Introduction

Bioanalytical techniques, as the name suggests, are the analytical tools to study the biological molecules; non-biological molecules involved with life, such as drugs; and biological processes. These tools are routinely used to identify, estimate, purify, and characterize the biomolecules. Quantification of molecules in biological samples is at the heart of bioanalysis and is routinely used to diagnose various diseases and metabolic disorders. For example, estimation of thyroxine and triiodothyronine concentrations in blood provides information about the activity of thyroid gland. Home pregnancy test kits look for the human chorionic gonadotropin (hCG) hormone in the urine, presence of which above a threshold concentration is an indicator of pregnancy. Bioanalytical methods are also used to detect drugs and their metabolites in biological samples. Initially, nonspecific assays were used to quantify the drugs in biological samples. Evolution of the existing assays, advancement in instrumentation, and introduction of newer techniques have made it possible to distinguish the drug molecules and their closely related metabolites in complex biological specimens.

Estimation of the analytes

Identification and quantification of analytes is perhaps the most common application of bioanalytical methods. Various diseases and disorders including cancers are diagnosed by estimating the levels of the characteristic biomarkers in a particular tissue or organ. Semenogelase, for example, is a biomarker for prostate cancer, one of the most frequently diagnosed cancers in human males.

Qualitative versus quantitative analyses

A qualitative analysis simply tells about the presence or absence of an analyte in a sample. An absence of analyte, however, may result due to concentrations below the detection level of the bioanalytical technique used. Qualitative analyses are used wherein detection of an analyte is sufficient to take further course of action. For example, identification of a banned performance-enhancing drug in athletics is sufficient enough to determine the qualification of the athlete to participate in the event. In certain cases, however, it is important to estimate the concentration of the analyte. A quantitative analysis would result in the determination of actual amount of the substance present in the sample. Consider a person suspected to be diabetic. A qualitative test for glucose is not good enough to ascertain if the person is diabetic. It is important to accurately determine the concentration of glucose in the blood to arrive at a conclusion. Breath alcohol detectors are used by traffic personnel to quantify the breath alcohol level, which in turn is proportional to blood glucose level and thereby enable them to identify the drunk drivers.