Table 2.

Standards for quantification of organic acids.

No.	Organic acid standard mix in μl	Tricarballylic acid in μl	Water in μl	Phosphoric acida 4 mol/l in μl
St 1	0	100	800	100
St 2	20	100	780	100
St 3	50	100	750	100
St 4	100	100	700	100
St 5	200	100	600	100
St 6	400	100	400	100
St 7	600	100	200	100
St 8	800	100	0	100

^aFor quantification of organic acids by GC–MS phosphoric acid must be replaced by TFA.