1Low or no nucleic acid yield

Calculate total yield from concentration × actual recovered volume, including any measurement dilution factor. For example, 5 ng/µL in 100 µL gives 500 ng, whereas 10 ng/µL in 30 µL gives 300 ng. A more concentrated eluate does not necessarily contain more nucleic acid.

Typical observations: Low yield, dilute eluates, or inconsistent recovery.

Low concentration with adequate total recovery

Measure recovered volume rather than assuming the nominal elution volume. For a new extraction, reduce elution volume only within the matrix requirements. For an existing eluate, test an assay-compatible input before concentrating; any concentration method must retain the required fragment range.

Low input samples and carriers

A result below bulk quantification limits does not establish that cfDNA, cfRNA, or miRNA is absent. Use a suitable sensitive assay, such as target-specific qPCR or dPCR where appropriate, and report target copies relative to original sample volume when relevant. Record carrier use because it may dominate bulk readings. Prepare the carrier in its designated diluent where specified, and check compatibility with the downstream assay, including library preparation.

Assess cleanup and gel recovery by target mass

Calculate recovery as recovered target mass divided by the target mass entering purification. Use concentration and actual volume to calculate each mass. A concentration change alone does not establish recovery. Comparison with a DNA ladder provides only an approximate mass estimate. For a same-gel comparison, retain an input reference, account for the fraction of each preparation loaded, and compare the target band within an unsaturated imaging range. Known input equivalents can bracket recovery semiquantitatively.

2Lysis and sample handling problems

Inspect the sample before binding. The step at which clumps, color, or precipitates first appear helps distinguish inadequate disruption, sample-derived inhibitors, and a normal change in binding conditions. Clearing every visible solid is not a suitable general rule.

Further reading: Magen sample pretreatment guide.

Typical observations: Persistent clumps, viscous lysates, poor separation, or undissolved gel.

Distinguish debris from binding-stage precipitates

A precipitate formed after a binding reagent is added may need to be loaded. If clumps were present before alcohol addition, revisit pellet dispersion and lysis rather than assuming a normal binding precipitate. R4165, for example, requires binding-stage floccules to be dispersed and loaded with the liquid. Follow the rule for that step; excessive flocculation or repeated blockage calls for lower input in a new extraction.

For plant RNA, keep frozen powder frozen until prompt dispersion in lysis reagent, and check preparation of the prescribed reducing agent or antioxidant. For sputum, complete the applicable liquefaction before taking an aliquot. Liquefaction makes the sample more uniform; it does not establish that microbial cells have been adequately disrupted.

3Column and magnetic bead problems

Columns flow slowly or stop

Typical observations: Slow loading, liquid above the membrane, or no column flow.

Beads collect or transfer poorly

Typical observations: Bead clumps, slow magnetic clearing, bead loss, or particles in eluates.

Automation checks

Match the kit format, consumables, plate layout, sample allocation, total working volume, and program. Locate the beads and trace their collection and release. Check paused reagent additions at the correct destination and resumed step. Preloaded formats may still require bead resuspension or enzyme addition. For channel-pattern failures, inspect dispensing and transfer mechanics; for scattered wells, inspect local loading and mixing.

4Poor purity and inhibitor carryover

A low A260/A280 or A260/A230 ratio does not uniquely identify a contaminant. Residual guanidinium salts can contribute to absorbance around 230 nm and lower A260/A230, particularly when nucleic acid concentrations are low. Blank differences and background absorbance can also strongly affect ratios at low concentrations. Repeat the reading with a clean measurement surface and a blank matching the eluent before deciding to repurify the sample.

Carrier RNA contributes to the UV spectrum and may dominate the apparent concentration in low-input samples. The concentration and purity ratios then reflect the combined contributions of sample nucleic acids, carrier RNA, and residual reagents. An acceptable ratio does not establish the purity or recovery of the sample-derived target, while a low ratio alone does not establish downstream inhibition.

Plasmid preparation illustrates the effect of binding chemistry. In some Magen salt-mediated workflows, reduced RNA carryover makes UV estimates more representative of plasmid DNA, even though residual buffer components may lower A260/A230. Alcohol-mediated workflows may co-recover more RNA, inflating UV estimates when plasmid abundance is low. These are formulation-dependent effects; compare DNA-specific measurements and assay performance rather than ranking workflows by A260/A230 alone.

Further reading: Magen RNA absorbance guide, DNA and RNA quality guide, and Magen plasmid kit selection guide.

Choose a measurement that answers the question

Use the correct measurement blank

For UV measurements, blank with fresh nucleic acid-free solvent or buffer matching the sample solvent, including pH and ionic strength. Use water only when it matches the sample solvent. An inappropriate or contaminated blank can distort ratios or produce negative readings. Fluorescence assays require their specified standards and calibration procedure. A measurement blank, an extraction blank, and a PCR no-template control serve different purposes and are not interchangeable.

Carryover suspected from appearance or assay behavior

Typical observations: Low or unstable purity ratios, colored or turbid eluates, or suspected inhibition.

Judge cleanup by usable target recovery and assay performance, not by an improved absorbance ratio alone. A fluorescence result within range does not exclude PCR inhibition. Quantification bias concerns the estimated nucleic acid amount; a false-positive or false-negative assay result concerns detection of a specific target. Measuring total DNA does not establish that the intended target is present.

5DNA or RNA contamination

Confirm whether the route is intended to recover DNA, RNA, or both. Simultaneous recovery is expected in a total nucleic acid workflow. Selective removal is useful when the unwanted component interferes with the assay; separation alone does not prove its complete absence.

Typical observations: RNA in DNA preparations, DNA in RNA preparations, or target signal in negative controls.

DNase after capture has different follow-up requirements

Host-background digestion before microbial disruption has a different purpose from removing DNA after RNA capture. Confirm which target must remain and preserve the specified order. If additional nuclease treatment is performed after purification, complete the required inactivation or removal before the assay.

6Degradation and unexpected fragment recovery

Assess integrity using a method suited to the target size range. A smear can reflect original damage, mechanical shearing, or the expected sample profile. Small RNA and cell-free nucleic acids should not be judged against an intact tissue RNA or genomic DNA pattern.

For both DNA and RNA, review preservation compatibility, time before stabilization, storage temperature, and thawing history. Where available, compare a better-preserved aliquot from the same source.

Typical observations: Unexpected smearing, loss of long fragments, or missing target size fractions.

In a size-selection workflow, lower total DNA may reflect deliberate removal of unwanted fragments. Assess recovery of the intended population alongside the resulting fragment profile; a nominal cutoff is not an exact universal boundary. For plasma or serum with increased long DNA, investigate residual cells and storage before interpreting the higher total yield as increased cfDNA. Repurification cannot lengthen damaged molecules.

Exclude electrophoresis artifacts before assigning degradation

Run a known intact nucleic acid control of a suitable type alongside the sample. Review loading amount, sample buffer, denaturation where required, and gel running conditions. Recheck a fresh aliquot with clean reagents if needed. If the control also appears degraded, investigate shared preparation and electrophoresis conditions. If only the test sample is abnormal, investigate its history and carryover. Smearing alone does not identify when or why damage occurred.

7Precipitation and redissolution problems

Identify the pellet before removing liquid. After protein precipitation, the target may remain in the supernatant; after nucleic acid precipitation, retain the pellet. An enrichment pellet may instead require subsequent lysis. These fractions should not be handled by one general discard rule.

Typical observations: Little visible precipitate, loose or lost pellets, or incomplete redissolution.

A large enrichment pellet is not a direct measure of purity or target recovery, because other sample components may co-precipitate. Conversely, choosing only visible DNA strands can favor long molecules and underrepresent shorter DNA. Select the recovery route for the fragment population required.

8Poor downstream performance

Check the assay positive control before assigning failure to extraction. If it fails, resolve assay setup first. Otherwise, check template input, eluate volume, and buffer compatibility, then investigate inhibition, DNA background, and usable target content.

Typical observations: Weak or absent amplification, inconsistent Cq values, or poor library preparation.

Interpret dilution with the assay controls

At 100% qPCR efficiency, a tenfold template dilution delays Cq by about 3.3 cycles. A smaller delay, earlier Cq, or amplification appearing only after dilution can suggest relief of inhibition. Use measured assay efficiency where available. Pipetting error, excess template, and low-copy sampling can mislead; dilution alone does not prove inhibition.

Near the detection limit, dilution may remove target from the tested aliquot; use a suitable internal control when material is scarce. In two-step RT-qPCR, diluting cDNA checks PCR inhibition, not whether reverse transcription of the original RNA was inhibited.

Use controls to locate the problem

A positive extraction blank with a negative NTC directs attention toward extraction reagents and handling, while allowing for sporadic assay contamination. If both are positive, investigate assay setup as well. One negative blank cannot exclude intermittent contamination. For low-biomass sequencing, include blanks in the sequencing assessment. A process control covers only the stages after its addition and must resemble the target sufficiently to test the relevant release or lysis step.

When the target is not detected and a relevant control fails, investigate the failure before interpreting the result as a reliable negative. With acceptable controls, report the target as not detected under the tested conditions and within the method sensitivity; do not infer absolute absence. For low-copy samples, sampling variation can still affect detection.

Judge enrichment by target recovery

For host-depletion workflows, assess microbial recovery together with a host marker and controls. Lower host background alone does not establish adequate target recovery. Intact-cell enrichment may exclude released microbial DNA and is not a viability test. Select the route according to the intended target rather than total yield alone.

When to stop adding corrective steps

If the sample meets the assay requirements, an unusual absorbance ratio alone is insufficient reason for cleanup. When inhibition is demonstrated, compare a compatible cleanup or permitted dilution on an aliquot and retain untreated material where possible. Stop repeating cleanup when usable target loss outweighs the benefit. For substantial damage, collection failure, or a mismatched recovery route, use a better aliquot or workflow where available.