Highly sensitive analysis of multiple pesticides in foods combining solid‐phase microextraction, capillary electrophoresis‐mass spectrometry, and chemometrics

Abstract

A highly sensitive procedure to detect multiple pesticides at trace levels in foods is presented. Initially a comparative study between capillary electrophoresis (CE)-UV and CE-mass spectrometry (MS) is carried out analyzing five pesticides not studied up to now (pyrimethanil, pyrifenox, cyprodinil, cyromazine, and pirimicarb). The comparison between CE-UV and CE-MS is established in terms of separation efficiency, speed of analysis, reproducibility, and sensitivity. A good separation of these compounds is achieved by both techniques using a volatile aqueous buffer containing 0.3 M ammonium acetate/acetic acid at pH 4. Time analysis reproducibility is studied for the same day (n = 5) and three different days (n = 15), showing no significant differences between CE-UV and CE-MS. The study on peak areas reproducibility shows a slightly worse reproducibility for CE-MS compared with CE-UV. The best limit of detection (LOD) that can be achieved for these pesticides using CE-UV was 0.6 microg/mL. CE-MS provides LODs one order of magnitude better than CE-UV. Chemometrics are used to optimize the multiple parameters that play a role in solid-phase microextraction (SPME) and CE-MS analysis (e.g., extraction and desorption times, nebulizer pressure, dry gas flow, dry gas temperature, percentage of organic solvent and acid in the sheath liquid, etc.). The combined use of chemometrics and SPME-CE-MS clearly improves the LODs that can be achieved allowing the detection of pesticides at concentrations down to 15 ng/mL. The usefulness of this approach is demonstrated detecting multiple pesticides in different food samples as grapes and orange juice in a single run. The concentrations detected are below the maximum residue limits (MRLs) permitted for these pesticides in foods corroborating the value of our approach. This work demonstrates, to our knowledge for the first time, the good possibilities of the combined use of SPME-CE-MS and chemometrics.

Recent advances in the application of capillary electromigration methods for food analysis

“…Therefore, fast and sensitive analytical procedures are required by the analytical laboratories to face this important demand. In this sense, CE has mostly been applied to detect different type of pesticides in foods [120][121][122][123][124][125][126][127][128][129][130][131], although some other interesting applications as detection of veterinary drugs [132][133][134], toxins [135][136][137] and bacteria [138,139] have also been carried out by CE.…”

“…Our group has developed new CE procedures for highly sensitive detection of pesticides in foods [120][121][122]. In these works, a combination of chemometrics, SPE or SPME, on-line preconcentration strategies and CE with UV [121] or MS detection [120,122] As mentioned above, a useful strategy to sensitively analyze pesticides in foods is to develop adequate preconcentration strategies before their CE detection. Thus, carbendazim and thiabendazole (two fungicides) could be determined by CE in citrus fruits at levels 10 times lower than MRL established by the EU [125].…”

“…In a different work [127], a new sorbent for SPE of polar pesticides (phenoxy acids, triazines, ureas, oxime carbamates and carbamates) has been evaluated, showing its usefulness through MEKC determination of these pesticides in tap and river water samples [127]. Analysis of pesticides in foods by using CE-MS has shown to be an interesting alternative in order to improve both the sensitivity and specificity of the analysis [120,122,[129][130][131].…”

Chiral analysis of pollutants and their metabolites by capillary electromigration methods

“….) can be a good strategy [81,82], allowing the determination of these compounds at trace levels in environmental samples.…”

Homemade Capillary Electrophoresis Coupled to a Mass Spectrometer

“…[19] This system allows for the stable formation of ions in the MS system; however, its disadvantage is that the auxiliary liquid dilutes the sample. [20,21] …”