Intra-assay precision

A study was conducted to measure the concentration of D-fenfluramine HCl (desired product) and L-fenfluramine HCl (enantiomeric impurity) in the final pharmaceutical product, in the possible presence of its isomeric variants (57). Sensitivity, stabiUty, and specificity were enhanced by derivatizing the analyte with 3,5-dinitrophenylisocyanate using a Pirkle chiral recognition approach. Analysis of the caUbration curve data and quaUty assurance samples showed an overall assay precision of 1.78 and 2.52%, for D-fenfluramine HCl and L-fenfluramine, with an overall intra-assay precision of 4.75 and 3.67%, respectively. The minimum quantitation limit was 50 ng/mL, having a minimum signal-to-noise ratio of 10, with relative standard deviations of 2.39 and 3.62% for D-fenfluramine and L-fenfluramine. 

Table 5.20 Intra-assay precision and accuracy of the LC-ToF-MS determination of Idoxifene. Reprinted from J. Chromatogr, B, 757, Comparison between liquid chromatography-time-of-flight mass spectrometry and selected-reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of Idoxifene in human plasma , Zhang, H. and Henion, J., 151-159, Copyright (2001), with permission from Elsevier Science...

Nominal concentration (jUg/ml or pg/g) Intra-assay precision (CV%) ( =10) Intra-assay precision (CV%) (n=6) Intra-assay accuracy (%> ( =10) Intra-assay accuracy (%) ( =6) Recovery (%) (mean SD)... 

Repeatability (intra-assay precision) Precision under the same operating conditions over a short interval of time (e.g., 10 subsequent injections) " ... 

Intra-assay precision is evaluated by analyzing aliquots of a homogeneous material several times by one person on one day with the same equipment. Each analysis is independent, so the intra-assay precision is telling us how reproducible the analytical method can be. Intraassay variability is greater than instrument variability, because more steps are involved. Examples of specifications might be that instrument precision is <1 % and intra-assay precision is 2%. 

Define the following terms instrument precision, injection precision, intra-assay precision, ruggedness, intermediate precision, and interlaboratory precision. 

Inter- and Intra-Assay Precision Intraassay precision and accuracy are assessed within one batch (QCs, standards, etc.), whereas interassay precision and accuracy are assessed using separate batches. 

Finally a validation step for the overall MISPE procedure is mandatory to allow the use of the method itself in place of the regulatory methods. The issues to be considered here are the accuracy and precision of the method based on the MISPE protocol, its limit of quantification, selectivity and ruggedness. In particular the inter- and intra-assay precision need to be checked with real samples and certified reference materials and methods [23,24]. 

The inter- and intra-assay precision (% C.V.) of this method were reported to be less than 8% across the range of the limits of quantification (0.05-10 ng/ml). The accuracy (% bias) for all spiked control concentrations did not exceed 4%. Same-day turnaround of results for over 100 samples was possible and was used to support an acute dose tolerance and pharmacokinetic study that involved the analysis of 1600 samples. 

Deflazacourt is an inactive prodrag which after oral administration is rapidly converted to the active 21-hydroxydeflazacort. It has anti-inflammatoiy activity, and is used in the treatment of rheumatoid arthritis. Ifa et al. [87] developed a method for the determination of 21-hydroxydeflazacort in human plasma. The analyte and dexamethasone-21-acetate as the IS are extracted from plasma using a diethyl ether LLE. After evaporation to dryness and reconstitution in mobile phase, the compoimds are analysed using LC-MS with positive-ion APCl in SRM mode, monitoring the transitions m/z 400 124 for the analyte and m/z 435 397 for the IS. The linearity was tested in the range of 1 00 ng/ml. The intra-assay precision and accuracy were better than 5.5% and 7.1%, respectively. 

Precision Instrument repeatability - ten replicate injections. RSD<1% Intra-assay precision. Multiple analysis of aliquots of a sample during one day. RSD < 2% Intermediate precision. Multiple analysts, instruments, days in one laboratory. Reproducibility by inter-laboratory studies to detect bias. 

ICH Q2A defines repeatability as the variability of the assay results under the same operating conditions over a short interval of time. Repeatability is also termed intra-assay precision. A reportable value of an assay is often the average of a specified number of replicate values, where the replicates are processed using the same sample preparation. Thus, it is not possible to obtain a true repeat of the assay s reportable value. Repeatability can be modeled as the within-assay variability of the replicates however, it should be noted that this precision is at the level of the replicate and not at the level of the reportable value. If the reportable value is an average of K replicates the variance of the reportable values will be less than that of the replicates by a factor of l/K (the standard deviation will be less by a factor of (1/ k ). 

Precision describes the variability in a set of measurements, i.e. how closely repeated measurements on a single sample agree. Precision can be calculated for samples within an individual itin (intra-assay precision) or across multiple runs (inter-assay precision). Precision is customarily expressed as the percentage coefficient of variation (%CV, or simply CV), which is the standard deviation expressed as a percentage of the mean ... 

In 1997, Probst et al modified Furata et al. s method to quantify rocuronium and its 17-desacetyl metabolite in heparinized plasma. This group performed parallel studies of the previously described LLE extraction and an on-column ion pairing using Extrelut solid-phase extraction cartridges. The intra-assay precision (n = 5) at two concentrations (400 and 1052ngmL ) for both parent drug and metabolite showed mean concentrations within... 

The repeatability or intra-assay precision is defined as the precision of determinations performed in the same way and within a short space of time. Its determination is of particular interest in the analytical testing for the imiformity of the content of a measmed active ingredient (content uniformity test). 

A free-standing liquid junction interface was coupled to a flat edge glass CE microchip for the analysis of small molecules (drugs, metabolites). It was demonstrated for the detection of recovered carnitine, acylcarnitines, imipramine, and desipramine spiked into urine or plasma at 5-500 p,g/mL level. Separations were typically performed in < 1 min and intra-assay precisions ranged from 4.1% to 7.3% Relative Standard Deviation RSD. A similar device, but fabricated in polymeric Zeonor material, was demonstrated for the analysis of carnitine standards. ... 

Intra-assay precision Run samples (S5 replicates) in a single run. Samples used for precision testing may include commercial QC samples, but precision testing should also include species-specific samples of the relevant matrix (e.g., serum, plasma, urine) for the intended study samples Test S3 samples at low, medium, and high concentrations across the calibration curve range Calculate mean, SD, and CV% CV 20%, CV<25% at LLOQ... 

Intra-assay precision to establish reproducibility/ repeatability of an assay by comparing replicates within a single run... 

Because rosightazone is a fluorescent compound, the method with a fluorescence detector is presented with excitation at 247 nm and emission at 367 nm. The low limit of quantitation of rosiglitazone in plasma is 3 ng/ml. The interassay and intra-assay precision values are better than 10% at all concentrations. ... 

Applications of CIEF for the separation of isoforms of transferrin have been reported by several groups. - Transferrin contains different number of sialic acid residues, with an additional -1 charge added per residue. Also, transferrin bound to different amount of iron atoms has been separated by CIEF. Glycoforms of recombinant tissue-type plasminogen activator (rtPA) is another sialic acid containing protein which has been the subject of analysis by CIEF. - " A rapid (<10 min) one-step method was developed using a coated capillary, HPMC, and urea in a mixture of pH 3-10 and pH 5-8 ampholytes. Ten species could be detected. Intra-assay precision was less than 5% for peak migration times and 10% for normalized peak areas. 

Intra-assay precision for trazodone (100 pg L ) and m- CPP (5 pg L ) was 1.5 and 2.8%, respectively. Ohkubo et al used UV detection (254 nm) for trazodone and coulometric detection (PGE, -I-0.84V vs Pd) for m-CPP. The analysis was performed using a octyl-modified silica column with acetonitrile-aq. potassium dihydrogen orthophosphate (5gL ) (23 -1-77), final pH adjusted to pH 2.5 with orthophosphoric acid, as eluent. Plasma (1 mL) was extracted by SPE on nitrile-modified silica cartridges. Pilsicainide (Figure 6.20) was used as the internal standard. The LoDs for trazodone and m-CPP were 50 and 2.5 pgL, respectively. Note that at the electrometer sensitivity required to determine m-CPP, the EC response to the parent compound would have been beyond the linear range of the coulometric detector. 

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