A high-efficiency sample introduction system for capillary electrophoresis analysis of amino acids from dynamic samples and static dialyzed human vitreous samples

Quantifying Sample Collection and Processing Impacts on Fiber-Based Tear Fluid Chemical Analysis

Purpose

Noninvasive analyses of tear fluid from humans and animal models in clinical and research settings most commonly use absorbent material for collection and processing. Still, the impact of these analytical techniques on tear chemical analyses remains largely unknown. The purpose of this study was to quantify the impacts of phenol red thread fiber-based tear sample collection and processing on the primary amine content.

Methods

Human tears were collected by placing the folded end of phenol red thread on the palpebral conjunctiva of the right eye for 20 seconds. The wetted thread was then processed using elution or extraction, and capillary electrophoresis with light-emitting diode-induced fluorescence detection was used for analysis and quantitation.

Results

Distinct processing methods impacted tear analysis differently. Primary amines adsorbed onto the thread partitioned in a chromatographic manner and thus any single portion of the wetted thread might not be representative of the whole sample. Quantitative assessment of five small molecule standards after on-thread processing showed significant overestimation of the actual concentration, with increased accuracy for larger volume samples. Yet collection of larger tear volumes introduced error in volume determination owing to evaporation and reduced small molecule separation resolution.

Conclusions

These results indicated that absorption-based tear fluid collection and processing significantly alter chemical content analysis, suggesting that the impacts of methods used should be regularly evaluated to standardize results drawn from different studies.

Translational Relevance

This study identifies potential inconsistencies and inaccuracies in tear analyses that are widespread across the published literature and clinical care.

Capillary and microchip electrophoresis in microdialysis: recent applications

The theme of this review is to highlight the importance of microscale electrophoretic-based separation systems in microdialysis (microD). The ability of CE and MCE to yield very rapid and highly efficient separations using just nanolitre volumes of microdialysate samples will also be discussed. Recent advances in this area will be highlighted, by illustration of some exciting new applications while the need for further innovation will be covered. The first section briefly introduces the concept of microD sampling coupled with electrophoresis-based separation and the inherent advantages of this approach. The following section highlights some specific applications of CE separations in the detection of important biomarkers such as low-molecular-weight neurotransmitters, amino acids, and other molecules that are frequently encountered in microD. Various detection modes in CE are outlined and some of the advantages and drawbacks thereof are discussed. The last section introduces the concepts of micro-total analysis systems and the coupling of MCE and microD. Some of the latest innovations will be illustrated. The concluding section reflects on the future of this important chemical alliance between microD and CE/MCE.