What is an acceptable RPD?

Relative percentage differences (RPDs) are used to assess <5xPQL – any RPD is acceptable; >5xPQL – 0-50% RPD is acceptable.

What is a duplicate sample?

A sample collected concurrently, i.e. in the course of the same sample survey under comparable conditions, with a first sample. It acts in much the same way as a replication except that in some cases the only thing which can be replicated is the act of taking a second independent sample.

How do you calculate sample duplication?

Precision assessment is reported as Relative Percent Difference (RPD) between the two results (sample and duplicate) and calculated using the following equation: %RPD = (sample result – duplicate result) * 100 (sample result + duplicate result)/2 • Here is a simple example.

What is the difference between RPD and RSD?

The most commonly used estimates of precision are the relative standard deviation (RSD) and, when only two samples are available, the relative percent difference (RPD). Accuracy is the closeness of a measured result to an accepted reference value. Accuracy is usually measured as a percent recovery.

What is the use of having duplicate or replicate sample analysis?

Duplicate samples: two samples taken from and representative of the same population and carried through all steps of the sampling and analytical procedures in an identical manner. Duplicate samples are used to assess variance of the total method including sampling and analysis.

What is a matrix spike duplicate?

A Matrix Spike and Spike Duplicate (MS/MSD) are representative but randomly chosen client samples that have known concentrations of analytes of interest added to the samples prior to sample preparation and analysis. They are processed along with the same un-spiked sample.

What is a duplicate analysis?

Duplicate Analysis – definition(s) They are two separate samples taken from the same source, stored in separate containers and analyzed independently. Split Samples – Two or more representative portions taken from one sample in the field or in the laboratory and analyzed by different analysts or laboratories.

What is the difference between copying and duplicating?

Duplicate creates a copy of an item in the same location as the original. Copying (or “Copy To”) creates a copy of an item in a different location that you specify.

Why are the duplicate measurements performed on two separate portions of each standard?

The differences are divided by 2 because they arise from imprecision in both measurements, which adds quadratically, and the desired result is the precision of one measurement.

What is RPD in stats?

Relative percent difference or “RPD” means a comparative statistic used to calculate precision or random error. RPD is calculated using the following equation: RPD = absolute value (primary sample measurement – duplicate sample measurement) / ([primary sample measurement + duplicate sample measurement] / 2) × 100.

What does matrix spike mean?

A matrix spike is a type of quality-control sample used to evaluate the effects of sample matrices on the performance of an analytical method. For example, naturally occurring organic matter can be co-extracted with the organic analytes in the sample and interfere with the gas chromatographic analysis.

Why are the standards should be run in duplicate?

It might be tempting to run each sample in only a single well, but running samples in duplicate allows for the calculation of sample variation (%CV), and thus provides a measure of the precision of the assay.