**6. Conclusions**

440 Modern Metrology Concerns

procedures affected by multiple variables. Highly confusing measurement uncertainties of such procedures may be only correctly budgeted by correct computer- simulations of the

The potential impact of such notion for method-dependent quantities has been demonstrated in polymerase chain reaction (PCR) (Yang et al., 2005). As described in earlier section, PCR is frequently used as a way to quantify genetic materials, especially in the format of real-time PCR (or q-PCR). In a PCR process, there are several experimental conditions that need to be tightly controlled. Among them, reaction temperature can be a critical control parameter as melting, annealing, and elongation steps of PCR are all profoundly affected by temperature. Numerous commercial thermal cyclers for PCR are available. How well do those thermal cyclers operate if we observe them with a metrological criticism in terms of temperature control? In our investigation (Kim et al., 2008), most PCR instruments showed satisfactory accuracy in static temperature control. However, in dynamic temperature control for PCR, substantially different performances were observed

Fig. 5.1. Real-time monitoring of in tube-temperature during PCR cycles for different commercial thermal cyclers. Unlike the ideal case (A), shortened annealing time due to slow response (B), or overshooting (C) and undershooting of temperature were observed (data

Slower acting instruments did not reach the programmed temperature in a fast PCR. On the other hand, some fast acting instruments showed under- or overshooting, which could lead to drastically different results. Such imperfection of instruments is not well known, and proper measures against such imperfections are not well taken, which would cause substantial disparity in performing bioassays based on PCR. It will be very helpful if the degree of imperfection of instrumentation is analyzed, and is considered in preparation of a measurement protocol. For example, an extreme PCR speed needs to be avoided for users of

Various bioassays of method-dependent quantity are crucial in QC or QA of biological products. Confidences on biological products are heavily dependent on the credibility and

from Bioanalysis Laboratory at KRISS).

slower-acting thermal cyclers.

procedures.

(Fig. 5.1).

It is certain that metrology for biological measurement will be a critical prerequisite for successful industrialization of modern biotechnology. It will be the fundamental basis of accurate and confident quality control and quality assurance of new products from biotechnology. This notion has been well acknowledged by the international community of metrology, mainly BIPM and CCQM as well as related professional world organizations such as WHO, IFCC, and USP. Because of the extraordinary complexities of biological materials, there were strong doubts about realization of metrology in this area. However, the scientists in national metrology institutes have devoted themselves to construct technical pathways toward the metrology for biology. A number of monumental achievements have been made, and metrology for certain areas especially quantitation of DNA has been established at a highly consistent level. These achievements have a strong symbolic value supporting that we could eventually establish metrology for biology even against many technical difficulties. At this stage, such efforts are now spread toward various important biologicals such as proteins, cells, microorganisms, and glycans. For those biologicals, extensive characterization of exactly what agreed to measure (the measurands) is first coming before quantification, which needs for the attention of not only the experts in metrology but also the experts in the related professional communities. Close communications and active collaborations among scientists in the various disciplines seem to be essential to make significant advancement in metrology for biology. The technical issues in metrology for biology need to be shared among many scientists to invite them to this challenging but interesting area. In this regard, we hope this chapter becomes a little window to look into the world of metrology for biology.
