THE
PICKFORD
TEST SLIDE

An Alternative to the HSE/NPL Mark II Test Slide for Airborne Asbestos Analysis

WHY CHOOSE PICKFORD TEST SLIDES

Alternative Test Slides such as the Pickford Test Slide are approved in UK provided they are certified as equivalent in performance to that of the HSE/NPL Mark II Slide, which should qualify them for use in other countries such as Australia, New Zealand and North America. Click here for peer reviewed paper published in JOEH.

EXPLODED VIEW OF TEST SLIDE

The Pickford Test Slide is of rugged stainless-steel construction dimensionally similar to a standard microscope slide, and houses four ‘chips’ side by side, labelled Sets A, B, C and D. Each chip is 0.5 mm thick fused quartz, with a set of 20 etched grooves 1 µm wide and 100 µm long. The grooves range from 90 nm deep for Set A, down to 5 nm deep for Set D. When not in use, each Slide is housed in a 3D printed container, embodying magnets which hold the Slide safely within.

On each chip, the set of grooves is surrounded by metal deposits forming a series of circular and radial guidelines to assist observers locate the grooves. The most visible set of phase objects (Set A) is designed to reveal the nature of the grooves to an observer, and has the same function as blocks 1 to 4 of the HSE/NPL Mark II Slide. Sets B, C and D are equivalent to blocks 5, 6 and 7 of the HSE/NPL Mark II Slide.

THE PICKFORD TEST SLIDE IS AN ALTERNATIVE TO THE HSE/NPL MARK II TEST SLIDE FOR AIRBORNE ASBESTOS ANALYSIS

Each Pickford Test Slide is certified by the Environmental Analysis Laboratory of the Southern Cross University as being equivalent in performance to that of the UK HSE/NPL Mark II Test Slide, as required by the UK HSE ‘Asbestos: Analysts Guide’, HSG248, 2021, Section A1.37.

DESCRIPTION OF TEST SLIDE

The Test Slide, known as the Pickford Phase Contrast Test Slide, was developed over a period of 7 years based on Patents held in the United Kingdom, United States of America and Australia, and is designed as an alternative to, or replacement of the present HSE/NPL Mark II Test Slide.

The Test Slide is of rugged stainless-steel construction dimensionally similar to a standard microscope slide, and houses four ‘chips’ side by side, labelled Set A, B, C and D. Each chip is 0.5mm thick fused quartz, with a set of 20 etched grooves 1µm wide and 100 µm long.

The grooves range from 90 nm deep for Set A, down to 5 nm deep for Set D. When not in use, each Slide is housed in a 3D printed container, embodying magnets which hold the Slide safely within.

The quartz chips are overlaid with a coating which fills the grooves. The coating and quartz have different refractive indices, so each groove forms a phase object whose visibility depends on groove depth. On each chip, the set of grooves is surrounded by metal deposits forming a series of circular and radial guidelines to assist observers locate the grooves.

The most visible set of phase objects (Set A) is designed to reveal the nature of the grooves to an observer, and has the same function as blocks 1 to 4 of the HSE/NPL Mark II Slide. Sets B, C and D are equivalent to blocks 5, 6 and 7 of the HSE/NPL Mark II Slide.

Set A as viewed with a phase contrast microscope at 40x magnification

Atomic Force Microscope measurements of etch groove depth

An electron microscope micrograph of four 29 nm deep etched grooves

Some of the nanofabrication steps for etching the grooves

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Acknowledgement of Country

PhaseSlides acknowledges the Traditional Owners of Country throughout Australia and recognise their continuing connection to lands, waters and culture. We pay our respects to their Elders past, present and emerging.

THE PICKFORD TEST SLIDE