Evaluation of fritless solid‐phase extraction coupled on‐line with capillary electrophoresis‐mass spectrometry for the analysis of opioid peptides in cerebrospinal fluid

Abstract

Fritless SPE on-line coupled to CE with UV and MS detection (SPE-CE-UV and SPE-CE-MS) was evaluated for the analysis of opioid peptides. A microcartridge of 150 μm id was packed with a C18 sorbent (particle size > 50 μm), which was retained between a short inlet capillary and a separation capillary (50 μm id). Several experimental parameters were optimized by SPE-CE-UV using solutions of dynorphin A (DynA), endomorphin 1 (End1), and methionine-enkephaline (Met). A microcartridge length of 4 mm was selected, sample was loaded for 10 min at 930 mbar and the retained peptides were eluted with 67 nL of an acidic hydro-organic solution. Using SPE-CE-MS, peak area and migration time repeatabilities for the three opioid peptides were 12-27% and 4-5%, respectively. SPE recovery was lower for the less hydrophobic DynA (22%) than for End1 (66%) and Met (78%) and linearity was satisfactory in all cases between 5 and 60 ng/mL. The LODs varied between 0.5 and 1.0 ng/mL which represent an enhancement of two orders of magnitude when compared with CE-MS. Cerebrospinal fluid (CSF) samples spiked with the opioid peptides were analyzed to demonstrate the applicability to biological samples. Peak area and migration time repeatabilities were similar to the standard solutions and the opioid peptides could be detected down to 1.0 ng/mL.

Developments in coupled solid‐phase extraction–capillary electrophoresis 2013–2015

“…Medina‐Casanellas et al. developed an in‐line SPE‐CE‐MS method for the determination of opioid peptides in human cerebrospinal fluid (CSF) . A microcartridge of 150 μm id was packed with a C18 sorbent (particle size >50 μm), which was retained without using frits between a short inlet capillary and a separation capillary (50 μm id).…”

“…Experimental conditions: sample loading, 10 min at 930 mbar; elution, 63 s at 50 mbar; separation voltage, 25 kV; EIEs: 434.7 (Dynorphin A (1‐7)), 611.2 (Endomorphin 1), and 574.2 (Met‐enkephalin). Reproduced with permission from .…”

Analysis of serum transthyretin by on-line immunoaffinity solid-phase extraction capillary electrophoresis mass spectrometry using magnetic beads

“…However, other authors have preferred the term “in‐line” because the microcartridge is fully integrated with the separation capillary . Both terms are actually coexisting in the literature, something that has generated some controversy . SPE‐CE‐MS has been extensively explored using the silica or polymeric sorbents typically used in off‐line SPE (e.g.…”

“…SPE‐CE‐MS has been extensively explored using the silica or polymeric sorbents typically used in off‐line SPE (e.g. C18) , because of the versatility, the large active surface area, the compatibility with the on‐line electrophoretic separation and detection and the commercial availability at a reasonable price. However, the limited selectivity of such sorbents hinders very often the analysis of complex samples, such as biological fluids, even with MS detection .…”

Recent developments in capillary and microchip electroseparations of peptides (2013–middle 2015)

“…A fritless SPE microcartridge of 150 μm id and 4 mm length packed with C18 sorbent (particle size >50 μm) and retained between a short inlet capillary and a separation capillary (50 μm id) was applied to analysis of opioid peptides (dynorphin, endomorphin 1, and Met‐enkephalin) in cerebrospinal fluid (CSF) , see Fig. .…”