A Better Way to Prepare QC Samples
A Netherlands supplier of equipment for online liquid chromatography has come up with a way to improve the gathering and analysis of process stream samples. The main benefit is faster turnaround time for sampling that needs to be performed at nanoliter levels.
In many pharmaceutical production processes, concentrations of drugs in process streams are often too high for direct analysis on high-performance liquid chromatography (HPLC) columns, says LC Packings (Amsterdam, Netherlands). QC technicians must first remove an aliquot and, through a series of dilutions, prepare a sample with the right concentration for injection. Not only is this process time consuming, but measurements involved in dilution introduce potential errors in back-calculating concentrations and yields. Direct nanoliter (vs. microliter) sampling and injection would go a long way towards streamlining in-process pharmaceutical analysis and making this critical activity more accurate.
In a feasibility study conducted at LC Packings (Amsterdam, Netherlands), scientists injected 20 mL of a concentrated test sample directly onto a conventional HPLC column. The resulting chromatogram is presented in Figure 1, trace A. The trace shows clearly that the column is overloaded and the detector's linear dynamic range has been exceeded.
Figure 1
Trace B is the result of injecting a 200-fold dilution of the same sample. Trace C shows the same separation of a 100 nL injection of the concentrated sample, obtained with LC Packings' Famos microsampling workstation.
Comparing traces B and C confirms that direct analysis with nanoinjections provides analytical precision equivalent to that obtained by serial dilution. The overall chromatographic injection reproducibility of the 100-nL injection volumes was equal to 0.7 percent on peak height and 0.8 percent on peak area. The relative difference in peak area and peak height between the 20-mL conventional injection and the 100-nL injection was 1.2 percent.
The Famos workstation
Famos is a programmable, fully automated nanosampling workstation which directly interfaces with conventional HPLC as well as micro- and capillary chromatography units. When applicable, Famos uses different puncturing needles to pierce the septa of the sample vial and LC. Consequently very small sample volumes can be processed without sample loss. LC Packings claims that 1-mL samples can be transferred without losing material.
Figure 2
Famos has a reproducibility of less than 0.4 percent for full-loop injections over the entire range of nanoliter to microliter volumes. Linearity is at least 0.999 for injection volumes between 50 nL and 5 mL (Figure 2).
by Angelo DePalma
For more information on nanosampling or the Famos workstation, contact: Hans Vissers, LC Packings, Baarsjesweg 154, 1057 HM Amsterdam, The Netherlands. Tel: +31-20-683-9768. Fax: +31-20-685-3452.