ADVANCES IN SEPARATION SCIENCE continued
chiral SFC and HPLC modes. ChromegaChiral CCO-F4T3 surface chemis- try—4-fluoro-3-(trifluoromethyl) phenyl cellulose bonded to 5-μm silica particles—appears to have preferential affinity for analytes containing trifluoromethyl groups. GreenSep Naphthyl is a unique phase for SFC of natural products such as quinines. The naphthyl phase is planar with a strong pi-electron cloud. This seems to provide differential interaction with other aromatics, including heteroaromatics found in natural prod- ucts. Recently, Supelco and ES announced a cooperation agreement whereby Supelco will distribute ES SFC columns on a global basis.
Field-flow fractionation (FFF) Postnova Analytics (Salt Lake City, Utah) introduced AF2000 MultiFlow
asymmetric-flow field-flow fractionation (AF4) instruments for the separation and characterization of polymers, proteins and nanoparticles. Measurement range is 1 nm to 100 μm, and particles can be separated in liquids with pH of 2 to 11. Channel flow is 0–10 mL/min with a cross-flow of 0–8 mL/min; Pmax
is 35 bar. A metal-free flow chamber with a ceramic frit
and a range of membranes offer broad sample compatibility. Instrument setup and runs are controlled with NovaFFF expert software, which in- cludes a method wizard.
Figure 6 – Thermo Scientific Dionex Integrion HPIC System. (Image courtesy of Thermo Fisher Scientific.)
The most distinguished feature of the System S 150 ion chromatograph from Sykam Chromatography (Ersing, Germany) is the Sykam Auto- Suppressor, which recirculates regenerant solution through cation exchange in the hydrogen form. This is the source of hydronium ions that are responsible for the pH shift in the carbonate-containing eluent.
Supercritical fluid chromatography (SFC) Sepiatec GmbH (Berlin, Germany) introduced the Prep SFC basic system for
preparative SFC with small (analytical-scale) columns. Dual independent pumps deliver CO2
and modifier (usually methanol) with a maximum flow of 20 mL/min with a Pmax of 6000 psi. This is compatible with conventional
analytical-scale columns with internal diameters ranging from 4 to 10 mm and lengths up to 250 mm.
Injector, columns and the UV detector flow cell are housed in a heated compartment with a Tmax
of up to eight gas–liquid separator vials. These vials contain the product and release the CO2
same user interface as the company’s larger Prep SFC 100 and 360.
SFC columns Initial columns for SFC were often first developed and optimized for HPLC. ES Industries (West Berlin, Germany) showed that SFC is much better with phases optimized for SFC. For example, about a third of the small-molecule drugs in the development pipeline contain fluorine, and the company’s GreenSep Fluorobasic phases are ideal for SFC of fluoro- amines. Peak shapes are excellent, even without adding trifluoracetic acid or alkyl amines.
For a chiral selector, ES chemists focused on 2-fluoro-5-methylphenyl cel- lulose. ChromegaChiral CCO-F2 columns have been used successfully with
AMERICAN LABORATORY 24 of 70 °C. Separated fractions are collected in one without contaminating the lab. The software has the
The PN3621 MALS detector is part of Postnova’s FFF suite. It scatters light from samples as small as 7.8 nL, despite a sample cell volume of 63 μL. Scattered light is detected by 21 photosensors placed in a ring surround- ing the sample cell. The molar mass range is 103
–109 Chromatographs of the future
Micro-GCs Qmicro B.V. (Enschede, The Netherlands) introduced the Qmicro gas chro- matography module, which has a unique foreflush and backflush injector and a range of micro-detectors for gas analysis. Submodules provide flex- ibility. The thermal conductivity detector is chip-mounted internally, but the FID and MS are external.
Columns are in a second module, along with the heater. A wide range of wall-coated open-tubular and porous-layer open-tubular columns are available with fused-silica or metal tubes. The column+ heater module clicks into place on the base chassis. Limit of detection is about 500 ppb, depending upon the analyte and columns. Communication and control are via industry-standard protocols. The base unit is 20 cm × 20 cm with a depth of about 8 cm, making it small enough to fit almost anywhere, such as on top of an MS or inside a rack mount.
Super-fast nano-LC In LC, commercial instruments have a hard time keeping up with advances in column technology. The next column advance may be capillaries featuring internal diameters under 10 μm and submicron packings or wall-coated phases. Mary Wirth’s lab at Purdue University (Lafayette, Ind.) appears to be leading in the development of this tech- nology, which offers tremendous column efficiency through generation of an effect often called slip flow. The flow profile obtained when using larger-diameter packing materials resembles a blunt parabola with trail- ing edges. However, in slip flow, the small interstitial spaces between the nanoparticles facilitate “slipping” of the polar mobile phase along
MAY 2016 Da.
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