ABC-BIO flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

LLOQ acceptance criteria

The lowest calibrator with signal-to-noise of at least 5, accuracy within plus or minus 20 percent of nominal, and precision CV no greater than 20 percent across runs.

4PL calibration curve

A four-parameter logistic model fitting signal against log concentration, with parameters for minimum, maximum, slope, and inflection point; standard for immunoassays.

Stable-isotope internal standard

A labeled analog of the analyte differing only in mass; it co-elutes and corrects for extraction losses and ionization variability in LC-MS/MS quantification.

Matrix effect assessment

Comparison of post-extraction spiked blank response to neat solvent response at the same concentration; ion suppression or enhancement is expressed as a percentage ratio.

Carryover acceptance

Residual analyte signal in a blank injected immediately after a high-concentration sample must not exceed 20 percent of the LLOQ response.

Dilution integrity test

A QC sample above the upper limit of quantification is diluted and re-assayed; measured accuracy must fall within plus or minus 15 percent of nominal.

Selectivity in bioanalysis

Demonstrated by assaying blank matrix from at least six individual lots; interference at the analyte retention time must be under 20 percent of LLOQ.

Extraction recovery

Ratio of analyte response from an extracted spiked sample to response from a post-extraction spiked blank at equal concentration, expressed as a percentage.

Calibration standard acceptance

At least 75 percent of standards and 67 percent of each concentration level must be within plus or minus 15 percent, or 20 percent at LLOQ.

Solid-phase extraction principle

Analytes partition between a liquid sample and a solid sorbent; conditioning, loading, washing, and elution steps yield selective cleanup and concentration.

Protein precipitation

Addition of organic solvent, acid, or salt denatures matrix proteins, releasing bound analyte; fast but yields dirtier extracts than SPE.

ELISA sandwich format

Capture antibody immobilizes antigen, a detection antibody conjugated to enzyme generates signal proportional to antigen concentration; suited to large analytes.

Surrogate analyte strategy

When the true analyte is unstable or unavailable, a stable structural analog is quantified and results are reported relative to the surrogate.

Run acceptance batch rule

A batch passes only if at least 67 percent of QCs and 50 percent at each level are within plus or minus 15 percent of nominal.

Internal standard response variability

Peak-area ratios of analyte to internal standard are tracked per injection; IS response outside a defined window flags extraction or injection failure.

Beer-Lambert law

Absorbance equals molar absorptivity times path length times concentration; linearity fails at high absorbance or with polychromatic or stray light.

Chromatographic resolution formula

Resolution equals two times the difference in retention times divided by the sum of the two peak widths at baseline.

Baseline resolution criterion

A resolution value of at least 1.5 separates two peaks with essentially complete return to baseline between them.

Van Deemter equation

Plate height equals the eddy diffusion term plus longitudinal diffusion over velocity plus mass transfer times velocity; minimum height defines optimum flow.

Retention factor k

k equals retention time minus void time, divided by void time; it expresses how much longer a solute is retained than an unretained marker.

Selectivity factor alpha

Alpha equals the retention factor of the later-eluting peak divided by that of the earlier peak; values above one indicate separation is possible.

Henderson-Hasselbalch equation

pH equals pKa plus the logarithm of the ratio of conjugate base to acid concentration; used to predict ionization and buffer behavior.

Buffer capacity maximum

Buffer capacity peaks when pH equals the pKa of the buffering species, where equal acid and base forms resist pH change most effectively.

Gravimetric factor

The ratio of the molar mass of the sought analyte to that of the weighed precipitate, multiplied by stoichiometric coefficients, converts precipitate mass to analyte mass.

Standard addition method

Known analyte increments are added to aliquots of sample; extrapolating the linear response to zero signal yields the original concentration, correcting for matrix effects.

Signal averaging improvement

For random noise, signal-to-noise improves with the square root of the number of averaged scans; systematic drift is not reduced by averaging.

Internal standard in GC

A compound added at constant amount before analysis; ratioing analyte peak area to internal standard area corrects for injection volume variability.

Equivalence point versus endpoint

The equivalence point is the stoichiometric completion of the reaction; the endpoint is the observed signal change, ideally matched by indicator selection.

Standard deviation of the mean

The standard error equals the sample standard deviation divided by the square root of n; it quantifies uncertainty in a mean of replicate measurements.

Limit of detection

The concentration giving signal three times the standard deviation of the blank, corresponding to the lowest reliably detectable amount.

Theoretical plates N

N equals sixteen times the square of retention time divided by peak width squared; higher plate counts indicate more efficient separation.

Gradient elution purpose

Mobile phase composition changes during the run, increasing elution strength to resolve analytes with widely differing polarities in one separation.

Karl Fischer titration

A coulometric or volumetric method measuring water content via iodine consumption in the presence of sulfur dioxide and a base.