Tuesday, May 27, 2008
Monday, May 26, 2008
Sunday, May 25, 2008
GC Assay Xylene: o-, m- and p- isomers
Dimethylbenzene:
Separation of Para- and Meta-Xylene on Capillary GC Column
Analysed on PEG 25M and FFAP g.c. columns. using a flame ionisation detector with N,N-dimethyl-. formamide as an internal standard.
Column Temp: 90 ℃, Constant.
Inlet / Detector Temp: 250℃.
Run time: 10 min.
Chromatogram: p- isomer comes first, then m- isomer later, o-isomer last.,
| p-Xylene | m-Xylene | o-Xylene |
Adopted from EPA Method 624
Why Solvent Filter/Degassers Matter?
Why change another Mobile Phase or new column, Got a noisy baselines.
Why Solvent Filter/Degassers Matters? ------ is a high-efficiency in-line system that is designed to remove dissolved gases from a solvent, then the mobile phase is withdrawn from the solvent reservoir and the degassed liquid is delivered to the pump.
If the on-line degassers work 120% well, then need to clean/replace the Solvent Filter.
However, Do you still remember how to clean that?
Oh......Now I recalled some tough experiences in 3-years-Yellow Jackets Life. At 2005, made "a big mistake"-- put the Solvent Filter in the Ultra- Sonicator with MeOH. The Agilent Solvent Filter is made of glass, then the porous structure on the glass was damaged.
Why Solvent Filter/Degassers Matters? ------ is a high-efficiency in-line system that is designed to remove dissolved gases from a solvent, then the mobile phase is withdrawn from the solvent reservoir and the degassed liquid is delivered to the pump.
- Degas eluents as particulates are removed
- Eliminate spurious peaks caused by outgassing in detectors
- Eliminate pump downtime caused by air locks and particulates in check valves
- Decrease piston wear; increase column life
- Filter safety into plastic-coated or heavy-walled solvent reservoirs
However, Do you still remember how to clean that?
Oh......Now I recalled some tough experiences in 3-years-Yellow Jackets Life. At 2005, made "a big mistake"-- put the Solvent Filter in the Ultra- Sonicator with MeOH. The Agilent Solvent Filter is made of glass, then the porous structure on the glass was damaged.
What solvents to be used to flush the HPLC lines to remove contaminants?
For "Dirty Analyst" --- A**P**/ Cin** *-- At least 27 different ingredients in them.
So Question is: What solvents to be used to flush the HPLC lines to remove contaminants?
My Answer is: Prepare solvent mixture consists of IPA and water, 50% each will effectively clean contaminations in the solvent tubes, capillaries, flow cells etc… in an HPLC system. Water will clean salts and other possible contaminants and IPA will clean both polar and non polar possible contaminants. Or just bypass the column with a tubing, then Using a low flow rate of 0.5 ml/min, flush the entire HPLC system for couple of hours to remove any contaminations. Or can also keep the flushing for overnight after preparing enough solvent mixture.
Go Home have a good resting, then when come back at early morning, A new trouble-free HPLC system is ready to go.
So Question is: What solvents to be used to flush the HPLC lines to remove contaminants?
My Answer is: Prepare solvent mixture consists of IPA and water, 50% each will effectively clean contaminations in the solvent tubes, capillaries, flow cells etc… in an HPLC system. Water will clean salts and other possible contaminants and IPA will clean both polar and non polar possible contaminants. Or just bypass the column with a tubing, then Using a low flow rate of 0.5 ml/min, flush the entire HPLC system for couple of hours to remove any contaminations. Or can also keep the flushing for overnight after preparing enough solvent mixture.
Go Home have a good resting, then when come back at early morning, A new trouble-free HPLC system is ready to go.
How to select buffers for my HPLC Separations?
How to select buffers for my HPLC separations?
Buffer Selection
| Buffer | pKa | pH Range | UV Cutoff (A > 0.5) |
| Trifluoroacetic acid (TFA) | <<> | 1.5-2.5 | 210 nm (0.1%) |
| KH2PO4/Phosphoric Acid | 2.12 | 1.1-3.1 | <200> |
| Tri-K-Citrate/hydrochloric acid 1 | 3.06 | 2.1-4.1 | 230 nm (10mM) |
| Potassium Formate/formic acid | 3.8 | 2.8-4.8 | 210 nm (10 mM) |
| Tri-K-Citrate/hydrochloric acid 2 | 4.7 | 3.7-5.7 | 230 nm (10mM) |
| Potassium acetate/acetic acid | 4.8 | 3.8-5.8 | 210 nm (10mM) |
| Tri-K-Citrate/hydrochloric acid 3 | 5.4 | 4.4-6.4 | 230 nm (10mM) |
| Ammonium formate | 3.8 9.2 | 2.8-4.8 8.2-10.2 | (50 mM) |
| Bis-tris propane� HCI/Bis-tris propane | 6.8 | 5.8-7.8 | 215 nm (10mM) |
| Ammonium acetate | 4.8 9.2 | 3.8-5.8 8.2-10.2 | (50 mM) |
| KH2PO4/ K2PO4/ | 7.21 | 6.2-8.2 | <> |
| Tris� HCI/Tris | 8.3 | 7.3-9.3 | 205 nm (10 mM) |
| Bis-tris propane� HCI/Bis-tris propane | 9.0 | 8.0-10.0 | 225 nm (10mM) |
| Ammonium hydroxide./ammonia | 9.2 | 8.2-10.2 | 200 nm (10mM) |
| Borate (H3BO3/Na2B4O7 10 H2O | 9.24 | 8.2-10.2 | |
| Glycine� HCI/glycine | 9.8 | 8.8-10.8 | |
| 1-methylpiperidine� HCI/1-methylpiperidine | 10.1 | 9.1-11.1 | 215 nm (10 mM) |
| Diethylamine HCI/diethylamine | 10.5 | 9.5-11.5 | |
| Triethylamine HCI/triethylamine | 11.0 | 10.0-12.0 | <> |
| Pyrollidine HCI/pyrollidine | 11.3 | 10.3-12.3 | |
PS: 0.05 M or 0.01 M is suitable for current assay requirement.
Pesticides 1,2-ethylene dibromide (EDB) and 1,2-dibromo-3-chloropropane (DMCP)
Pesticides Analysis of 1,2-ethylene dibromide (EDB) and 1,2-dibromo-3-chloropropane (DMCP) by (Agilent 6890 Micro-ECDs) after microextraction with hexane in acc ordance with U.S. EPA method 504.
Relative standard deviation (% RSD) for the entire method was less than 7% over a concentration range greater than two orders of magnitude with method detection limits of 0.003 ug/L or lower. So Nice!
Assay Details:
Inj. Vol.: 2-mL splitless injection Inlet Split/splitless; 200 °C, pulsed splitless mode (20 psi for 1 min)
Carrier Helium: 6 psi (40 °C); 3.5 mL/min constant flow.
Column: (A) 30 m, 0.53-mm id, 0.8-mm film DB-608, an equivalent of HP-608. (B) 30 m, 0.53-mm id, 1.0-mm film RTX-1701, an equivalent of HP-PAS 1701.
Oven Temp: 40 °C (4 min); 10 °C/min to 240 °C;
Detector: 330 °C.
Makeup Gas: nitrogen, constant column and makeup flow (60 mL/min)
Relative standard deviation (% RSD) for the entire method was less than 7% over a concentration range greater than two orders of magnitude with method detection limits of 0.003 ug/L or lower. So Nice!
Assay Details:
Inj. Vol.: 2-mL splitless injection Inlet Split/splitless; 200 °C, pulsed splitless mode (20 psi for 1 min)
Carrier Helium: 6 psi (40 °C); 3.5 mL/min constant flow.
Column: (A) 30 m, 0.53-mm id, 0.8-mm film DB-608, an equivalent of HP-608. (B) 30 m, 0.53-mm id, 1.0-mm film RTX-1701, an equivalent of HP-PAS 1701.
Oven Temp: 40 °C (4 min); 10 °C/min to 240 °C;
Detector: 330 °C.
Makeup Gas: nitrogen, constant column and makeup flow (60 mL/min)
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