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Journal ArticleDOI

A Recycling Method for LST® Contaminated During Heavy Liquid Separation in Palynological Processing

02 Oct 2017-Palynology (AASP: The Palynological Society)-Vol. 41, Iss: 4, pp 498-503
TL;DR: In this article, the authors presented the methods for recycling LST® and removing contamination through a combination of filtration through activated charcoal and 0.45 µm nylon membranes, which was found to be unnecessary.
Abstract: An aqueous solution of LST® is one of many heavy liquids used to concentrate palynomorphs. It and aqueous solutions of sodium polytungstate (SPT) are replacing toxic heavy liquids, such as bromoform and zinc bromide, and to a lesser extent zinc chloride, in many palynology laboratories. Both non-toxic heavy liquids can be recycled through filtering and evaporation of water and/or ethanol added to the sample during processing, and commonly are. Both media, and especially LST®, are somewhat reactive with organic matter, and in humic-acid rich samples become contaminated and discoloured. This paper presents the authors' methods for recycling LST® and removing contamination through a combination of filtration through activated charcoal and 0.45 µm nylon membranes. Filtration through Celite® was found to be unnecessary.

Summary (2 min read)

1. Introduction

  • Heavy liquid or dense-media separation has been an integral component of palynology preparation since the earliest stages of the discipline (Brown 2008).
  • The use of mineral salts for heavy density separation was introduced in the mid-1980s (Callahan 1987; Gregory & Johnston 1987) and quickly spread to the micropalaeontological community (Krukowski 1988; Savage 1988).
  • Krukowski (1988) advocated vacuum filtering through No. 4 qualitative filter paper followed by evaporation, and if contaminated with iron and thus blueish in colour, adding a drop or two of 3% hydrogen peroxide to return SMT to its original state.

2. Materials and methods

  • Discoloured LST waste was obtained from two laboratories.
  • A provided three aliquots of waste LST , one discoloured lightly brown (sample 1), one discoloured dark brown to black (sample 2), and one discoloured pink by Safranin-O (sample 3); all had starting specific gravities of approximately 1.7.
  • B’s waste was lightly brown discoloured and had a starting specific gravity of less than 1 (sample 4).
  • Sample 1 was used as the experimental sample.

2.3. Method 3: activated charcoal plus Celite

  • The activated charcoal was filtered out by passing through P8 cellulosic paper suspended in a glass funnel.
  • The filtrate was filtered again through a pad of Celite formed in a 60-mL glass-fritted Buchner funnel (run 3).
  • The final filtrate was then passed through a 0.45 mm nylon membrane.

2.4. Method 4: activated charcoal

  • The mixture was stirred until the colour of the solution changed from brownish to black, then, while tipping the beaker to allow the suspension to settle, the liquid was observed to be colourless.
  • This suspension was poured into a medium-sized filter funnel (7.0 cm diameter) and passed through P8 cellulosic paper.
  • The resultant filtrate was then passed through a 0.45 mm nylon filter.

2.5. Reconcentration

  • Many methods of reconcentration of cleaned LST are possible.
  • At Morehead State University, the final filtrate is placed on a magnetic stirrer hot-plate set to about 125 C until reduced by 2/3, taking care not to crystallise the LST at high solution density (>2.8 SG).
  • Reconcentrated LST can be stored in clean Nalgene bottles and sealed as per laboratory practice.

2.6. Optical microscopy

  • Samples from the initial tests of methods 1, 3 and 4 were examined for (1) remnant organic matter and (2) crystalline material using both white and blue light illumination on a Leitz Ortholux II microscope with 630£ total magnification.
  • The blue light source was a CoolLED pE-100 lamp.
  • Photomicrographs were obtained with a Leica MC170 HD camera and captured via the Leica Application Suite software package.

3.1.1. Method 1

  • The resulting filtrate in method 1, run 1 was clear; however, significant problems with this method became apparent during run 2.
  • In run 2, the filtrate maintained its brown colour.
  • Close observation of a second trial of run 2 revealed that the highdensity LST pushed through the Celite particles, forming ‘tunnels’ (Plate 1), which resulted in contaminants not being removed.

3.1.2. Method 2

  • The sample turned neon-orange, and could not be cleared beyond light yellow-brown with multiple runs through activated charcoal (Plate 2, vials BGVN-1-7 & BGVN-1-13).
  • //pubs.geoscienceworld.org/palynology/article-pdf/3976880/tpal_a_1283368_o.pdf by Morehead State Univ Camden-Carroll Lib user on 25 March 2020 density could not be increased via heating, and the sample was judged to be unusable, also known as Downloaded from https.

3.1.5. Optical characterisation

  • Contaminated LST is weakly fluorescent , as are samples from method 1.
  • Samples from method 1 also contained fragments of silica .
  • LST from methods 3 and 4 were non-fluorescing and contained no particulate matter .

4. Conclusions and recommendations

  • While method 3 worked well, method 4 appeared to work equally well and involves fewer steps and less waste material .
  • LST can be successfully cleaned and re-condensed using basic practices comparable to those in place in many laboratories for cleaning zinc bromide (ZnBr2) and Plate 3.
  • //pubs.geoscienceworld.org/palynology/article-pdf/3976880/tpal_a_1283368_o.pdf by Morehead State Univ Camden-Carroll Lib user on 25 March 2020 zinc chloride (ZnCl2), also known as Downloaded from https.
  • Even if it does, however, the LST is soluble in water and rehydration merely adds another step to the process.
  • The authors cannot demonstrate that the recycled LST achieved through this method is carbon-free and suitable for use with samples meant for radiocarbon dating using accelerator mass spectrometry (AMS); however, it is suitable for routine palynological preparations, and has been used successfully for such at Morehead State University.

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A recycling method for LST
Ò
contaminated during heavy liquid separation
in palynological processing
Brandon G. Van Ness
a
, Morgan K. Black
b
, Clayton R. Gullett
b
and Jennifer M.K. OKeefe
b
a
Department of Biology and Chemistry, Morehead State University, Morehead, KY, USA;
b
Department of Earth and Space Sciences, Morehead State
University, Morehead, KY, USA
ABSTRACT
An aqueous solution of LST
Ò
is one of many heavy liquids used to concentrate palynomorphs. It and
aqueous solutions of sodium polytungstate (SPT) are replacing toxic heavy liquids, such as bromoform
and zinc bromide, and to a lesser extent zinc chloride, in many palynology laboratories. Both non-toxic
heavy liquids can be recycled through ltering and evaporation of water and/or ethanol added to the
sample during processing, and commonly are. Both media, and especially LST
Ò
, are somewhat reactive
with organic matter, and in humic-acid rich samples become contaminated and discoloured. This paper
presents the authors methods for recycling LST
Ò
and removing contamination through a combination of
ltration through activated charcoal and 0.45 mm nylon membranes. Filtration through Celite
Ò
was found
to be unnecessary.
KEYWORDS
LST
Ò
; heavy liquids;
recycling; discolouration;
palynological processing
1. Introduction
Heavy liquid or dense-media separation has been an integral
component of palynology preparation since the earliest stages
of the discipline (Brown 2008). Over the past 20 years, a slow
transition is being made away from toxic heavy liquids, includ-
ing bromoform and zinc bromide, and to a lesser extent zinc
chloride to less toxic sodium polytungstate (SPT; Munsterman &
Kerstholt 1996; Campbell et al. 2016), sodium metatungstate
(SMT; Krukowski 1988) and LST
Ò
(Patrick & Patrick 1997;OKeefe
& Eble 2012; Caffrey & Horn 2013). While initially expensive, the
use of these liquids is becoming preferential because of their
low toxicity and ease of recycling (Proske et al. 2015; Campbell
et al. 2016).
Recycling methods for standard heavy liquids used in paly-
nology, micropalaeontology and kerogen studies are well
established in the literature, including those for clarifying media
discoloured by oil and humic acids (Hanna 1927; von Bitter et al.
1978). Many palynology laboratories recycle heavy media using
ltration and reconcentration (Wagoner et al. 1961; Gray 1965;
Burgess 1974); however, these methods do not remove colour
from samples contaminated with humic acids. Barker (1981),
recognising this as a signi cant problem when preparing kero-
gen isolates, advocated treatment of contaminated zinc bro-
mide with hydrogen peroxide and ltration through Celite
Ò
,
while older works suggested decolourisation with Fullers Earth
(Hanna 1927; von Bitter et al. 1978), or a variety of re-distillation
methods coupled with decolourisation with Fullers Earth (Hauff
& Airey 1980).
The use of mineral salts for heavy density separation was
introduced in the mid-1980s (Callahan 1987; Gregory & Johnston
1987) and quickly spread to the micropalaeontological
community (Krukowski 1988; Savage 1988). As alternate heavy
liquids became more common, several methods for recycling
SMT, SPT and LST
Ò
, a proprietary heavy medium (Patrick & Pat-
rick 1997), have been published. Patrick & Patrick (1997)outline
a recycling method. The recycling method on most suppliers
websites calls for simply re-concentrating spent LST
Ò
through
boiling; however, a owchart that includes additional recycling
procedures is present on some suppliers webpages (e.g. http://
www.chem.com.au/heavy_liquid.html#recycle, http://www.heavy
liquids.com/application.html#Recycle). This ow chart generally
indicates ltering at 5 mm to remove particles, re-concentrating
and carbon ltration. These directions have been recognised as
insufcient from the earliest use of mineral salts in
micropalaeontology.
Krukowski (1988 ) advocated vacuum ltering through No. 4
qualitative lter paper followed by evaporation, and if contami-
nated with iron and thus blueish in colour, adding a drop or
two of 3% hydrogen peroxide to return SMT to its original state.
Savage (1988) recommended washing all lters and apparatus
that came in contact with SPT into a recovery container with
distilled water, then evaporating the liquid in an oven. Six et al.
(1999) advocate ltration of SPT through a complex column
packed with layers of glass wool, activated carbon, glass wool,
resin, glass wool, activated carbon, and more glass wool; this
method, which does remove colour effectively, is more complex
than necessary. More recently, Proske et al. (2015), recycled
LST
Ò
by passing it through glass lters twice, then re-condens-
ing the ltrate. This process is equivalent to the pre-recycling
treatment of LST
Ò
at Morehead State University, Morehead, KY,
USA, whereby particulate matter is removed as the used LST
Ò
is
passed through a 0.45 mm lter. This does not, however,
CONTACT Jennifer M.K. OKeefe j.okeefe@moreheadstate.edu
© 2017 AASP The Palynological Society
PALYNOLOGY, 2017
VOL. 41, NO. 4, 498503
http://dx.doi.org/10.1080/01916122.2017.1283368
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by Morehead State Univ Camden-Carroll Lib user
on 25 March 2020

remove colour gained during heavy-density separation from
the dilute LST
Ò
(Plate 1, crude LST
Ò
).
The goal of this paper was to develop and share an efcient,
inexpensive method for recycling LST
Ò
contaminated by humic
acids in palynology laboratories. The method described below
is straightforward and was easily accomplished by technicians
with little chemistry or palynology experience.
2. Materials and methods
Discoloured LST
Ò
waste was obtained from two laboratories.
Laboratory A provided three aliquots of waste LST
Ò
, one discol-
oured lightly brown (sample 1), one discoloured dark brown to
black (sample 2), and one discoloured pink by Safranin-O (sam-
ple 3); all had starting specic gravities of approximately 1.7.
Laboratory Bs waste was lightly brown discoloured and had a
starting specic gravity of less than 1 (sample 4). Sample 1 was
used as the experimental sample. Only method 4 was used
with samples 24.
2.1. Method 1: Celite
Ò
As an initial test (run 1), a pipette column was prepared by
packing a 5-mL pipette with approximately 2 g of Celite
Ò
diato-
maceous earth (enough to ll the pipette half-way). One half
millilitre of contaminated LST
Ò
from sample 1 was poured
Plate 1. Filtration apparatus for method 1, run 2 showing tunnels through the Celite
Ò
.
PALYNOLOGY 499
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through the Celite
Ò
. The procedure was scaled up to 60 g of
Celite
Ò
in a glass-fritted Buchner funnel (run 2); 20 mL of LST
Ò
was poured through the system. The density of the LST
Ò
was
reduced to approximately 1.34 g/mL and the scaled-up method
re-tested. All subsequent methodologies used LST
Ò
with this
lower density for the initial test.
2.2. Method 2: hydrogen peroxide
Approximately 0.5 mL of 30% hydrogen peroxide was added to
10 g of contaminated LST
Ò
solution and vortexed. This was
then ltered through activated charcoal multiple times.
2.3. Method 3: activated charcoal plus Celite
Ò
Activated charcoal (Norit
TM
, Neutral) was mixed with contami-
nated LST
Ò
from sample 1 using a ratio of 1 g to 40 g. The acti-
vated charcoal was ltered out by passing through P8 cellulosic
paper suspended in a glass funnel. The ltrate was ltered again
through a pad of Celite
Ò
formed in a 60-mL glass-fritted Buch-
ner funnel (run 3). The nal ltrate was then passed through a
0.45 mm nylon membrane.
2.4. Method 4: activated charcoal
Contaminated LST
Ò
from sample 1 was mixed with activated
charcoal (Norit
TM
, Neutral) in a 250-mL beaker using a ratio of
40 g to 1 g; in this test, approximately 160 g of contaminated
LST
Ò
was treated. The mixture was stirred until the colour of
the solution changed from brownish to black, then, while tip-
ping the beaker to allow the suspension to settle, the liquid
was observed to be colourless. This suspension was poured into
a medium-sized lter funnel (7.0 cm diameter) and passed
through P8 cellulosic paper. The resultant ltrate was then
passed through a 0.45 mm nylon lter.
2.5. Reconcentration
Many methods of reconcentration of cleaned LST
Ò
are possible.
At Morehead State University, the nal ltrate is placed on a
magnetic stirrer hot-plate set to about 125
C until reduced by
2/3, taking care not to crystallise the LST
Ò
at high solution den-
sity (>2.8 SG). Reconcentrated LST
Ò
can be stored in clean
Nalgene
Ò
bottles and sealed as per laboratory practice.
2.6. Optical microscopy
Samples from the initial tests of methods 1, 3 and 4 were exam-
ined for (1) remnant organic matter and (2) crystalline material
using both white and blue light illumination on a Leitz Ortholux
II microscope with 630£ total magnication. The blue light
source was a CoolLED pE-100 lamp. Photomicrographs were
obtained with a Leica MC170 HD camera and captured via the
Leica Application Suite software package.
3. Results
3.1. Colour change
3.1.1. Method 1
The resulting ltrate in method 1, run 1 was clear; however, sig-
nicant problems with this method became apparent during
run 2. In run 2, the ltrate maintained its brown colour. Close
observation of a second trial of run 2 revealed that the high-
density LST
Ò
pushed through the Celite
Ò
particles, forming
tunnels (Plate 1), which resulted in contaminants not being
removed.
3.1.2. Method 2
The sample turned neon-orange, and could not be cleared
beyond light yellow-brown with multiple runs through acti-
vated charcoal (Plate 2, vials BGVN-1-7 & BGVN-1-13). The
Plate 2. Vials of treated and untreated aliquots of sample 1. From the left, untreated LST
Ò
as received from Laboratory A (density 1.7 g/mL); diluted LST
Ò
(density 1.34 g/
mL) used for analyses; method 2, run 1 (BGVN-1-7); method 2, run 2 (BGVN-1-13); method 3 (BGVN-1-15).
500 B. G. VAN NESS ET AL.
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density could not be increased via heating, and the sample was
judged to be unusable.
3.1.3. Method 3
The re-condensed ltrate is nearly clear and reached its original
density (Plate 2 , vial BGVN-1-15).
3.1.4. Method 4
Sample 1 achieved a pale golden colour virtually identical to
that of a virgin sample of LST
Ò
(Plate 3, gure 1). Sample 2
achieved a pale golden colour following multiple rounds of l-
tration (Plate 3, gures 24). Sample 3 is colourless (Plate 3, g-
ures 4 and 5), as is sample 4 (Plate 3, gures 6 and 7).
3.1.5. Optical characterisation
Contaminated LST
Ò
is weakly uorescent (Plate 4, gure 2), as
are samples from method 1. Samples from method 1 also con-
tained fragments of silica (Plate 4, gure 1). LST
Ò
from methods
3 and 4 were non-uorescing and contained no particulate mat-
ter (Plate 4, gures 3 and 4).
4. Conclusions and recommendations
While method 3 worked well, method 4 appeared to work
equally well and involves fewer steps and less waste mate-
rial (Figure 1). LST
Ò
can be successfully cleaned and re-con-
densed using basic practices comparable to those in place
in many laboratories for cleaning zinc bromide (ZnBr
2
)and
Plate 3. Results of method 4. Figure 1 is sample 1; gures 2, 3 and 4 are raw sample 2, 2£ ltered sample 2 and 4£ ltered sample 2, respectively; gures 5 and 6 are
raw and treated sample 3, respectively; and gures 7 and 8 are raw and treated sample 4, respectively.
PALYNOLOGY 501
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by Morehead State Univ Camden-Carroll Lib user
on 25 March 2020

zinc chloride (ZnCl
2
). The process is easily followed by tech-
nicians, and rapid, provided the LST
Ò
is not allowed to crys-
tallise. Even if it does, however, the LST
Ò
is soluble in water
and rehydration merely adds another step to the process.
We cannot demonstrate that the recycled LST
Ò
achieved
through this method is carbon-free and suitable for use with
samples meant for radiocarbon dating using accelerator mass
spectrometry (AMS); however, it is suitable for routine palyno-
logical preparations, and has been used successfully for such at
Morehead State University.
Acknowledgements
Development of this methodology is based upon work supported by the
National Science Foundation under Cooperative Agreement No. 1355438
through a Kentucky NSF EPSCoR RSP grant to OKeefe in support of Black
and Gullett.
Disclosure statement
No potential conict of interest was reported by the authors.
Plate 4. Figure 1, contaminated LST
Ò
showing weak yellow uorescence; gure 2, particulate matter remaining in sample 1 following method 1. Figures 3 and 4 are
results of methods 3 and 4, which are non-uorescent and contain no particulate matter (unfortunately, dirt on a light-path mirror is present in the image).
Figure 1. Flowchart showing recommended decolouration method.
502 B. G. VAN NESS ET AL.
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Citations
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Journal ArticleDOI
TL;DR: A comprehensive, illustrated guide to the extraction, concentration and microscope slide production of palynomorphs from samples of sediments, sedimentary rocks and other materials is presented in this article.
Abstract: A comprehensive, illustrated guide to the preparation (i.e. extraction, concentration and microscope slide production) of palynomorphs from samples of sediments, sedimentary rocks and other materials is presented. The traditional technique, based upon mineral acid digestion of the sample matrix, is subdivided into four phases. These are: sampling and pre-preparation; acid digestion; palynomorph concentration; and presentation of palynomorphs for study and archiving of materials. Modifications for preparing Quaternary and modern materials such as acetolysis are outlined, as are methods of preparation which do not use hazardous acids. One of the most effective non-acid preparation techniques uses sodium hexametaphosphate as a clay deflocculant and works well on clay-rich samples which are not intensely lithified. Hydrogen peroxide is another reagent which can be used for this purpose. The contamination of samples by material from other samples or modern pollen can lead to spurious data and interpretations. Strenuous efforts to avoid contamination should be made. Modifications of the traditional preparation technique are described for 14 specific sample materials. For example, many pure limestones only require digestion with hydrochloric acid. Moreover, coal is typically simply oxidised using nitric acid or Schulze's solution then reacted with dilute potassium hydroxide solution to produce organic substances which are then rinsed away using water. Traditional preparation techniques are used for all palynomorph groups irrespective of their biological affinity, however certain of these require some specific modifications. For example chitinozoa and megaspores are substantially larger than acritarchs, dinoflagellate cysts, miospores and pollen, therefore modifications to the technique must be used, principally in the sieve sizes used. Some attempts have been made to automate palynomorph processing. The equipment for this is discussed, together with other technological solutions such as microwave digestion. Eight techniques closely associated with palynological processing and the microscopical observation of palynomorphs such as scanning electron microscopy are also reviewed.

29 citations

Journal ArticleDOI
TL;DR: In this article, the most common processing techniques applied to palynomorphs and their known issues are synthesized and general recommendations are made to minimize processing bias and maximize NPP recovery.
Abstract: Abstract This chapter synthesizes the most common processing techniques applied to palynomorphs and their known issues. We primarily focus on non-pollen palynomorphs (NPPs), but include studies on pollen grains where the information might be relevant. An overview of recent (2017–19) NPP publications is used to connect the most common techniques to known taphonomic issues. Finally, general recommendations are made to minimize processing bias and maximize NPP recovery.

21 citations


Cites background from "A Recycling Method for LST® Contami..."

  • ...Since the 1980s there has been a progressive shift to non-toxic and more easily recyclable heavy liquids such as sodium polytungstate (Munsterman and Kerstholt 1996), sodium metatungstate (Krukowski 1988) and lithium heteropolytungstate (O’Keefe and Eble 2012; Caffrey and Horn 2013; Van Ness et al. 2017; Leipe et al. 2019)....

    [...]

  • ...…been a progressive shift to non-toxic and more easily recyclable heavy liquids such as sodium polytungstate (Munsterman and Kerstholt 1996), sodium metatungstate (Krukowski 1988) and lithium heteropolytungstate (O’Keefe and Eble 2012; Caffrey and Horn 2013; Van Ness et al. 2017; Leipe et al. 2019)....

    [...]

  • ...Although commonly thought of as innocuous to palynomorphs, increasing numbers of studies are showing, or suggesting, HF to be detrimental (Reid and John 1981; Van Geel 2001; Mudie et al. 2010; Mertens et al. 2012; O’Keefe and Eble 2012)....

    [...]

  • ...Van Geel (2001) speculated that HF acid treatment might damage fungi and Clarke (1994) found that large buoyant fungal forms were lost during a treatment procedure involving HF. O’Keefe and Eble (2012) demonstrated that processing methods that use HF reduce the overall concentration values of palynomorphs obtained from clay-rich samples....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the authors introduce a safer pollen preparation method, based on the use of low-toxic heavy liquid lithium hetero polytungstate (LST Fastfloat) and provide instructions for pollen preparation with the LST Fastflow method.
Abstract: Pollen analysis is a commonly used method to interpret vegetation and environmental change. The standard pollen preparation technique in minerogenic sediments involves the use of hydrofluoric acid (HF) which is highly toxic. Currently the European legislation requires that hazardous chemicals should be substituted with less hazardous or nontoxic chemicals if possible. In the present paper the authors introduce a safer pollen preparation method, based on the use of low-toxic heavy liquid lithium hetero polytungstate (LST Fastfloat) and provide instructions for pollen preparation with the LST Fastflow method. Furthermore, five paired samples were processed from clayey and silty sediments with LST Fastfloat and conventional HF methods and the pollen and spore counting results obtained from these two methods were compared to test if there is statistically significant differences between the taxa. Calculation of the 95 % confidence interval revealed statistical agreement in all studied taxa except one taxon in one sample pair. However, the study revealed systematic differences within two taxa, Betula and Pinus. Thus caution is needed when comparing results obtained by HF and heavy liquid (LST Fastfloat) methods.

3 citations


Cites background from "A Recycling Method for LST® Contami..."

  • ...The use of heavy liquids such as sodium metatungstate (known as sodium polytungstate, SPT) and lithium based or sodium based heteropolytungstates (LST), have become more common during the last decades (Van Ness et al., 2017)....

    [...]

References
More filters
Book
01 Jan 1965

188 citations


"A Recycling Method for LST® Contami..." refers background in this paper

  • ...Many palynology laboratories recycle heavy media using filtration and reconcentration (Wagoner et al. 1961; Gray 1965; Burgess 1974); however, these methods do not remove colour from samples contaminated with humic acids....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a new non-toxic alternative, sodium polytungstate, has been compared to bromoform, and the results show similar sporomorph recovery using both heavy liquids provided that specific gravity 2.1 is used.

113 citations


"A Recycling Method for LST® Contami..." refers background in this paper

  • ...…away from toxic heavy liquids, including bromoform and zinc bromide, and to a lesser extent zinc chloride to less toxic sodium polytungstate (SPT; Munsterman & Kerstholt 1996; Campbell et al. 2016), sodium metatungstate (SMT; Krukowski 1988) and LST (Patrick & Patrick 1997; O’Keefe & Eble 2012;…...

    [...]

Journal ArticleDOI

96 citations


"A Recycling Method for LST® Contami..." refers background in this paper

  • ...The use of mineral salts for heavy density separation was introduced in the mid-1980s (Callahan 1987; Gregory & Johnston 1987) and quickly spread to the micropalaeontological community (Krukowski 1988; Savage 1988)....

    [...]

  • ...The use of mineral salts for heavy density separation was introduced in the mid-1980s (Callahan 1987; Gregory & Johnston 1987) and quickly spread to the micropalaeontological community (Krukowski 1988; Savage 1988)....

    [...]

Journal ArticleDOI
TL;DR: Swimmer et al. as mentioned in this paper used a column with activated carbon to remove organic contaminants and with cation exchange resin to return the solution to the sodium form before insoluble precipitates can form.
Abstract: Studies of soil organic matter (SOM) dynamics rely heavily on physical fractionation of the soil (Christensen, 1992). Most physical fractionation procedures involve some degree of soil dispersion followed by the separation of fractions on the basis of size or density. A variety of organic and inorganic liquids have been employed for density separations. In recent years, sodium polytungstate (SPT) has become a preferred density agent. We describe here a method developed for cleaning and recycling SPT used in density fractionations of soils. The method involves percolating dilute SPT solutions through a column ®lled with activated carbon to remove organic contaminants and with cation exchange resin to return the solution to the sodium form before insoluble precipitates can form. Density separation is often used to isolate light and heavy fractions (Greenland and Ford, 1964; Barrios et al., 1996; Wander and Traina, 1996). Furthermore, because soil structure plays a major role in the turnover and stabilization of SOM, the physical location of SOM within the soil matrix is an important consideration (Stevenson and Elliott, 1989; Carter and Gregorich, 1996), and this has led to increased use of density fractionations. For example, recent studies have di€erentiated interand intraaggregate particulate organic matter by density separation (Besnard et al., 1996; Jastrow, 1996). Sodium polytungstate has several advantages over other high-density liquids. It is less toxic than organic liquids or solutions of ZnBr2 or Nal, has a lower viscosity at high concentrations than other inorganic solutions, and can be used to produce a wide range of densities (1.0±3.1 g cmy3). Although SPT was more inhibitory than LudoX (a colloidal Si suspension) in follow-up mineralization studies of isolated density fractions (Magid et al., 1996), Ludox cannot be used to achieve the higher densities required in some studies (e.g. Cambardella and Elliott, 1994; Golchin et al., 1994). The maximum density achievable with Ludox is 1.4 g cmy3 (Meijboom et al., 1995). Although more expensive than other agents, SPT solutions are reusable. Simple recycling procedures are used by geologists and paleontologists (Savage, 1988), but these procedures must be modi®ed for SOM studies because small amounts of carbon may be exchanged between the soil and SPT. This carbon should be removed from the SPT solution before reuse, especially if stable isotope measurements on isolated fractions are needed. Furthermore, SPT as supplied can be contaminated with carbon (we measured 1.22 2 0.03 mg C gy1 SPT) and, thus, may require cleaning before use in SOM studies. In addition, because the Na ion disassociates with polytungstate in aqueous solution during the fractionation procedure, other cations present in the soil (especially Ca) can associate with polytungstate and form insoluble species that precipitate when the SPT solution is recycled and concentrated (M. Swimmer, Geoliquids, Prospect Heights, IL, personal communication). Our recycling procedure uses a column (Fig. 1) ®lled with activated carbon (Darco S-51, 4±12 mesh; Norit Americas, Atlanta, GA) and cation exchange resin (benzene diethenyl polymer, H-form; Sybron Chemicals, Birmingham, NJ 08011). Before using the column, we rinse it with 2 l of deionized water to Soil Biology and Biochemistry 31 (1999) 1193±1196

89 citations


"A Recycling Method for LST® Contami..." refers methods in this paper

  • ...Six et al. (1999) advocate filtration of SPT through a complex column packed with layers of glass wool, activated carbon, glass wool, resin, glass wool, activated carbon, and more glass wool; this method, which does remove colour effectively, is more complex than necessary....

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Journal ArticleDOI
TL;DR: Sodium metatungstate (SMT), 3Na2WO4 · 9WO3 · H2O, is a nontoxic, high-density (1.00-3.10 g/cm3) separating compound which results in nearly neutral (pH 6) solutions of relatively low viscosity as discussed by the authors.
Abstract: Sodium metatungstate (SMT), 3Na2WO4 · 9WO3 · H2O, is a nontoxic (Sax, 1979), high-density (1.00-3.10 g/cm3) separating compound which results in nearly neutral (pH 6) solutions of relatively low viscosity. It was presented as a medium for density gradient centrifugation by Plewinsky and Kamp (1984). Since then, investigators have used SMT (or sodium polytungstate) as a high-density medium for routine mineral separations, for recovery of conodonts from insoluble residues, for separation of various feldspar species from one another, and for segregation of inorganic mineral fractions (ash) from coal.

47 citations

Frequently Asked Questions (1)
Q1. What have the authors contributed in "A recycling method for lst contaminated during heavy liquid separation in palynological processing" ?

This paper presents the authors ’ methods for recycling LST and removing contamination through a combination of filtration through activated charcoal and 0. 45 mm nylon membranes.