Application Note LCMS-110 Development of a Targeted Quantitative LC-MS/MS Method for 431 Positive and Negative Ion Pesticides in a Single Analysis

Transcription

1 Application Note LCMS-110 Development of a Targeted Quantitative LC-MS/MS Method for 431 Positive and Negative Ion Pesticides in a Single Analysis Abstract A rapid, targeted quantitative UHPLC-triple quadrupole mass spectrometry method was developed for the simultaneous analysis of 431 pesticides in both positive and negative ion mode. Authors Zicheng Yang, Louis Maljers Bruker Daltonics Inc., Fremont, California, USA A Bruker Advance UHPLC system coupled to the Bruker EVOQ Elite LC-TQ demonstrated parts per trillion level sensitivity and excellent linearity when applying the method to the analysis of pesticides in a variety of food matrices. Introduction Pesticides are chemicals used to eliminate or control a variety of agricultural pests that can damage crops and livestock and reduce farm productivity. The most commonly applied pesticides are insecticides, herbicides, rodenticides, and fungicides. The US Environmental Protection Agency (EPA) information on US pesticide usage from 2007 estimated that over 2.4 billion kilogram of pesticides were used worldwide. Agricultural use is by far the biggest pesticide consumer. The increasing use of pesticides, illegal use and poor agricultural practices can create significant human, cattle, and pet health concerns through the presence of pesticides and metabolite residues in food. Keywords Pesticides EVOQ LC-TQ LC-MS/MS Compound Based Scanning Positive / negative switching Instrumentation and Software EVOQ LC-TQ

2 The number and frequency of pesticides used for horticultural purposes has increased considerably over the last 50 years. With over 1,100 pesticides documented globally, there has been a commensurate drive to shorten analysis times despite their widely varying physiochemical properties. Consequently, multi-residue pesticide analysis has become an increasingly complex and challenging task. Due to its wide scope of application, speed, sensitivity and selectivity, LC-MS/MS has now become the technique of choice for analyzing these complex samples. Experimental Sample Preparation Celery, bean, tomato and garlic matrix samples were prepared for LC-MS/MS analysis using a standard QuEChERS extraction procedure. Chromatography Parameters Instrument: Analytical column: Column Temperature: Injection Volume: Flow rate: Mobile Phase A: Bruker Advance UHPLC system YMC-Pack ODS-AQ 3 µm, 150mm x 3mm (I.D.) 40 C 5 µl (100 µl Loop) 400 µl/min. 5 mm ammonium fluoride in water Mobile Phase B: Gradient conditions: MS Parameters Methanol 0.0 min, 10% B 0.2 min, 10% B 2.0 min, 70% B 8.0 min, 80% B 10.0 min, 100% B 15.0 min, 100% B 15.1 min. 10% B 18.1 min. 10% B Instrument: Bruker EVOQ Elite with Heated Electrospray Ionization Spray Voltage (Positive): 4000 V Spray Voltage (Negative): 4000 V Cone Gas Flow: 20 units Cone Temperature: 250 C Heated Probe Gas Flow: 40 units Heated Probe Temperature: 400 C Nebulizer Gas Flow: 60 units Exhaust Gas: on q2 pressure: 2.0 mtorr (Argon) Table 1: Subset of the 431 pesticide list derived from the full mass spec method (refer to the Appendix for the full list). Compound Name Retention Time (min) Q1 First Q3 First Collision Energy (ev) Q1 First Q3 First Collision Energy (ev) Polarity Acephate Positive 23 Mesotrione Negative 17 Monocrotophos Positive 17 Bentazone Negative 17 Clethodim Isomer Positive 14 1-Naphthol Negative 14 Chlorotoluron Positive 14 Fludioxinil Negative 14 Ametryn Positive 14 Fipronil Negative 16 Prometryne Positive 16 Hexaflumuron Negative 31 Novaluron Isomer Positive 29 Fluazinam Negative 23 Benfuracarb Positive 23 Temephos Positive 23 Lufenuron Negative 23 Teflubenzuron Negative 23 Scan Time (ms)

3 Compound Based Scanning method Figure 1: Graphic representation of the Compound Based Scanning method for the 431 pesticides. Results The 431 pesticides cover a wide range of different chemical properties which effect the sensitivity and optimum polarity for their detection. The 5 mm ammonium fluoride in the UHPLC mobile phase assisted negative ion pesticide sensitivity without significantly affecting positive ion pesticide performance. The optimized method generated lower limits of detection (LLOD) of 100 ppt for most of the compounds with over 3.5 orders of dynamic range and good linearity (Figure 2). Continuous polarity switching was used in a single analysis without any negative performance effects. Sensitivity and linearity for co-eluting compounds (where one is negative and the other is positive) was still very good. For example, a concentration of 50 ppt for the positive compound Fenbuconazole and 100 ppt for the negative compound Fipronil with a r 2 >0.99 (Figure 3) were quantified easily by the described pesticide method.

4 Pesticides at LLOD level Figure 2: Example chromatogram of selected pesticide MRMs at the LLOD level. Linearity Figure 3: Linearity for positive and negative overlapping peaks.

5 Wide calibration ranges ppb Figure 4: Example calibration curves for a few selected compounds. Working with different matrix samples Figure 5: Example chromatograms of the matrix samples Celery, Bean, Tomato, and Garlic.

6 Bruker Daltonics is continually improving its products and reserves the right to change specifications without notice. Bruker Daltonics , LCMS-110, Conclusion The Bruker EVOQ Elite LC-TQ mass spectrometry system enabled the targeted quantification of 431 positive and negatively charged pesticides with a single method in 18 minutes. Good linearity, sensitivity and RSD s were achieved for all the components, proving the robustness and sensitivity of the EVOQ Elite for rapid multi-residue pesticide quantification. For research use only. Not for use in diagnostic procedures. Bruker Daltonik GmbH Bruker Daltonics Inc. Bremen Germany Phone +49 (0) Fax +49 (0) Billerica, MA USA Phone +1 (978) Fax +1 (978) ms.sales.bdal@bruker.com -