Chromatographic separation of putative precursors of cholestanol
This paper describes convenient syntheses for labeled and unlabeled cholest-5-en-3-one, cholest-4-en-3-one, epicholesterol, cholest-4-en-3 beta-ol, and cholest-4-en-3 alpha-ol. The thin-layer chromatography, high-performance liquid chromatography, and gas-liquid chromatography of these compounds and of cholestanol and epicholestanol are also described. The synthesized compounds are potential precursors in the biosynthesis of cholestanol in mammals.
Planar Chromatography in Clinical Chemistry
Planar chromatography (PC) like any other chromatographic technique is a multistage distribution process. It is a form of liquid chromatography in which the stationary phase is supported on a planar surface rather than a column. Separations in PC occur because of differential migration velocities through the sorbent layer in a fixed separation time. The sample zones are fixed in space at the completion of the separation, allowing off-line monitoring. There are two planar techniques: paper chromatography and thin-layer chromatography (TLC). In recent years, TLC has superseded paper chromatography owing to greater speed, versatility, and reproducibility. Improvements in techniques and equipment as well as the ready availability of high-quality plates with uniform layers have extended and increased the use of TLC in clinical chemistry and other disciplines, offering quantitative as well as qualitative analysis. High-performance thin-layer chromatography (HPTLC), in particular, has developed to the extent that separation and quantitation can provide results that are comparable with other analytical methods such as high-pressure liquid chromatography (HPLC). The widespread application of TLC is also due to the fact that it is simple, robust, and flexible, and has a large sample throughput. Furthermore, coupled spectroscopic methods (TLC/mass spectrometry (TLC/MS), TLC/Fourier transform infrared spectrometry (TLC/FTIR) etc.) have considerably enhanced the reproducibility of TLC. 
 
 
 
TLC is often critically compared with column chromatography such as HPLC. This is a matter of endless dispute. Each technique has its own advantages and limitations. TLC is only inexpensive when qualitative results are needed. When reliable quantitative data are required, TLC is as expensive as column chromatography. In the authors' opinion, complementary rather than competitive chromatography offers the best solution to analytical requirements.
Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.