density and salinity lab Flashcards
(13 cards)
what is LOD
lowest detectable concentration of an analyte that can be reliably detected
what is LOQ
limit of quantification refers to the lowest concentration that can be reliably quantified with acceptable precision and accuracy
what are conservative elements
Non-reactive, Concentrations stable over time (only change with dilution), Long residence time
what are non-conservative elements
Have short residence times, Typically, reactive, Change seasonally and usually with biology
why do we use bod bottle and top loading balance to determine sw density
This method is a direct way to determine density by measuring mass and volume. Since density is mass per unit volume, weighing seawater and DI water using the same container allows for an accurate mass ratio comparison.
why can we use a refractometer to determine density
Light bends when it passes through a liquid, and this bending is related to the liquid’s composition. Higher salinity means more dissolved ions, which increases the refractive index.
why can we use a density meter to determine density
This high-precision instrument measures the oscillation frequency of a quartz U-tube filled with liquid. Since the frequency changes with mass (and therefore density), it provides a highly accurate density measurement.
why can we use a conductivity meter to determine density
Since dissolved salts increase a solution’s ability to conduct electricity, measuring conductivity allows for an indirect determination of salinity using equation
why do we overfill a bod bottle
to eliminate air bubbles (extra volume) and ensure accurate volume (has fixed volume when properly sealed)
what is a correction factor
A correction factor is an adjustment applied to measured data to account for systematic errors or known discrepancies between observed and expected values. It is typically determined through calibration with a reference standard.
why is there such a small amount of water used in the density meter
ensures minimal variability, reaching temperature equilibration quickly, and avoids air bubbles
what is a single point calibration
A single-point calibration is a calibration method where you use one known standard value to adjust or validate an instrument’s readings. Essentially, the instrument is calibrated based on this single reference point, and the assumption is that the instrument’s behavior is consistent across a range of measurements.
