Determination of chromium(III) picolinate in dietary supplements by flow injection - electrospray ionization - tandem mass spectrometry, using cobalt(II) picolinate as internal standard

Abstract

In this work, a principle of flow injection analysis (FIA) was applied for sample introduction to an electrospray ionization - ion trap mass spectrometer (ESI-ITMS) with the aim to quantify chromium(III) picolinate (CrPic₃) in commercial supplements by multiple reaction monitoring, and using cobalt(II) picolinate as internal standard (IS). FIA system was operated with ammonium formate 10 mmol L^-1 in methanol-water (1:1, v/v) as a carrier solution at a flow rate 200 μL min^-1; 100 μL injections were performed in 2-min intervals. Setting ion transitions m/z 419 → 270 and 304 → 260 for the analyte and IS, respectively, and 100 ms integration time, the method detection and quantification limits 12 ng g^-1 and 40 ng g^-1 of Cr (as CrPic₃) in the air-dried powder. Acetonitrile extracts of the real-world samples presented varying from sample-to-sample chemical composition and IS efficiently compensated for ionization interferences. Mean results from triplicate analysis of four different supplements were obtained with relative standard deviation 0.1-4.0%, indicating acceptable precision. Trueness of the proposed FIA-ESI-ITMS/MS procedure was demonstrated by 95.8-108% percentage recoveries attained in the analysis of the CrPic₃-spiked samples. For comparative purposes, total Cr was determined by ICP-MS. The quantitative results obtained indicate the necessity of analytical control of Cr(III) supplements commercially available and demonstrate that the proposed FIA-ESI-ITMS/MS procedure is well-suited for the determination of CrPic₃ in such products.

Keywords: Chromium picolinate; Dietary Supplements; Flow injection analysis; Internal Standard; Tandem mass spectrometry.