High-performance thin-layer chromatography sample preparation

High-performance thin-layer chromatography (HPTLC) presents better resolution, sensitivity, and precision than classical TLC, and allows determination of the analytes with sufficient accuracy (e.g., determination of preservatives in creams and lotions) besides this, sample preparation may be simple. However, due to the high versatility of other techniques, this is probably the less commonly used of the chromatographic techniques in this area. 

Ruh, H., Sandhoff, R., Meyer, B., Gretz, N., and Hopf, C. 2013. Quantitative characterization of tissue globotetraosylceramides in a rat model of polycystic kidney disease by primadrop sample preparation and indirect high-performance thin layer chromatography-matrix-assisted laser desorption/ionization-time-of flight-mass spectrometry with automated data acquisition. Anal. Chem., 85 6233-6240. 

TLC is a sensitive technique, and it is important to think small with respect to sample size. The highest resolution will always be obtained with the smallest sample commensurate with the ability to visualize the analyte. This is also one of the prerequisites for reproducibility, especially if densitometry is to be used for quantitation (see Chap. 13.8). Zones that are too concentrated re.sult in integrated curve areas that behave in a nonlinear way on regression plots. Depending on the nature of the analyte, sample. sizes as small as picogram amounts are not uncommon, especially in high-performance thin layer chromatography (HPTLC). This is especially true in the analysis of fluorescent substances. Thus, for ultimate sensitivity it is sometimes desirable that a fluorescent derivative of the analyte be prepared. 

The separation and identification of natural dyes from wool fibers using reverse-phase high-performance liquid chromotog-raphy (HPLC) were performed on a C-18 column. Two isocratic four-solvent systems were developed on the basis of the Snyder solvent-selectivity triangle concept (1) 10% acetonitrile, 4% alcohol, and 2% tetrahydrofuran in 0.01 M acetic acid and (2)7% acetonitrile, 8% alcohol, and 5% tetrahydrofuran in 0.01 M acetic acid. Samples were also eluted in 30% acetonitrile. Spot tests and thin-layer chromatography were performed on all samples to confirm HPLC results. The systems also were found to be potentially useful in the identification of early synthetic dyes. A system of sample preparation that minimizes the reaction of samples was discussed. The application of this HPLC separation technique to samples from 20th century Caucasian rugs and American samples unearthed from the foundation of Mission San Jose was examined. 

Formation, factors affecting concentrations, legal limits and occurrence of polycyclic aromatic hydrocarbons in smoked meat products and smoke flavor additives are briefly reviewed by Simko. The most widely employed techniques such as thin-layer chromatography (TLC), gas chromatography (GC), and high-performance liquid chromatography (HPLC) are evaluated. Moreover, sample preparation, pre-separation procedures, separation and detection systems being used for the determination have been evaluated with emphasis on the latest developments in applied food analysis and... 

This entry describes the classical and modem sample preparation methods that have been used prior to qualitative and quantitative analysis by thin-layer chromatography (TLC) and high-performance (HP) TLC. Extraction and cleanup methods that are covered include classical methods such as liquid-liquid extraction (LLE) and Soxhlet extraction, as well as modern methods such as solid-phase extraction (SPE), pressurized liquid extraction (PLE), and supercritical fluid extraction (SEE). Modern methods have not been as widely apphed in TLC as for other modes of chromatography, e.g., column high-performance liquid chromatography (HPLC). 

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