Food, Flavors, & Fragrances Article

Rapid Screening Method for Carbamates in Orange Oil

Using an Ultra Carbamate HPLC Column

• Fast analysis times, for increased sample throughput.
• Simple methodology saves time—no sample preparation.
• Accurate mass identification, for definitive results.

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 carbamates in water, but not in other commodities. Matrices like citrus oil contain numerous interferences 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 electrospray 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 identification, 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 carbamates in a complex matrix such as orange oil.

Figure 1: Reference standard carbamates resolve quickly on an Ultra Carbamate HPLC column. (extracted ion chromatograms)

aldicarb sulfone aldicarb sulfoxide oxamyl methomyl 3-hydroxycarbofuran aldicarb propoxur carbofuran carbaryl methiocarb BDMC (IS) 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 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 temperature: 120°C Nozzle: (+) 62V Capillary: (+) 2.75kV LC_FF0473

Figure 2: Positive identification of carbamates in orange oil injected with no sample preparation. (extracted ion chromatograms)

aldicarb sulfone aldicarb sulfoxide oxamyl methomyl 3-hydroxycarbofuran aldicarb propoxur carbofuran carbaryl methiocarb BDMC (IS) 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 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 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 temperature: 120°C Nozzle: (+) 62V Capillary: (+) 2.75kV LC_FF0472

Table I: Carbamates were positively identified in matrix using both retention time and mass.
		Calculated ion monoisotopic mass	Standard ion monoisotopic mass	Standard Retention Time (min.)	Orange oil ion monoisotopic mass	Orange oil Retention 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 116.0751*	11.92	116.052*	11.53
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

RESTEK PRODUCTS

HPLC Columns

• Ultra Carbamate 3µm & 5µm Columns

Reference Standards

• 531.1 Carbamate Pesticide Calibration Mixture
• 531.2 Carbamate Pesticide Calibration Mixture

View All Current Promotions