Introducing the Varian 356-LC Refractive Index Detector

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Introduction

The Varian 356-LC detector is being introduced to replace the ProStar 355 detector.

The 356-LC detector was designed and built at Polymer Labs, UK.

The Varian 356-LC is a high performance refractive index detector designed to meet virtually all customer needs for refractive index detection.

This universal detector is ideal for the analysis of non-absorbing compounds such as polymers, carbohydrates, alcohols, and fatty acids.

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Overview

On/Off switch

Status LEDShowing Power, Purge, zero and error

Leak drain Hinges for “Barbie” shower

211 mm

477 mm

296 mm

Access panel to connections

The Varian 356-LC has been designed to integrate into the ProStar range of detectors.

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Inlet

Outlet

Waste for internal leaks

Overview

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Principle of Operation

Refractive index detectors are universal detectors designed for analysis of compounds that do not strongly absorb UV light and, therefore, cannot be assayed with a UV detector.

The usual compounds analyzed are sugars, polymers, aliphatic amines, organic acids, and alcohols.

The Varian 356-LC is functionally identical to other deflection type

refractive index detector, it comprises: • LED light source,

• 6 µL flowcell with reference and sample compartments

• split photodiode detector

The complete assembly is housed in a thermally controlled block to maintain baseline stability.

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Principle of Operation

Generic diagram of the Varian 356-LC Refractive Index Detector

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Principle of Operation

When both cell compartments contain the same solvent, the light beam is positioned equally on the two detector diodes I1 and I2

When solvent containing a compound passes through the sample side of the cell the difference in refractive index causes the light beam to be proportionally deflected (according to Snell’s refraction law).

The change in light intensities between I1 & I2, is proportional to concentration and refractive index of the sample solution.

Refractive index is a bulk property of the mobile phase and is very sensitive to changes in ambient temperature

RI detectors are also sensitive to flow-rate changes and cannot be used for gradient elution.

I1 I2

I1I2

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Internal Flow Path

Normal Operating Conditions:

•The incoming solvent passes into & out of the sample side of the flowcell, then to waste

Purge Conditions:

•The incoming solvent passes into sample & reference side of the flowcell, before going to waste

The Varian 356-LC has only 15 µL of volume between inlet and cell to keep dispersion to a minimum

The maximum recommended flow rate permitted through the Varian 356-LC Detector is 10 mL/min

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Operational Parameters

Purge

When Purge is selected, the purge indicator light is highlighted, and solvent flow is diverted through the reference side of the RI cell, instead of the sample side; before going to waste. The purge time can be adjusted to compensate for different solvents & eluent flow rates.

Auto-Zero

The detector output is re-set to zero when the auto-zero function is selected. An error will occur if the auto-zero process takes longer than 5 minsn

Response Time

The Varian 356-LC has a default response time of 1.0 second, with a settable range of 0.1 –5.0 seconds.

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Operational Parameters

Sensitivity

The sensitivity of the Varian 356-LC can be adjusted to provide greater flexibility. The three possible sensitivity settings are described below:

• Low - Suitable for highly concentrated samples (e.g. Prep LC)

• Standard - Default setting, ideal for the majority of LC applications

• High - Suitable for samples of low concentration in order to maximize signal‑to‑noise.

Temperature

The temperature of the Varian 356-LC can be set between 30-50 °C (1 °C increments) or turned off. The default value is 35 °C. It is recommended that the temperature should be set at least 5 °C above ambient temperature in order to ensure a stable thermal environment.

 

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Operational Parameters

Polarity

The output of the Varian 356-LC refractive index detector can be either positive or negative; therefore it is essential that the polarity of the detector signal be configured. The polarity parameter is used to invert the sign of the refractive index data. A positive polarity leaves the data unaffected, whilst a negative polarity essentially inverts the chromatogram.

 

Baseline Offset

The baseline offset of the Varian 356-LC can be set between the ranges –100 to +100 µRIU.

 

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Front Panel Status

The Varian 356-LC, like other Varian modules, has no front-panel display or hard-key control. Full functionality is provided by Galaxie CDS, which gives the user greater flexibility and control than the ProStar 355.

Three indicator lights are located at the top left of the front panel of the module to display the status of the instrument

Status Color

ReadyNot Ready (i.e. changing

temp)Error

Green Orange

Red

Auto-zero on Green

Purge on Green

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Galaxie Control

The Varian 356-LC can be connected directly to the PC via an RS232 connection, for full Galaxie Control

Status window displays all current detector conditions

Detector output and status quickly accessed in overview window

A/Z & purge function easily accessed

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Galaxie Control

All detector parameters can be changed via the configuration window

Send button downloads settings to detector

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Key Benefits

Sensitivity

The Varian 356-LC provides three sensitivity settings, HIGH, STD & LOW, that can be selected according to the type of analysis. For example, the LOW setting is ideal for preparative LC in order to prevent the signal from saturating at the high concentrations typically encountered.

Baseline Stability

Flow cell thermostating in the Varian 356-LC eliminates temperature effects on the RI baseline. Stable baselines mean lower detection limits for both analytical and preparative applications. Temperatures are controlled in one degree increments from 30 °C to 50 °C.

Superior Peak Shape

The custom designed 6µL ‘flow-efficient’ cell for minimal peak dispersion delivers outstanding peak shape, and superior resolution.

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Key Benefits: Superior Peak Shape

At 1 mL/min the Varian 356-LC peak width* is 50% narrower than the ProStar 355

Varian 356-LC

ProStar 355

*measure at ½ height

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Key Benefits: Superior Resolution

Resolution 1.17

Resolution 1.18

The Varian 356-LC provides better resolution between peaks than the ProStar 355.

This is beneficial when analysing compounds of similar properties under isocratic conditions.

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Key Benefits: Automating the 356-LC

Fully Automated via Galaxie

Galaxie Software from Varian provides control and automation capabilities. The detector can be automatically purged prior to analysis for overnight operation. The Varian 356-LC can be externally controlled, permitting a device (for instance, a pump) to automatically activate functions such as electronic optical zero and reference cell flush.

Digital Data Acquisition

Unlike the ProStar 355 the Varian 356-LC offers the user a digital data signal, which can be taken directly into a PC, using an RS232 cable, without the need for an MIB800 module.

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Automation via Galaxie Software

Detector settings can be saved in a Galaxie method along with pump program for individual applications

Automatic Purge and A/Z are possible within a Galaxie method

Varian 356-LC can be automated using a sequence of Galaxie methods

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Applications: Carbohydrates in Fruit Juice

A cost-effective and simple separation to identify food adulteration in fruit juice can be achieved using the Varian 356-LC and PL-Hiplex columns.

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Applications: Maltodextrin in Sports Drink

The low dispersion characteristics of the Varian 356-LC provides excellent resolution for maltodextrin analysis in sports beverages.

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Applications: Epoxy Resins

The Varian 356-LC is ideal for GPC analysis, when combined with Galaxie and Cirrus GPC software.

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Product Positioning

The Varian 356-LC and PL-ELS 2100 ELSD are both universal detectors and should have distinct positions in the market place:

ELSDs are typically more expensive than RID, and there is no justification for the higher cost and added complexity of method development if the RI detector can already adequately perform the analysis.

The Varian 356-LC should be positioned as a high performance general use refractive index detector with low noise, excellent thermal control & advanced capabilities such as automatic purge & auto zero using Galaxie software.

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Varian 356-LC Features & Benefits

Feature BenefitLow dead-volume flow-cell Improved resolution and sensitivity

Active temperature compensation Lower base-line drift and improved reproducibility

Galaxie Control Improved productivity through automated, unattended sequence runs

Easy to use and consistent user interface Improved traceability using Galaxie operation logs

Digital data output Simple to set up

Better value – do not need an expensive analog to digital interface board

Long-Life LED Reduced maintenance and quick start-up as the LED is always on and has a indefinite life time

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Varian 356-LC Specifications

200mm

450mm

200mm

415mm

450mm

RI range (RIU) 1.0~1.75

Range (µRIU) 150-600x10-6 RIU/FS

Linearity (µRIU) 600

Sensitivity (mV/µRIU) LOW (2), STD (4), HIGH (8)

Short-term noise (nRIU) <5.0

Drift (nRIU/hr) <250

Response time (s) 0.1–5.0

Temperature control (°C) OFF, 30–50 (1 °C increments)

Cell volume (µL) 6.0

Light source LED 880 nm

Analog output 1V FSD

Digital output 24 bit (10 Hz) via serial port

Flow rate range (mL/min) 0.1–10

Dimensions (w x d x h) (unpacked) 296 x 475 x 212 mm 

PC control (software) Galaxie Software

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Ordering Information

Varian 356-LC Detector PL0880-0000

Packing ListManual for Varian 356-LC detector PL0880-0010 1.5M PTFE Outlet Tubing assembly PL0880-0300 Aux I/O Cable (5 m) PL0860-0055 RS232 Communication cable PL091-24950Green Half Moon Door 01 107288 00 Door Cap 09 102066 00

AccessoriesAnalogue Cable PL0880-0310Mains Inlet Fuses (pk 5) PL0860-0420

Field UpgradesLED assembly PL0880-0110 Flow Cell PL0880-0120 Cell Seals (Top) PL0880-0150Cell Seals (Bottom) PL0880-0160Purge Valve PL0880-0210

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Product Information Folder (PIF)

* The Varian 356-LC PIF contains additional information *

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