ตารางแสดงค่า Ka และ pKa ที่ 25 oC ของกรดบางชนิดที่ใช้เตรียมสารละลายบัฟเฟอร์
กรด
Ka
pKa
Oxalic acid
5.37x10-2
1.27 (pKa1)
H3PO4 (phosphoric acid)
7.08x10-3
2.15 (pKa1)
Citric acid
7.41x10-4
3.13 (pKa1)
HCOOH (formic acid)
1.78x10-4
3.75
Succinic acid
6.17x10-5
4.21 (pKa1)
Oxalate-
5.37x10-5
4.27 (pKa2)
Citrate-
1.74x10-5
4.76 (pKa2)
CH3COOH (acetic acid)
1.74x10-5
4.8
Succinate-
2.29x10-6
5.64 (pKa2)
2-(N-Morpholino) ethane sulfonic acid (MES)
8.13x10-7
6.09
Cacodylic acid
5.37x10-7
6.27
H2CO3 (carbonic acid)
4.47x10-7
6.35 (pKa1)
Citrate2-
3.98x10-7
6.40 (pKa3)
N-(2-Acetamido)-iminodiacetic acid (ADA)
2.69x10-7
6.57
Piperazine-N, N -bis(2-ethanesulfonic acid) (PIPES)
1.74x10-7
6.76
N-(2-Acetamido)-2-aminoethanesulfonic acid (ACES)
1.58x10-7
6.80
H2PO4- (dihydrogen phosphate)
1.51x10-7
6.82 (pKa2)
3-(N-Morpholino)propanesulfonic acid (MOPS)
7.08x10-8
7.15
N-2-Hydroxyethylpiperazine-N -2-ethanesulfonic acid (HEPES)
3.39x10-8
7.47
N-2-Hydroxyethylpiperazine-N -3-propanesulfonic acid (HEPPS)
1.10x10-8
7.96
N-[Tris(hydroxymethyl)methyl]glycine (Tricine)
8.91x10-9
8.05
Tris(hydroxymethyl)aminomethane (TRIS)
8.32x10-9
8.08
N, N-Bis(2-hydroxyethyl)glycine (Bicine)
5.50x10-9
8.26
Glycylglycine
5.62x10-9
8.25
Boric acid
5.75x10-10
9.24
NH4+ (ammonium)
5.62x10-10
9.25
Glycine
1.66x10-10
9.78
HCO3- (bicarbonate)
4.68x10-11
10.33 (pKa2)
Piperidine
7.58x10-12
11.12
HPO42- (monohydrogen phosphate)
4.17x10-13
12.38 (pKa3)
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