Best Practices for Sample Preparation and Analysis At A Bioanalytical Lab

Sample preparation is an integral part of bioanalysis. Bioanalytical studies require converting the study sample into a composition that is suitable for the instrument. This change can be a simple filtration or dilution step or can be a complex sample preparation protocol. Hence, identifying an ideal sample preparation technique is the first step of any bioanalysis. A robust sample preparation step ensures that all downstream protocols yield reliable results, making it crucial for all drug development projects.

The drug development process has several phases of studies requiring sample preparation protocols. These protocols can be exhaustingly lengthy, requiring considerable quantities of reagents. Besides, bioanalytical laboratory services must ensure that their analytical instruments are updated to meet stringent requirements of sensitivity and selectivity at every stage of the drug discovery and development process. 

Not to mention, biological samples are inherently complex. They pose a formidable challenge in sample preparation and analysis. Contaminants present in complex samples can cause several issues, including nonspecific interaction with analytes, clogging extraction devices, and co-extraction with target compounds. Moreover, analytes are often present in trace levels, and thus they require purification or preconcentration procedures. Hence, the current article shares the best practices for sample preparation and analysis at a bioanalytical lab.

Best practices for sample preparation and analysis

Liquid samples

Reducing viscosity allows samples to flow freely through the extraction device, whereas adjusting sample pH improves the subsequent extraction. Hence, biofluids are often diluted before the clean-up step to reduce viscosity and adjust sample pH. This pH will depend on the sample preparation technique, the analyte of interest, and the bioanalytical technique. On the other hand, dilution brings consistency to the biological sample. For example, the viscosity of urine samples will depend on the hydration levels of the patient. Hence, dilution will standardize the study samples, which is particularly important when analyzing a large batch of urine samples.

Solid samples

Most sample analyses, especially for GC-MS and LC-MS/MS systems, require liquid samples. Hence, solid or semi-solid samples are pre-treated to convert them into a liquid state. Numerous techniques are available for converting solid study samples into a liquid state, such as grinding and homogenization, saponification, and buffer or solvent extraction. Let us now understand the best practices for specific biofluids.

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Urine contains urea, creatinine, salts, and enzymes. One may employ hydrolysis to improve the detection limits of the drug. Besides, there are alternative approaches to hydrolysis, such as base or acid hydrolysis. On the other hand, for oral samples such as saliva, one must consider whether the study sample is neat saliva or collected through a device. This device can introduce surfactants and buffers. Hence, researchers must evaluate its effects on analyte recovery or subsequent matrix effects.

Whole blood, plasma, and serum have unique barriers, which can be divided into exogenous and endogenous challenges. Besides, dietary differences among patients may lead to variations in the lipid profile. Moreover, changes in viscosity may cause issues related to vacuum manifolds. Often drug conjugate to transporter proteins in the blood. These drugs can be released using extraction techniques such as SPE and SLE. Besides, one should adjust the pH to denature the protein and add solvent to break the protein-analyte bond.