Guidance:

Using Tough Dirty and Complex Samples and/or  Mobile  Phases

Controlling Contamination Guide at Waters’ website (register first)

Maintenance of HPLC/UPLC – Optical Detection

• Sonication of all stainless-Steel filters in the system:
• 10% acetic acid in 45:45 water:Methanol followed by methanol then water (5 min each)
• In worse cases use 10% nitric acid in water.

It is better to just replace the reservoir filters

• Use “wash” vials: injection of full loop volume after each set of tough samples:

VARIOUS OPTIONS:

1. 20% acetic acid in water (for salts)

2. 5% NH4OH (for salts)

3. IPA (for lypophilic compounds)

4. Acetone (for polymeric residues)

5. DMSO:H2O (for bio-residues)

6. 1 mM EDTA (for metallic residues or chelating agents such as amino acids).

• Purge injector in the end of every sample set using water/MeOH/MeCN mixtures according to the method
• Wash the detector cell (using union or column’s bypass) with the appropriate wash solution

• Water (for salts)

• Methanol or (better) isopropanol (for oily residues)

• 10% acetic acid in water (for salts)

• 0.1 mM EDTA (for chelating agents)

Routine maintenance of HPLC-MS or ELSD

1. Reservoir filters sonication of bottle A (H2O with FA) once a month
2. In-line filter in the pump, sonication once a month
3. Water for LC-MS should be clean of residues (check supplier)

Preventative measures:

1. Use “wash” vials for injection of full loop volume after each set of tough samples:

OPTIONS:

1. 20% acetic acid in water (for salts)
2. 5% NH4OH (for salts)
3. IPA (for lypophilic compounds)
4. Acetone (for polymeric residues)
5. DMSO:H2O (for bio-residues)
6. 1 mM EDTA (for metallic residues or chelating agents such as catalysts).

1. Purge injector in the end of every sample set:  (Masslynx: Use an inlet method with purge injector in the shutdown method)

Follow-up

1. Inject 100ul 50:50 MeCN:H2O after every tough sample to wash contamination
2. Inject blank (sample’s solvent) after every concentrated sample