Automated Size Selection and Cleanup System

What is the Automated Size Selection and Cleanup System?

An automated size selection and cleanup system uses magnetic bead ratios or automated gel electrophoresis to narrow the fragment size distribution of a library, replacing manual bead cleanups and improving reproducibility. It is chosen where insert size consistency drives sequencing performance.

Overview

Size selection removes adapter dimers and fragments outside the target window. Magnetic bead systems select by adjusting the ratio of beads to sample, so the cut-off is tuned by volume rather than by gradient. Automated versions dispense beads, mix, incubate, separate and transfer supernatant on a magnetic plate, and can perform two-sided selection that sets both a lower and an upper size cut-off in one protocol. Gel-based instruments instead separate fragments electrophoretically and recover a narrow size window, giving tighter distributions that matter for whole-genome libraries and for applications sensitive to insert size. Both approaches are often integrated into library preparation platforms. Key variables are bead lot, mixing time and temperature, all of which should be controlled and documented to keep selection reproducible.

How does it work?

A sequencing library is a pool of DNA fragments flanked by known adapter sequences that the sequencer recognises. Preparation starts with fragmentation by enzymatic digestion, tagmentation or sonication, which produces a defined size distribution. End repair and 3' adenylation make the ends ligatable, and adapters carrying sample indexes are attached by ligation or added during tagmentation. Size selection with magnetic beads or gel-free methods removes fragments outside the target window, and limited-cycle PCR enriches the library and completes the index sequences. Each step is separated by a magnetic bead cleanup that removes enzymes, salts and short fragments. For RNA libraries, reverse transcription and strand-specific second-strand synthesis precede the same workflow. Quality control after preparation measures concentration by fluorometry and fragment size distribution by capillary electrophoresis.

What are the key features?

• Automated bead dispensing, mixing, separation and supernatant transfer
• Two-sided selection sets lower and upper size cut-offs
• Programmable bead ratios for different target insert sizes
• Gel-based option recovers a narrow fragment size window
• 96-well plate processing with barcode sample tracking
• Reagent lot and protocol records for traceability

What are the technical specifications?

A typical automated size selection and cleanup system configuration offers samples per run of 8–96, selection range of approx. 150 bp–20 kb (method dependent), selection precision (bead) of approx. ±15% of cut-off size, selection precision (gel) of approx. ±5% of cut-off size, recovery of approx. 70–90% and protocol time of approx. 30–90 min. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Automated Size Selection and Cleanup System is used in library cleanup after adapter ligation, removal of adapter dimers before sequencing, insert size refinement for whole-genome libraries and PCR product and amplicon purification. Across the wider Library Preparation Systems class, laboratories also deploy it for whole-genome and exome library construction, RNA sequencing library preparation and single-cell and low-input library workflows.

Which standards and certifications apply?

Relevant standards and methods include ISO 20395, ISO 15189, CLSI MM09, IEC 61010-1 and ISO 17025. Certification candidates for this model are CE, ISO 9001 manufacturing and IEC 61010-1 safety; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Set up library preparation in a pre-PCR room separated from post-PCR and sequencing areas, and use dedicated pipettes, racks and reagents that never leave the room. Contamination from previous libraries shows up as unexpected index combinations, so include a no-template control in every batch and monitor index hopping between runs. Reagents are sensitive to freeze-thaw cycles, so aliquot enzymes and record lot numbers. Validate each new kit or automation script against a reference sample, checking yield, insert size and library complexity before routine use. Because library yield determines sequencing data quality, keep documentation that links each library to its sample, index, kit lot and operator so results can be traced during audits.

How do I select the right Automated Size Selection and Cleanup System?

Select an automated size selection system when insert size consistency is critical or when manual bead cleanups have become a source of variation. Specify selection range and precision, method type, sample capacity, recovery, protocol time and how reagent lots are recorded for traceability.

How does it compare with other Library Preparation Systems variants?

Begin with the sequencing platform and the input material. Short-read instruments need libraries with adapters matched to their flow cell chemistry, while long-read instruments need high molecular weight input and minimal PCR. Estimate the input amount per sample, because low-input and single-cell workflows require specialised chemistries. Then choose between manual kits for occasional use, magnetic bead automation for 8–96 samples per batch with walk-away operation, and full liquid-handling platforms for hundreds of samples with integrated normalisation and pooling. Check fragmentation method, index type and multiplexing level, size selection method, required equipment such as magnet racks or thermo mixers, and whether the supplier provides validated protocols for your sample type. Manual library preparation is a common source of batch effects, so automation usually pays back where sample numbers are high.