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Using an API 3200™Mass Spectrometer and an Ultra Quat HPLC Column
Houssain EI Aribi, Ph.D., LC/ MS Product and Application Specialist, MDSSCIEX* , BeckyWittrig, Ph.D., HPLC Product Manager, C.Vernon Bartlett, HPLCR&D Scientist,
and Julie Kowalski, I nnovations Team Chemist, Restek Corporation
• Complete resolution of paraquat
&
diquat
- with a simple, isocratic mobile phase!
Superior sensitivity-Sppb paraquat or
0.1 ppb diquat-without preconcentration.
• Significantly faster than
conventiona l methodologies.
Restek chemists designed the Ultra Quat HPLC
column specifically for analyses of qua ternary
amine compounds. This uniq ue column makes
possible a simple HPLClUV analysis for paraquat
and diquat ' - a significant improve ment over alter
native methodologies. Now, in collabora tion with
scientists at MDS Sciex, we have developed a fast,
highly sensitive
LC/MS
method for analyzing these
challenging target compounds.
Charged quatern ary amines, such as paraquat and
diquat, exhibit little or no retention on C18 or
other alkyl stationary phases. In our HPLC/UV
procedure, our Ultra Quat mobi le phase modifier
(Ultra Quat Reagent Solution, cat.# 32441) increas
es the interactions between paraquat and diquat
and the Ultra Quat stationary phase, providing the
necessary retention and resolution. For comp atibil
ity with MS detection, however, we needed a
volatile mobile phase additive. Low concentrations
of heptafluorobutyr ic acid (HFBA) effectively
shield the positive charges of paraquat and diquat ,
increasing interactions between the quatern ary
amines and the Ultra Quat stationary phase.
Figur e 1 shows the excellent sepa rat ion of
paraq uat and diquat, at a concentratio n of SJ.lglmL
each in water, achieved by using an API 3200" 1
mass spectrometer. We used multiple reaction
monitoring (MRM) - a standa rd technique for
quantitative
LC/MS/MS
-
for this application. In
MRM, pairs of target precursor ions and unique
fragment ions are used for quick and accurate
identification of target species. Collision induced
Figure 1
Fast, sensitive LCiMS/MSanalysis of paraquat and
diquat, using an API 3200'" mass spectrometer and an
Ultra Quat HPLC column.
Peak Ust
1.
diquat
2. paraquat
Paraquat and diquat herbicides
Sample:
Inj.:
lOI1L
"D-C~
7~
"
CB3 - N _
_
N-CB3' 2CI
Cone.:
5119/ mL
eachcomponent
Sample diluent: DI water
Sample temp.: ambient
paraquat dichloride [CAS# 1910-42-51
Column:
Ultra Quat
(cal.# 5181352)
Dimensions:
50
x
2.1 mm
Particle size:
311rTl
diquat dibromide
[CAS
#
85-00-71
Pore size:
100A
ICEV0333
Conditions:
Mobile phase: 10mMheptafluorobutyric acid:acetonitrile, 95:5
(v/v)
Flow:
0.3mL/ min.
Temp.:
ambient
Del.:
Applied Biosystems API 3200
Interface:
electrospray
IonMode:
positive
Temp.:
600'C
Ion
Spray"
voltage:
5500V
Collisionexit
potential:
3V
Curtain
Gas":
15psi
Gas supply 1: 70psi
Gas supply 2: 60psi
Quantitation:
(MRM)
Ql/Q3:
unit resolution
Dwell time:
200ms
Precursor Ion
Fragment Ion
CollisionEnergy
DP
(amu)
(amu)
(V)
(eV)
diquat, 183+
157+
30
30
paraquat, 93(2+)
171+
20
20
*Data courtesy of Houssain EI Aribi, Ph.D., LC/ M5 Product and ApplicationSpecialist, MDS SCIEX, 71 Four
Valley Drive, Concord,Ontario, Canada, L4K4V8
2006.03
800-356-1688 •
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