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2008 vol. 2
Food, Flavors & Fragrances
Concern over the presence of pesticides in food
products, particularly citrus, is growing, resulting
in an increasing number of countries regulating
insecticides such as carbamates. EPA Method
531.1 describes a method for the analysis of carba-
mates in water, but not in other commodities.
Matrices like citrus oil contain numerous interfer-
ences and often require time-consuming sample
preparation. However, the method described here
requires no sample preparation and provides fast
analysis times, significantly increasing sample
throughput.
Carbamates are most easily determined via HPLC
analysis because derivatization is required for GC
analysis. The rapid screening method shown here
uses the Ultra Carbamate HPLC column, which is
designed specifically for analyzing carbamates and
is compatible with both traditional detectors and
mass spectrometry. This column works well with
mass spectrometry amenable buffers and allows an
initial mobile phase composition of 20% organic,
which promotes complete ionization at the elec-
trospray source.
Orange oil was spiked at 10ppm with a carbamate
mix and analyzed (Figures 1-2). The monoisotopic
masses and retention times were compared to an
injected standard and found to match closely
(Table I). The high mass accuracy of the Leco
Unique TOF-MS allowed positive analyte identifi-
cation, even in a complex mixture containing
compounds with the same nominal mass (within 1
amu) as the target carbamate. By using the Ultra
Carbamate column in conjunction with the Leco
Unique TOF-MS, we were able to develop a quick,
easy, and accurate screening method for carba-
mates in a complex matrix such as orange oil.
References:
B. Mayer-Helm, L. Hofbauer, J. Muller. Rapid Communications in Mass
Spectrometry, 20 (2006), page 529-536
Rapid Screening Method for Carbamates in Orange Oil
Using an Ultra Carbamate HPLC Column
Julie Kowalski, Ph.D., Innovations Chemist
• Fast analysis times, for increased sample
throughput.
• Simple methodology saves time—
no sample preparation.
• Accurate mass identification, for definitive
results.
Figure 1
Reference standard carbamates resolve quickly on an
Ultra Carbamate HPLC column. (extracted ion chromatograms)
Figure 2
Positive identification of carbamates in orange oil injected
with no sample preparation. (extracted ion chromatograms)
Peak List:
1. aldicarb sulfone
2. aldicarb sulfoxide
3. oxamyl
4. methomyl
5. 3-hydroxycarbofuran
6. aldicarb
7. propoxur
8. carbofuran
9. carbaryl
10. methiocarb
11. BDMC (IS)
LC_FF0473
Sample: 531.1 Carbamate Pesticide Calibration Mix (cat.# 32273)
and Internal Standard 4-bromo-3,5-dimethylphenyl-N-methylcarbamate
(cat.# 32274), 50:50; Inj.: 1µL; Conc.: 50µg/mL;
Sample diluent: methanol
Column: Ultra Carbamate; Cat.#: 9177352;
Dimensions: 50mm x 2.1mm; Particle size: 3µm; Pore size: 100Å
Conditions:
Mobile phase: A: 2mM ammonium acetate:methanol, 90:10
B: 2mM ammonium acetate:methanol, 10:90
Time (min.)
%B
0
20
20
100
25
100
LC_FF0472
Sample:
531.1 Carbamate Pesticide Calibration Mix
(cat.# 32273) and Internal Standard
4-bromo-3,5-dimethylphenyl-N-methylcarbamate
(cat.# 32274) 50:50 spiked into unprocessed
orange oil at 10ppm
Inj.:
3µL
Conc.:
10ppm
Sample diluent: methanol
Matrix:
orange oil
calculated ion standard ion
standard orange oil ion orange oil
monoisotopic monoisotopic retention monoisotopic retention
mass
mass
time (min.)
mass
time (min.)
aldicarb sulfone
[M+H]+ 223.075
223.099
3.81
223.142
3.67
aldicarb sulfoxide [M+H]+ 207.080
207.103
4.31
207.122
4.09
oxamyl
[M+NH4]+ 237.102
237.085
4.97
237.110
4.41
methomyl
[M+H]+ 163.054
163.074
5.84
163.086
5.36
3-hydroxycarbofuran [M+H]+ 238.108
238.121
8.32
238.128
7.73
aldicarb
[M+H]+ 191.085
191.0728
11.92
116.052* 11.53
116.0751*
propoxur
[M+H]+ 210.113
210.152
13.53
210.153
13.14
carbofuran
[M+H]+ 222.113
222.140
13.98
222.120
13.66
carbaryl
[M+H]+ 202.087
202.084
15.48
202.101
15.17
methiocarb
[M+H]+ 226.090
226.097
19.22
226.060
19.12
BDMC
[M+H]+ 258.013
258.042
19.89
258.005
19.84
* m/z 116.052 is a fragment ion with higher intensity than the [M+H]+ ion and was used for
identification in orange oil
Table I
Carbamates were positively identified in matrix using both
retention time and mass.
Flow:
200µL/min.
Temp.:
ambient
Det.:
Leco Unique
®
LC/TOFMS
Interface:
ESI
Ion mode:
Positive
Temp.:
130°C
Nebulizer pressure: 100kPa
Desolvation gas (N2): 4,000cc/min.
Interface temp.:
120°C
Nozzle:
(+) 62V
Capillary:
(+) 2.75kV
Peak List:
1. aldicarb sulfone
2. aldicarb sulfoxide
3. oxamyl
4. methomyl
5. 3-hydroxycarbofuran
6. aldicarb
7. propoxur
8. carbofuran
9. carbaryl
10. methiocarb
11. BDMC (IS)
See Figure 1 for conditions.
Increase sample
throughput—
no sample prep
required!
3µm Column, 2.1mm
cat. #
price
50mm
9177352
Ultra Carbamate Column