Separation of acid-soluble constituents of soil humic acids by dissolution in alkaline urea solution and precipitation with acid

Chemical and Biological Technologies in Agriculture

Table 2 Positions and relative intensities of the fluorescence peaks

Fraction	Peak^a	Fujisaki		Dando		Takizawa
Fraction	Peak^a	λ _ex/λ _em ^b	QSU	λ _ex/λ _em ^b	QSU	λ _ex/λ _em ^b	QSU
Whole	H1	270/505	65	265/505	54	275/540	134
	H2	–	–	310/510	36	–	–
	H3	365/505	27	360/505	23	–	–
	H4	430/510	18	460/515	16	450/540	48
NaOH
Precipitated	H1	270/505	54	270/510	56	275/545	180
	H2	–	–	310/510	38	–	–
	H3	365/505	22	365/505	23	–	–
	H4	430/505	16	450/510	18	450/535	57
DAX-8-adsorbed	F1	220/430	107	220/430	100	220/430	104
	F2	255/435	77	255/440	71	255/435	80
	F3	310/435	57	310/435	55	310/435	59
NaOH + urea
Precipitated	H1	270/505	48	270/510	69	275/545	181
	H2	–	–	310/510	48	–	–
	H3	360/505	21	365/505	27	–	–
	H4	430/505	16	450/510	21	450/540	59
DAX-8-adsorbed	F1	220/435	105	210/435	96	220/435	154
	F2	260/435	89	260/440	72	260/440	127
	F3	305/435	58	–	–	305/440	81
	P	–	–	275/315	32	–	–
DAX-8-non-adsorbed (>1 kDa)	F1	–	–	215/430	30	225/440	29
	F2	270/465	31	–	–	–	–
	F3	–	–	310/435	15	–	–
	P	280/330	14	270/310	12	270/310	26