# US 6,503,758 B1 · Systems and methods for measuring nitrate levels

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- Number: US 6,503,758 B1
- Document ID: US6503758B1
- Status: Granted
- Kind: B1
- Application number: 09/687,190
- Filed: 2000-10-12
- Granted: 2003-01-07
- Earliest claimed: 1999-10-12
- Assignees: President and Fellows of Harvard College
- Inventors: George A. Allen; Petros Koutrakis; Yiming Ding
- Web page: https://patentgrep.com/patent/US6503758B1

## CPC

- G01N 31/005: {investigating the presence of an element by oxidation (G01N31/12 takes precedence)}
- G01N 1/2205: {with filters}
- G01N 33/0037: {NOx}
- G01N 1/40: Concentrating samples
- G01N 2001/2223: {aerosol sampling devices}
- Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- Y10T 436/17: Nitrogen containing
- Y10T 436/173076: Nitrite or nitrate
- Y10T 436/176921: As part of an elemental analysis
- 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)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The systems and methods described herein relate to the measurement of nitrate levels in a sample of gas, for example, air, exhaust, or other sources of gas. Moreover, the systems and methods described herein are capable of operating using short sample collection periods, permitting rapid data collection and finely time-resolved nitrate monitoring over a span of time. Additionally, ambient nitrate can effectively be distinguished from other airborne particles, such as sulfate and carbon.

## Claims

### Claim 1

A system for measuring nitrate levels, comprising
a sample inlet for receiving a sample of gas,
a collection body coupled to said sample inlet,
a filter mounted within said body to collect particles from said sample of gas,
a heater coupled to the body to heat the body,
a gas inlet coupled to said body to provide a flow of gas through said body,
a detector coupled to said body to measure an NOx concentration, and
an extractor coupled to said sample inlet and to said collection body to substantially remove NO2 from the gas sample, wherein the extractor comprises a hydroxyl-bearing solvent and a base, and further wherein the hydroxyl-bearing solvent is glycerol and the base is an organic base.

### Claim 2 (depends on 1)

The system of claim 1, wherein the organic base is an amine.