Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Stability Testing of Metronidazole by Ultraviolet Fluorescence Method

Video generation prompt: Prepare a metronidazole solution, expose one sample to ultraviolet light, and keep the other as a control. Then measure the fluorescence intensity using a UV fluorescence spectrophotometer. Clearly present the procedures for sample preparation, UV irradiation, and instrument measurement.

Evaluation guide:
(i) Target concept: UV-induced photodegradation of metronidazole reduces its fluorescence quantum yield, enabling stability assessment via comparative fluorescence intensity measurement.
Minimum mechanism: Metronidazole must remain chemically intact in solution (no decomposition products altering absorption/emission profile); UV exposure must be sufficient to cause measurable fluorescence quenching but insufficient to induce visible degradation (e.g., color change); fluorescence measurement must occur post-exposure under identical instrumental conditions.
(ii)Storyline: Frame 1–3: Two identical filled vials placed side-by-side on bench; UV lamp off. Frame 4–6: UV lamp activates and illuminates only the right vial; the left vial remains unlit; both vials retain a clear, colorless liquid appearance. Frame 7–8: Lamp deactivates; spectrophotometer aligns with the right (previously irradiated) vial for its reading, and that vial now looks visibly dimmer than it did while glowing under the lamp. Frame 9–10: Spectrophotometer aligns with the left (control) vial for its reading, and the control vial's fluorescence looks brighter than the irradiated vial's did at the same step; any on-screen numeric readout is optional and does not need to show legible or precisely ordered digits; the qualitative brightness difference between the two readings is what establishes the result. Throughout: fixed overhead/frontal viewpoint; no object relocation; consistent lighting geometry; no non-fluorescent phenomena (e.g., bubbles, cloudiness, color shift) observed.

Manual:
Experimental Procedure
1. Prepare two identical metronidazole solutions in clear glass vials.
2. Place vials side-by-side; expose only one to UV light for defined duration.
3. Measure fluorescence intensity of each vial using UV fluorescence spectrophotometer.
Observation of Experimental Phenomena
- UV-irradiated vial shows reduced fluorescence intensity vs. control vial.
- No color change, precipitation, or turbidity occurs in either vial.
Summary of Experimental Principles
Metronidazole degrades under UV light, decreasing its native fluorescence signal; quantified via comparative fluorescence intensity measurement.

Prompt Grounding rubric:
level_1: None of the required apparatus is shown: no metronidazole-solution vial, no UV lamp, and no fluorescence spectrophotometer appear anywhere in the video; there is nothing suggesting a two-sample (control vs. irradiated) setup at all.
level_2: Only one required element appears in isolation (e.g., a single glass vial of clear liquid, or a lamp-like object, or a boxy benchtop instrument with a sample port), and it is never joined by the others; the two vials are never shown together, and no vial is ever brought near the spectrophotometer's sample port.
level_3: Two visually matching glass vials of clear liquid sit together on a bench, and a separate benchtop UV fluorescence spectrophotometer with a sample port is also visible in the same scene; a UV lamp is positioned over one vial while the other vial has no lamp near it.
level_4: Everything in score 3 holds, and additionally the lamp only ever shines on the one vial it is positioned over (never the other), the two vials keep the same left/right placement from their first appearance to their last, and the spectrophotometer's sample port is shown receiving first one vial and then the other, matching the prompt's prepare-then-irradiate-then-measure sequence.
level_5: Everything in score 4 holds, and additionally the previously irradiated vial is visually distinguishable from the control vial at the measurement stage (through a visible glow/dimming difference, a clear lamp-on/lamp-off state, or an on-screen label such as "control"/"UV-exposed"); the spectrophotometer is shown taking one reading per vial as two separate measurement events (any on-screen numbers are not required to be legible or correctly ordered to satisfy this level); and no extra vials, lamps, or instruments appear beyond what the procedure calls for.

Scientific and Causal Correctness rubric:
level_1: No plausible photodegradation-quenching phenomenon is depicted: both vials glow with the same intensity, or neither vial glows while the UV lamp is on, or the liquid turns yellow/brown or becomes cloudy/precipitates, none of which occur in this stability test on the timescale shown.
level_2: A brightness difference between the two vials is shown, but it is wrong for the phase in which it appears: e.g., while the UV lamp is still on, the un-irradiated control vial (sitting outside the lamp's beam) glows as bright as or brighter than the vial actually under the lamp; both vials glow at the same time regardless of which one the lamp is over; or, by the time the irradiated vial reaches the spectrophotometer, it still glows at full, undimmed brightness despite having sat under the lamp for some time.
level_3: While the UV lamp is on, only the vial under the lamp shows any fluorescence glow and the control vial stays dark; by the time both vials reach the spectrophotometer for their reading, the previously irradiated vial appears visibly dimmer (lower fluorescence) than the control vial, consistent with UV exposure lowering metronidazole's native fluorescence.
level_4: Everything in score 3 holds, and additionally the glow appears only while the lamp is actively on the irradiated vial (not before exposure or after the lamp is switched off), the dimmer-vs-brighter comparison is shown for both vials passing through the same measurement step in the same way (a like-for-like comparison), and neither vial shows an unrelated change (no color shift, no bubbling, no cloudiness) that would misrepresent the phenomenon.
level_5: Everything in score 4 holds, and additionally the control vial's glow at measurement looks the same as it did before any UV exposure (it has not degraded on its own), the irradiated vial's dimming reads as a genuine intensity reduction rather than the vial simply sitting farther from the light source or camera, and if the spectrophotometer's screen shows any readout at all, the visual impression unambiguously indicates the irradiated sample's signal is the lower of the two (exact digits are not required to be legible).

Spatiotemporal Consistency rubric:
level_1: The metronidazole vials or the UV lamp cut or jump between positions from one frame to the next (e.g., a vial that was on the left side of the bench is suddenly on the right, or the lamp blinks out and shows up somewhere else on the bench a moment later); the spectrophotometer's position or orientation changes abruptly between shots with no transition; the liquid level or clarity inside a vial changes instantaneously with no visible cause; the room's ambient lighting shifts erratically apart from the controlled UV-lamp on/off cycle (e.g., a shadow vanishes and then reappears with no cause); a vial visibly deforms or changes transparency with no cause.
level_2: Multiple medium-severity breaks: e.g., UV lamp turns on/off with visible flicker or strobing; vial contents jitter or shimmer unnaturally; spectrophotometer arm moves with jerky motion; background objects blink in/out; one vial rotates while the other stays fixed.
level_3: The two vials stay in the same left-right arrangement on the bench for the entire clip, the UV lamp stays fixed in place above the vial it was set over, and the spectrophotometer does not change location; whenever something moves (the lamp switching on, a vial being brought to the spectrophotometer's sample port), the motion is continuous and physically plausible rather than jumping or popping into a new position.
level_4: Everything in score 3 holds, and additionally the UV lamp's transition from off to on is a single smooth brightening rather than flashing or pulsing, any motion of a vial toward the spectrophotometer is shown from start to finish without skipped segments, and the three steps in the prompt (preparing the vials, irradiating one, then measuring both) occur in that order without repeating or reversing a step.
level_5: Everything in score 4 holds, and additionally the camera framing stays fixed with no panning, tilting, or zooming during the sequence, the liquid surface in each vial stays level and undisturbed once the vials are set down, and the relative arrangement of the lamp, the two vials, and the spectrophotometer (which side each sits on, how far apart they are) is unchanged from the beginning of the clip to the end.