Domain: Engineering — Food and Bioprocess Engineering
Target concept: Thiamine Determination (Fluorometric Method)

Video generation prompt: Add 2 mL of rice extract to a test tube, then add an alkaline potassium ferricyanide solution. Mix thoroughly and expose to a UV lamp.

Evaluation guide:
(i) Target concept: UV-induced blue-white fluorescence of thiochrome derived from thiamine oxidation
Minimum mechanism: Rice extract must contain free thiamine; alkaline potassium ferricyanide must oxidize thiamine to thiochrome in situ; thiochrome must remain soluble in the alkaline reaction mixture; UV photons at 365 nm are absorbed and re-emitted as a bluish-white fluorescence from the liquid in the tube. Note this is a simplified, non-extraction version of the assay: the standard method separates thiochrome into an isobutanol layer before viewing, so here the reaction mixture's own residual brownish-yellow ferricyanide color can dampen or partially mask the glow (an inner-filter effect) rather than allowing a perfectly clean emission.
(ii)Storyline: Frame 0–1: Empty test tube stationary in frame. Frame 2–3: Pipette delivers colorless liquid (rice extract) into tube up to ~2 mL level. Frame 4–5: Second pipette delivers brownish-yellow alkaline potassium ferricyanide solution into same tube. Frame 6–7: Hand performs continuous inversion/vortex mixing; liquid fully homogenized with no layering. Frame 8–10: UV lamp activates; violet glow appears on lamp housing, then a bluish-white fluorescence emerges within the liquid column (possibly muted by the mixture's own brownish-yellow tint), with no delay in onset and no persistence after the lamp is switched off. All events occur from fixed frontal close-up view; no cutaways; no off-screen actions; visibility maintained for tube, reagents, lamp head, and hand motion path.

Manual:
Experimental Procedure
1. Place a clean test tube upright on bench.
2. Add 2 mL of colorless rice extract to the tube.
3. Add alkaline potassium ferricyanide solution (brownish-yellow) to the tube.
4. Mix thoroughly by gentle inversion or vortexing.
5. Expose tube to UV lamp (365 nm) for observation.
Observation of Experimental Phenomena
A bluish-white fluorescence appears within the liquid phase only after UV exposure begins, though it may look somewhat muted by the mixture's own brownish-yellow color; no fluorescence occurs before UV exposure, and the emission ceases promptly once the UV lamp is switched off.
Summary of Experimental Principles
Thiamine in rice extract reacts with alkaline potassium ferricyanide to form thiochrome, which fluoresces blue-white under UV light (365 nm). The standard AOAC assay first extracts thiochrome into isobutanol to separate it from the reaction mixture's own brownish-yellow color, which can otherwise dampen or partially mask the fluorescence (an inner-filter effect); this procedure omits that extraction step, so the glow is viewed directly in the aqueous reaction mixture and may appear somewhat muted rather than at full brightness. The response still requires both reagent addition and UV excitation to appear.

Prompt Grounding rubric:
level_1: None of the required setup elements appear together: no test tube, no rice extract, no alkaline potassium ferricyanide solution, no UV lamp, no mixing action, and no moment where the tube is exposed to UV light.
level_2: A test tube with some liquid appears, but the rice extract isn't identifiable (wrong container, no clear ~2 mL amount, or nothing suggesting rice extract specifically); the ferricyanide solution is never visibly added; the UV lamp appears but is never switched on or pointed at the tube; or any mixing shown happens on the wrong container.
level_3: The tube holds a liquid with a meniscus near a plausible 2 mL mark (or a pipette clearly delivers about that amount); a second liquid with a noticeably different color and thickness is then added to the same tube; the contents are mixed by hand; and a UV lamp is present and aimed at the tube.
level_4: The 3-point setup is present, and the four steps happen in the right order with nothing skipped or extra: rice extract added first, ferricyanide solution added second, the two mixed together, and only then does UV exposure begin, with no pouring shown before the tube is in place and no stirring shown after the lamp is already lit.
level_5: Beyond the 4-point sequence, the test tube is a standard laboratory tube with visible graduation marks, the rice extract looks colorless and clear before anything is added, the ferricyanide solution is visibly brownish-yellow as it goes in, the mixing motion (inversion or swirling) is smooth and consistent rather than one quick shake, the UV lamp gives off a visible violet-tinged glow (not plain white or blue) and lights mainly the tube rather than the whole background, and the entire sequence stays in a fixed close-up view showing just the tube, the reagents, and the lamp head.

Scientific and Causal Correctness rubric:
level_1: No color or brightness change happens when the UV lamp comes on: the tube's contents look the same brownish-yellow (or colorless) under UV as before, with no distinguishable glow; or a bluish-white glow shows up with the lamp off or before the ferricyanide reagent has even been added.
level_2: A glow appears, but not tied to the chemistry being shown: it shows up before the UV lamp is on, or without the ferricyanide reagent added, or the color is clearly wrong for this reaction (green, red, or plain white instead of bluish-white), or the glow seems to come from the lamp housing or background rather than the liquid in the tube.
level_3: Once the UV lamp is on and only after the rice extract and ferricyanide solution have been mixed, the liquid in the tube visibly develops a bluish-white glow; the glow is distinguishable from the mixture's own brownish-yellow tint even if somewhat muted by it, and there is no glow at all before the lamp is switched on.
level_4: The 3-point response is present, and in addition the glow visibly builds up over roughly the first second or two of UV exposure rather than snapping on at full strength, holds steady rather than flickering while the lamp stays on, and fades out promptly if the lamp is shown being switched off.
level_5: Beyond the 4-point response, the glow stays confined to the liquid itself rather than smearing across the tube wall or hovering above the meniscus as a separate halo, looks roughly even along the length of the liquid column rather than showing an isolated bright patch or dark gap, and the liquid stays a single well-mixed phase throughout: no cloudy precipitate or separated layer forms during or after the UV exposure.

Spatiotemporal Consistency rubric:
level_1: Severe breaks in continuity: the test tube instantly appears in a different spot or orientation between shots with no motion connecting them, reagent bottles or the pipette vanish or appear without being carried in or out of frame, the UV lamp's glow or position jumps discontinuously, the mixing motion suddenly reverses or skips, or the room lighting flips between bright and dark with no lamp movement to explain it.
level_2: Smaller continuity problems: a hand carrying the pipette enters the frame but the pipette tip is never actually shown reaching the tube opening; the mixing motion starts abruptly at full speed with no build-up; the UV lamp switches on with no visible button press, click, or indicator light; or the shadows cast by the tube and hand point in different directions from one moment to the next.
level_3: The test tube stays in the same spot on the bench throughout; the pipette and reagent bottle stay visible and close to the tube while each liquid is added; the hand doing the mixing enters from the same side each time; the UV lamp stays fixed in position and orientation once placed; and the lighting stays steady enough that shadows from the tube and hand don't swap direction or intensity between shots.
level_4: The 3-point continuity is present, and in addition the motions are smooth and physically believable: the pipette moves straight down into the tube without wobbling sideways, the mixing motion flows continuously rather than freezing or jumping, the UV lamp's glow brightens gradually rather than snapping instantly to full intensity, and no object appears to stretch, warp, or resize between frames.
level_5: Beyond the 4-point smoothness, depth relationships stay consistent: the tube in the foreground, the hand and pipette in the midground, and the lamp base in the background keep believable relative sizes and positions as anything moves; the straight walls of the test tube stay straight with no lens-distortion warping; the mixing motion shows no jittery double-image or strobe-like look; and the ambient room light and the UV-induced glow change together smoothly rather than one jumping while the other lags.