• Application Note

Measurement of n-Methylcarbamoyloxime and n-Methylcarbamates in Water by Direct Aqueous Injection HPLC with Postcolumn Derivatization

Measurement of n-Methylcarbamoyloxime and n-Methylcarbamates in Water by Direct Aqueous Injection HPLC with Postcolumn Derivatization

  • Waters Corporation

This is an Application Brief and does not contain a detailed Experimental section.


This Application brief demonstrates the measurement of n-Methylcarbamoyloxime and n-Methylcarbamates in water by direct aqueous injection HPLC with postcolumn derivatization.


Carbamates are used worldwide as commercial pesticides for food crops. The resulting agricultural runoff can carry them into surface water, groundwater, and other drinking water resources. The United States Environmental Protection Agency (US EPA) requires that drinking water and raw surface water to be monitored for the presence of carbamate pesticides and related compounds using an established EPA Method 531.2. The European Union (EU) regulation regarding drinking water, provides a general rule for pesticides and metabolites. This regulation limits the maximum admissible concentration (MAC) at 0.1 μg/L (ppb) for each individual component, with the total concentration not to exceed 0.5 ppb. Detection of regulated compounds at ever decreasing levels is a challenge faced by many water testing laboratories. Because the concentration of these substances in real samples may be in the low parts per billion (ppb) or μg/L, optimal sensitivity is the ultimate goal.


HPLC conditions


Waters Alliance system for carbamate analysis




Waters Carbamate Analysis column 3.9 x 150 mm @ 30 °C


400 μL of standard

Flow Rate:

1.5 mL/min


Fluorescence, Ex- 339 nm, Em- 445 nm, Gain- 10


Waters Empower software

Sample Preparation

Oasis SPE Method for Carbamates

Method for Oasis HLB Cartridge, 6 cc, 200 mg 

For LC analysis, exchange to acetonitrile, then adjust to 1 mL.

Standard mix preparation

Pipette 25 μL of AccuStandard mix M-531M and M-531-IS each into 100 mL of preserved reagent water for a final concentration of 25 parts per billion (ppb) per analyte. Preserved reagent water is prepared by dissolving 9.35 g of potassium dihydrogen citrate and 0.2 g of sodium thiosulfate (anhydrous) in water and diluting to 1 L.

Eluent Preparation

Filter and degas all eluents through a 0.45 μm filter.

A: Water

B: Methanol

C: Acetonitrile

Eluent gradient

Post Column Reagent Preparation

Reagent 1: 0.05 N sodium hydroxide

Dissolve 2 g NaOH in water and dilute to 1 L, filter and degas.

Reagent 2: PA/2-mercaptoethanol

Dissolve 19.1 g of Borax (Na2B4O7•10H2O) Sodium borate in 1 L of water. To this, add a solution of 0.1 OPA (o-phthaldialdehyde) in 10 mL methanol. Swirl to dissolve, filter, and degas. To this, add 1.0 mL of 2-mercaptoethanol, ently swirl to dissolve. Protect from light. Post-column reaction temperature is 80 °C.

Results and Discussion

Standard chromatogram of 25 ppb for each analyte.

* Internal Standard

EPA Method 531.2 target analytes.


  1. Waters Alliance Systems for Carbamate Analysis: 720000126EN
  2. Carbamates in Drinking Water: 720000609EN
  3. A Fully Automatic Multi-Analyte Quantification Protocol for Carbamates – A Comparison of LC-MS and LC-MS/MS: 720000672EN
  4. LC-MS of 52 Carbamates: A Fully Automated Protocol: WA20274

720002726, July 2008

Back To Top Back To Top