ADV06-15_1-412

• 22 •

2008 vol. 3

Reduce Downtime with Robust Lipidomics Method

Why lose days to downtime? Restek columns, such as the 10,000 injection

Rxi®-5ms

column

shown here, are rugged and built for consistent long-term performance.

By Julie Kowalski, Ph.D., Innovations Chemist, and John Hanley Jr.*, Ph.D., Platform Development Manager

*Lipomics Technologies

Lipidomic studies of cholesterol synthesis, absorp-

tion, and excretion, provide information central to

the investigation of cardiovascular disease and

other disorders. High-throughput methods are

critical to lipidomics and are used to screen thou-

sands of samples in order to identify biomarkers

and clinical diagnostics with significant predictive

power. Labs can save days of downtime by using an

Rxi®-5ms column in assays similar to our test

method for cholesterol and low-level sterol

metabolites.

Here, extremely reproducible results were

obtained using an Rxi®-5ms column, which gave

highly consistent separations—even after 10,000

injections (Figure 1). In our method, biological

samples were treated to form trimethylsilyl deriva-

tives. Two injections were made: one to quantify

minor sterols using a 10:1 split, and another, using

a 100:1 split, to analyze cholesterol. To achieve

maximum sensitivity for low-level sterols, multiple

SIM retention time windows were set up.

Stable retention times are critical to our testing

program as revalidation is required if significant

drift occurs. Revalidation requires days of down-

time because inter-day variability must be

assessed. The Rxi®-5ms column was chosen for

this method, in part, because its long lifetime and

stable performance reduced the number of col-

umn changes and revalidations, resulting in more

days of productive analyses.

We found the performance of the Rxi®-5ms col-

umn to be remarkably consistent and reliable for

high-throughput testing. The Rxi®-5ms column

should be considered by labs running similar

lipidomic methods that would benefit from a

highly reproducible performance—or by any lab

interested in reducing downtime and increasing

productivity.

Figure 1

Stable, highly reproducible results on the Rxi®-5ms

column mean less downtime and more productive days.

Product Listing

Reduced downtime for

column changes and

revalidation significantly

increased lab productivity.

Rxi®-5ms Columns (fused silica)

(Crossbond

5% diphenyl/95% dimethyl polysiloxane)

df (µm)

temp. limits

length

cat. #

price

0.25mm 0.25

-60 to 330/350°C

30-Meter

13423

Column:

Rxi

-5ms, 30m, 0.25mm ID, 0.25µm

(cat.# 13423)

Sample:

lipid plasma extract as trimethylsilyl

derivatives

Inj.:

1µL, split (10:1),

4mm gooseneck inlet liner w/wool

Inj. temp.:

310°C

Carrier gas:

helium, constant flow

Flow rate:

1.0mL/min.

Oven temp.:

250°C (hold 1 min.) to 320°C @

30°C/min. (hold 1.6 min.)

Det:

Transfer line temp.: 330°C

Ionization:

Mode:

SIM

GC_PH01053

Compound:

m/z

1. coprostanol

370.40

2. d5-cholestanol (IS)

220.20

3. 7

-hydroxycholesterol

456.40

4. cholestanol

306.30

5. d5-epicholestanol (IS)

220.20

6. 7-dehydrocholesterol

325.25

7. desmosterol

343.25

8. lathosterol

458.35

9. d4-lathosterol (IS)

462.40

10. campesterol

382.35

11. 4-cholestenone

382.30

12. stigmasterol

394.15

13. lanosterol

393.35

14.

-sitosterol

396.35

15. d7-

-sitosterol (IS)

403.45

injection 1

injection 10, 000

Consistent

performance

for over 10,000

injections!

Bioanalytical

800-356-1688 •

www.restek.com