Table 1.
Different spectrophotometric methods for the determination of caffeine.
| S. number | Method | Linearity range for caffeine | UV-vis spectral range | Sample | Solution | Reference |
|---|---|---|---|---|---|---|
| 1 | Chemometric methods for spectral investigation (1) Inverse least square (2) Principal component analysis |
12–56 μg/mL | 225–285 nm | Pharmaceuticals (Metamizol, acetaminophen, and caffeine) |
0.1 M HCl | [12] |
|
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| 2 | Simple and derivative spectrophotometry | 12–28 μg/mL | 200–350 nm | Pharmaceuticals (Phenylpropanolamine HCl, caffeine, and diazepam) |
Water, chloroform, and petroleum ether | [13] |
|
| ||||||
| 3 | Derivative ratio spectra-zero crossing procedure | 1–5 μg/mL | 244.8–276.9 nm | Pharmaceuticals (Paracetamol, propyphenazone, and caffeine) |
0.1 M HCl | [18] |
|
| ||||||
| 4 | Ratio spectra spectrophotometry and chemometric methods viz, classical least squares, and inverse least squares | 4–40 μg/mL | 225–285 nm | Pharmaceuticals (Chlorphenoxamine hydrochloride and caffeine) |
0.1 M HCl | [14] |
|
| ||||||
| 5 | Multivariate calibration and N-way partial least squares (PLS) | 2–6 μg/mL | 210–300 nm | Pharmaceuticals (Acetylsalicylic acid, paracetamol, and caffeine) |
Water | [15] |
|
| ||||||
| 6 | Multivariate calibration method and chemometric methods viz, partial least squares, and principle component regression | .05–20 μg/mL | 190–300 nm | Pharmaceuticals (Phenytoin, barbital, and caffeine) |
Water/methanol (1 : 1, v/v) | [16] |
|
| ||||||
| 7 | Continuous wavelet transform and derivative transform (using Savitzky-Golay filters) | 2–50 μg/mL | 220–300 | Pharmaceuticals (Paracetamol and caffeine) |
0.1 M HCl | [17] |
|
| ||||||
| 8 | H-point standard addition method | 0.1–3.0 μg/mL | 453 nm | Pharmaceuticals (Paracetamol and caffeine) |
Water | [24] |
|
| ||||||
| 9 | Simultaneous equation method and Q-absorbance equation at isosbestic point | 2–32 μg/mL | 200–400 nm | Pharmaceuticals (Paracetamol and caffeine) |
Water | [19] |
|
| ||||||
| 10 | Isoabsorption assay method | — | 200–300 nm | Pharmaceuticals (Caffeine and sodium benzoate) |
Water | [20] |
|
| ||||||
| 11 | Simultaneous equation method and absorbance ratio method | 0–25 μg/mL | 200–400 nm | Pharmaceuticals (Acetylsalicylic acid and caffeine) |
0.1 N NaOH | [21] |
|
| ||||||
| 12 | Simultaneous equation method and absorbance ratio method | 1.14–2.05 μg/mL | 200–400 nm | Pharmaceuticals (Acetylsalicylic acid and caffeine) |
0.1 N HCl | [22] |
|
| ||||||
| 13 | Partial least squares regression, genetic algorithm coupled with PLS, and principle component-artificial neural network | 1–18 μg/mL | 200–400 nm | Pharmaceuticals (Paracetamol, ibuprofen, and caffeine) |
Methanol/0.1 N HCl (3 : 1, v/v) | [23] |
|
| ||||||
| 14 | Simple spectrophotometric method with coupling reagent | 0.1–1 μg/mL | 500–750 nm | Alkaloids (caffeine and theophylline) | Water | [25] |
|
| ||||||
| 15 | First-derivative spectrophotometry | 4–40 μg/mL | 220–360 nm | Pharmaceuticals (Chlorpheniramine maleate and caffeine) |
Ethanol | [26] |
|
| ||||||
| 16 | Derivative spectrophotometric methods (first, second, and third-order spectra) | 2–10 μg/mL | 190–350 nm | Beverages (caffeine) | Water | [27] |
|
| ||||||
| 17 | Simple spectrophotometric method | 5–25 μg/mL | 271 nm | Paullinia cupana var. sorbilis (tannins and caffeine) | Sulfuric acid (2.5%) | [28] |
|
| ||||||
| 18 | Simple spectrophotometric method (Solvent study) | 0–20 μg/mL | 180–400 nm | Tea (caffeine) | Water, ethyl acetate, chloroform, and methanol | [34] |
|
| ||||||
| 19 | UV-spectrophotometry | 10–60 μg/mL | 200–600 | Soft and energy drinks (caffeine) | Carbon tetrachloride | [35] |
|
| ||||||
| 20 | Simple spectrophotometric method | 10–50 μg/mL | 200–400 nm | Drugs (caffeine) | Water | [36] |