Application of response surface methodology for determination of methyl red in water samples by spectrophotometry method

• A simple method for the extraction of methyl red by using chemometrics was developed.
• The significant variables were optimized by using a BBD combined with DF.
• This technique provides good repeatability and high extraction recovery.

In this study a rapid and effective method (dispersive liquid–liquid microextraction (DLLME)) was developed for extraction of methyl red (MR) prior to its determination by UV–Vis spectrophotometry. Influence variables on DLLME such as volume of chloroform (as extractant solvent) and methanol (as dispersive solvent), pH and ionic strength and extraction time were investigated. Then significant variables were optimized by using a Box–Behnken design (BBD) and desirability function (DF). The optimized conditions (100 μL of chloroform, 1.3 mL of ethanol, pH 4 and 4% (w/v) NaCl) resulted in a linear calibration graph in the range of 0.015–10.0 mg mL−1 of MR in initial solution with R2 = 0.995 (n = 5). The limits of detection (LOD) and limit of quantification (LOQ) were 0.005 and 0.015 mg mL−1, respectively. Finally, the DLLME method was applied for determination of MR in different water samples with relative standard deviation (RSD) less than 5% (n = 5).

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