Hi,

My wife did analysis involving benzyl alcohol, acetate and aldehyde. She used WCOT column from varian, and it was eluting at high temperatures, above 210 °C. The column was 60m capillary 0.032, He was carrier gas, and the analysis took quite a lot (because the analysis was done also for some low boiling components), so it took about 25 minutes. If you need any further info, please let me know.

Of course you should pay attention to oven t­° (it depends on what else compound will be with those you already listed). Briefly, your IS and analyte(s) should be fully separated from each other. The column should be a polar one, on my opinion. Probably HP5MS (from Agilent) would do. Anyway, each manufacturer has a plenty of examples in GC column catalogue.

First you need to use a DB-5 ou HP-5 columns for good separation.

I agree with Mohamed Bouhrara, this should be easy to do

I did that analysis very often during my PhD. HP-5(MS) does the job. The program i used was: 100°C for 0.5 min then 10°C/min to 300, inlet T = 250°C, retention times were ca. 3 min for benzaldehyde and 3.5-4 min for benzylalcohol on the HP5-MS column. So actually you don't need to go to 300, but that was our std-method. Alternatively DB1701 is also good, but retention times are somewhere within 5-10 min, don't remember that exactly anymore, sorry. Internal std. could be toluene, but I don't know your reaction cond. so check something which is chemically similar to your compounds but does not interfere with your reaction. Hope that gives you a good starting point for your analysis ...

First of all think about the concentration you want to measure, then think about a suitable solvent! Due to the polarity of the alcohol I would recommend a polar column like a Wax. Be careful polar columns are quite sensitive to Oxygen and the upper temperature Limit is quite low in comparison to a non polar column like a Hp5 or equivalent. In the case of selecting a polar stationary Phase your solvent should Be polar as well like acetone or ethylacetate, but Not an alkane like hexane.

br Erich

If your samples will only (likely) have benzyl alcohol, benzaldehyde, and an intelligently chosen internal standard, almost any column chemistry should work to give you a separation of the compounds, so I would go with a 5% phenyl/95% methyl phase Basically an XX-5 column (or XX-5MS column) where the XX depends on the manufacturer (VB, DB, HP, Rtx, Rxi, SPB, BPX). For what you are doing the columns from any reputable vendor (Restek, Supelco, Agilent/HP/J&W, SGE, etc...) should be fine. For actual "conditioning" of the column, see the manufacturer's instructions that come with the column.

To keep your analysis time down to something reasonable, you will likely be able to get away with a 15 or 30 m long column, 0.25 mm inner diameter and a film thickness probably of 0.25 um.

You will want to use a split injection with a split ratio that ranges between 25:1 to 100:1, and you will want to inject 1 uL of sample (max).

For a simple mixture of these two compounds, plus an internal standard, you should be able to find isothermal conditions that will get your results done in 5-10 min per sample without too much difficulty.

I am assuming that you will have relatively high concentrations of the analytes. What solvent will they be in and what concentration? You will want to do some math to work out how much to dilute your samples prior to injection. Likely you will want to inject somewhere around 50 ng of analyte onto the column.

If your solvent is aqueous you will need to solvent exchange into something like hexane that is compatible with GC.

There are still dozens of things to think about in setting this up and optimizing the method. If these answers make absolutely no sense to you, I would suggest reading a general analytical chemistry text that deals with the basics of GC. If you are a true beginner, something like the Separations and GC chapters out of Harris' Quantitative Chemical Analysis (a recent edition) would be a decent starting point. Once you've moved beyond the basics, Grob and Barry's Modern Practice of Gas Chromatography (4th edition) covers pretty much all you need to know about GC and then some.

You could use almost any polar capillar column that you haver. About the conditions, I agree with those proposed by Michael Fuchs, but you can adjuste them to improve the resolution. The volumen injection could be 0.2 microllitres. The internal standard some organic alcohol whose signal does not interfer with the other signal analites. The nitrogen flow could be 5 mL/min. The most important parameters would be the nature of column and the temperature programme.

When dealing with aqueous systems you could take FFAP column. I used 25mx0.25mmx0.30um, programmed at 8.5'@70C (to get rid of 60% ethanol in matrix), 15C/min to 220C, 2'@220C (20.5 min at all). He 30 mL/min, sampler@200C, 1uL, split 50, detector@250C, 40mL/min H2+400mL/min O2. Benzyl alcohol appeared at 18.3 min, phenol used as IS eluted nearby at 19.1 min. Quite a neat resolution in reasonable time. Good luck.

Don't forget to consider the impact of the injection technique. GC injection is almost an art, a feeling I would say. There are wonderful books about GC injection techniques, among which I would suggest those by Konrad Grob:

http://www.ranker.com/list/konrad-grob-books-list/reference

A DB-5 column can be good. For GC temperature ramp you could start at 70°C and ramping up till 200-250°C at 3 °C/min (that is more than enough to elute your compund). The temperature program depends on the kind of side products you have together with Benzyl alcohol. If there are also products much heavier than benzyl alcohol in your reaction mixture you have to increase the final temperature. Anyway 250 °C is already a good final temperature all-purpose.

Regards

I have carried out the same analysis: HP-5 column (Agilent), oven temperature from 50 to 250, heating rate 20/min. The n-Dodecane was used as standard. The seperation between benzyl alcohol and benzaldehide is easy to achieve:)

A non-polar column will be good. Example (Elite wax-supplied by Perkin elmer)..You can use cyclohexanone/acetophenone as the internal standard. Make sure the chosen internal standard is stable and does not react with the reactants/solvent.

The maximum oven temperature this column could reach is 250°C. You could start the GC program from 90 °C ( rate 3 °C/min) and ramp it to 150 °C (rate 5°C/min) and the final temp (230 °C with rate of 3°C/min). Do not set the final temp at 250 °C as its the maximum temp of the column and it could cause column bleeding..so..final temp should be atleast 20°C less than the max column temp. It will best if you could find the boiling point of ur expected products so that u could play around with the GC program.

Best wishes.

U can refer this paper by my colleague.

Applied Catalysis A: General 445– 446 (2012) 252– 260

Analytical column, Agilent HP-5 capillary column, 60 m×0.53mm×1.0 µm

Oven program 100 0C for 3 minutes, 10 0C/min to 240 0C, 40 0C/min to 280 0C, hold for 3 min.

Injector temperature 230 0C, FID temperature 300 0C.

The inlet split ratio was 5 to 1.

4.0 mL/min nitrogen

40 mL/min hydrogen

450 mL/min oxygen

You could use any capillar column with medium polarity.

Capillary column

Oven temperature: 80-200 by ramp 5 degree/min and at 200 degree for 20 min

Injection and Detector temp should be 230-240 degree

Flow rate can be controlled with the column length

Split ratio: 30-50

Capillary column: SE-30

Oven: 150-220 with 10 degree/min

The minimum temperature for Injector: 205

Flow rate can be controlled with the column length

Split ratio: 5/1

If your GC has a HP-5 column and FID detector then the suitable GC program is as follows -

FID temperature - 280 C

Inlet temperature - 250 C

carrier gas - Air and N2

Flame gas - H2

Oven program ramping -

1) initial temp - 100 C; hold time - 1 min

2) rate - 15 C/min; temp - 180 C; hold time - 2 min

3) rate - 30 C/min; temp - 280 C; hold time - 9 min

This is the best program for your analysis.

You can use a stinless-still or glass column (at least 1.5 m) packed with DC 200 as stationary phase.

It is important that your injector temperature should be slightly higher than the alcohol analyzed.

Pay attention also to detector that it should be 300 degree.

Agilent HP-5 column is good for benzyl alcohol. We use this column and we don't have any problem.

You can use capillary column (ZB-1, 30 m length, 0.5 nm ID and 3.0  film thickness). For Temperature condition you have to do programming depending upon the BP of the substrates you have used in your reaction. Starting from the lower temp to higher temp. There are so many condition which some RG contributors have already mentioned. Its depends upon the column, temp. But if there is any possibility of emerging peaks you may increase the split ratio. I hope you can get your answer after the above discussion.

All the best...........

Years ago I studied toluene oxidation and that time I had used SE-30 column and He as carrier. I used a temperature programing from 70 to 215 oC. There is a rule that you injector and detector must be at least 50 oC higher than your column.

If you are studying benzilic alcohol oxydation to benzaldehyde you cannot use benzilic acid as internal standard or bezylbenzoate. I suggest you could be using acetophenone.

thank you dear my friend for your valuable advises. you are right. with the GC education course we also were informed with your advises.

Which sampler we should use for determination of Benzyl alcohol? Either HSS or ASL? According to selection of sampler, column conditions and other chromatographic parameters will also vary.

hello, did you find peak on GC. ? i can't see the corresponding peak on GC chart. Hüseyin Gümüş

• I recently published a paper related to toluene oxidation: doi: 10.18540/jcecvl10iss7pp20308