Surveyor plus lc system

Mixture of aflatoxins (aflatoxin B₁, aflatoxin B₂, aflatoxin G₁ and aflatoxin G₂) standards, having 10ng ml^-1 concentration (each) in acetonitrile, was subjected to auto sampler (10 μl sample injection) and chromatographed on Surveyor Plus LC system (Thermo Fisher scientific) equipped with Luna® C₁₈ column (150 x 4.6 mm; 3μm particle size, Phenomenex, USA), for the separation of aflatoxins analytes from samples and matrix matched external standards with an isocratic flow rate of 0.4 ml min^-1. The column temperature was maintained at 30 °C. The injection volume was set 10 μl on auto-sampler and a mobile phase consisting of methanol:acetonitrile:water (22:22:56 v/v) was used for a 20 min run.

The cell free supernatant (two hundred ml) produced by mutant Koji strain M-100(6) was extracted (using separating funnel) with two hundred ml of chloroform. The organic solvent (chloroform) was evaporated using rotary evaporator. The residue was dissolved in methanol (two ml), filtered through membrane filter (0.45 μm, nylon membrane, Millipore) and subjected to aflatoxins analysis using LC-MS (Quadrupole Linear Ion Trap Mass Spectrometer Finnegan LTQ XL hyphenated with Surveyor Plus LC system, manufactured by Thermo Fisher Scientific, USA. Samples were analyzed using previously developed analytical method [51 (link)]. The samples were initially infused to the Mass Spectrometer by direct syringe pump through positively ionized electro spray ionization (ESI) probe: spray voltage 5 kV, sheath gas flow rate 70 arbitrary units, auxiliary gas flow rate 20 arbitrary unit, capillary temperature 335 °C, capillary voltage 45 V, and tube lens voltage 110 V.