SKC Limited Chromic Acid Test Kit User Manual

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Chromic Acid Mist Test Kit

Operating Instructions

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Contents

Introduction

Synopsis of the method .............................................................................................................. 2

Getting started ........................................................................................................................... 2

Sampling

Loading the filter paper ............................................................................................................... 4

Calibration .................................................................................................................................. 5

Analysis

The chemicals ............................................................................................................................ 6

The apparatus ............................................................................................................................ 7

The comparator .......................................................................................................................... 8

Removing the filter paper for analysis .......................................................................................... 8

Administration and Next Steps

Record keeping ........................................................................................................................ 10

Results ..................................................................................................................................... 10

Supplies ................................................................................................................................ 11

Safety Data Sheets

Acetone .................................................................................................................................... 12

Alkali treated filter membranes .................................................................................................. 13

Sulphuric acid solution .............................................................................................................. 14

1,5 diphenylcarbazide ............................................................................................................... 15

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Introduction

This kit has been designed to comply with MDHS method 52/3 obtainable from the Health & Safety Executive for the testing of Chromic Acid Mist.

We strongly recommend reading MDHS 52/3 prior to commencing any sampling.

Synopsis of the method

Using either a ‘seven hole head’ or - more recently - the ‘IOM sampler’ to hold an alkali treated filter paper, an air sample is taken at 2 litres per minute over the time period of one hour.

This can be positioned over a tank with the optional clamp.

After sampling, the filter paper is removed from the sampling head and using the chemical kit and comparator, an analysis and quantification can be made of the Chromic Acid Mist levels.

Getting started

Refer to your air sampling pump manual for detailed descriptions on setting the pump sampling flow rate and time period. Most pumps can be started and stopped manually. The flow rate must be set using an external calibration device such as a rotameter or other such calibrator. This must be done with the filter sampling head assembled and inline.

For convenience we recommend an SKC Universal Deluxe air sampling pump which can be set to automatically stop after one hour.

This manual contains all the information required to process the filter with the chemical kit that you have purchased.

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Introduction

CAUTION!

Observe precautions when handling treated filters, and chemicals provided, as they may cause harm to health.

We recommend only using stainless steel forceps/tweezers to handle alkali treated filters.

Safety Data Sheets are provided at the rear of this manual.

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Sampling

Tips and advice on setting up a sampling train (the sample pump with a filter) can be found in the SKC Step by Step guide.

The process of loading a filter paper and calibrating this sampling train is similar to the set up required for inhalable dust sampling using an IOM sampler.

If you do not have this guide, a free copy can be downloaded from the SKC website at -

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Loading the filter paper

The IOM comprises a two piece cassette and the filter is loaded into the cassette which is then placed inside the sampler.

The front cover of the sampler is then screwed onto the thread of the body.

Diagram showing the positioning of the filter paper within an IOM Sampler.

Note that the filter is cream/ white in colour.

A blue paper if present is a separator only and is not used in sampling.

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front

cover

filter

cassette

front

body

cassette

grid

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Sampling

Calibration

Assuming an IOM head, SKC Universal pump, and rotameter for calibration.

The IOM head with filter is clipped/ held down onto the foam seal on top of the rotameter ensuring a good seal with no leaks. With the toolkit the flow is adjusted by turning the flow adjustment screw.

This is located to the bottom left side of the universal sampler and marked ‘flow adjust’. Adjust to to 2L/min.

As the screw is turned the float or ball should move up or down inside the rotameter tube.

For other types of sampler or calibrator, or for more indepth directions, refer to the equipment manuals.

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Analysis

The chemicals

The kit contains the following chemicals:

• 1,5Diphenylcarbazide  0.125gvial  10off

• Sulphuricacid0.25M,  500ml   1off

• Acetone    250ml   1off

• De-ionisedwater   500ml   1off

Use only 25 mm alkali-treated filter membranes prepared in accordance with MDHS 52/3.

1,5 diphenylcarbazide solution 0.25% w/v is obtained by transferring the contents of one vial (0.125 g) to the 60 ml plastic bottle labelled Diphenylcarbazide 0.25% w/v.

Using rhe 25 ml measuring cylinder, transfer 25 ml acetone to the bottle and swirl until the powder has dissolved. Measure 25 ml deionised water and add to the bottle. Replace the cap tightly and mix thoroughly.

Protect from light.

There is sufficient reagent for 25 determinations of hexavalent chromium.

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Analysis

The apparatus

The kit comprises:

1 off Alkali treated filter membranes (pack of 24) 10 off 1,5 Diphenylcarbazide 0.125g vial 1 off Sulphuric Acid 500ml 1 off Acetone 250ml 1 off De-ionised Water 500ml 3 off Plastic beaker 1 off Glass measuring cylinder 25ml 1 off Glass measuring cylinder 10ml 1 off Glass measuring cylinder 5ml 1 off Plastic bottle labeled 60ml 5 off Comparator moulded cell and cap 10ml 1 off Wash bottle 250ml 1 off Forceps 1 off Lovibond comparator with CrVI disc 26620 1 off Handbook with health and safety data

A holding clamp to position the filter head above the facility tank is available as an optional extra.

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Analysis

The comparator

The Lovibond 2000 comparator fitted with chromium VI comparator disc 26620 covers the range 0-0.1 mg chromium VI per cubic metre of air in steps of:

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

This is suitable for the measurement of 120 litres of sample drawn at 2 litre/minute for 60 minutes.

Removing the filter paper for analysis

1. Transfer your sampling system to clean, non hazardous area to perform the analysis.

2. Remove filter using forceps, taking care not to cause damage, and place filter into 50 ml plastic beaker.

3. Using 10 ml measuring cylinder, add 8 ml 0.25M sulphuric acid to the beaker.

4. Wait 10 minutes for dissolution of any hexavalent to take place, swirling solution occasionally.

5. Using 5 ml measuring cylinder add 2 ml diphenylcarbazide solution to beaker and swirl to mix. Allow to stand 10 minutes.

6. Transfer one new unused filter membrane to a clean 50 ml plastic beaker using forceps and repeat steps 2 - 4 above.

7. Fill a comparator cell to 10 ml mark with ‘sample’ solution and place in right hand compartment of Lovibond comparator. Place a second cell containing deionised water in left hand compartment.

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Analysis

8. Check that comparator colour standards disc Chromium 66200 is inserted. Hold comparator against good north daylight (not fluorescent lighting) and rotate comparator disc until match with ‘sample’ solution is obtained.

9. The value appearing in the window of the comparator is the amount of hexavalent chromium in milligrams per cubic metre (mg/m3) of air based on a sample volume of 120 litres. Note this value.

10. Repeat steps 6 and 7 above using the solution from step 5. Note the reading for reference. In ideal conditions there should be no reading from this solution as it was made with a clean unused filter. If a reading is obtained this highlights a problem with procedures:

11. check on the purity of reagents and filters

12. check for contamination caused by unclean apparatus

13. Record results (see page 10).

14. Clean all apparatus between measurements and at the end of testing. The filter head should be cleaned to avoid cross-contamination between samples.

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Administration and Next Steps

Record keeping

Ensure all results obtained from sampling are adequately recorded!

This data must be kept for a period of time as defined in H.S.E. guidance, so it is vital to maintain these in an easy-retrieve format.

Each sample position should clearly be identified for record purposes and the results of the analysis recorded.

Record facility identity, date of sampling, the identity of the person carrying out the test and the sampling position, and in accordance with guidelines laid out in MDHS 52/3 and by the H.S.E.

Results

Any result higher than normal or in excess of the maximum limit should be investigated to determine the reason.

If in doubt of how to proceed or if you are concerned about the results obtained, consult the Health & Safety Executive for guidance.

Refer to MDHS 52/3 and EH40 for further advice and exposure limit values.

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