SPEKTROFOTOMETER

SPEKTROFOTOMETER :

ALAT YANG DIGUNAKAN UNTUK MENGUKUR ABSORBANSI ATAU TRANSMISI TERHADAP SUATU SAMPEL

SECARA GARIS BESAR KOMPONEN PERALATAN :

A

SUMBER

B

MONOKROMATOR

C

SAMPEL

D

DETEKTOR

E

PEMBACA

A

B

C

D

E

A.SUMBER CAHAYA

Memberikan cahaya baik tampak,UV ataupun IR

Terdiri dari berbagai panjang gelombang

Jenisnya (kontinyu dan diskontinyu)

Contoh :

Kontinyu : Wolfram lamp ( 350 760 nm) untuk pengukurantampak atau UV dekat.

Diskontinyu : Hg lamps

Lampu Deuterium dan lampu hidrogen spektrum kontinyu di daerah UV (200 dan 450 nm)

Sekarang banyak digunakan lampu kwarts-iodida untuk pengukuran di daerah tampak dan UV

Focus Hg lamp on slit.

Focus projection lens on screen

Align mirror and W. lamp. (The W lamp has a single vertical filament so no slit or lens is necessary.)

Focus W lamp for continuous spectrum.

Align the two spectra by aligning mirror.

Block any stray light with cardboard.

White light dispersed by a prism into the colors of the optical spectrum.

Czerny-Turner monochromator

Diagram of a Czerny-Turner monochromator.In the common Czerny-Turner design, the broad band illumination source (A) is aimed at an entrance slit (B). The amount of light energy available for use depends on the intensity of the source in the space defined by the slit and the acceptance angle of the optical system. The slit is placed at the effective focus of a curved mirror (the collimator, C) so that the light from the slit reflected from the mirror is collimated (focused at infinity). The collimated light is refracted by the prism or diffracted from the grating (D) and then is collected by another mirror (E) which refocuses the light, now dispersed, on the exit slit (F). At the exit slit, the colors of the light are spread out (in the visible this shows the colors of the rainbow). Because each color arrives at a separate point in the exit slit plane, there are a series of images of the entrance slit focused on the plane. Because the entrance slit is finite in width, parts of nearby images overlap. The light leaving the exit slit (G) contains the entire image of the entrance slit of the selected color plus parts of the entrance slit images of nearby colors. A rotation of the dispersing element causes the band of colors to move relative to the exit slit, so that the desired entrance slit image is centered on the exit slit. The range of colors leaving the exit slit is a function of the width of the slits. The entrance and exit slit widths are adjusted together.

Color Wavelength FrequencyViolet 380450nm 668789THzBlue 450495nm 606668THzGreen 495570nm 526606THzYellow 570590nm 508526THzOrange 590620nm 484508THzRed 620750nm 400484THz

Relationship with frequency

Wavelength is determined using the formula

where v is the phase speed of the wave and f is its frequency. In the case of electromagnetic radiation, such as light, in a vacuum, this speed is the speed of light, 299,792,458m/s or about 3108 m/s. For sound waves in air, this is the speed of sound, 343 m/s (1238 km/h) in air at room temperature and atmospheric pressure. Usually, SI units are used, where the wavelength is expressed in metres, the frequency in hertz, and the propagation speed is in metres per second.

For example, the wavelength for a 100 MHz electromagnetic (radio) wave is about: 3108 m/s divided by 100106 Hz = 3 metres. Electronic engineers often use a shortcut formula: wavelength in metres = 300 Mm/s divided by the frequency in MHz, to avoid counting the (many) zero digits in the decimal or scientific notations.

It should be noted that for many wave phenomena, wavelength is not the distance that particles travel during a period. For instance, in acoustics and water waves, the particle displacements during a period are only a small fraction of the wavelength, apart from extreme conditions like breaking waves and shock waves.

It should also be noted that frequency and wavelength can change independently, but only when the speed of the wave changes. For example, when light enters another medium, its speed and wavelength change while its frequency does not (cf. refraction).

Wavelength of a sine wave.

CUVETTE (WADAH SAMPEL)

CUVETTE (WADAH SAMPEL)

CUVETTE (WADAH SAMPEL)

Structure and operating principles

SCHEMATIC FILTER FOTOMETER

Schematic diagram grating/prisma spektrofotometer

Schematic diagram double beam spektrofotometer

SPEKTROFOTOMETER