**1. Introduction**

Foods are contaminated through various activities performed by man such as the accidental or intentional discharge of chemicals or waste substances from domestic, industrial and agricultural sites into the environment [1, 2]. However, most of these contaminants are non-biodegradable, which can be easily transferred from

the ground surface to the underground water because of their ability in dissolving sparingly in water [3, 4]. At long run, the contaminants pollute the foods through their respective circulatory movements in the environment [5]. The contaminants include inorganic matters such as heavy metals [6–8], as well as organic chemicals such as heat generated compounds [polycyclic aromatic hydrocarbons (PAHs) and acrylamide)] [9], organic polymers (bromodiphenyl ethers, chlorobiphenyls, chlorodibenzodioxins, chlorodibenzofurans etc), mycotoxins (aflatoxins), perfluoroalkyl acids [10–12]. Other contaminants with emerge-concerns include phthalates, bisphenol A, alkylphenols [13], phytosterols, estrogens, phytoestrogens [14], pharmaceuticals/veterinary drugs, synthetic dyes and pesticides [15–18].

Advantageously, pesticides have been used in domestic and agricultural practices for decades increasing the gross domestic products (GDP) of many countries around the globe. But their dangers in handling and excessive usage have been the issues of concern due to their residual accumulations in food chain resulting in many health problems that include cancers etc. However, there are challenging issues (problems) in the determination of multiple pesticide residues in food samples at lower concentration levels. These problems include extensive ranges of their chemical properties such as neutral, acidic and basic [19], vapor pressure/Henry's law constant [20], solubility [21], partition coefficient in octanol/water (log*P*) [22] and acid dissociation constant (pKa) [23]. Besides, the analytical samples also play challenging roles for pesticides extraction during sample preparation because of their features that include non-polar, polar, fatty and waxy samples [24, 25].

Even though, the conventional methods such as liquid–liquid extraction (LLE), liquid-phase microextraction (LPME) as well as solid phase extraction (SPE) techniques were previously used as the sample preparation methods for the multiple pesticides analysis [16] but possesses poor efficiency and selectivity of the targeted, which were their major drawn backs [26]. Also, many detectors and quantification instruments were used previously for the analyses of multiple pesticide residues [26]. These instruments include the gas chromatography-atomic emission detector (GC-AED) [27] and the high performance liquid chromatography (HPLC) [28]. Others instruments include gas chromatography-tandem mass spectrometry (GC– MS/MS) [29] and liquid chromatography–tandem mass spectrometry (LC–MS/MS) [30]. Unfortunately, the poor sensitivity of these instruments is their major setbacks. Fortunately, the shortcomings of the conventional sample preparation techniques and that of the detecting and quantifying instruments could be corrected through optimization such as the use of response surface methodology (RSM) [26, 31].

Accordingly, these compel food safety analysts to improve better ways of analyzing multi-pesticide residues in food samples through effective sample preparations and instrumentation techniques. For instance, RSM optimization of the intrumental prameters for LC–MS/MS (advanced) instrument such as the setup of the mobile phases could overcome the afformentioned problems encountered in samples to obtain better results of multiple pesticides residues at the lower concentration levels.

Usually, mobile phases comprise of Milli-Q-water (A) and an organic solvent (B) setup are used in the liquid chromatography instruments for the analyses of pesticide residues in various samples of food materials [26, 32, 33]. In fact, the organic solvents such as acetonitrile (ACN) and methanol are significantly used in the reverse-phase of liquid chromatography (LC) due to their excellent compatibility [34].

Thus, the aim of this research is to comparatively study the most recently used (reported) setup of mobile phases and some few suggested ones (**Table 1**). The best mobile phases setup that provided highest average total chromatographic peak area (ATCPA) as an index that correspond to the concentration of analytes in the multi-pesticide mixture of standard solutions was selected after the LC–MS/MS instrumentation.


**Table 1.** *Auto-tuning and mass-Hunter optimization results of the instrument using the multi-pesticides mixture of standard solutions.*
