Elution peak splitting

In Figure 5 an over-loading experiment is depicted (Schurig et al., 1990). The second fraction was eluted by increasing the temperature to 70°C. Incidentally, this leads to peak splitting due to temperature fluctuations in the oven (thermal christmas-tree -effect). 

Bonazzi et al. used an HPLC method and a second derivative ultraviolet spectroscopy method for the analysis of benazepril and other angio-tensen-converting enzyme inhibitors [17]. For HPLC, 20 pL sample solutions containing the drug and an internal standard dissolved in 1 1 acetonitrile/20 mM sodium heptanesulfonate (pH 2.5) were used. HPLC was performed on a 5 pm Hypersil ODS column (25 cm x 4.5 mm) with a mobile phase mixture consisting of (A) 20 mM sodium heptanesulfonate (pH 2.5) and (B) 19 1 acetonitrile-tetrahydrofuran, eluted at a flow rate of 1 mL/min, and with detection at 215 nm. The A/B mixture used was 52 48 for benazepril. A low pH of 2.5 was essential to avoid peak splitting and band broadening. 

Hydroquinone and the 4-methoxyphenol-, 3-ethoxyphenol-, and 4-benzyloxy-phenol ethers were extracted fiom cosmetic formulations and analyzed on a phenyl column (A = 295nm) using a 45/55 THF/water mobile phase. Elution was complete in 9 min. Baseline resolution and excellent peak shapes were obtained. This is an interesting result since THF is known to produce peak splitting at elevated levels for some analytes. Standard curves ranging fiom 50 to 400 mg/L were used. Detection limits of 2 mg/L were reported [800]. 

IPA/ethyl acetate mobile phase [1222], Elution was complete in <4 min. The authors note that the extremely limited solubility of these compounds in water led to the use of a nonaqueous mobile phase. They further noted that higher concentrations of acetonitrile led to peak splitting perhaps due to on-column solubility issues. Linear curves were generated from 10 to lOOng injected and detection limits of 30 ng injected were reported. 

Each standard at about 0.1 mg/mL was analyzed first to assess solvent effect and retention time. Solvent effect could cause peak splitting for standards eluted early in the gradient. Therefore, these standards should not be dissolved in pure methanol or acetonitrile. They should be dissolved in solvents with higher water composition such as 50-80% water. If solubility was a problem, <1% acid or base was added. Standard compounds at about 0.1 mg/mL were also used to optimize ion optics settings and to maximize ion signals in the mass spectrometer. 

Figure 2.72 The course of an analysis with large quantities of solvent using the PTV cold injection system filled with a 1 cm Chro-mosorb plug lOOpL PCB solution (200pg/ jL). After the dead time, a broad solvent peak is registered. After the solvent peak is eluted, the split valve is closed and the PTV heated up. A smaller roughly triangular solvent peak is produced from adsorbed material. After...

A Cl column with methanol/water mobile phase permits elution of APE in order of increasing ethoxy number. In the case of NPE, there is some peak splitting due to the isomer composition of the nonyl chain, something not observed with OPE (103,104). 

The three pools of xylanase activity contained 224 mL they were combined, concentrated as before to 12 mL, and split into two portions of 6 rnL. Each was added to a 45-mm i.d., 1.3-m-long Sephadex G-50-50 column and eluted with 1 mL/min of the pH 7.2 sodium phosphate buffer. Two peaks of xylanase activity resulted. The first to elute, Xylanase I, represented approximately 2.5% of the original endo-xylanase activity, while Xylanase II represented about 10%. 

---