*4.3.3 High performance liquid chromatography (HPLC)*

HPLC is the most commonly used technique for the quantification of drugs in formulations. The principal advantages of HPLC compared to column chromatography are improved resolution of the separated substances, faster separation time and the increased accuracy, precision and sensitivity.

HPLC is based on the same separation modes of column chromatography i.e. adsorption and partition. Unmodified silica (silanol group) is the most widely used in adsorption HPLC. Partition HPLC is divided into two categories, normal-phase and reverse-phase, based on the relative polarities of the stationary and mobile phases.

In order to develop HPLC method and to select the appropriate column type, the analyst needs to know:

a.Suitable solvent for the drug.

b.Molecular structure.

c.Nature of analysis: whether for quantification analysis or stability-indicating method.

The following diagram (**Figure 4**) gives a general guide to the selection of a chromatographic method for separation of compounds of molecular weight ˂ 2000; for samples of higher molecular weight the method of choice would be size-exclusion [25, 26].

**35**

*Drug Analysis*

**Figure 4.**

*DOI: http://dx.doi.org/10.5772/intechopen.88739*

**5. Quality assurance and quality control**

*General guide for selection of chromatographic method.*

cesses and resources.

or her disposal.

governed by specified rules.

good clinical laboratory practices (GcLP), … etc.

The major elements of quality management are:

In the pharmaceutical Industry, quality management is defined as the aspect of

a.A quality system describing the organizational structure, procedures, pro-

b.A systematic action or actions necessary to ensure adequate confidence that a

The concepts of quality assurance, GMP and quality control are interrelated aspects of quality management. They are inter-related and have fundamental importance to the production and control of pharmaceutical products.

In fact quality assurance covers quality control in exactly the same manner as it covers other functions such as manufacturing and ware-housing. It approves methods and standards and sees to it that good laboratory practices are operative. Each manufacturing unit must have a quality control department independent from the production and other departments and under the control of a qualified and experienced personnel and has one or several quality control laboratories at his

Quality control is integral part to all modern industrial processes and the pharmaceutical industry is not an exception. Testing a pharmaceutical product involves physical, chemical and sometimes microbiological analysis. It is a critical function of any business offering a product or service to consumers. In the field of pharmaceutical chemistry, quality control is vital to the successful development, manufacturing, and use of drugs meant to save lives. It determines the quality and stability of drug products via pharmaceutical analysis; it includes areas such as method validation, handling raw materials and finished products, documentations, inspections that impact the development of pharmaceutical products that are

Pharmaceutical products are developed and produced according to GMP requirements and other associated codes e.g. good laboratory practices (GLP), and

management function that determines and implements the quality policy.

product (or service) will satisfy given requirement for quality.

**Figure 4.**

*Pharmaceutical Formulation Design - Recent Practices*

water (usually a mixture of organic solvents).

with those of reference standard.

process or storage).

TLC is widely used in pharmaceutical analysis for:

d.Following synthetic reactions for their completion.

e.Forensic application in drug poisoning or addiction.

*4.3.3 High performance liquid chromatography (HPLC)*

the increased accuracy, precision and sensitivity.

phy (HPTLC) [24].

impurities. Separation in TLC occurs by either adsorption or partition. For adsorption, the stationary phase consists of a thin layer of sorbent (e.g. silica) which is activated by heating at 105°C to evaporate water and the mobile phase is devoid of

The term retention time used in TLC is referred to as Rf value which is the distance traveled by the compound from the origin (where the compound is spotted on the plate) divided by the distance traveled by the solvent. Although TLC is widely used for qualitative analysis, it does not in general provide quantitative information of high precision and accuracy. Changes in the practice of TLC have resulted in improved performance of separation and quantitative measurement. These developments are referred to as high-performance thin-layer chromatogra-

a.Identification of the components of a mixture by comparing their Rf values

b.Detection of any impurities (synthetic route, stability during manufacturing

c.Separation of a mixture of compounds and recovery by elution technique.

HPLC is the most commonly used technique for the quantification of drugs in formulations. The principal advantages of HPLC compared to column chromatography are improved resolution of the separated substances, faster separation time and

HPLC is based on the same separation modes of column chromatography i.e. adsorption and partition. Unmodified silica (silanol group) is the most widely used in adsorption HPLC. Partition HPLC is divided into two categories, normal-phase and reverse-phase, based on the relative polarities of the stationary and mobile

In order to develop HPLC method and to select the appropriate column type, the

c.Nature of analysis: whether for quantification analysis or stability-indicating

The following diagram (**Figure 4**) gives a general guide to the selection of a chromatographic method for separation of compounds of molecular weight ˂ 2000; for samples of higher molecular weight the method of choice would be size-exclu-

**34**

phases.

analyst needs to know:

method.

sion [25, 26].

a.Suitable solvent for the drug.

b.Molecular structure.

*General guide for selection of chromatographic method.*
