
Run time 15 min 15 min
Quantitation Peak area Peak area

Determination of Di-n-Butyl Phosphate in Organic Streams of FBTR Mixed Carbide Fuel Reprocessing Solution by
34
Gas Chromatographic Technique
Two of the protons in the resulting methyl ester origin-
nate from the diazomethane. The other one is the donated
acidic proton from the DBP. A calibration graph (Figure
1) was made for DBP concentration in the range from
200 to 1800 ppm in n-dodecane with correlation coeffi-
cient of 0.99587 and RSD 1.2% and each standard was
esterified using diazomethane procedure as described above.
By using this calibration graph the concentration of DBP
present in the unknown samples were calculated. Table 2
gives results of gas chromatographic determination of DBP
and TBP in radioactive lean organic streams of various
fuel burn-up of FBTR carbide fuel reprocessing solution.
The table confirms that the TBP percentage remains more
or close to 30% and the concentration of DBP is fairly
high, its concentration depends on strength of the nitric
acid, concentration of plutonium and contact time during
the solvent extraction process. The higher DBP concen-
tration in the low burn-up fuel is probably due to delayed
stripping of heavy metal ions during the commissioning
of the reprocessing plant with low burn-up fuel. Figure 2
Figure 1. Typical calibration graph for the determination of
DBP by gas chromatographic technique after methylation
using diazomethane.
Table 2. Results of gas chromatographic determination of
DBP and TBP in lean organic streams of various fuel burn-
up of FBTR mixed carbide fuel reproce ssing solution.
S.No Fuel Burn-up
(MWd/T)
Nature of the
sample
% of TBP
determined
Conc. of DBP
(g/L)
1 Low burn-up Lean Organic29.971 2.654
2 25000-1 Lean Organic29.508 1.664
3 25000-2 Lean Organic29.383 2.387
01 23 4 56 7 8 910111213 min
500
1000
mV
ch1
DBP
Figure 2. Typical Gas chromatogram of standard Di-n-
butyl phosphate (1. 659 g/L).
shows the typical gas chromatogram of standard DBP
(1.659 g/L) after methylation using diazomethane. Figure
3 refers the typical gas chromatogram of DBP and TBP
in radioactive lean organic solvent of FBTR carbide fuel
(25,000 MWD/T burn-up) reprocessing solution. In Fig-
ures 2 and 3 the DBP peak was well separated from hy-
drocarbon and TBP peaks respectively with the separa-
tion factor (α) greater than 1. Table 3 shows the results of
comparison of Gas Chromatographic and Ion chroma-
tographic methods from repeatedly used degraded 30%
TBP-NPH solvent loaded with uranium. Errors estimated
in the present gas chromatographic method is about 5%.
All the estimated values of different concentration range
of DBP were higher in GC than the estimated values of
DBP by IC. This positive error in GC estimation of DBP
may be due to pre-concentration of the solution during
the conversion of DBP into its methyl ester under hot
condition. The peak area obtained was compared with
standard calibration graph of DBP obtained by injecting
DBP standards every day after methylation using diazome-
thane. The relative standard deviation was 1.2% for the
repeated nine injections. Tab le 1 refers the comparison of
column parameters used for the separation of DBP from
other components. The column selection studies carried
out for the separation of DBP is reveal that the best col-
umn is XE-60 than SE-30. This is due to the polar nature
of column XE-60 separates the non polar hydrocarbon
(C-10 to C-14) peaks as a single peak from DBP and
TBP (Figure 2 and 3), hence there is no interference of
hydrocarbon peak for the separation, identification and
quantitative estimation of DBP in the degraded solvent
using XE-60. Whereas non polar nature of column SE-30,
hydrocarbons C10 to C14 (non polar) peaks were indi-
vidually well separated. It was found that use of column
SE-30 the retention time of peak C-14 (tetradecane, re-
tention time 4.5 min) and the retention time of DBP peak
were same. Therefore SE-30 column is not suitable for the

Determination of Di-n-Butyl Phosphate in Organic Streams of FBTR Mixed Carbide Fuel Reprocessing Solution by 35
Gas Chromatographic Technique
01 2 3 4 56 7 8 910min
200
400
600
ch1
mV
DBP
TBP
Figur3.pical Gasra oB(1.664 g
able 3. Estimated values of DBP by present method and
Concentration of DBP(g/L) estimated by
e Ty chromatogmf DP /L) &
TBP (29.51%) in lean organic solution of FBTR mixed car-
bide (25,000 MWD/T Burn-up) reprocessing solution.
T
Ion chromatographic method.
Sample no Gas chromatography method Ion-chromatography
a
(described in this work)
method
1 14.71 14.42
2 7.82 7.45
3 2.63 2.41
aError the estimates by Gaatographic method is a.
ualitative and quantitative estimation of DBP in pres-
ntent in the radioactive lean organic
s
incere thanks to Shri S. C.
REFERENCES
[1] W. W. W. Sch. D. Navratil, “Sci-
Determination
s ins chrombout 5%
q
ence of various hydrocarbons particularly diluent NPH
(Normal Paraffin Hydrocarbon) in the degraded solvent of
reprocessing plants.
5. Conclusions
Analysis of DBP co
streams of FBTR mixed carbide fuel reprocessing solu-
tions by gas chromatography method was demonstrated.
It is simple, only needs the conversion of DBP into its
methyl ester prior to injection. The major advantage of GC
method is the simultaneous determination of MBP, DBP
and TBP and hydrocarbons in a single aliquot without any
interference using 10% XE-60 column. The reproducibil-
ity and linearity of the method suggest that it is well sui-
table for the determination of DBP over a concentration
in the range from 200 to 1800 ppm and relevant to organic
streams of purex process.
6. Acknowledgement
Authors wish to express their s
Chetal, Director, IGCAR for motivating them to excel.
The authors are also thankful to Shri. M. Venkataraman,
Head, RPOD, for the encouragement provided during the
course of this work.
ulz, L. L. Burger and J
ence and Technology of Tributylphosphate,” Applications
of Tributyl Phosphate in Nuclear Fuel Processing, CRC
Press, London, Vol. 3, 1990, pp. 267-327.
[2] A. Petru, P. Rajec, R. Cech and J. Kuruc, “
of Radiolytic Products of Two-Phase Tributylphos Pha-
te—Water Systems by Capillary Isotachophoresis,” Jour-
nal of Radioanalytical and Nuclear Chemistry, Vol. 129,
No. 2, 1989, pp. 229-232.
doi:10.1007/BF02039819
[3] T. Tsujino and I. Ishihara, “Radiation Damage to TBP/-
Kerosene Solvent, (II),” Journal of Nuclear Science and
Technology, Vol. 3, No. 4, 1966, pp. 144-149.
doi:10.3327/jnst.3.144
[4] P. Bocek, V. Dolnik, M. Deml and J. Janak, “Separation
673(00)96825-0
and Determination of the Degradation Products of Tribu-
tyl Phosphate by High-Speed Analytical Isota Chophore-
sis,” Journal of Chromatography A, Vol. 195, No. 2,
1980, pp. 303-305.
doi:10.1016/S0021-9
e, Analyst, Vol. 13,
. Hill, “Ion Chromatographic Deter-
[5] M. P. Muller, J. Cojean and A. Delog
No. 1985, pp. 160.
[6] R. P. Lash and C. J
mination of Dibutylphosphoric Acid in Nuclear Fuel Re-
processing Streams,” Journal of Liquid Chromatography
& Related Technologies, Vol. 2, No. 3, 1979, pp. 417-427.
doi:10.1080/01483917908060072
[7] R.W. Wilkinson and T. F. Williams, “801. The Radiolysis
of Tri-n-Alkyl Phosphates,” Journal of the Chemical So-
ciety, 1961, pp. 4098-4107. doi:10.1039/jr9610004098
[8] M. V. Krishnamurthy and R. Sampathkumar, “Radia-
tion-Induced Decomposition of the Tributyl Phos-
phate-Ni- tric Acid System: Role of Nitric Acid,” Journal
of Radioanalytical and Nuclear Chemistry, Vol. 166, No.
5, 1992, pp. 421-429. doi:10.1007/BF02167787
[9] K. E. Grant, G. M. Mong, S. A. Clauss, K. L. Wahl and J.
A. Campbell, “Determination of Monobutyl Phosphate
and Dibutyl Phosphate in Mixed Hazardous Wastes by
Ion-Pair Chromatography,” Journal of Radioanalytical
and Nuclear Chemistry, Vol. 220, No. 1, 1997, pp. 31-35.
doi:10.1007/BF02035343
[10] L. Stieglitz, W. Ochsenfeld and H. Schieder, “The Influ-
H. Virelizier, C. Moulin, J. C. Tabet and
Analytical Chemistry, Vol. 72, No. 6, 2000, pp. 1186-
ence of the Radiolysis of Tributyl Phosphate on the
Plutonium Yield in the Purex Process for High Plutonium
Content,” KfK-691, Karlsruhe Nuclear Research Center,
1968.
[11] C. Lamouroux,
C. K. Jankowski, “Direct Determination of Dibutyl and
Monobutyl Phosphate in a Tributyl Phosphate/Nitric Aque-
ous-Phase System by Electrospray Mass Spectrometry,”

Determination of Di-n-Butyl Phosphate in Organic Streams of FBTR Mixed Carbide Fuel Reprocessing Solution by
Gas Chromatographic Technique
36
1191.
doi:10.1021/ac990613y
[12] S. Maji and K. S. Viswa
rescence of Tb3+ in Tb
nathan, “Ligand-Sensitized Fluo-
3+ Dibutylphosphate Complexes:
Application for the Estimation of DBP,” Spectrochimica
Acta, Part A, Vol. 64, 2006, pp. 972-976.
doi:10.1016/j.saa.2005.09.006
[13] S. C. Tripathi and P. Bindu, “Studies on th
of Harmful Radiolytic Produ
e Identification
cts of 30% TBP-n-Do-
decane- HNO3 by Gas Liquid Chromate Graphy I. For-
mation of Diluent Degradation Products and Their Role
in Plutonium Retention Behaviours,” Separation Science
and Technology, Vol. 36, No. 7, 2001, pp. 1463-1478.
doi:10.1081/SS-100103882
[14] C. J. Hardy, “Analysis of Alkyl Esters of Phosphoricac
by Gas Chromatography,” Jo
id
urnal of Chromatography A ,
Vol. 13, 1964, pp. 372-376.
doi:10.1016/S0021-9673(01)95133-7
[15] A. Brignocchi and G. M. Gasparini, “
tographic Determination of the Deco
The Gas Chroma-
mposition Products
of Tributyl Phosphate,” Analytical Letters, Vol. 6, No. 6,
1973, pp. 523-530. doi:10.1080/00032717308058700
[16] J. Glastrup, “Diazomethane Preparation for Gas Chroma-
tographic Analysis,” Journal of Chromatography A, Vol.
827, No. 1, 1998, pp. 133-136.
doi:10.1016/S0021-9673(98)00745-6
[17] C. J. Hardy and D. Scargill, “Studies on Mono- and
Di-n-Butylphosphoric Acids. II the Solubility and Distri-
bution of Mono- and Di-n-Butylphosphoric Acids in
Aqueous-Organic Solvent Systems,” Journal of Inorganic
and Nuclear Chemistry, Vol. 11, No. 2, 1959, pp. 128-
143. doi:10.1016/0022-1902(59)80057-9
[18] P. Velavendan, S. Ganesh, N. K. Pandey, U. Kamachi
and R. Nata-
Mudali and R. Natarajan, “Gas Chromatographic Deter-
mination of Di-n-Butyl Phosphate in Radioactive Lean
Organic Solvent of FBTR Carbide Fuel Reprocessing,”
Nuclear and Radiochemistry Symposium, Visakhapatnam,
Vol. 1, 22-26 February 2011, pp. 250-251.
[19] P. Velavendan, N. K. Pandey, U. K. Mudali
rajan, “Ion Chromatographic Determination of Di-n-Butyl
Phosphate in Degraded Organic Solvent,” Nuclear and
Radiochemistry Symposium, Visakhapatnam, Vol. 1,
22-26 February 2011, pp. 234-235.