Environmental Article

Complete Resolution of 13
DNPH Carbonyls as Derivatives

Using the New Allure® AK HPLC Column

By Randy Romesberg, HPLC Innovations Chemist, and Becky Wittrig, Ph.D, HPLC Product Marketing Manager

Superior separation of difficult carbonyls—including butyraldehyde and methyl ethyl ketone—compared to C18 columns.
Allows the use of a simple water:acetonitrile mobile phase for easier preparation and waste disposal.
Significantly faster run time than conventional C18 columns—less than 12 minutes.

Carbonyls are collected and measured from a variety of samples, including air, exhaust, and cigarette smoke. For example, the California Air Resources Board (CARB) was established in 1967 to address many aspects of air pollution, including air quality problems caused by motor vehicles. CARB Method 1004 is used by the automotive industry to monitor a range of carbonyl compounds (e.g. aldehydes and ketones) in engine exhaust.

Sample collection cartridges impregnated with 2,4-dinitrophenylhydrazine (DNPH), or impingers containing acidified DNPH, are used to sample air or exhaust. After conversion to DNPH derivatives, the carbonyl compounds are collected and analyzed by HPLC. Since the DNPH derivatives absorb strongly at 360nm, detection limits below 1ppm are easily achievable. The original CARB method uses two C18 columns in series for analysis, although other columns can be used, as long as they provide an equivalent or better separation.

The new Allure® AK HPLC column was developed specifically for the analysis of aldehydes and ketones. With a single 200mm column, excellent resolution of these compounds can be achieved in less than 12 minutes (Figure 1). While C18 phases often cannot separate butyraldehyde and methyl ethyl ketone (MEK), the Allure® AK column shows excellent resolution of this difficult pair. In addition, a simple mobile phase gradient of water:acetonitrile can be used with the Allure® AK column, while C18 phases require the addition of THF to achieve acceptable resolution.

When analyzing aldehydes and ketones by HPLC, such as the carbonyls specified in CARB method 1004, the new Allure® AK column will give you the resolution and fast analysis times that you require.

Figure 1: 1 Excellent resolution of carbonyl compounds in less than 12 minutes, using the Allure® AK HPLC column and a simple water:acetonitrile mobile phase gradient.

Peak
Ret. Time (min.)

DNPH derivative of:

1. formaldehyde
4.74

2. acetaldehyde
5.78

3. acrolein
6.86

4. acetone
7.09

5. propionaldehyde
7.31

6. crotonaldehyde
8.19

7. methacrolein
8.55

8. butaraldehyde
8.79

9. methylethylketone
9.06

10. benzaldehyde
10.03

11.valeraldehyde
10.39

12. m-tolualdehyde
11.08

13. hexanaldehyde
11.36

LC_EV0393

Sample: dinitrophenylhydrazine (DNPH) derivatives of aldehydes/ketones

Inj.: 10µL

Conc.: 3µg/mL each analyte, as aldehyde/ketone

Sample diluent: acetonitrile

Column: Allure™ AK (cat.# 9159525-700)

Dimensions: 200 x 4.6 mm

Particle size: 5µm

Pore size: 60Å

Conditions:

Mobile phase A) water : B):acetonitrile

Time (min.)

%B

0

60

8

70

10

100

Flow: 1.5mL/min.

Temp.: 30°C

Det.: UV @ 360nm

LC_EV0393