Dipotassium L-Tartrate  
Ｌ-酒石酸カリウム  
 
 
Standards for Use  
Permitted for use in grape juice used for wine production and grape wine  only. 
 
Compositional Specifications  
Substance Name  Dipotassium L-Tartrate  
Structural Formula  
 
 
 
 
Molecular Formula  C4H4K2O6 •1/2H 2O 
Molecular Weight  235.28  
Chemical Name  [CAS number]  
Dipotassium (2 R,3R)-2,3-dihydroxybutanedioate hemihydrate [6100 -19-2] 
Content   Dipotassium L-Tartrate , when dried, contains not less than 99.0% of 
dipotassium L-tartrate  (C4H4K2O6 = 226.27 ). 
Description   Dipotassium  L-Tartrate  occurs as colorless to white crystals or fine 
granular powder.  
Identification  
(1) A solution of Dipotassium L-Tartrate  (1 in 10) is dextrorotatory.  
(2) Dipotassium L-Tartrate  responds to  test (1) for Potassium  Salt and to all the tests 
for Tartrate in the Qualitative Tests.  
Specific Rotation  [α]D20: +27.2 to +29.7   (5 g, water, 50 mL, on the dried basis).  
pH  7.0–9.0  (0.5 g, water 50 mL).  Attachment  Purity  
(1) Lead   Not more than 2 μg/g as Pb ( 2.0 g, Method 3, Control Solution: Lead  
Standard Solution 4.0 mL, Flame Method).  
(2) Arsenic   Not more than 3 μg/g as As (0.50 g, Method 1, Standard Color: Arsenic 
Standard Solution 3.0 mL, Apparatus B).  
(3) Oxalate   Not more than 100 μg/g as C 2H2O4. 
Test Solution  Weigh 0.100 g  of Dipotassium L-Tartrate , previously dried, and add 
sulfuric acid TS ( 0.01 mol/L) to dissolve it and to make exactly 20 mL.  
Control Solution  Weigh 140 mg  of oxalic acid dihydrate, and add sulfuric acid TS  
(0.01 mol/L) to dissolve it and to make exactly 1000 m L. To exactly 1 mL of this solution, 
add sulfuric acid TS (0.01 mol/L) to make exactly 200 mL.  
Proce dure  Analyze 10  μL each  of the test solution and the control  solution by liquid 
chromatography using the operating conditions given below. Measure the peak area of 
oxalic acid for each of the test and control solutions by the automatic integration method.  
The peak area of oxalic acid for the test solution is not larger than that for the control 
solution.  
Operating Conditions  
Detector: Ultraviolet spectrophotometer (wavelength: 210 nm).  
Column: A stainless steel tube (6 –8 mm internal diameter and 30 cm length). If 
necessary, t wo-connected  columns may be used.  
Column packing material: 8 -μm H -form cation -exchange resin for liquid 
chromatography.  
Guard column: Use a column with the same internal diameter that is packed with 
the same packing material as for the column above.  
Column temperature: 50°C.  
Eluent: Sulfuric acid TS (0.01 mol/L).  
Flow rate: 0.6 mL/min.  
Loss on Drying   Not more than 4.0% (150 C, 4 hours).  
Assay  Weigh accurately about 0.2 g of Dipotassium L-Tartrate , previously dried, add 3 
mL of formic acid, and dissolve it by warming. Add 50 mL of acetic acid f or nonaqueous 
titration, and titrate with 0.1 mol/L perchloric acid. Usually , a potentiometer is used to 
confirm the endpoint. When crystal violet –acetic acid TS (1 mL) is used as the indicator, 
the endpoint is when the color of the solution changes from purple through blue to green. 
Separately, perform a blank test to make any nec essary correction.  
Each mL of 0.1 mol/L perchloric acid =11.31 mg of C4H4K2O6  
Reagents, Solutions, and Other Reference Materials  
Sulfuric Acid TS (0.01 mol/L)  Add water to 10 mL of sulfuric acid TS (1 mol/L) to make 
1000 mL.