High-temperature HPLC

Stoll, D.R., Carr, P.W. (2005). Fast, comprehensive two-dimensional HPLC separation of tryptic peptides based on high temperature HPLC. J. Am. Chem. Soc. 127, 5034-5035. 

While smaller particles in shorter columns can reduce run times, resolution and efficiency are sometimes compromised. We would like to pack smaller particles in longer columns for better efficiency, but the backpressures generated are outside the capability of current commercial HPLC instrumentation. One way to alleviate the pressure issue is to use high-temperature HPLC. 

Very High Temperature HPLC—Dielectric Constant Effects.265... 

VERY HIGH TEMPERATURE HPLC—DIELECTRIC CONSTANT EFFECTS... 

Very-high-density polymers are run in a special high-temperature HPLC. This device can automatically dissolve, filter, inject and run these samples at 200°C in a solvent such as chlorobenzene. 

High-temperature HPLC (methanol at 120 °C, retention times in the range of seconds) and low temperature HPLC (5 to 10 °C), which can be used to analyze solute configurations, are techniques with practical advantages. However, they will for the time being remain in the research laboratories, like even bolder approaches such as the chip HPLC. 

Titania- and zirconia-based materials have been used for high-temperature HPLC applications, due to their high stability at high temperatures, coated with phosphates to reduce the strong Lewis acid properties (Figure 3.15). 

For fast column and mobile-phase saeening, a column switching valve inside the column compartment enables the successive use of up to six different columns. The choice of detectors for high-temperature HPLC of polyolefins and their copolymers is very limited. The prototype instmment contained a high-temperature differential RI detertor for isoaatic elution mode (e.g., SEC and LCCC) and an ELSD for gradient and isocratic elution modes. The ELSD was attached to the chromatograph via a heated transfer line. 

Recently, it has heen demonstrated that high-temperature HPLC (HT-HPLC) can he used as an alternative method for the determination of the CCD of semicrystalline copolymers of ethylene and polar comonomers. ... 

Teirrperamre is often a forgotten variable in HPLC but ean influenee the robustness and seleetivity of many separations or if exploited eair provide novel high temperature separation eonditions with either high effieieney, a unique seleetivity or enable new deteetion methods to be applied. 

In contrast to GC, in which, particularly at high temperatures, the stationary phase may give rise to a continuous background at the detector, this is not normally observed in HPLC unless the pH of the mobile phase is such that degradation of the stationary phase occurs. Under these circumstances, both an increased background and a reduction in chromatographic performance may be observed. 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

---