The choice of solvent in TLC is critical as it directly influences the separation and resolution of the components in a mixture. Several factors are considered when selecting an appropriate solvent:

1. Polarity: The solvent's polarity should be compatible with the substances being analysed and the stationary phase. A general guideline is "like dissolves like"; polar compounds are better separated using polar solvents, and non-polar compounds with non-polar solvents.

2. Solvent Strength: The solvent must adequately dissolve the sample and carry it up the plate without causing excessive or insufficient separation.

3. Compatibility with the Stationary Phase: The solvent should not react with or dissolve the stationary phase. For instance, silica gel, a common stationary phase in TLC, is compatible with a wide range of solvents except for strongly basic ones.

4. Evaporation Rate: Ideally, the solvent should have an evaporation rate that allows for easy drying of the plate after development without affecting the separated spots.

5. Environmental and Safety Considerations: Less toxic and environmentally harmful solvents are preferred for safety and sustainability.

Experimentation and experience often guide the final choice, with initial trials conducted using solvents of varying polarities to determine the most effective solvent system for a given analysis.

Temperature variations can significantly impact the efficiency and resolution of separations in column chromatography (CC) due to their influence on several key factors:

1. Solubility: Temperature changes can alter the solubility of components in the mobile phase, potentially affecting how well compounds are separated as they move through the column.

2. Viscosity of the Mobile Phase: Higher temperatures generally decrease the viscosity of liquids, which can increase the flow rate of the mobile phase through the column. While this might seem beneficial in terms of speed, too fast a flow can lead to poorer separation.

3. Interaction with the Stationary Phase: Temperature can affect how components interact with the stationary phase. Increased temperatures might reduce the retention time of compounds by decreasing their interaction with the stationary phase, leading to faster elution but potentially less resolution.

4. Diffusion Rates: Elevated temperatures increase the diffusion rates of molecules, which can lead to broader peak shapes in the chromatograms, affecting the resolution negatively.

Therefore, maintaining a consistent and optimal temperature is crucial for reproducible and high-quality separations in CC. In some advanced applications, temperature gradients are deliberately used to control separations more finely.

In gas chromatography (GC), the purity of the carrier gas is paramount for several reasons, all contributing to the accuracy, sensitivity, and reliability of the analysis:

1. Baseline Stability and Noise: Impurities in the carrier gas can lead to fluctuations in the baseline, increased noise, and false peaks, complicating the interpretation of chromatograms and potentially masking or mimicking the presence of analytes.

2. Detector Sensitivity: Contaminants in the carrier gas can adversely affect the sensitivity of detectors like the Flame Ionisation Detector (FID) or Mass Spectrometer (MS), leading to poorer detection limits and quantification errors.

3. Peak Shape and Resolution: Impurities can interact with analytes or the stationary phase, leading to peak broadening, tailing, or splitting, which diminishes the resolution between closely eluting compounds.

4. Longevity of the Column and Equipment: Clean carrier gases reduce the risk of contamination and degradation of the column and other sensitive components of the GC system, extending their operational life and maintaining performance.

Hence, high-purity gases, typically 99.999% pure or better, are used in GC to ensure that the analyses are not compromised by gas-related contaminants.

Chromatography can indeed be employed to separate and analyse inorganic compounds, although the techniques and considerations might differ slightly from those used for organic compounds. Here's how chromatography is adapted for inorganic analysis:

1. Ion Chromatography (IC): IC is a powerful technique specifically designed for separating ions and polar molecules. It is widely used to analyse inorganic compounds, especially water-soluble ions such as cations (e.g., Na⁺, K⁺, Ca²⁺) and anions (e.g., Cl⁻, SO₄²⁻, NO₃⁻).

2. Stationary and Mobile Phases: Inorganic chromatography often involves stationary phases that can interact specifically with inorganic ions, such as ion-exchange resins. The mobile phase may contain complexing agents or buffers to maintain a consistent pH and ionic strength, which are critical for the separation of ionic species.

3. Detection Methods: Conductivity detectors are commonly used in IC because many inorganic compounds are ions in solution. Other detectors, like UV-Vis spectrophotometers and mass spectrometers, can also be used, depending on the specific inorganic analytes and their properties.

The choice of chromatographic method and conditions for inorganic analysis is guided by the charge, size, and polarity of the inorganic species, as well as the matrix of the sample being analysed.

The complexity of a mixture, in terms of the number of components, the range of their chemical properties (such as polarity, volatility, and molecular weight), and the concentration levels, significantly influences the choice of chromatographic technique:

1. Number of Components: Mixtures with a large number of components often require high-resolution techniques like GC or high-performance liquid chromatography (HPLC) to achieve effective separation.

2. Range of Chemical Properties: Mixtures containing a wide range of polarities or molecular weights may necessitate the use of more versatile chromatographic methods, such as HPLC, which can accommodate a broader range of mobile and stationary phases. Techniques like gradient elution in HPLC are particularly useful for such mixtures.

3. Volatility and Stability: For volatile and thermally stable compounds, GC is typically preferred. Non-volatile or thermally labile compounds are better suited to liquid chromatographic techniques.

4. Sample Quantity and Concentration Levels: Techniques like TLC and CC might be chosen for preparative purposes or when larger sample quantities are involved. Analytical techniques like GC and HPLC are chosen for their sensitivity and precision, especially when dealing with trace analysis.

Ultimately, the chromatographic technique is selected based on a careful consideration of the mixture's complexity along with the specific requirements of the analysis, such as resolution, sensitivity, and throughput.