Sains Malaysiana 46(12)(2017): 2339–2348 http://dx.doi.org/10.17576/jsm-2017-4612-10 Optimization Method for Simultaneous Extraction and Detection of Imazapic and Imazapyr Herbicides in Soil and Water Using HPLC-UV with Verifcation of LC-MS (Kaedah Pengoptimuman bagi Mengekstrak dan Mengesan Herbisid Imazapic dan Imazapyr secara Serentak dalam Tanah dan Air Menggunakan HPLC-UV dengan Ujian Pengesahan LC-MS) BAJRAI, F.S.M.,* ISMAIL, B.S. & MARDIANA-JANSAR, K. ABSTRACT The residual activity of herbicides in soil and water may be detrimental to the environment. This issue has caught the attention of environmentalists and among the herbicides concerned are a mixture of Imazapic and Imazapyr, also known as OnDuty®, which is currently being used in the Clearfeld® Production System. These herbicides are widely used to control weedy rice in rice felds. In order to determine their residues in both soil and water, an accurate and simple method of extraction has to be developed. In the present study, extraction processes followed by HPLC-UV separation was developed and validated for simultaneous determination of imazapic and imazapyr in two matrices, namely soil and water. Verifcation of chemical compounds was then determined by using LC-MS (ToF). Recovery values of imazapic and imazapyr using 10 µM ammonium acetate extraction from blank samples spiked at levels between 1 mg L -1 and 10 mg L -1 in soil and water were 83% to 106% (with RSD ≤9%). The limit of detection (LOD) ranged from 0.25 to 0.46 mg L −1 while the limit of quantifcation (LOQ) was from 0.74 to 1.37 mg L -1 . LC-MS (ToF) mass spectrum analyses of imazapyr and imazapic were obtained at m/z 262.12 with the retention time of 2.39 min and m/z 276.13 with the retention time of 3.06 min, respectively. This method would be helpful in determining the level of pesticides in soil and water in a shorter time (< 6 min). Keywords: Herbicides; HPLC-UV; LC-MS (ToF); imazapyr; imazapic ABSTRAK Aktiviti sisa herbisid di dalam tanah dan air boleh memudaratkan alam sekitar. Isu ini telah mendapat perhatian daripada pencinta alam sekitar dan antara herbisid berkenaan adalah campuran Imazapic dan Imazapyr, juga dikenali sebagai OnDuty®, yang kini digunakan dalam Sistem Pengeluaran Clearfeld®. Herbisid ini digunakan secara meluas untuk mengawal rumpai padi di sawah padi. Dalam usaha untuk menentukan sisa racun tersebut dalam kedua-dua tanah dan air, maka satu kaedah yang tepat dan mudah untuk pengekstrakan perlu dibangunkan. Dalam kajian ini, satu kaedah pengekstrakan menggunakan 10 µM ammonium asetat diikuti oleh pemisahan HPLC-UV telah dibangunkan dan disahkan untuk penentuan serentak terhadap imazapic dan imazapyr dalam dua matrik, iaitu tanah dan air. Selanjutnya, ujian pengesahan sebatian kimia dilakukan dengan menggunakan LC-MS (ToF). Nilai pemulihan imazapic dan imazapyr dicapai dalam sampel kosong yang disuntik pada kepekatan antara 1 dan 10 mg L -1 di dalam tanah dan air adalah 83% hingga 106% (dengan RSD ≤9%) dengan had pengesanan (LOD) antara 0.25 hingga 0.46 mg L -1 manakala had kuantifkasi (LOQ) adalah daripada 0.74 kepada 1.37 mg L -1 . Analisis LC-MS (ToF) bagi mengenal pasti berat spektrum imazapyr dan imazapic masing- masing dapat dicapai pada m/z 262.12 dengan masa penahanan 2.39 min dan m/z 276.13 dengan masa penahanan 3.06 min. Kaedah ini akan dapat membantu dalam menentukan tahap herbisid dalam tanah dan air dalam masa yang singkat (<6 min). Kata kunci: Herbisid; HPLC-UV; LC-MS (ToF); imazapic; imazapyr INTRODUCTION Herbicides are being used in the agricultural sector to control weeds in plantations as well as in rice felds (Rekha et al. 2006), in order to enhance food production, reduce labour cost and control weeds more effectively. Since weeds can be controlled at the initial stages of their growth, ploughing activities would be reduced and thus moisture and nutrient content in the soil maintained. In rice felds, weeds are among the main problems besides pests and diseases. Since 1990, weedy rice has been a serious problem in paddy growing areas (Karim et al. 2004). The imidazolinone group of herbicides along with new varieties of paddy namely MR220 CL1 and MR220 CL2 were introduced to farmers in order to control weedy rice (Azmi et al. 2012). Application of the imidazolinone herbicides is currently becoming more popular in paddy planting areas of Malaysia. Imazapic and imazapyr (slightly different in structure as portrayed in Figure 1) belong to the imidazolinone group and are used in combination