# US 2019/0170711 A1 · Detection and quantitation of guanidinoacetate, creatine, and creatinine by mass spectrometry

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- Number: US 2019/0170711 A1
- Document ID: US20190170711A1
- Status: Published application
- Kind: A1
- Application number: 16/056,240
- Filed: 2018-08-06
- Published: 2019-06-06
- Earliest claimed: 2017-08-14
- Assignees: Quest Diagnostics Investments Incorporated
- Applicants: Quest Diagnostics Investments LLC
- Inventors: Thomas C. Lynn
- Web page: https://patentgrep.com/patent/US20190170711A1

## CPC

- G01N 30/7266: {by electric field, e.g. electrospray}
- G01N 30/72: Mass spectrometers {(mass spectrometers per se H01J49/00)}
- G01N 30/7233: {interfaced to liquid or supercritical fluid chromatograph (interfaces in general for introducing or extracting samples to be analysed with specially adapted mass spectrometer, see H01J49/04)}
- G01N 30/88: Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
- G01N 33/70: involving creatine or creatinine
- G01N 2030/045: {internal}
- G01N 2030/884: {organic compounds}
- G01N 2560/00: Chemical aspects of mass spectrometric analysis of biological material
- 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

Provided are methods for detecting or determining the amount of guanidinoacetate (GAA), creatine, and creatinine by mass spectrometry.

## Claims

### Claim 1

A method for detecting or determining the amount of guanidinoacetate (GAA), creatine, and creatinine comprising:
(a) purifying GAA, creatine, and creatinine in the sample;
(b) ionizing GAA, creatine, and creatinine in the sample to produce one or more ion(s) of GAA, creatine, and creatinine;
(c) detecting the ion(s) from step (b) by mass spectrometry;
wherein the amount of the GAA, creatine, and creatinine ion(s) is related to the amount of GAA, creatine, and creatinine in the sample.

### Claim 2 (depends on 1)

The method of claim 1, wherein said purifying comprises liquid chromatography.

### Claim 3 (depends on 2)

The method of claim 2, wherein said liquid chromatography comprises high performance liquid chromatography (HPLC).

### Claim 4 (depends on 1)

The method of claim 1, wherein said GAA, creatine, and creatinine are underivatized.

### Claim 5 (depends on 1)

The method of claim 1, wherein said ionization comprises electrospray ionization (ESI).

### Claim 6 (depends on 1)

The method of claim 1, wherein said ionization comprises ionizing in positive mode.

### Claim 7 (depends on 1)

The method of claim 1, further comprising adding an internal standard.

### Claim 8 (depends on 7)

The method of claim 7, wherein said internal standard is isotopically labeled.

### Claim 9 (depends on 1)

The method of claim 1, wherein the sample is urine.

### Claim 10 (depends on 1)

The method of claim 1, wherein the sample is serum.

### Claim 11 (depends on 1)

The method of claim 1, wherein the limit of quantitation of the methods is less than or equal to 0.4 mg/L.

### Claim 12 (depends on 1)

The method of claim 1, wherein the limit of quantitation of the methods is less than or equal to 0.3 mg/L.

### Claim 13 (depends on 1)

The method of claim 1, wherein said ionizing comprises generating a guanidinoacetate (GAA) precursor ion with the mass/charge ratio of 118.1±0.5.

### Claim 14 (depends on 13)

The method of claim 13, wherein the method further comprises generating one or more fragment ions with the mass/charge ratio of 72.1±0.5.

### Claim 15 (depends on 1)

The method of claim 1, wherein said ionizing comprises generating a creatine precursor ion with the mass/charge ratio of 132.1±0.5.

### Claim 16 (depends on 15)

The method of claim 15, wherein the method further comprises generating one or more fragment ions with the mass/charge ratio of 90.1±0.5.

### Claim 17 (depends on 1)

The method of claim 1, wherein said ionizing comprises generating a creatinine precursor ion with the mass/charge ratio of 114.1±0.5.

### Claim 18 (depends on 17)

The method of claim 17, wherein the method further comprises generating one or more fragment ions with the mass/charge ratio of 44.1±0.5.