Instructions for Integrated Hydride Generation Accessory Fo

7/27/2019 Instructions for Integrated Hydride Generation Accessory Fo

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Document part number -8499 402 10001 v.0.01

Instructions for the Integrated Hydride Generation Accessory for

iCAP 6500

The Integrated Hydride Generation Accessory is an accessory for measuringhydride forming elements and mercury with better analytical sensitivity than canbe obtained from direct measurement by ICP. This document explains the set upand maintenance of your Enhanced Hydride Generation Accessory for the iCAP6500 ICP Emission Spectrometer with the following sections:

Parts List Assembly instructions

Principle of Hydride GenerationReagentsSample PreparationMaintenance of the unitSpare parts and Consumables

Parts List:

• One Gas liquid Separator (GLS) with 4 colour coded PEEK barbedconnectors (red, blue, green and black) and one PEEK compression fitting

•

One O-ring• One bag of glass beads• 5 Teflon membranes• 0.2m of Tygon 1.6mm ID for connection of Tygon peristaltic pump tubing

to red and blue barbed connectors on GLS• One Teflon torch adaptor for connection to centre tube holder • 0.7m length of Tygon tubing 3/16 ID for connection from top of GLS to

torch adaptor • Tygon peristaltic pump tubing (2 of each) with the following colour coded

bridges:sample = greendrain = black/whiteacid blank = orange/yellowreductant = black

• 1 Ultem sampling probe• I piece of emery cloth to aid connecting tubing• 1m of PTFE sample tubing for connection from sample probe to green

pump tubing• Two lengths of Santoprene tubing to connect sample probe to PTFE

sample tubing and to green Tygon sample tubing




• 0.7m of natural Polyurethane tubing, 4.0 OD for connection of gas supplyfrom iCAP to compression fitting on GLS

• 1m of PTFE drain tubing 3mm ID for connection to black/white drainTygon tubing

Assembly of Enhanced Hydride Generation Accessory for use with theiCAP 6500

• The unit is supplied with all the pump tubing connected.• The user will need to attach the pump tubing to the peristaltic pump on the

iCAP ands set up the Gas Liquid Separator.• The unit should sit comfortably in the kitchen area of the ICP (to the left of

the peristaltic pump), and the lengths of Tygon peristaltic pump tubingsupplied are sufficiently long so that the acid blank (orange/yellow) and

reductant (black) pump tubing will go directly into their respective solutioncontainers.• The sample and drain Tygon peristaltic tubing are supplied connected to

the Ultem sampling probe and 3mm ID PTFE drain tubing respectively.• The Gas Liquid Separator needs to be prepared as described below

before use.

Gas Liquid Separator (GLS)When assembled, the Reaction Zone of the GLS contains 4mm glass beads,which minimise the dead volume of the zone and ensure proper mixing of thecarrier gas and liquid reagents. It also contains a semi-permeable Teflon

membrane to prevent moisture and salts from being carried over into theMeasurement Cell. These parts are supplied with the unit, and must be fittedbefore the accessory is used.

To prepare the Gas Liquid Separator 1. Refer to the figure below, and unscrew the cap of the GLS.2. Add a sufficient quantity of the 4mm glass beads supplied to fill the

Reaction Zone. There should be three or four layers of beads on the floor of the Expansion Volume (at the top of the reaction zone column). If youoverfill this section the gas will not have enough room to expand and thiswill result in liquid escaping up towards the plasma. If the section is

underfilled then it will decrease the sensitivity.3. Take care to prevent the glass beads from falling into the Drain, wherethey may cause blockage.

4. Take one of the 47mm Teflon membranes supplied. Orientate it so thatthe Teflon covered face is on the underside, and place it in position on topof the beads in the space underneath the screw thread for the cap.

5. Carefully re-fit the ‘O’ Ring seal and cap, ensuring that the position of themembrane is not disturbed.




Schematic of the Gas Liquid Separator

Pump Tubing

The unit is supplied with four types of pump tubing which fit onto the iCAP 6500four channel peristaltic pump. The colours of the pump tubing bridgescorrespond to the colour coded connectors on the Gas Liquid Separator unit, asfollows:

BLACK channel DrainGREEN channel SampleRED channel Reductant reagentBLUE channel Acid reagent

Fitting pump tubing to the iCAP 6500 ICP Emiss ion Spectrometer




(Please refer to the figure below as a visual aid)

Schematic of Assembly of Enhanced Hydride Generation Accessory

The peristaltic pump of the iCAP 6500 operates in an anti-clockwise direction.

• Place the GLS to the left of the pump, in the kitchen area.• All of the pump tubing (with the exception of the drain) will attach with the

inlet on the right hand side of the pump i.e. from the sample/reductant/acidblank solutions across the pump and into the GLS.

• The drain is the only tubing that needs to be connected in the oppositedirection, i.e. the tubing is passed under the pump so that the drain outletis on the left hand side.

Drain




The BLACK (Drain) channel must be fitted to pump tubing with BLACK/WHITEbridges i.e. a single piece of pump tubing will have a black bridge fitted at oneend, and white bridge fitted at the other end. This tubing has an ID of 3.17mmand an OD of 4.85mm. It runs from the black connector of the GLS, across theperistaltic pump and to a drain. Connect a suitable length of the 1.6mm ODtubing, using the barbed connector supplied, from the end of the black/whitepump tubing (at the peristaltic pump) to a suitable low level drain or wide neckedplastic container. Please note that the drain tubing is connected anti-clockwise tothe unit, to allow draining from the GLS.

Sample UptakeThe GREEN/YELLOW (sample) channel must be fitted to pump tubing with twoGREEN bridges. This tubing has an ID of 1.85mm and an OD of 3.53mm. Thispump tubing goes from the sample, across the pump to the Gas LiquidSeparator.

ReductantThe RED (Reductant) channel must be fitted to pump tubing with two BLACKbridges. This tubing has an ID of 0.76mm and an OD of 2.43mm. This pumptubing goes from the reductant, across the pump to the Gas Liquid Separator.The PEEK barb is fitted with an additional piece of 1.6mm ID Tygon tubing, for easy connection to the peristaltic pump tubing.

AcidThe BLUE (Acid) channel must be fitted to pump tubing with YELLOW/ORANGEbridges. This tubing has an ID of 0.5mm and an OD of 2.33mm. This pumptubing goes from the acid, across the pump to the Gas Liquid Separator. ThePEEK barb is fitted with an additional piece of 1.6mm ID Tygon tubing, for easyconnection to the peristaltic pump tubing.

To fit the pump tubing:

1. Release the plungers to free the pump platens.2. Take the pump tubing, and feed it around the pump rollers.3. Stretch the pump tubing slightly, and fit the bridges under the bridge

retaining pillars.4. Push the ends of the tubing over the appropriate push on connectors on

the Gas Liquid Separator connection panel.5. Move the platen arm back over the rollers, and confirm that the tubing is

properly located beneath it.6. Return the plunger to the normal position, and adjust the pressure screw

to release the pressure on the tubing.

Pump Speed




As the pump speed is increased, the analytical sensitivity increases, but so doesthe consumption of samples and reagents. The flush time required will bedecreased at higher pump speeds. Reducing the pump speed reduces thereagent consumption at the expense of the analytical sensitivity and increasedflush time. The default pump speed is 30RPM, and good results can be obtainedwith pump speeds up to 45RPM.




Gas SupplyConnect a supply of argon (normally from the nebuliser supply on the front of thesample introduction area of the iCAP 6500), with the supplied 4mm o.d. rigidblack tubing. The pressure should be regulated between 0.34 - 1 bar (5 - 14 psi),to the gas inlet at the rear of the Gas Liquid Separator.

For each hydride group element, there is an optimum Carrier Gas Flow rate thatwill give the maximum sensitivity for that element. For mercury, the analyticalsensitivity increases as the Carrier Gas Flow rate decreases. Low Carrier GasFlow rates require longer flush times (to allow the hydride to travel to theplasma), and, except for mercury, offer no benefits. Higher Carrier Gas Flowrates allow the use of shorter flush times, at the expense of some analyticalsensitivity, and can be used if you want to complete your analysis as quickly aspossible.

Principle of Hydride GenerationThe analyte elements in the sample solution are reduced to volatile hydridesusing Sodium Borohydride (or Stannous Chloride for Mercury analysis), and arecarried in an Argon gas stream into the plasma of the iCAP 6500.

ReagentsSample solutions and reagents used in Hydride generation are corrosive andmay be toxic. Ensure that you take all necessary precautions when handlingthese materials. Sodium Borohydride is unstable, and will gradually evolvehydrogen on standing. Ensure that any containers used for this reagent aresuitably vented, and do not store the reagent for any length of time.

The optimum composition of the reagents used depends upon the element beingmeasured and the composition of the sample. The reagent compositionsdescribed below will be suitable for the analysis of simple aqueous solutions.

Acid Blank ReagentThis reagent is suitable for all type of measurement. 50%v/v (6M) hydrochloricacid solution.

Borohydride Reductant ReagentThis reagent is suitable for all hydride elements, and for mercury.0.5% m/v sodium tetrahydroborate(III) (sodium borohydride, NaBH4), stabilisedin 0.5% m/v sodium hydroxide (NaOH).The Reagent should be filtered through acoarse filter paper immediately after preparation. The Reagent slowly evolveshydrogen gas, and so must be stored in a vented container. The Reagent willremain usable for 2-3 days if stored in a refrigerator at 4°C, but it is preferable toprepare it immediately before use.




Stannous Chloride Reductant r eagentThis reagent is suitable for mercury analyses only. 0.1 - 10% m/v of stannouschloride (SnCl2) in 1 - 10% v/v hydrochloric acid. If you have pre-reduced your sample with hydroxylamine hydrochloride, or if your sample contains littleor no oxidising residues, you can use the lower concentrations of stannouschloride. We strongly recommend the use of Low Mercury grades of stannouschloride, which are available from most major chemical suppliers. Some gradesof stannous chloride form a milky suspension, not a clear solution, particularly atthe higher concentrations. Providing that the suspension is stable, and shows notendency for the solids to settle out, it can be used without affecting the analysis.

Sample PreparationSuccessful analyses using the Hydride Generation technique depend critically onthe sample preparation procedure used. It is not possible to provide details for alltypes of samples, but the following factors should be considered:

1. It is normal practice to acidify samples for trace metal analysis, and manytypes of sample require acid digestion to bring them into a suitable formfor analysis.

2. The hydride generation technique is most successful when the samplesare presented in a hydrochloric acid solution, and every effort should bemade to design a sample preparation procedure that ends with the finalsolution in hydrochloric acid.

3. The acid concentration in the samples affects the size of the analyticalsignal. Samples, blanks and standards should therefore all contain thesame concentration of acid. A final acid concentration of 10% v/v (1.2M)will be suitable for many analyses.

4. The sensitivity of the Hydride Generation technique depends on theoxidation state of the analyte element, and the lower oxidations states(AsIII, SbIII, BiIII SeIV, and TeIV) are more sensitive. It is therefore normalpractice to pre-reduce the analytes before analysis. As and Sb can bepre-reduced with a potassium iodide/ascorbic acid mixture. Se and Tecan be pre-reduced by boiling in 6M hydrochloric acid for ten minutes.The BiV oxidation state is unstable, and all bismuth solutions contain BiIII.Bismuth analyses therefore do not normally require pre-reduction.

5. Many transition metals (such as copper and nickel) interfere with thereduction reaction

6. Some samples may contain mercury in the form of organo-mercurycompounds. The Stannous Chloride reductant reagent will only reduceionic mercury, and the degree to which the Borohydride reductant reactswith organo-mercury compounds varies with the type of compound. It istherefore normal practice to use an oxidative digestion for samples for mercury analyses, to convert the organomercury compounds to ionicmercury.




Method Development on iTEVATo use the unit, you must disable the Drain Sensor from the Control Center pageof iTEVA on the menu option Tools/Instrument Options/Sample Introduction. Theanalysis parameters below have been tested with a range of volatile elementsand found to be satisfactory. You should still optimise these values based onyour solutions for maximum sensitivity.

Parameter As Bi Hg Sb Se(nebuliser)Carrier Gas Flow L/min 0.3 0.3 0.3 0.3 0.3

Pump Speed rpm 30 30 30 30 30RF Power W 1350 1350 1350 1350 1350

Auxiliary Gas Flow L/min 0.5 0.5 0.5 0.5 0.5Coolant Gas Flow L/min 16 16 16 16 16

Maintenance of the unit After each use, it is advised that the entire Hydride Generator kit is flushedthrough with deionised water (by placing the sample, acid and reductantperistaltic tubing in DI and aspirating through the system for 10 minutes). TheGas Liquid Separator is unlikely to become worn or damaged in normaloperation, but may become dirty, and so require cleaning.

To clean the Gas Liquid Separator:

1. Remove the Top Cap and Semi-Permeable Membrane.2. Inspect the internal volume of the Gas Liquid Separator, and remove any

deposits.3. Confirm that the Reaction Zone is filled with glass beads.4. Fit a new Semi-Permeable Membrane, and refit the ‘O’ ring seal and cap.

After extended use, the pump tubing will become worn and must be replaced.You should inspect the tubing at regular intervals by removing it from the pump,and examining the part of the tube that is in contact with the pump rollers. If thetubing appears to be stretched, or does not have a circular cross section, itshould be replaced.

Please note that the tubing in the Acid channel will gradually become opaque.This does not affect normal operation, and is not an indication that the tubingrequires replacement.

After you have replaced the pump tubing, or if you suspect that there is ablockage, you should check the flow rates of the Reductant, Acid and Samplechannels. The flow rates should be:




Acid channel 0.7mL/minReductant channel 1.6mL/minSample channel 7.5ml/minDrain channel 14mL/min

Consumables and SparesSpare Peristaltic Pump Tubing (6 pieces of each for sample, acid blank,reductant and drain) 9423 460 10011Spare Teflon Semi-Permeable Membrane (set of 5) 9423 460 10021Spare Glass Beads for GLS (one bag) 9423 460 10031Spares kit for Hydride Generator (includes spares for all connective tubing andperistaltic pump tubing) 8423 180 50151

Instructions for Integrated Hydride Generation Accessory Fo

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