Biochemical tests form a critical part of analytical chemistry technology, particularly in Kenya where diverse industries such as healthcare, agriculture, and food processing rely on accurate biochemical analysis to ensure quality, safety, and compliance with regulatory standards. Proficiency in collecting biochemical samples is foundational for reliable test results. This chapter equips Analytical Chemistry Technology professionals with the knowledge and skills to collect various biochemical samples including lipids, proteins, carbohydrates, enzymes, and vitamins, emphasizing proper techniques, sample integrity, and contextual application in Kenyan laboratories.

1.1 Collect Biochemical Samples

Collecting biochemical samples requires understanding the nature of the analytes, appropriate sampling methods, and preservation techniques to maintain sample integrity until analysis. Each biochemical class demands specific considerations owing to chemical properties, stability, and susceptibility to degradation or contamination. Kenyan laboratories handling samples from hospitals, food processing plants, or agricultural cooperatives must adhere to standardized protocols to produce accurate analytical outcomes.

1.1.1 Lipids

Lipids, comprising fats, oils, and related compounds, are hydrophobic molecules essential in biological systems and food quality assessment. Their analysis in clinical and industrial laboratories depends on proper sample collection to avoid oxidation and hydrolysis that can alter lipid profiles.

Types of Lipid Samples

• Serum and plasma samples: Used in clinical biochemistry for cholesterol and triglyceride analysis; collected via venipuncture using anticoagulants that do not interfere with lipid assays.
• Food lipid extracts: Obtained from edible oils, dairy products, or meat samples; require homogenization and solvent extraction.
• Environmental lipid samples: Collected from soil or water bodies to monitor pollution; extraction involves organic solvents.
• Plant lipid samples: Collected from leaves or seeds for agricultural research; preservation requires immediate freezing.
• Microbial lipids: Extracted from bacterial or fungal cultures for biochemical studies; samples must be processed rapidly to prevent degradation.

Sampling Techniques for Lipids

• Use glass containers to prevent plasticizer contamination common with plastic bottles.
• Collect blood samples after fasting to reduce postprandial lipemia affecting lipid levels.
• Minimize exposure to light and air during sampling to prevent lipid oxidation.
• Maintain samples at 4°C during transport and freeze if analysis is delayed beyond 24 hours.
• Use antioxidants like butylated hydroxytoluene (BHT) in solvents to stabilize lipids during extraction.

Preservation and Transport of Lipid Samples

• Store samples in airtight, amber-colored containers to reduce oxidative damage.
• Transport samples in coolers with ice packs to maintain low temperatures.
• Analyze samples within 24 hours; otherwise, freeze at -20°C or lower.
• Avoid repeated freeze-thaw cycles which degrade lipid integrity.
• Label samples clearly with collection time, type, and preservative used for traceability.

Common Challenges in Lipid Sample Collection

• Hemolysis during blood collection can release intracellular lipids, skewing results.
• Improper fasting status of patients affects serum lipid concentrations.
• Contamination with detergents or solvents during food sample extraction.
• Incomplete homogenization leading to non-representative lipid content.
• Delayed processing causing enzymatic hydrolysis and free fatty acid formation.

1.1.2 Proteins

Proteins are fundamental biomolecules analyzed for clinical diagnostics, food quality, and biochemical research. Accurate protein analysis depends on meticulous sample collection to prevent degradation by proteases and maintain native structure when required.

Types of Protein Samples

• Serum and plasma: Common in clinical biochemistry for total protein, albumin, and globulin fractions.
• Tissue homogenates: Used in research to study protein expression and function.
• Food proteins: Extracted from meat, dairy, and plant sources for nutritional and quality assessment.
• Microbial proteins: Collected from cultured bacteria or fungi for enzyme assays or proteomics.
• Urine proteins: Monitored in kidney function tests; require careful collection to avoid contamination.

Sample Collection Methods for Proteins

• Use vacutainers with appropriate anticoagulants (e.g., EDTA, heparin) depending on the assay.
• Collect tissue samples aseptically and immediately freeze or use protease inhibitors.
• Homogenize food samples under cold conditions to prevent protein denaturation.
• For urine, collect midstream samples in sterile containers to reduce contamination.
• Transport samples on ice and avoid prolonged exposure to room temperature.

Preservation and Storage of Protein Samples

• Add protease inhibitors to prevent enzymatic degradation especially for tissue and microbial samples.
• Store serum and plasma at 4°C if analysis is within 24 hours; otherwise, freeze at -80°C for long-term storage.
• Freeze tissue samples in liquid nitrogen to preserve protein conformation.
• Avoid repeated freeze-thaw cycles to maintain protein integrity.
• Clearly label samples with collection time, preservative, and storage conditions.

Factors Affecting Protein Sample Integrity

• Delayed processing leading to proteolysis and loss of target proteins.
• Improper anticoagulant choice causing protein precipitation or interference.
• Contamination with hemoglobin or lipids altering protein assays.
• Temperature fluctuations during transport causing denaturation.
• pH changes in samples affecting protein solubility and stability.

1.1.3 Carbohydrates

Carbohydrates are vital energy sources and structural molecules analyzed in clinical, food, and agricultural laboratories. Sampling techniques must consider the solubility and susceptibility of carbohydrates to microbial degradation.

Types of Carbohydrate Samples

• Blood glucose samples: Collected for diabetes monitoring; require specific anticoagulants and rapid processing.
• Food carbohydrate extracts: From cereals, fruits, and vegetables; analyzed for sugar content and quality.
• Plant tissue samples: Used to study starch and cellulose content in agriculture.
• Microbial carbohydrate extracts: Analyzed for exopolysaccharides or cell wall components.
• Urine carbohydrate samples: Collected for metabolic disorder screening.

Sampling Procedures for Carbohydrates

• Collect blood using fluoride oxalate tubes to inhibit glycolysis.
• Homogenize food samples thoroughly to obtain representative carbohydrate content.
• For plant samples, freeze immediately after collection to halt enzymatic activity.
• Use sterile containers for microbial samples to prevent contamination.
• Transport samples on ice and analyze promptly to avoid microbial fermentation.

Preservation and Transport of Carbohydrate Samples

• Store blood samples at 4°C and analyze within 2 hours to prevent glucose loss.
• Freeze plant and microbial samples at -20°C for longer storage.
• Avoid prolonged exposure to heat which can cause carbohydrate degradation.
• Use preservatives such as sodium azide in microbial carbohydrate samples to inhibit microbial growth.
• Label samples with collection time and storage conditions for traceability.

Challenges in Carbohydrate Sample Collection

• Glycolysis in blood samples causing falsely low glucose readings.
• Sample contamination by microbes leading to fermentation and altered carbohydrate levels.
• Incomplete homogenization of food samples causing uneven carbohydrate distribution.
• Delays in freezing plant samples resulting in enzymatic breakdown.
• Use of inappropriate containers that adsorb sugars affecting concentration measurements.

1.1.4 Enzymes

Enzymes catalyse biochemical reactions and are key analytes in clinical diagnostics and research. Their activity is highly sensitive to environmental conditions, making proper sample collection and handling critical.

Types of Enzyme Samples

• Serum and plasma samples: For enzymes such as ALT, AST in liver function tests.
• Tissue extracts: Used for enzyme localization and activity studies.
• Microbial cultures: Analyzed for industrial enzyme production.
• Food samples: Enzymes like amylase and protease are measured for quality control.
• Environmental samples: Soil or water samples analyzed for enzymatic activity indicating microbial presence.

Collection Techniques for Enzymes

• Collect blood samples using anticoagulants that do not inhibit target enzymes.
• Homogenize tissue samples in cold buffer solutions with enzyme stabilizers.
• Use aseptic techniques for microbial cultures to prevent contamination.
• Store food samples under refrigeration immediately after collection.
• Transport environmental samples with minimal delay to preserve enzyme activity.

Preservation and Storage of Enzyme Samples

• Keep samples on ice during transport to slow enzyme degradation.
• Use enzyme stabilizing agents like glycerol or specific inhibitors when necessary.
• Freeze samples at -80°C for long-term storage without loss of activity.
• Avoid repeated freeze-thaw cycles that denature enzymes.
• Maintain pH and ionic strength of buffers to preserve enzyme conformation.

Portfolio of Evidence: Documentation and Traceability

• Record sample source, collection time, and conditions meticulously.
• Maintain chain-of-custody logs to ensure sample integrity.
• Label samples with unique identifiers linked to laboratory information systems.
• Document preservation methods and any deviations from standard protocols.
• Store records securely to support audit and quality assurance processes.

1.1.5 Vitamins

Vitamins are essential micronutrients analyzed in clinical and food laboratories. They are chemically diverse and often sensitive to light, temperature, and oxidation, necessitating careful sampling.

Types of Vitamin Samples

• Serum and plasma: For fat-soluble (A, D, E, K) and water-soluble vitamins (B-complex, C).
• Food samples: Fortified foods and supplements analyzed for vitamin content.
• Urine samples: Used for assessing water-soluble vitamin excretion.
• Plant samples: Leaf and fruit tissues analyzed for natural vitamin content.
• Pharmaceutical preparations: Quality control of vitamin formulations.

Sampling Methods for Vitamins

• Collect blood samples in amber tubes to protect photosensitive vitamins.
• Homogenize food samples rapidly and protect from air exposure.
• Use sterile containers for urine to avoid contamination.
• Freeze plant samples immediately to preserve vitamin stability.
• Collect pharmaceutical samples in original packaging to prevent degradation.

Preservation and Storage of Vitamin Samples

• Store samples in dark containers at 4°C or frozen depending on vitamin type.
• Avoid exposure to light and air to prevent photodegradation and oxidation.
• Analyze samples promptly; delays can cause significant vitamin loss.
• Use antioxidants such as ascorbic acid in sample preparation to protect vitamins.
• Clearly label samples with collection details and storage instructions.

Factors Affecting Vitamin Sample Quality

• Exposure to light causing degradation of vitamins A and C.
• Temperature fluctuations accelerating vitamin loss.
• Improper container materials reacting with vitamin compounds.
• Delayed sample processing leading to enzymatic breakdown.
• Contamination with microbial flora altering vitamin content.

Chapter Summary

This chapter covered the essential procedures involved in performing biochemical tests, starting with the collection of various biochemical samples including lipids, proteins, carbohydrates, enzymes, and vitamins. It then detailed the preparation of key reagents necessary for testing, focusing on buffer solutions and solvents to maintain appropriate chemical conditions. The process of preparing biochemical samples for analysis was explained to ensure accuracy and reliability in test results. The chapter further explored presence-absence tests using specific reagents such as Benedict's solution for reducing sugars, the Biuret test for proteins, Millon’s test for tyrosine-containing proteins, and the Ninhydrin test for amino acids. These tests help in identifying the biomolecular composition of samples. Finally, methods for separating biomolecules were introduced to facilitate further analysis and characterization. Throughout, the chapter emphasized practical laboratory techniques critical for biochemical analysis.