Calculate the friability percentage from the given weights.

Initial average weight ($W_i$) = 6.80 g
Final average weight ($W_f$) = 6.72 g
The friability percentage is calculated as:

The acceptable limit for friability of most tablets, according to pharmacopoeial standards (e.g., USP), is generally not more than $1\%$. Since the calculated friability is approximately $1.176\%$, which is greater than $1\%$, the tablets fail the friability test.

As a Pharmacy Technologist in the Quality Control (QC) department, the decision would be to reject the batch of ibuprofen tablets. The QC department should inform the QA department that the batch does not meet the required quality standards for friability. The QA department would then be responsible for initiating an investigation into the manufacturing process to identify the root cause of the high friability and prevent future occurrences, and for communicating this non-conformance to the Zambia Medicine Regulatory Authority.

D.1.
Lambert-Beer's Law states that the absorbance of a solution is directly proportional to the concentration of the analyte and the path length of the light through the solution. It is mathematically expressed as:

Where:

• $A$ is the absorbance (unitless)
• $\epsilon$ is the molar extinction coefficient or molar absorptivity (L/mol/cm)
• $b$ is the path length of the light through the sample (cm)
• $c$ is the concentration of the analyte (mol/L)

D.2.

Absorbance ($A$) = 0.782
Extinction coefficient ($\epsilon$) = 0.221 L/mol/cm
Path length ($b$) = 1 cm (standard cuvette path length)

The concentration of paracetamol is $\boxed{\text{3.538 mol/L}}$.

D.3.
The wavelength of 250 nm falls within the ultraviolet (UV) region of the electromagnetic spectrum. For analysis in the UV region, quartz or fused silica cuvettes are typically used because they do not absorb UV light, unlike glass cuvettes which absorb UV radiation.

D.4.
A graph for paracetamol qualitative analysis (UV-Vis spectrum) would show absorbance as a function of wavelength. Paracetamol typically exhibits a maximum absorbance ($\lambda_{max}$) around $243-257$ nm.

E.
Erythromycin being in Biopharmaceutical Classification System (BCS) Category IV means that it has low solubility and low permeability. This implies that the drug is poorly absorbed from the gastrointestinal tract, leading to low and variable bioavailability, which can make it challenging to formulate into an effective oral dosage form.

E.a.
Strategies to suggest in formulating erythromycin tablets (a BCS IV drug) include:

• Solubility enhancement: Techniques such as micronization, nanonization, solid dispersion, cyclodextrin complexation, or salt formation can increase the dissolution rate and solubility of erythromycin.
• Permeability enhancement: Using permeation enhancers (e.g., surfactants, bile salts) in the formulation to improve its ability to cross biological membranes.
• Lipid-based formulations: Formulating erythromycin into lipid-based systems (e.g., self-emulsifying drug delivery systems - SEDDS) can improve both solubility and permeability.
• Prodrug approach: Modifying the chemical structure of erythromycin to a prodrug that has better solubility and/or permeability, which then converts back to the active drug in the body.

F.a.
High-Performance Liquid Chromatography (HPLC) works by separating components of a mixture based on their differential partitioning between a stationary phase (a packed column) and a mobile phase (a liquid solvent) that is pumped through the column under high pressure. The sample is injected into the mobile phase, and as it travels through the column, components that interact more strongly with the stationary phase will elute later, while those that interact less strongly will elute earlier. A detector then measures the separated components as they exit the column.

Three uses of HPLC are:

• Quantitative analysis: Determining the amount or concentration of a specific compound in a sample (e.g., drug content in a tablet).
• Qualitative analysis: Identifying the components present in a mixture by comparing their retention times and spectral data with known standards.
• Separation and purification: Isolating specific compounds from complex mixtures for further analysis or use.

F.b.
Parameters used for qualitative analysis of API during HPLC analysis include:

• Retention time ($t_R$): The time it takes for the API to elute from the column under specific chromatographic conditions. This is compared to the retention time of a known standard.
• Spectral data: If a UV-Vis detector or mass spectrometer is coupled with the HPLC, the characteristic UV spectrum or mass fragmentation pattern of the API can be used to confirm its identity.

F.c.
Parameters used for quantitative analysis of API during HPLC analysis include:

• Peak area: The area under the chromatographic peak corresponding to the API, which is directly proportional to its concentration.
• Peak height: The height of the chromatographic peak, also proportional to concentration, especially for narrow peaks. These values are typically compared against a calibration curve generated from known concentrations of the API standard.