Search results for: 'fill cysteine tri oh 13c 15'

Trifluoroethanol-d2

Ref.	Packaging	I.E.(%)	Price	Add to...
S-2210X-V04A	2 x 0.75 mL	98% D	$415.10

1-3 weeks

Sodium Palmitate-1-13C

CC3700P
2 - 4 weeks

99% ¹³C

D-Sorbitol-1-13C

CC3775P01
2 - 4 weeks

99% ¹³C

Myristic Acid-1-13C

CC3875P
2 - 4 weeks

99% ¹³C

Myristic Acid-14-13C

CC3876P
2 - 4 weeks

99% ¹³C

Cholic Acid-24-13C

CC536P
2 - 4 weeks

99% ¹³C

D-Xylose-1-13C

CC5475P
2 - 4 weeks

99% ¹³C

D-Xylose-2-13C

CC5476P
2 - 4 weeks

99% ¹³C

D-Xylose-3-13C

CC5477P
2 - 4 weeks

99% ¹³C

D-Xylose-4-13C

CC5478P
2 - 4 weeks

99% ¹³C

D-Xylose-5-13C

CC5480P
2 - 4 weeks

99% ¹³C

Capric Acid -10-13C

CC586P
2 - 4 weeks

99% ¹³C

Lauric Acid-1-13C

CC591P
2 - 4 weeks

99% ¹³C

Lauric Acid -12-13C

CC592P
2 - 4 weeks

99% ¹³C

Ethyl Acetoacetate-3-13C

CC6100P
2 - 4 weeks

99% ¹³C

Ethyl Acetoacetate-4-13C

CC6101P
2 - 4 weeks

99% ¹³C

Ethyl Acetoacetate-1-13C

CC6105P
2 - 4 weeks

99% ¹³C

Glycine-1-13C

CC1070P1

$260.00

2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

Glycine-2-13C

CC1080P1

$360.00

2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

Vitamin B5 (Di-Β-Alanine-13C6,15N2) Calcium Salt

CCN6000P
2 - 4 weeks

99% ¹³C, 98% ¹⁵N, 97% CP

Urea-13C, 1 g

CC4500P1

$150.00

2 - 4 weeks

• 99% ¹³C
• 1 g

Glycerol-2-13C, -d8

CCD1055P
Stock

99% ¹³C, 98% D

L-Methionine-13C, -d1

CCD2010P
2 - 4 weeks

99% ¹³C, 98% D

L-Methionine-13C, -d2

CCD2011P
2 - 4 weeks

99% ¹³C, 98% D

L-Threonine-13C4, 15N

CCN3900P025

$830.00

2 - 4 weeks

• 250 mg
• 98% ¹³C, 98% ¹⁵N

L-Threonine-13C4, 15N

CCN3900P1

$2,750.00

stock

• 1 g
• 98% ¹³C, 98% ¹⁵N

L-Threonine-13C4, 15N

CCN3900P01

$390.00

stock

• 100 mg
• 98% ¹³C, 98% ¹⁵N

L-Threonine-13C4

CC3920P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

Acetic Acid-1-13C

CC100P1
2 - 4 weeks

• 99% ¹³C
• 1 g

L-Glutamine-2-13C

CC1010P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Glutamine-4-13C

CC1030P
2 - 4 weeks

• 99% ¹³C
• 98% CP

Acetic Acid-2-13C

CC105P1
2 - 4 weeks

• 99% ¹³C
• 1 g

L-Isoleucine-1-13C

CC1300P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Leucine-1-13C

CC1500P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Leucine-3-13C

CC1515P
2 - 4 weeks

• 99% ¹³C
• 98% CP

D-Mannose-1-13C

CC1925P1
2 - 4 weeks

• 99% ¹³C
• 1 g

D-Mannose-6-13C

CC1935P1
2 - 4 weeks

• 99% ¹³C
• 1 g

L-Methionine-2-13C

CC2020P
2 - 4 weeks

• 99% ¹³C
• 98% CP

Oleic Acid-1-13C

CC2140P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Palmitic Acid-1-13C

CC2180P1

$3,220.00

2 - 4 weeks

• 99% ¹³C
• 1 g

Palmitic Acid-2-13C

CC2183P1
2 - 4 weeks

• 99% ¹³C
• 1 g

L-Phenylalanine-4-13C

CC2230P
2 - 4 weeks

• 99% ¹³C
• 98% CP

D-Ribose-1-13C

CC2800P025
2 - 4 weeks

• 99% ¹³C
• 250 mg

L-Asparagine-1-13C

CC310P
2 - 4 weeks

• 99% ¹³C
• 98% CP

Sodium Butyrate-1-13C

CC3410P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Butyrate-2-13C

CC3415P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Butyrate-4-13C

CC3435P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Spirulina Algal Cells, 13C

CC3635P1
2 - 4 weeks

• 1 g
• 98% ¹³C

Sodium Propionate-1-13C

CC3725P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Propionate-2-13C

CC3730P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Propionate-3-13C

CC3735P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Pyruvate-1-13C

CC3750P1

$610.00

2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Pyruvate-1-13C

CC3750P10

$5,370.00

2 - 4 weeks

• 99% ¹³C
• 10 g

Sodium Pyruvate-3-13C

CC3752P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Stearic Acid-1-13C

CC3800P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Stearic Acid-2-13C

CC3805P1
2 - 4 weeks

• 99% ¹³C
• 1 g

Choline Chloride-1-13C

CC535P01
2 - 4 weeks

• 100 mg
• 99% ¹³C

Capric Acid-1-13C

CC585P05
2 - 4 weeks

• 99% ¹³C
• 500 mg

D-Galactose-1-13C

CC820P1
2 - 4 weeks

• 99% ¹³C
• 1 g

D-Galactose-2-13C

CC821P1
2 - 4 weeks

• 99% ¹³C
• 1 g

L-Methionine-13C, -d3

CCD2012P1
2 - 4 weeks

• 1 g
99% ¹³C, 98% D

Sodium Acetate-2-13C

CC3395P1

$180.00

2 - 4 weeks

• 1 g
• 99% ¹³C

Sodium Acetate-1-13C

CC3390P1

$100.00

2 - 4 weeks

• 99% ¹³C
• 1 g

Sodium Acetate-1-13C

CC3390P10

$770.00

2 - 4 weeks

• 99% ¹³C
• 10 g

Sodium Acetate-2-13C

CC3395P10

$1,460.00

2 - 4 weeks

• 10 g
• 99% ¹³C

L-Ascorbic Acid-2-13C

CC281P
2 - 4 weeks

99% ¹³C

L-Ascorbic Acid-3-13C

CC282P
2 - 4 weeks

99% ¹³C

Glycocholic Acid-Glycyl-1-13C

CC537P
2 - 4 weeks

99% ¹³C

L-Serine-2-13C, 15N

CCN3010P
2 - 4 weeks

99% ¹³C

L-Glutamine-1-13C

CC1000P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Glutamine-3-13C

CC1020P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Glutamine-5-13C

CC1040P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Leucine-2-13C

CC1510P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Methionine-1-13C

CC2000P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Methionine-Methyl-13C

CC2010P025

$210.00

2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Phenylalanine-1-13C

CC2200P1

$660.00

2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Phenylalanine-2-13C

CC2210P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Phenylalanine-3-13C

CC2220P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Proline-1-13C

CC2500P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Alanine-1-13C

CC25P1

$620.00

2 - 4 weeks

• 1 g
• 99% ¹³C
• 95% CP

L-Serine-1-13C

CC3000P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Serine-2-13C

CC3010P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Serine-3-13C

CC3020P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Asparagine-4-13C

CC320P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Alanine-2-13C

CC35P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 95% CP

L-Tryptophan-1-13C

CC4000P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Tyrosine-1-13C

CC4200P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Tyrosine-2-13C

CC4210P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Tyrosine-3-13C

CC4220P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Alanine-3-13C

CC45P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 95% CP

L-Valine-1-13C

CC5000P1

$430.00

2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Valine-2-13C

CC5010P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

Acetic Acid-2-13C, -d4

CCD106P
2 - 4 weeks

99% ¹³C, 98% D

Sodium Acetate-1-13C, -d3

CCD3390P
2 - 4 weeks

99% ¹³C, 98% D

Sodium Acetate-2-13C, -d3

CCD3395P
2 - 4 weeks

99% ¹³C, 98% D

L-Leucine-3-13C, 15N

CCN1530P
2 - 4 weeks

99% ¹³C, 98% ¹⁵N

L-Methionine-2-13C, 15N

CCN2020P
2 - 4 weeks

99% ¹³C, 98% ¹⁵N

Glycine-1-13C, 15N

CCN1070P1
2 - 4 weeks

• 1 g
• 99% ¹³C, 98% ¹⁵N
• 95% CP

Glycine-2-13C, 15N

CCN1080P025
2 - 4 weeks

• 250 mg
• 99% ¹³C, 98% ¹⁵N
• 95% CP

Glycine-2-13C, 15N

CCN1080P1
2 - 4 weeks

• 1 g
• 99% ¹³C, 98% ¹⁵N
• 95% CP

Glycine-1-13C, 2,2-d2

CCD1070P
2 - 4 weeks

99% ¹³C, 98% D

L-Lysine-1-13C Hydrochloride

CC1700P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Lysine-2-13C Hydrochloride

CC1710P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Lysine-6-13C Hydrochloride

CC1750P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Ascorbic Acid-1-13C

CC280P5
2 - 4 weeks

• 99% ¹³C
• 5 g

L-Tyrosine-Phenyl-4-13C

CC4230P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Glutamic Acid-2-13C

CC910P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Glutamic Acid-4-13C

CC930P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Glutamic Acid-5-13C

CC940P
2 - 4 weeks

• 99% ¹³C
• 98% CP

L-Leucine-2-13C, 15N

CCN1510P025
2 - 4 weeks

• 250 mg
99% ¹³C, 98% ¹⁵N

L-Lactic Acid-3,3,3-d3

CD1411P
2 - 4 weeks

98% D

Sodium L-Lactate-2-d

CD3540P
2 - 4 weeks

98% D

Acetic Acid-1-13C, -d4

CCD101P1
2 - 4 weeks

• 99% ¹³C, 98% D
• 1 g

B-Alanine-1-13C, 15N

CCN65P
2 - 4 weeks

• 99% ¹³C, 98% ¹⁵N
• 95% CP

B-Alanine-2-13C, 15N

CCN66P
2 - 4 weeks

• 99% ¹³C, 98% ¹⁵N
• 95% CP

L-Aspartic Acid-1-13C

CC350P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Aspartic Acid-2-13C

CC360P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Aspartic Acid-3-13C

CC370P01
2 - 4 weeks

• 100 mg
• 99% ¹³C
• 98% CP

L-Aspartic Acid-4-13C

CC380P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Glutamic Acid-1-13C

CC900P1
2 - 4 weeks

• 1 g
• 99% ¹³C
• 98% CP

L-Glutamic Acid-3-13C

CC920P025
2 - 4 weeks

• 250 mg
• 99% ¹³C
• 98% CP

L-Methionine-1-13C, Methyl-d3

CCD2000P
2 - 4 weeks

99% ¹³C, 98% D

D-Mannitol-1-13C, 1,1-d2

CCD1920P
2 - 4 weeks

99% ¹³C, 98% D

5-Aminolevulinic Acid HCL 4-13C

CC49P025
2 - 4 weeks

• 250 mg
• 99% ¹³C

5-Aminolevulinic Acid HCL 4-13C

CC49P1
2 - 4 weeks

• 1 g
• 99% ¹³C

L-Alanine-1-13C, 15N

CCN25P1
2 - 4 weeks

• 1 g
• 99% ¹³C, 99% ¹⁵N
• 95% CP

L-Alanine-2-13C, 15N

CCN35P1
2 - 4 weeks

• 1 g
• 99% ¹³C, 99% ¹⁵N
• 95% CP

B-Alanine-3-13C, 15N

CCN67P01
2 - 4 weeks

• 100 mg
• 99% ¹³C, 98% ¹⁵N
• 95% CP

Acetic Acid-1-13C, 2,2,2-d3

CCD100P
2 - 4 weeks

99% ¹³C, 98% D

L-Alanine-1-13C, 3,3,3-d3

CCD25P
2 - 4 weeks

99% ¹³C, 98% D

Sodium Pyruvate-2-13C, 3,3,3-d3

CCD3751P
2 - 4 weeks

99% ¹³C, 97% D

Sodium Pyruvate-3-13C, 3,3,3-d3

CCD3752P
2 - 4 weeks

99% ¹³C, 97% D

L-Tryptophan-Indole Ring-2-13C

CC4010P
2 - 4 weeks

• 99% ¹³C
• 98% CP

5-Aminolevulinic Acid HCL 5-13C

CC50P025
2 - 4 weeks

• 250 mg
• 99% ¹³C

5-Aminolevulinic Acid HCL 5-13C

CC50P1
2 - 4 weeks

• 1 g
• 99% ¹³C

L-Threonine-2,3,4,4,4-d5

CD3900P
2 - 4 weeks

98% D

L-Threonine-15N, 2-d1

CDN3900P
2 - 4 weeks

L-Threonine-15N

CN3900P025

$1,810.00

2 - 4 weeks

• 250 mg
• 98% ¹⁵N

L-Aspartic Acid-1-13C, 15N

CCN350P
2 - 4 weeks

• 99% ¹³C, 98% ¹⁵N
• 98% CP

DL-Alanine-2-13C, 3,3,3-d3

CCD35P
2 - 4 weeks

• 99% ¹³C, 97% D
• 98% CP

L-Aspartic Acid-2-13C,15N

CCN360P025
2 - 4 weeks

• 250 mg
• 99% ¹³C, 98% ¹⁵N
• 98% CP

L-Arginine-5-13C, 4,4,5,5-d4 Hydrochloride

CCD270P
2 - 4 weeks

99% ¹³C, 98% D

2-(4-Aminophenyl)Acetic Acid-1-13C

CC115P0025
2 - 4 weeks

• 99% ¹³C
• 250 mg

Glycerol-1,1,2,3,3-d5

CD1055P1

$250.00

Stock

• 98% D
• 1 g

Glycerol-1,1,2,3,3-d5

CD1055P10

$1,790.00

Stock

• 98% D
• 10 g

Sodium L-Lactate-3,3,3-d3

CD3541P
2 - 4 weeks

98% D

Formaldehyde-13C, -d2

CCD755P
2 - 4 weeks

CAS number: 63101-50-8
D¹³CDO

Thiamine-(4-Methyl-13C-Thiazol-5-Yl-13C3) Hydrochloride

CC3870P
2 - 4 weeks

99% ¹³C

Glycocholic Acid-2,2,4,4-d4

CD532P
2 - 4 weeks

98% D

Potassium Palmitate-16d

CD2436P
2 - 4 weeks

98% D

Capric Acid -10,10,10-d3

CD585P01
2 - 4 weeks

• 99% D
• 100 mg

Benzaldehyde-a-13C,d6

CCD472P
2 - 4 weeks

C₆D₅¹³CDO

Acetone-2-13C,-d6

CCD6203P
2 - 4 weeks

CAS number: 32479-94-0
CD₃¹³COCD₃

Benzaldehyde-a-13C,a-d1

CCD471P
2 - 4 weeks

CAS number: 155638-70-3
C₆H₅¹³CDO

1-Methylxanthine-Methyl-13C,d3

CCD6350P
2 - 4 weeks

CAS number: 1202865-49-3
¹³CC₅D₃H₃N₄O₂

2-Methoxy-13C,d3-Estrone

CCD650P
2 - 4 weeks

CAS number: 1217460-84-8
¹³CC₁₈D₃H₂₁O₃

4-Methoxy-13C,d3-Estrone

CCD651P
2 - 4 weeks

CAS number: 1217437-34-7
¹³CC₁₈D₃H₂₁O₃

4-Methoxy-13C,d3-Estradiol

CCD660P
2 - 4 weeks

CAS number: 1217442-62-0
¹³CC₁₈D₃H₂₃O₃

2-Methoxy-13C,d3-Estradiol

CCD661P
2 - 4 weeks

CAS number: 1217470-09-1
¹³CC₁₈D₃H₂₃O₃

L-Alanine-3-13C, 2-d

CCD45P1
2 - 4 weeks

¹³CH₃CD(NH₂)CO₂H

Palmitic Acid-16-13C,16,16,16-d3

CCD2181P
2 - 4 weeks

99% D

L-Alanine-3-13C, 3,3,3-d3

CCD47P
2 - 4 weeks

CAS number: 285978-08-7
¹³CD₃CH(NH₂)CO₂H

L-Alanine-3-13C, 2,3,3-d3

CCD48P
2 - 4 weeks

¹³CD₂HCD(NH₂)CO₂H

Arachidonic-5,6,8,9,11,12,14,15-d8 Acid

CD247P001
2 - 4 weeks

7.45D Per Molecule

Fmoc-L-Threonine-(tBu)-13C4,15N

CCN3930P01

$870.00

stock

• 100 mg
• 98% ¹³C, 98% ¹⁵N
• 95% CP

L-Tryptophan-13C11,15N2,α,β,β,2,4,5,6,7-d8

CCDN4050P01
2 - 4 weeks

• 100 mg• 97% ¹³C
• 98% CP

L-Histidine-13C6, 15N3, α,β,β,2,5-d5

CCDN1200P01
2 - 4 weeks

• 100 mg• 99% ¹³C, 98% D, 98% ¹⁵N
• 95% CP

L-Phenylalanine-13C9, 15N, α,β,β,2,3,4,5,6-d8

CCDN2200P01
2 - 4 weeks

• 100 mg• 99% ¹³C, 98% D, 98% ¹⁵N
• 95% CP

L-Valine-13C5,15N,2,3,4,4,4-d5-(4-methyl-d3)

CCDN5000P01
2 - 4 weeks

• 100 mg• 99% ¹³C, 98% D, 98% ¹⁵N
• 95% CP

L-Alanine-13C3, 15N, 2,3,3,3-d4

CCDN55P01
2 - 4 weeks

• 100 mg • 99% ¹³C, 98% D, 98% ¹⁵N
• 95% CP

Acetic Anhydride-13C4

CC101P
2 - 4 weeks

99% ¹³C

Caproic Acid-1,2-13C2

CC1185P
2 - 4 weeks

99% ¹³C

Linolenic Acid 13C18

CC1630P
2 - 4 weeks

98% ¹³C

Malonic Acid-1,3-13C2

CC1916P
2 - 4 weeks

99% ¹³C

D-Mannose-13C6

CC1955P
2 - 4 weeks

99% ¹³C

Caprylic Acid- 1,2-13C2

CC2125P
2 - 4 weeks

99% ¹³C

Caprylic Acid-1,2,3,4-13C4

CC2132P
2 - 4 weeks

99% ¹³C

Oleic Acid, Methyl Ester-13C18

CC2142P
2 - 4 weeks

98% ¹³C

Oleic Acid-1,2,3,7,8,9,10-13C7

CC2143P
2 - 4 weeks

99% ¹³C

Oleic Acid-1,2,3,7,8-13C5

CC2144P
2 - 4 weeks

99% ¹³C

Oleic Acid-9,10-13C2

CC2145P
2 - 4 weeks

99% ¹³C

Palmitic Acid-1,2,3,4-13C4

CC2182P
2 - 4 weeks

99% ¹³C

Potassium Oleate-1,2,3,7,8-13C5

CC2431P
2 - 4 weeks

99% ¹³C

Potassium Oleate-13C18

CC2432P
2 - 4 weeks

99% ¹³C

Potassium Palmitate-13C16

CC2436P
2 - 4 weeks

99% ¹³C

17Α-Hydroxyprogesterone-2,3,4-13C3

CC2445P
2 - 4 weeks

98% ¹³C

Progesterone-2,3,4-13C3

CC2446P
2 - 4 weeks

99% ¹³C

D-Ribose-13C5

CC2805P
2 - 4 weeks

99% ¹³C

Ritalinic Acid-(Phenyl-13C6)

CC2810P
2 - 4 weeks

99% ¹³C

Sodium Palmitate-2,4,6,8,10,12,14,16-13C8

CC3710P
2 - 4 weeks

99% ¹³C

Succinic Acid-13C4

CC3820P
2 - 4 weeks

99% ¹³C

Succinic Acid-2,3-13C2

CC3822P
2 - 4 weeks

99% ¹³C

Succinic Acid-1,2-13C2

CC3823P
2 - 4 weeks

99% ¹³C

Dimethyl Sulfate-13C2

CC3850P
2 - 4 weeks

99% ¹³C

Myristic Acid 13C14

CC3877P
2 - 4 weeks

99% ¹³C

Myristic Acid-1,2-13C2

CC3878P
2 - 4 weeks

99% ¹³C

3,3′,5-Triiodothyronine-Tyrosine Ring-13C6 Hydrochloride

CC3950P
2 - 4 weeks

99% ¹³C

3,3′,5′-Triiodothyronine-Diiodophenyl-13C6 Hydrochloride

CC3951P
2 - 4 weeks

99% ¹³C

3,3′-Diiodo-L-Thyronine-(Phenoxy-13C6) (T2)

CC3952P
2 - 4 weeks

99% ¹³C

L-Thyroxine-(Ring-13C12)

CC3953P
2 - 4 weeks

99% ¹³C