Analysis of Herbicides in Drinking Water

Food & Beverage Analysis of Herbicides in Drinking Water Herbicides are used throughout the world to combat the growth of unwanted plant life. These polar compounds are hydrophilic, so they may find their way into drinking water sources. Because they show some level of toxicity to humans, quantitative and qualitative information can be used to determine whether a water source is safe for humans, or if processing is warranted to remove harmful contaminants. While gas chromatography has historically been the preferred technique for analysis of herbicides in water samples, the use of LC-MS/MS for this application is gaining acceptance. This is due to the power of MS/MS to provide detailed identification of multiple analytes, but also in part due to the variety of HPLC stationary phases that are available. In particular, several HPLC phases are available that provide great retention and peak shapes for polar analytes, such as herbicides, even under mostly aqueous mobile phase conditions. The combination of these factors may possibly eliminate the need for time-consuming sample preparation. Experimental A drinking water sample was spiked with 11 herbicides and metabolites, and then shaken. LC-MS/MS analysis was performed directly on the spiked sample. Ascentis Express RP-Amide and Ascentis Express F5 HPLC columns were used. These columns are based on Fused-Core® particle technology, and provide a breakthrough in HPLC column performance. They provide the high speed and high efficiency of sub-2 µm particles but with the low backpressure associated with 3 µm particles, allowing faster analysis on any HPLC system. Results & Discussion Table 1 shows the retention times of all analytes on each column. A run time of less than 10 minutes was achieved with each column. Slight elution pattern differences were observed, as expected. The chromatogram obtained with the Ascentis Express RP-Amide column is shown in Figure 1. This column contains a stationary phase with an embedded polar group (EPG) that is 100% aqueous compatible. Compared to a C18 column, it provides increased selectivity for polar compounds, especially those that can act as a hydrogen-bond donor. Using Ascentis® Express RP-Amide and Ascentis Express F5 HPLC Columns Table 1. Retention Times (min) Peak ID Analyte Ascentis Express RP-Amide Ascentis Express F5 1 Atrazine desethyl desisopropyl 1.5 1.6 2 Atrazine desisopropyl 3.6 3.7 3 Atrazine desethyl 4.9 4.5 4 Simazine 6.6 5.5 5 Terbutylazine desethyl 7.0 5.6 6 Atrazine 7.7 6.1 7 Propazine 8.7 6.5 8 Terbutryn 8.8 6.6 9 Terbutylazine 8.9 6.9 10 Alachlor 9.4 7.0 11 Metolachlor 9.4 7.7 Figure 1. Ascentis Express RP-Amide sample/matrix: Drinking water spiked with 11 herbicides and metabolites column: Ascentis Express RP-Amide, 10 cm x 2.1 mm I.D., 2.7 µm particles (53913-U) mobile phase: (A) 5 mM ammonium formate, 0.1% formic acid in water; (B) 5 mM ammonium formate, 0.1% formic acid in methanol gradient: 0 min: 5% B; 12 min: 95% B column temp.: 40 °C detector: MS/MS See Table 1 for Peak IDs. 6.0 10.05.0 9.04.0 8.03.0 2 1 3 4 5 6 7 8 9 10 11 7.0 Min 2.01.0 Food & Beverage Analysis Order/Customer Service (800) 325-3010 • Fax (800) 325-5052 Technical Service (800) 325-5832 • sigma-aldrich.com/techservice Development/Custom Manufacturing Inquiries (800) 244-1173 Safety-related Information sigma-aldrich.com/safetycenter World Headquarters 3050 Spruce St. St. Louis, MO 63103 (314) 771-5765 sigma-aldrich.com Enabling Science to Improve the Quality of Life ©2012 Sigma-Aldrich Co. LLC. All rights reserved. SAFC, SIGMA-ALDRICH and SUPELCO are trademarks of Sigma-Aldrich Co. LLC, registered in the US and other countries. Ascentis and PESTANAL, are registered trademarks of Sigma-Aldrich Co. LLC. Solutions within. is a registered trademark of Sigma-Aldrich Co. LLC. CHROMASOLV is a registered trademark of Sigma-Aldrich Laborchemikalien GmbH. Fused-Core is a registered trademark of Advanced Materials Technology, Inc. Supelco brand products are sold through Sigma-Aldrich, Inc. Purchaser must determine the suitability of the product(s) for their particular use. Additional terms and conditions may apply. Please see product information on the Sigma-Aldrich website at www.sigmaaldrich.com and/or on the reverse side of the invoice or packing slip. OXP 11547/ T412134 1082 Visit our Beverage resources sigma-aldrich.com/food-beverages Figure 2 shows the chromatogram obtained with the Ascentis Express F5 column. This column employs a pentafluorophenylpropyl stationary phase, able to undergo different analyte-phase interactions than those possible with a traditional C18 phase or an EPG phase. These differences create an alternate selectivity and result in changes in the elution pattern. Note a faster gradient was possible with the F5 column installed in the system. Both Ascentis Express columns were able to provide retention of these polar analytes free from the column void volume. The F5 phase showed improved retention, selectivity, and peak shape, especially for the more polar analytes. The combination of modern stationary phase chemistries, rugged particle design, and the selectivity of LC-MS/MS provided a fast method for this application without the need for sample preparation. Featured and Related Products Description Qty. Cat. No. Ascentis Express HPLC Columns (2.7 µm particles) C18, 10 x 2.1 mm I.D. 1 53823-U C18, 15 x 2.1 mm I.D. 1 53825-U RP-Amide, 10 cm x 2.1 mm I.D. 1 53913-U RP-Amide, 15 cm x 2.1 mm I.D. 1 53914-U F5, 10 cm x 2.1 mm I.D. 1 53569-U F5, 15 cm x 2.1 mm I.D. 1 53571-U Ascentis Express Guard Columns (2.7 µm particles) Holder 1 53500-U C18 Cartridge, 5 mm x 2.1 mm I.D. 3 53501-U RP-Amide Cartridge, 5 mm x 2.1 mm I.D. 3 53514-U F5 Cartridge, 5 mm x 2.1 mm I.D. 3 53594-U Analytical Standards Atrazine desethyl desisopropyl, PESTANAL® 250 mg 36667-250MG Atrazine desisopropyl, PESTANAL 250 mg 36628-250MG Atrazine desethyl, PESTANAL 250 mg 36629-250MG Simazine, PESTANAL 250 mg 32059-250MG Atrazine, PESTANAL 250 mg 45330-250MG-R Propazine, PESTANAL 250 mg 45640-250MG Terbutryn, PESTANAL 250 mg 45677-250MG Terbutylazine, PESTANAL 250 mg 45678-250MG-R Alachlor, PESTANAL 250 mg 45316-250MG Metolachlor, PESTANAL 100 mg 36163-100MG Analytical Reagents and Solvents Ammonium formate, for HPLC, >99.0% 17843 Formic acid, for HPLC, 50% in water 09676 Methanol, LC-MS CHROMASOLV®, >99.9% 34966 Figure 2. Ascentis Express F5 column: Ascentis Express F5, 10 cm x 2.1 mm I.D., 2.7 µm particles (53569-U) gradient: 0 min: 5% B; 8 min: 95%B All other conditions the same as Figure 1. See Table 1 for Peak IDs. 2.0 6.01.0 5.0 9.04.0 2 1 3 4 5 6 7 8 9 10 11 8.03.0 7.0 Min Including products from