Geological Survey (USGS), Environmental Protection Agency (EPA), and Food and Drug Administration (FDA) websites, include, but are not limited to Examples of different types of blanks, primarily gleaned from U.S. Thus, it is important to gain an understanding of the terminology used, and what these blanks potential correct. Because blanks may be collected at any point during an analytical scheme, they may account for different items that may arise during the analysis. Proper handling and treatment of blanks is absolutely essential, since, in many cases, analytical results are calculated by subtracting the contribution of the blank to the analytical signal. Any analytical signal emanating from a blank sample that is absent in a blank solvent can be attributed to contamination. Types of Blanksīlank samples are collected, stored, treated, and analyzed in a manner as close to that for authentic samples as possible to account for contaminants and other potential interferents or potential sample degradation. The source of errant peaks in an ultrahigh-pressure liquid chromatography (UHPLC) separation were difficult to identify until a solvent (reagent) blank was used, and it was determined that inexperienced researchers had introduced contamination directly into the source bottle of acetonitrile used in the analysis. For example, appropriate use of blanks recently solved a riddle in our laboratory. This month's column explores the various types of blanks, and their use to provide further insight to sample preparation schemes. Because blanks are used to trace sources of artificially introduced contamination, it is important to consider their particular analysis, and any potential problems, in determining necessary blanks, and often more than one type of blank is needed.īlanks serve a vital role in quantitative analysis, and are often required by regulatory agencies as part of their quality control schemes. However, it was noted fairly recently that even ASTM International (via Committee D19) is still struggling with defining what constituents should be present (1).

The concept of blanks-samples lacking the analyte of interest used to determine or track the source of contamination or sample degradation and taken through the analytical process-is somewhat straightforward.

Surprisingly, although the students collect, treat, and analyze the blank appropriately, they often do nothing with the data they obtain. Before consuming the tonic water, students are asked to collect a urine sample to use as a blank, because urine may contain an endogenous compound that fluoresces on the shoulder of the quinine fluorescence band. The experiment provides a great example of the adsorption, distribution, metabolism, excretion phenomenon important to pharmacology and toxicology.

Following a liquid–liquid extraction, levels of urinary quinine are determined via fluorescence spectroscopy. When I teach my instrumental analysis course, one of my favorite experiments is when the students receive a bottle of tonic water, and then are asked to collect urine samples after consuming it.

Method spike definition