# US 12,181,435 B2 · Methionine concentration measurement method

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- Number: US 12,181,435 B2
- Document ID: US12181435B2
- Status: Granted
- Kind: B2
- Application number: 17/895,169
- Filed: 2022-08-25
- Published: 2023-01-05
- Granted: 2024-12-31
- Earliest claimed: 2018-11-07
- Assignees: King Fahd University of Petroleum and Minerals
- Applicants: King Fahd University of Petroleum and Minerals
- Inventors: Abdel-Nasser M. Kawde; Nurudeen Adewale Odewunmi
- Web page: https://patentgrep.com/patent/US12181435B2

## CPC

- G01N 27/3277: {being a redox reaction, e.g. detection by cyclic voltammetry (voltammetry per se G01N27/42, G01N27/48)}
- G01N 27/308: {at least partially made of carbon}
- G01N 27/48: using polarography, i.e. measuring changes in current under a slowly-varying voltage
- G01N 33/66: involving blood sugars, e.g. galactose
- G01N 33/68: involving proteins, peptides or amino acids {(involving lipoproteins G01N33/92)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A method of using a graphite electrode to measure a concentration of glucose or methionine from a biological sample is described. A mechanical pencil lead may be used as the graphite electrode, and the biological sample may come from a patient's serum. The glucose or methionine may produce a peak current response within a range of 0.4-0.8 V when the sample is subjected to linear scan voltammetry.

## Claims

### Claim 1

A methionine concentration measurement method, comprising:
measuring a current response of an aqueous sample comprising methionine at a voltage of 0.4-0.8 V, wherein the measuring is conducted in an electrochemical cell with a graphite electrode, a reference electrode, and a counter electrode; and
determining the concentration of the methionine in the aqueous sample by comparing the current response to a correlation chart,
wherein the methionine is present in the aqueous sample at a concentration of 1.0 μM-10.0 mM,
wherein the aqueous sample comprises an inorganic base at a concentration of 0.02-1.0 M and a metal salt at a concentration of 0.1-10 ppm,
wherein the metal salt comprises at least one metal ion selected from the group consisting of Cu2+, Ag+, Zn2+, Fe2+, and Fe3+.

### Claim 2 (depends on 1)

The method of claim 1, wherein the inorganic base is NaOH, and the aqueous sample has a pH of 12.0-14.0.

### Claim 3 (depends on 1)

The method of claim 1, wherein the graphite electrode has no surface modification.

### Claim 4 (depends on 1)

The method of claim 1, wherein the graphite electrode has a diameter or width of 0.1-2.0 mm and a length of 3.0-20.0 mm in contact with the aqueous sample during the measuring.

### Claim 5 (depends on 1)

The method of claim 1, wherein the aqueous sample further comprises at least one selected from the group consisting of ascorbic acid, alanine, fructose, uric acid, and cysteine, each independently at a concentration of 0.01-1.00 mM.

### Claim 6 (depends on 1)

The method of claim 1, wherein the reference electrode is an Ag/AgCl electrode, and the counter electrode comprises platinum.

### Claim 7 (depends on 1)

The method of claim 1, further comprising removing a precipitated protein from the aqueous sample prior to the measuring.

### Claim 8 (depends on 7)

The method of claim 7, wherein the removing comprises mixing an alcohol with the serum at a volume ratio of 1:4-4:1 to produce the precipitated protein, and
centrifuging the precipitated protein.

### Claim 9 (depends on 1)

The method of claim 1, wherein the measuring involves applying linear scan voltammetry to the aqueous sample.

### Claim 10 (depends on 1)

The method of claim 1, further comprising constructing a calibration curve from a current response of two or more standard solutions.

### Claim 11 (depends on 1)

The method of claim 1,
wherein the metal salt comprises Ag+, the Ag+ having a concentration of 2-6 ppm in the aqueous sample.

### Claim 12 (depends on 11)

The method of claim 11, wherein the methionine is present in the aqueous sample at a concentration of 0.01-0.50 mM.

### Claim 13 (depends on 11)

The method of claim 11, wherein the voltage is 0.63-0.67 V.

### Claim 14 (depends on 11)

The method of claim 11, wherein the metal salt is AgNO3.

### Claim 15 (depends on 11)

The method of claim 11, wherein the measuring produces silver oxide nanoparticles on the graphite electrode.