Why 371,445 and 519 in my LCMS system?

So sweet question, today, remind me 2005 Fall, The First Question I asked at Tech.
All the optimal conditions were set up, where were they from?

One reasons could be they are from Contaminant Peaks from C18 Column Bleed. The contaminant ions, at M/Z 371, 445, and 519, when seen on the LC/MSD and LC/MSD Trap systems in positive ion mode, are believed to be C18 column bleed peaks of polysiloxane [O-Si(CH3)2-]n

Methylsulfonylmethane (MSM, or Dimethylsulfone)

Methylsulfonylmethane (MSM, or dimethylsulfone) is an organosulfur compound with the formula (CH3)2SO2. It occurs naturally in some primitive plants and is present in small amounts in many foods and beverages and it is marketed as a dietary supplement, although its benefits are disputed.

Purity and Limit of Dimethyl Sulfoxide ( DMSO) by Gas-Chromatography with FID.

Reference Standard: USP DMSO and MSM RS.
Column: 3m m x 0.5 mm capillary column coated with a 5 um phase G2.
Oven Temp: 120 degree C.
Inlet/ FID temp: 250 degree C.
Inlet Split ratio is 2:1.
He ( carrier gas) = 5 ml/min.
C-Air/H2 = 400:40 ml/min.

Result: MSM Purity is 101.03%, Dimethyl Sulfoxide ( DMSO) is 0.041%, Chromatography purity is 99.91%.

Good to go for Lunch.

How to Use ChemStation to Calculate System Suitability

How to Use ChemStation to Calculate System Suitability

Cool.....Work Hard, Think Smart........

Basic Principles of Headspace Analysis 2

PS: Thanks for the PerkinElmer

Basic Principles of Headspace Analysis

A headspace sample is normally prepared in a vial containing the sample, the dilution solvent, a matrix modifier and the headspace. Volatile components from complex sample mixtures can be extracted from non-volatile sample components and isolated in the headspace or gas portion of a sample vial. A sample of the gas in the headspace is injected into a GC system for separation of all of the volatile components.

Phases of the Headspace Vial

G = the gas phase (headspace)
The gas phase is commonly referred to as the headspace and lies above the condensed sample phase.

S = the sample phase
The sample phase contains the compound(s) of interest. It is usually in the form of a liquid or solid in combination with a dilution solvent or a matrix modifier.

Once the sample phase is introduced into the vial and the vial is sealed, volatile components diffuse into the gas phase until the headspace has reached a state of equilibrium as depicted by the arrows. The sample is then taken from the headspace.

From USP <467>

Headspace Operating Parameters Sets
	1	2	3
Equilibration Temp (oC)	80	105	80
Equilibration Time ( Min)	60	45	45
Transfer-line Temp (oC)	85	110	105
Carrier Gas: N2, He @ appropriate pressure
Pressurization Time ( s)	30	30	30
Injection Volume ( ml)	1	1	1

The FID Detection Limitation ( g/s)

One more question for the FID.

The FID detection limitation ( g/s) is : 2NW/A.

Where,
N is the Baseline noise (A)
W is the Mass of n-Hexadecane (g)
A is the Average area amount of n-Hexadecane ( A• s)

So, how to calculate the Baseline Noise (A)?

(1) The Noise (N: peak to peak) is measure over a representative section of baseline equal to 20 times the width of the analyte peak ( Wi).

(2) When the instrument is under optimal conditions that produce a continuous, electronic output, the Noise ( N ) may be measured from the Peak to Peak Variation ( N: peak to peak) in the baseline signal.

N = N:peak to peak

Nice....