30 August / September 2019
Increasing HPLC / UHPLC Sample Throughput: Doing More in Less Time
In many analytical laboratories, options to increase sample throughput for LC analyses are highly desirable. This is especially pertinent in high sample volume or time critical environments such as in-process testing, clinical, forensic or doping laboratories. As well as getting more done and outputting data quicker, there are additional benefits, such as improving the overall laboratory efficiency, better instrument utilisation, increased analytical capacity and reduced solvent consumption. This short article demonstrates how throughput for existing isocratic and gradient analytical LC methods can be increased using existing HPLC instruments and where applicable, by upgrading to UHPLC.
Figure 1: Increasing sample throughput of an existing isocratic HPLC method (A) using UHPLC (B) and modifi ed HPLC (C) options. Mobile phase: MeCN:H2
O (3:7 v/v),
Injection volume: (A) 5 µL, (B) 0.7 µL, (C) 1.4 µL, Detection: UV (214 nm), Sample: 1. 1,2,3-Trimethoxybenzene, 2. 1,2,4-Trimethoxybenzene, 3. 1,4-Dimethoxybenzene, 4. Methoxybenzene, 5. 1,3-Dimethoxybenzene, 6. 1,3,5-Trimethoxybenzene, 7. Toluene.
Introduction
Maximising sample throughput for LC applications is useful for many laboratories. It is possible to obtain signifi cant reductions in method run times by quantitatively translating the method to a shorter length column with smaller particles (either fully porous or solid core). The principle for increasing sample throughput, whilst maintaining the original method performance, is to ensure the column length
(L) to particle size (dp ) ratio (L/dp ) is kept
consistent. This results in similar separation performance being observed in a reduced time. Software LC method translation tools (e.g. the ACE Translation Tool) include all the necessary equations to accurately scale method parameters including injection volume, fl ow rate, gradient profi le etc. and are described elsewhere [1] and can be downloaded for free [2]. Signifi cant improvements in throughput
can be realised, without sacrifi cing method performance and / or robustness. In addition to reducing analysis time, compelling reductions in solvent consumption are also achievable. The translation of methods to shorter columns is often discussed in the context of migrating methods to UHPLC, however, impressive improvements can also be realised using standard HPLC instrumentation, thus improving the utilisation of existing equipment platforms.
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