title: “A new method for determining condensed and uncondensed structures in lignin”

authors: Smit, Ruben

abstract: This thesis describes a new analytical method to determine the levels of uncondensed (protonated C5) and condensed (bonded through C5 to other phenyl propane units) guaiacyl (G) units in lignin.

This method is important because the proportion of condensed and uncondensed units in lignin determines, in part, how the lignin will behave during mechanical and chemical processing. Currently there are few analytical techniques that can simultaneously determine the proportions of condensed and uncondensed units in isolated lignins and even fewer that can elucidate this information for lignin in situ in wood.

The method combines two well-accepted techniques, thioacidolysis and quantitative ³¹P NMR spectroscopy. Thioacidolysis involves depolymerisation of lignin with ethanethiol and boron trifluoride at elevated temperatures. This leads to an organic-solvent soluble product in which almost all the phenylpropane units are phenolic. Subsequent quantitative ³¹P NMR spectroscopic analysis, of the thioacidolysis product derivatised with 2-chloro-4,4,5,5-teramethyl-1,3,2-dioxaphospholane gave the total amount of condensed and uncondensed units in the lignin.

The method proved highly successful at determining the amounts of uncondensed G, condensed G, syringyl (S) and p-hydroxyphenyl (H) units in milled wood lignin (MWL) and in situ lignins from softwoods, hardwoods, softwood compression woods and softwood pulp fibres. Also, for MWL samples the method proved useful for determining the amounts of uncondensed G, condensed G, S and H units present as free phenolic and etherified moieties. A further benefit of performing the method was that it allowed the levels of individual condensed units, such as β-5, 5-5 and 4-O-5, in MWL and in situ lignin to be determined.

Initial investigations with model compounds found that quantitative ³¹P NMR spectra were collected even when thioacidolysis was performed prior to ³¹P NMR spectroscopy. This was significant, as prior to this work we had been concerned that thioethyl incorporation into sterically crowded 5-5 and β-5 structures may have hindered quantitative analysis.

Dibenzodioxocin structures have recently been reported as important units in lignin polymer crosslinking, therefore the thioacidolysis of a dibenzodioxocin model compound was studied. The dibenzodioxocin reacted primarily via an acid catalysed ring rearrangement to yield a dibenzooxepine. The incomplete cleavage of dibenzodioxocin ring during thioacidolysis suggested that the method might be under reporting the levels 5-5 units.

Thioacidolysis/³¹P NMR spectroscopy was initially applied to MWL and in situ lignin from radiata pine wood. In both samples around 35% of the phenylpropane units were condensed. As MWL originates primarily from the secondary wall (SW), this finding suggests that the SW and middle lamella (ML) lignin in radiata pine are more similar than previously believed. Thioacidolysis/³¹P NMR spectroscopy was also applied to lignin in situ in wood from slabwood, corewood, earlywood and latewood regions of a mature radiata pine. In all samples around 35% of the phenylpropane units in the total lignin were condensed. While the concentration of lignin in these different regions of the tree has been shown to vary markedly, these results suggest that the proportion of condensed units remains the same.

Thioacidolysis/³¹P NMR spectroscopy was next applied to MWL and in situ lignin samples from a hardwood and a softwood compression wood. For eucalypt MWL, 37% of the free phenolic groups were S units but 73% of the phenolic groups released by thioacidolysis were S units. On the other hand for compression wood around 90% of the H units were found to be present as free phenolic groups, with few H units released during thioacidolysis. These results can be seen as further confirmation of the preference of S units to be present as etherified moieties and H units as free phenolic moieties in lignin.

The method was next applied to lignins in in situ thermomechanical and chemithermomechanical pulp fibres. The lignin in both thermomechanical pulping (TMP) and medium density fibreboard (MDF) fibres contained around 35% condensed units. This indicated that mechanical refining at elevated temperatures did not significantly change the proportions of condensed units in the lignin. However, for thermomechanical refining in the presence of added sulphite, results showed that around 38% of the C9 units in lignin were condensed moieties. This increased proportion of condensed units relative to radiata slabwood, was due to a decrease in the amount of uncondensed units, rather than an increase in the amount of condensed units. This lower yield of uncondensed units was attributed to α-sulphonation of the lignin during the pulping process, which may block the degradation of lignin by thioacidolysis. This effect was highlighted in the heavily sulphonated Ontario Paper Co. (OPCO) pulp, where a very low overall yield was observed.

Finally thioacidolysis/³¹P NMR spectroscopy was applied to a number of different kraft spent liquor lignins (KSLLѕ). KSLLѕ were found to contain up to 45% condensed G units. This increased proportion of condensed structures, relative to in situ pine lignin was consistent with numerous literature reports. However, thioacidolysis/³¹P NMR spectroscopy was found to be less applicable to these heavily modified lignins, as they were much less comprehensively degraded on thioacidolysis than wood lignins.

text: “A new method for determining condensed and uncondensed structures in lignin” This thesis describes a new analytical method to determine the levels of uncondensed (protonated C5) and condensed (bonded through C5 to other phenyl propane units) guaiacyl (G) units in lignin.

This method is important because the proportion of condensed and uncondensed units in lignin determines, in part, how the lignin will behave during mechanical and chemical processing. Currently there are few analytical techniques that can simultaneously determine the proportions of condensed and uncondensed units in isolated lignins and even fewer that can elucidate this information for lignin in situ in wood.

The method combines two well-accepted techniques, thioacidolysis and quantitative ³¹P NMR spectroscopy. Thioacidolysis involves depolymerisation of lignin with ethanethiol and boron trifluoride at elevated temperatures. This leads to an organic-solvent soluble product in which almost all the phenylpropane units are phenolic. Subsequent quantitative ³¹P NMR spectroscopic analysis, of the thioacidolysis product derivatised with 2-chloro-4,4,5,5-teramethyl-1,3,2-dioxaphospholane gave the total amount of condensed and uncondensed units in the lignin.

The method proved highly successful at determining the amounts of uncondensed G, condensed G, syringyl (S) and p-hydroxyphenyl (H) units in milled wood lignin (MWL) and in situ lignins from softwoods, hardwoods, softwood compression woods and softwood pulp fibres. Also, for MWL samples the method proved useful for determining the amounts of uncondensed G, condensed G, S and H units present as free phenolic and etherified moieties. A further benefit of performing the method was that it allowed the levels of individual condensed units, such as β-5, 5-5 and 4-O-5, in MWL and in situ lignin to be determined.

Initial investigations with model compounds found that quantitative ³¹P NMR spectra were collected even when thioacidolysis was performed prior to ³¹P NMR spectroscopy. This was significant, as prior to this work we had been concerned that thioethyl incorporation into sterically crowded 5-5 and β-5 structures may have hindered quantitative analysis.

Dibenzodioxocin structures have recently been reported as important units in lignin polymer crosslinking, therefore the thioacidolysis of a dibenzodioxocin model compound was studied. The dibenzodioxocin reacted primarily via an acid catalysed ring rearrangement to yield a dibenzooxepine. The incomplete cleavage of dibenzodioxocin ring during thioacidolysis suggested that the method might be under reporting the levels 5-5 units.

Thioacidolysis/³¹P NMR spectroscopy was initially applied to MWL and in situ lignin from radiata pine wood. In both samples around 35% of the phenylpropane units were condensed. As MWL originates primarily from the secondary wall (SW), this finding suggests that the SW and middle lamella (ML) lignin in radiata pine are more similar than previously believed. Thioacidolysis/³¹P NMR spectroscopy was also applied to lignin in situ in wood from slabwood, corewood, earlywood and latewood regions of a mature radiata pine. In all samples around 35% of the phenylpropane units in the total lignin were condensed. While the concentration of lignin in these different regions of the tree has been shown to vary markedly, these results suggest that the proportion of condensed units remains the same.

Thioacidolysis/³¹P NMR spectroscopy was next applied to MWL and in situ lignin samples from a hardwood and a softwood compression wood. For eucalypt MWL, 37% of the free phenolic groups were S units but 73% of the phenolic groups released by thioacidolysis were S units. On the other hand for compression wood around 90% of the H units were found to be present as free phenolic groups, with few H units released during thioacidolysis. These results can be seen as further confirmation of the preference of S units to be present as etherified moieties and H units as free phenolic moieties in lignin.

The method was next applied to lignins in in situ thermomechanical and chemithermomechanical pulp fibres. The lignin in both thermomechanical pulping (TMP) and medium density fibreboard (MDF) fibres contained around 35% condensed units. This indicated that mechanical refining at elevated temperatures did not significantly change the proportions of condensed units in the lignin. However, for thermomechanical refining in the presence of added sulphite, results showed that around 38% of the C9 units in lignin were condensed moieties. This increased proportion of condensed units relative to radiata slabwood, was due to a decrease in the amount of uncondensed units, rather than an increase in the amount of condensed units. This lower yield of uncondensed units was attributed to α-sulphonation of the lignin during the pulping process, which may block the degradation of lignin by thioacidolysis. This effect was highlighted in the heavily sulphonated Ontario Paper Co. (OPCO) pulp, where a very low overall yield was observed.

Finally thioacidolysis/³¹P NMR spectroscopy was applied to a number of different kraft spent liquor lignins (KSLLѕ). KSLLѕ were found to contain up to 45% condensed G units. This increased proportion of condensed structures, relative to in situ pine lignin was consistent with numerous literature reports. However, thioacidolysis/³¹P NMR spectroscopy was found to be less applicable to these heavily modified lignins, as they were much less comprehensively degraded on thioacidolysis than wood lignins.

year: 2000

title: Stratigraphic columns for the Neogene succession exposed in central parts of Hawke’s Bay Basin, eastern North Island, New Zealand

authors: Kamp, Peter J.J.

subjects: lithostratigraphy

abstract: This report is a compilation of stratigraphic columns for geological sections and outcrops of Neogene sedimentary units in central parts of Hawke’s Bay Basin, eastern North Island, New Zealand. The columns have been prepared as part of a basin analysis investigation undertaken by the Sedimentary and Petroleum Geology Research Group in the Department of Earth and Ocean Sciences at the University of Waikato and have been compiled into a common format from six recent MSc and PhD theses to make the information more readily available, principally to assist hydrocarbon exploration activities in the region. The columns represent a level of detail underpinning a rationalized lithostratigraphy of the Neogene basin fill. The systematic lithostratigraphic description of the basin fill is given in a companion report (Bland et al. 2007).

text: Stratigraphic columns for the Neogene succession exposed in central parts of Hawke’s Bay Basin, eastern North Island, New Zealand This report is a compilation of stratigraphic columns for geological sections and outcrops of Neogene sedimentary units in central parts of Hawke’s Bay Basin, eastern North Island, New Zealand. The columns have been prepared as part of a basin analysis investigation undertaken by the Sedimentary and Petroleum Geology Research Group in the Department of Earth and Ocean Sciences at the University of Waikato and have been compiled into a common format from six recent MSc and PhD theses to make the information more readily available, principally to assist hydrocarbon exploration activities in the region. The columns represent a level of detail underpinning a rationalized lithostratigraphy of the Neogene basin fill. The systematic lithostratigraphic description of the basin fill is given in a companion report (Bland et al. 2007).

year: 2007

title: Haumanu Hauora: refining public health institution policy to include Māori and climate change

authors: Masters-Awatere, Bridgette

abstract: The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

text: Haumanu Hauora: refining public health institution policy to include Māori and climate change The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

year: 2023-05-05