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Hard-to-Filter Samples (Performance Data)

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Filtering Orange Juice: Millex® HPF Filters (PVDF) Can Process Higher Volumes Than Other Filters Without Clogging.

Comparison of Millex® HPF syringe filters with PVDF membrane compared to Competitor W syringe filters with PVDF membrane and a prefilter. 10% solutions (v/v) of of orange juice (three different brands) were filtered through these syringe filters and volume at which the filter was clogged was recorded.
Comparison of Millex® HPF syringe filters with PVDF membrane compared to Competitor W syringe filters with PVDF membrane and a prefilter. 10% solutions (v/v) of of orange juice (three different brands) were filtered through these syringe filters and volume at which the filter was clogged was recorded.

Pharmaceutical Product Analysis: Drug Binding Characteristics of Millex® HPF Filters (PVDF and Nylon)

Since Millex® HPF filters contain glass fiber prefilters, they tend to bind the analyte of interest, as seen here with filtration of ranitidine solution through various Millex® syringe filters. All the Millex® HPF filters (PVDF and nylon) showed 15 – 25% drug binding for the first mL of sample filtered. But when the third mL fraction was collected, quantitative drug recovery was obtained. For Millex® syringe filters containing no prefilter (PVDF 0.45), no drug binding was observed even for the first mL of filtrate.

The bottom line: for easy-to-filter samples, always use a membrane-only syringe filter (without prefilter) to reduce analyte-binding. For hard–to-filter (particle laden / viscous) samples, use Millex® HPF filters and discard 3 -5 mL of filtrate prior to collecting the sample for downstream quantitative analysis.


Drug binding characteristics of Millex® HPF Filters. Prefilter-containing syringe filters (Millex® HPF filters, nylon or PVDF, 0.2 µm or 0.45 µm pore sizes) show greater analyte binding than a membrane-only filter, but all filters showed 100% analyte recovery after filtration of 3-5 mL.
Drug binding characteristics of Millex® HPF Filters. Prefilter-containing syringe filters (Millex® HPF filters, nylon or PVDF, 0.2 µm or 0.45 µm pore sizes) show greater analyte binding than a membrane-only filter, but all filters showed 100% analyte recovery after filtration of 3-5 mL.

Overall Performance Comparison Among Prefilter-Containing Syringe Filters

ProductsAvailable from Merck?Volume Throughput*Extractables**Analyte Binding
Water Acetonitrile Methanol

PVDF 0.45 µm

 Yes +/- + + +
PVDF 0.2 µm No NA NA NA NA NA
Nylon 0.45 µm Yes +/- - - - -
Nylon 0.2 µm Yes +/- - - - -
Hydrophilic PTFE 0.45 µm Yes +* + + + +
Hydrophilic PTFE 0.2 µm Yes +* + + + +

* Volume Throughput compared with Competitor W hydrophobic PTFE syringe filters with prefilter. Volume throughput was measured by filtering 3 different matrices (10% orange juice, 2 mg/ mL protein solution, antihistamine syrup solution) through various prefilter-containing syringe filters.

**Degree to which each device leached extractable impurities was measured by filtering the listed solvents through the various syringe filters and analyzing the filtrate using HPLC-UV analysis at 214 nm.

Millex® HPF Filters (Hydrophilic PTFE): Performance in Filtering Particulate-Laden/Viscous Samples

The ability of Millex® HPF filters with hydrophilic PTFE membrane to process various sample types (20% orange juice in water, v/v; protein shake 2 mg/mL, and Benadryl® antihistamine syrup) was tested by measuring the volume filtered before the filter clogged.
The ability of Millex® HPF filters with hydrophilic PTFE membrane to process various sample types (20% orange juice in water, v/v; protein shake 2 mg/mL, and Benadryl® antihistamine syrup) was tested by measuring the volume filtered before the filter clogged.

Water Flow Rate Comparison: Millex® HPF Filters vs. Competitor W Filters

The rate of water flow through various Millex® HPF filters was compared with water flow through Competitor W syringe filters that also have built-in prefilteres. For the PTFE/polypropylene syringe filters from Competitor W, they were first wetted by 50% ethanol followed by water rinse prior to flow rate measurement.
The rate of water flow through various Millex® HPF filters was compared with water flow through Competitor W syringe filters that also have built-in prefilteres. For the PTFE/polypropylene syringe filters from Competitor W, they were first wetted by 50% ethanol followed by water rinse prior to flow rate measurement.

Performance Comparison: Millex® HPF Filters (Hydrophilic PTFE) vs. Competitor W Filters (Hydrophobic PTFE)

Volume filtered by Millex® HPF with 0.2 µm Hydrophilic PTFE membrane was measured by filtering the listed solutions until the syringe filter clogged. Volume filtered before clogging was compared to volume filtered by Competitor W filters with 0.2 µm hydrophobic PTFE membrane (also with built-in prefilter). The hydrophobic membrane was wetted with 50% ethanol followed by rinsing with water before the samples were applied.
Volume filtered by Millex® HPF with 0.2 µm Hydrophilic PTFE membrane was measured by filtering the listed solutions until the syringe filter clogged. Volume filtered before clogging was compared to volume filtered by Competitor W filters with 0.2 µm hydrophobic PTFE membrane (also with built-in prefilter). The hydrophobic membrane was wetted with 50% ethanol followed by rinsing with water before the samples were applied.