4.3 Phng php quang ph hunh quang

Phng php quang ph hunh quang l phng php phn tch da trn php o cng hunh quang pht ra t mt cht ho hc khi n c kch thch do hp th bc x t ngoi, kh kin hoc cc bc x in t khc. Trong phng php ny, cng hunh quang ca cht th c so snh vi cng hunh quang ca cht chun o trong cng iu kin.

My

Vn hnh my quang ph hunh quang theo ch dn ca hng sn xut my.

Phng php tin hnh

Chun b dung dch nh m t trong chuyn lun, chuyn dung dch vo cc o ca my quang ph hunh quang v chiu vo n bc x kch thch vi bc sng n sc c ghi trong chuyn lun. o cng hunh quang ca dung dch bc sng pht hunh quang c ghi trong chuyn lun.

nh lng, a vo my cc ng dung mi hoc hn hp dung mi dng ho tan mu th v iu chnh my v im "0". a dung dch chun c chun b nh m t trong chuyn lun vo my v iu chnh nhy ca my kt qu c trn thang o ln hn 50. Nu thay i khe sng khi iu chnh ln th hai th phi t li im 0 v cng hunh quang ca chun cng phi c o li. Cui cng, a mu th vo my, o cng hunh quang v tnh nng ca dung dch th theo cng thc sau:

 

Cx = ( Ix x Cs ) / Is

 

Trong :

Cs v Cx ln lt l nng ca dung dch chun v dung dch th.

Is v Ix ln lt l cng hunh quang ca dung dch chun v dung dch th.

Khi cng hunh quang khng tht s t l thun vi nng , vic nh lng c th c thc hin da trn th chun.

Trong mt s trng hp, php nh lng c th c so snh vi mt mu chun i chiu c bn cht ho hc khc mu th (V d: thy tinh pht hunh quang hoc dung dch mt cht pht hunh quang khc vi mu th). Trong trng hp ny, nng ca cht th phi c xc nh bng th chun o trong cng iu kin vi mu th.